JP4943210B2 - Newspaper for offset printing - Google Patents

Description

  The present invention relates to a newsprint for offset printing, and in particular, to a newsprint for an offset rotary press having a light weight (low basis weight) and a high whiteness.

  In recent years, due to social demands such as resource saving, logistics cost reduction, and paper waste reduction, paper has been demanded to be highly formulated with deinked pulp and lightweight, especially in newspapers and magazines. The direction of weight reduction is very strong. However, the light weight of paper has a great negative effect on the paper quality. Particularly in newsprint paper, a decrease in opacity, which is an important required quality related to the print-through of printed characters or the like, is one of the major problems.

  Also, for newspaper paper, the printing method is rapidly changing from the relief printing method to the offset printing method due to the demands of the printing speed, colorization, automation, etc. Printing suitability on a rotary press is also important. Furthermore, in order to cope with the colorization and visualization of advertisement pages, a clear image is strongly demanded. For this reason, there is a growing demand for newspaper paper that is not only lighter in weight but also has a high opacity and whiteness and has a good ink fillability. In recent years, newspaper companies have tended to make their own advertising flyers and reprints that have been outsourced for the purpose of cost reduction. Therefore, there is a demand for newsprint paper that has the same printing workability as that of normal newsprint paper and has a good color appearance. The design of advertising flyers and reprints is different from that of regular newsprint, and there are many overlapping areas of four dark dots and solid printing. If the customer is an automobile manufacturer, fashion brand manufacturer, etc. Higher levels are often required for transparency, whiteness, and ink fillability.

From such a background, advertising flyers, printed materials for reprints, and the like are desired to have a high white color with a whiteness of 60% or more due to their good appearance. However, as the whiteness increases, they become more transparent and become opaque. There is a problem that the penetration of the back side of the printing surface deteriorates. Therefore, the newspaper is often used with a higher basis weight than that of ordinary newsprint. In fact, newsprint with both high whiteness and opacity and good prevention of show-through has a specified basis weight of 64 g / m ² or more. There has not yet been a newspaper with a basis weight of less than 64 g / m ² , a whiteness of 78% or more and an opacity of 90% or more.

  On the other hand, newsprint is lightweight and bulky, and requires high opacity, so as a raw material pulp, mechanical pulp with high lignin content such as groundwood pulp, refiner groundwood pulp, and thermomechanical pulp is blended at a high rate. Whiteness is low. Therefore, means for improving the whiteness of the newsprint is not limited to the mechanical pulp described above, but includes enhancing the bleaching of the raw material pulp to be blended. Technology for improving the whiteness of deinked pulp, which is the main raw material pulp of newsprint, includes, for example, printing with high whiteness and a small number of residual ink and undissolved ink when deinking newspapers and high-quality wastepaper One or more of hydrogen peroxide, NaOH, sodium silicate, and deinking agent was added, kneaded, bleached, and floated in this order two or three times. The technique to repeat is disclosed (refer patent document 1).

  In addition, for the purpose of producing high-whiteness waste paper pulp obtained by further bleaching deinked pulp obtained from printed waste paper, especially newspaper waste paper, waste paper deinked pulp obtained by deinking printed waste paper is further improved. In the bleaching process, waste paper pulp is dehydrated, mixed with hydrogen peroxide as an oxidizing bleaching agent at a pulp concentration of 25% or more, soaked, and then bleached using formamidine sulfinic acid as a reducing bleaching agent. Is disclosed (see Patent Document 2).

    Furthermore, although it is derived from used newspaper, it has high stability of whiteness after bleaching and has high-grade paper grade strength comparable to virgin pulp. Technology to provide the technology to be provided, technology to disintegrate and dehydrate the waste paper raw materials, mainly newspaper waste paper, digest this raw material, perform delignification treatment with oxygen, then deinking treatment, and then multistage bleaching Is disclosed (see Patent Document 3).

  However, such technology that promotes bleaching of raw pulp requires installation and enhancement of bleaching equipment, and whiteness is improved by bleaching, but it removes colored substances such as lignin, so it has the ability to absorb light. There is a problem that the opacity is lowered and the opacity is lowered, and there is a concern that the showthrough after printing is lowered.

  Increasing the content of high whiteness filler in paper is considered effective as a method to improve both whiteness and opacity, but increasing the paper content of newsprint increases the strength of the paper. Not only does the decrease occur, but the sheet cannot be sufficiently fixed in the paper layer, and easily oozes out of the paper layer by dampening water at the time of printing, particularly at the time of offset printing, causing a problem of blanket piling.

  Increasing the whiteness and opacity of the filler itself has also been studied, and white carbon, hydrated silicic acid (see Patent Documents 4, 5, and 6) that have high ink absorbency in fillers that are mainly used in acidic papermaking. Although there are technologies such as silicate materials, there is a limit to the filler content in these papers in consideration of paper strength reduction and powder falling, so it is not possible to completely eliminate the show-through of newspapers that are produced. It was.

  In the neutral papermaking method, there is a technique of using calcium carbonate as a filler (see Patent Document 7). However, in order to suppress the breakthrough, it is necessary to increase the filler content in the paper. Moreover, although there exists a technique (refer patent document 8) which uses a titanium dioxide-calcium carbonate composite as a filler, since expensive titanium dioxide is used as a raw material, it is not practical.

  In addition, by applying a surface treatment agent containing a fluorescent whitening agent and a water-soluble adhesive and giving a high fluorescent whitening degree to a specific layer, there is no decrease in whiteness, and excellent opacity, and There is a technology for newsprint for offset printing that has excellent color printing aptitude (see Patent Document 9). However, the optical brightener increases the apparent whiteness but does not improve the actual whiteness.

As a method of increasing the whiteness while maintaining the opacity, there is a technique of applying a pigment having a high whiteness or opacity together with an adhesive to a newsprint base paper, and a finely coated newsprint has been put into practical use. . For example, a technique for applying a coating composition comprising a conventional coating pigment and a specific aromatic vinyl-conjugated diene copolymer latex as a main component to 0.3 to 6.0 g / m ² on both sides (Patent Documents) 10 reference), needle pigment and an average oil absorption of 65 cc / 100 g or more coating layer containing a pigment from 1.0 in both 12 g / ^{m 2} provided technique (see Patent Document 11), a coating containing titanium dioxide Technology (see Patent Document 12) for providing a working layer of 0.2 to 3.0 g / m ² on both sides, 2.0 to 8.0 g / m of a coating layer containing 50 to 100 parts by weight of kaolin per pigment ² Newspaper technology for a cold offset type high-speed rotary press provided (see Patent Document 13). However, in this newspaper paper for offset printing of this pigment coating type, when providing a coating layer containing a pigment other than titanium dioxide having extremely high whiteness and hiding properties, it is necessary to obtain sufficient whiteness and opacity. It is necessary to increase the amount of coating, and if the basis weight of the base paper decreases, the paper strength of the newsprint paper decreases, and when printing, especially when printing on a high-speed newspaper rotary press, the paper strength is insufficient. Trouble occurs. In order to avoid this, it is difficult to reduce the basis weight of the base paper, and as a result, the pigment-coated type newsprint paper that has been put to practical use has a high basis weight. When a coating layer containing titanium dioxide is provided, the increase in basis weight is small, but there is a problem that titanium dioxide is expensive and the manufacturing cost increases.

Japanese Unexamined Patent Publication No. 06-049792 Japanese Patent Laid-Open No. 11-315487 JP 2000-027085 Japanese Patent No. 2666638 Japanese Patent No. 2960001 Japanese Patent No. 3026933 Japanese Patent No. 2889159 Japanese Patent Laid-Open No. 2001-240765 JP 2002-069896 A Japanese Patent No. 2896377 Japanese Patent No. 2504819 JP 2000-054287 A JP 2003-286686 A

  From the above situation, there is a demand for news paper for offset printing that has high whiteness and opacity, good back-through, and is lightweight, and in particular, high-white news paper that can be printed on an offset rotary press is desired. Yes. Accordingly, an object of the present invention is to provide a newsprint for offset printing that is lightweight and has high whiteness and opacity.

In order to solve the above-mentioned problems, the newsprint for offset printing according to the invention of claim 1 is newsprint for offset printing coated on the surface of the base paper, and is a raw material with respect to the total pulp solid content. Contains 30% by weight or more of thermomechanical pulp, which is Cryptomeria japonica, has a whiteness of 68% or more, a basis weight of 58 g / m ² or more and less than 64 g / m ² , and a whiteness of 78 % Or more and an opacity of 90% or more , and the ash content in the paper is 15% by weight or more .
The newsprint for offset printing of the invention according to claim 2 is newsprint for offset printing coated on the surface of the base paper, and the raw material is Cryptomeria japonica with respect to the total pulp solid content. It contains 20% by weight or more of a certain thermomechanical pulp, its whiteness is 68% or more, and contains 20% by weight or more of thermomechanical pulp whose raw material is hardwood, and its whiteness is 75% or more. The amount is 58 g / m ² or more and less than 64 g / m ² , the whiteness is 78% or more, the opacity is 90% or more , and the ash content in the paper is 15% by weight or more .
The newsprint for offset printing of the invention according to claim 3 is characterized in that it contains at least one of light calcium carbonate or light calcium carbonate-silica composite as a filler.
The newspaper for offset printing of the invention according to claim 4 is characterized in that it is processed by a high-temperature soft nip calender after clear coating.

According to the present invention, there is a remarkable effect that newsprint paper for offset printing having a quality that is lightweight but has high whiteness and excellent opacity can be obtained.
In addition, there is a remarkable effect that newspapers for offset printing having excellent quality with low ink see-through at the time of offset printing and good ink deposition properties can be obtained.
According to the present invention, a high white newsprint for an offset rotary press is obtained.

<Basis weight>
The newsprint for offset printing of the present invention is a lightweight one having a basis weight of 58 g / m ² or more and less than 64 g / m ² . When the basis weight is less than 58 g / m ² , desired whiteness and opacity cannot be obtained, and when the basis weight is 64 g / m ² or more, it is difficult to say that the weight is reduced. The newsprint for offset printing in the present invention needs to have a whiteness of 78% or more and an opacity of 90% or more.
The newspaper for offset printing according to the present invention will be described in detail below.

<Raw material pulp>
The raw material pulp used in the present invention is not particularly limited and can be used conventionally as a raw material pulp for newsprint. For example, chemical pulp (NBKP, LBKP, etc.), conifer mechanical pulp (GP, CGP, RGP) , PGW, etc.), thermomechanical pulp (TMP), waste paper pulp (DIP), or the like can be used. Of these, thermomechanical pulp is preferable. The newsprint of the present invention is required to have excellent printing surface by colorization, visualization, etc. Therefore, high smoothness is also required, but paper made using mechanical pulp as a raw material has low density, and calendar When the treatment is performed, the calendar effect tends to be strongly developed in a low density portion, and gloss unevenness may occur. On the other hand, since thermomechanical pulp has a lower density than other pulps and a high specific scattering coefficient, it can obtain higher opacity than other pulps. In particular, thermomechanical pulp (hereinafter referred to as cedar TMP) whose raw material is cedar wood (Cryptomeria japonica) is preferable. This includes, for example, Chemi-thermomechanical pulp described in JP-A-2004-225201. In addition, the thermomechanical pulp whose raw material is only cedar (Cryptomeria japonica) is more preferable. Moreover, the thermomechanical pulp (henceforth L-TMP) whose raw material is a hardwood is preferable, for example, the thermomechanical pulp of Unexamined-Japanese-Patent No. 2003-49385 is mentioned.

  As described in Japanese Patent Application Laid-Open No. 2004-225201, cedar TMP can adjust the whiteness by changing the addition rate of sodium sulfite as an impregnation agent and the bleaching conditions after defibration. The whiteness of the cedar TMP is preferably 68% or more, and more preferably 72% or more. Moreover, L-TMP can also adjust whiteness by changing bleaching conditions. The whiteness of L-TMP is preferably 75% or more, and more preferably 79% or more.

When other raw material pulp is used together with cedar TMP and L-TMP, it is preferable that the whiteness of the mixed pulp is 78% or more in a mixed pulp state in which all the other raw material pulps are blended with cedar TMP. 79% or more is more preferable, and 80% or more is still more preferable. Moreover, in the mixed pulp state in which all other raw material pulps are blended with cedar TMP and L-TMP, the whiteness of the mixed pulp is preferably 78% or more, more preferably 79% or more, and further 80% or more. preferable.
As for the usage-amount of cedar TMP, it is desirable that it is 30 weight% or more with respect to the total pulp solid content. Moreover, it is desirable to contain 20 weight% or more of cedar TMP and 20 weight% or more of L-TMP with respect to the total pulp solid content.

<Filler>
The filler contained in the newsprint of the present invention is not particularly limited, and those known in the papermaking field can be used. For example, light calcium carbonate, heavy calcium carbonate, light calcium carbonate-silica composite, white carbon, clay Amorphous silica, talc, titanium dioxide or the like can be used alone or in combination. Among these, light calcium carbonate and light calcium carbonate-silica composite are preferable.
The light calcium carbonate is preferably a rosetta type, spindle type, or columnar type. The average particle diameter is preferably 0.1 to ²⁰ μm and the specific surface area is preferably 3 to ²⁰ m ² / g. By being in this range, even if the content is high, paper dust accumulation is small at the time of printing, and it becomes possible to increase the ash content in the paper, so that the show-through during printing can be improved.

The light calcium carbonate-silica composite is described in JP2003-212539A and JP2005-272155A. The crystal form of light calcium carbonate, which is the core of the light calcium carbonate-silica composite, may be either calcite or aragonite, and the shape is needle-like, columnar, spindle-like, spherical, cubic, amorphous, rosetta-type Either of these may be used. Especially among these. When rosetta-type calcite-based light calcium carbonate is used, a light calcium carbonate-silica composite excellent in bulkiness, opacity improving effect and stiffness improving effect is obtained, and is preferably used in the present invention. Note that the rosetta type refers to a shape in which primary particles of spindle-shaped light calcium carbonate are aggregated radially to form secondary particles, and has a feature of higher specific surface area and oil absorption than other light calcium carbonates. Therefore, the ink is also absorbed by the composite during printing, and the show-through can be improved. The average particle size of the absorbent light calcium carbonate-silica composite is preferably 20 μm or less, more preferably 1 to 10 μm. By being in this range, an appropriate balance between surface strength and oil absorption can be maintained.
In the present invention, the whiteness of the light calcium carbonate or light calcium carbonate-silica composite is desirably 95% or more.

In the present invention, if the blending amount of the filler is too small, improvement in whiteness and opacity of the obtained paper is not sufficient, and therefore contains at least one of the light calcium carbonate or light calcium carbonate-silica composite, It is preferable to add so that the ash content in the paper is 15% by weight or more.
Usually, among the ash components brought in by DIP, the proportion of calcium carbonate is often large, but DIP also contains many ash components other than calcium carbonate, the proportion of which is used for newspaper waste paper, magazine waste paper, etc. Since it varies depending on the type of used paper and the collection status, it may cause quality fluctuations. In addition, the ash component contains toner and foreign matter, and may cause paper surface dirt and paper surface defects. In the present invention, ash content derived from DIP is also used as a filler. However, the ash component in DIP is washed out to some extent in the washing step, and calcium carbonate and light calcium carbonate-silica composite are newly added as fresh filler. Add so that the ash content in the paper is in the above range. Moreover, since there is a problem that paper strength is reduced even if the amount of filler added is too large, it may be blended according to the desired quality, but about 20% by weight or less is appropriate.
The blending ratio of the light calcium carbonate and the light calcium carbonate-silica composite is not particularly limited, but is about 2/1 to 4/1 in consideration of the balance between the whiteness and the opacity of the paper. In particular, it is desirable to add the light calcium carbonate-silica composite in an amount of 5% by weight or less, and adjust the light calcium carbonate addition amount so as to achieve the target ash content in paper.

<Internal medicine>
Furthermore, as necessary, as internal additives, inorganic coagulants (bands, etc.), organic coagulants, dry paper strength agents (polyacrylamide, cationized starch, etc.), wet strength agents (polyamideamine epichlorohydrin, etc.) ), An internal sizing agent (rosin emulsion, alkyl ketene dimer, alkenyl succinic anhydride, etc.), a yield improver, an antifoaming agent, a slime control agent, a bulking agent and the like can be appropriately added.

<Papermaking>
The newsprint for offset printing of the present invention is preferably made by a neutral papermaking method. Compared to acidic paper produced by the acidic papermaking method, neutral paper has excellent storability and can increase DIP. Collected waste paper is usually treated under alkaline chemicals to produce DIP. Under acidic papermaking conditions, the calcium ions of calcium carbonate contained in DIP react with the sulfate band to produce gypsum (calcium sulfate). It is difficult to use a large amount of DIP in acidic papermaking. Further, according to the neutral papermaking, it is possible to save resources by effectively using calcium carbonate derived from waste paper pulp.

<Paper machine>
The paper machine is not particularly limited, and those known in the papermaking field can be used. Gap formers, hybrid formers, and on-top formers having a double-side dewatering mechanism are desirable, but are not limited thereto. .

<Clear coating>
The offset newsprint of the present invention is a base paper that has been paper-made as described above, and is clear-coated by off-machine or on-machine. The clear coating refers to coating a coating liquid not containing a pigment with respect to a pigment (pigment) coating using a coating liquid containing a pigment. Clear coating can cover the surface of the base paper with a smaller coating amount than pigment coating, and makes the newsprint paper excellent in offset printability while keeping the density and thickness of the resulting newsprint paper small. be able to.

<Surface treatment agent>
As the main component of the coating liquid for clear coating, a surface treatment agent such as a water-soluble polymer substance that increases surface strength, a surface sizing agent that imparts water absorption resistance, and the like may be mixed. .
(Water-soluble polymer substance)
Examples of water-soluble polymer substances include starch, enzyme-modified starch, thermochemically-modified starch, oxidized starch, esterified starch, etherified starch (for example, hydroxyethylated starch), starch such as cationized starch, polyvinyl Polyvinyl alcohols such as alcohol, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, and terminal alkyl-modified polyvinyl alcohol, polyacrylamide, cationic polyacrylamide, anionic Polyacrylamides such as polyacrylamide and amphoteric polyacrylamide, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and methylcellulose; Ren butadiene copolymers, polyvinyl acetate, vinyl chloride - vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid esters. These may be used alone or in combination of two or more.

(Surface sizing agent)
As the surface sizing agent, styrene-maleic acid copolymer resin, styrene-acrylic acid copolymer resin, α-olefin-maleic acid copolymer resin, acrylate ester-acrylic acid copolymer resin, Cationic sizing agents, alkyl ketene dimer sizing agents and the like can be mentioned, but are not limited thereto. In the case of neutral papermaking, a cationic surface sizing agent is preferably used. Such a cationic surface sizing agent is not particularly limited, but for example, WO2005 / 003457, JP2005-105488, JP2005-248338, JP2006-16712, JP2006. -16713, JP-A-2006-97179, JP-A-2006-152510, JP-A-2006-161259, JP-A-2006-322093, and the like. In addition, the cationic surface sizing agents described in Japanese Patent Application Nos. 2005-223106, 2005-312381, 2006-17607, and the like, which are filed by the applicant of the present application, may be mentioned. Among these, cationic styrene surface sizing agents described in WO2005 / 003457, JP2005-016712, JP2005-016713, 2006-097179 and the like are particularly preferable.
(Other)
Various auxiliary agents such as a dispersant, a plasticizer, a pH adjuster, a defoaming agent, a water retention agent, an antiseptic, an adhesive, a coloring dye, and an ultraviolet ray inhibitor may be appropriately blended in the coating liquid as necessary. Good.

<Coating method>
The solid content concentration of the clear coating solution is appropriately adjusted depending on the composition, coating method, and the like, but is usually about 5 to 15% by weight.
Examples of the coating apparatus include, but are not limited to, a blade coater, a gate roll coater, a size press coater, and a rod metering size press. Of these, gate roll coaters and rod metering size presses are preferred.
The coating amount is 0.05 to ² g / m ² in terms of solid content for the water-soluble polymer substance, and about 0.01 to 0.2 g / m ² in terms of solid content for the surface sizing agent.

<Calendar processing>
As the calendar processing method, a high-temperature soft nip calender, a shoe calender, or the like is preferable, but not limited thereto. In particular, it is preferable to use a high-temperature soft nip calender because it is possible to suppress uneven unevenness of the solid printing portion due to the density difference of the paper. The processing temperature is 80 to 200 ° C., and the linear pressure is about 25 to 500 kN / m.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, naturally this invention is not limited to these. In the examples and comparative examples, “parts” and “%” indicate “parts by weight” and “% by weight” unless otherwise specified.

<Evaluation method>
About the newsprint obtained by the Example and the comparative example, after adjusting humidity on 23 degreeC and 50% RH conditions, the following items were evaluated. The results are shown in Table 1.
(A) Basis weight: Measured according to JIS P 8124.
(A) Paper thickness and density: Measured according to JIS P 8118.
(C) Ash content in paper: measured in accordance with JIS P 8251.
(D) Whiteness: Measured according to JIS P 8148.
(E) Opacity: Measured according to JIS P 8138.
(F) Beck smoothness: measured according to JIS P 8119.
(G) Evaluation of ink fillability

Using a Toshiba offset rotary press, four-color printing (black, indigo, red, and yellow) was performed at a printing speed of 700 rpm, and the black solid surface at the time of printing 10,000 copies was visually evaluated.
◎: There is no uneven unevenness ○: There is almost no uneven unevenness △: Uneven unevenness is observed slightly uneven unevenness: Many uneven unevenness is observed

(H) Evaluation of back-through Use a Toshiba offset rotary press to perform 4-color printing (black, indigo, red, yellow) at a printing speed of 700 rpm, and visually observe the solid black surface from the back when printing 10,000 copies. Evaluation based on the criteria.
Using a Toshiba offset rotary press ◎: No problem at all ○: No problem △: Slightly see-through is seen ×: See-through is noticeable

<Production of light calcium carbonate-silica composite>
In the reaction vessel, 10.3 parts by weight of Rosetta-type light calcium carbonate (average particle size 4.3 μm) was dispersed in water, where the SiO ₂ concentration was 18.0 wt / wt% and the Na ₂ O concentration was 6.1 wt / wt%. After adding 57 parts by weight of the sodium silicate solution, water was added to make the total amount 200 parts by weight. This mixed slurry is heated with sufficient stirring with an agitator, and a 10% sulfuric acid solution is added to the slurry at 85 ° C. with a metering pump. It was. Under such conditions that the added sulfuric acid is sufficiently dispersed, sulfuric acid is added at a constant rate so that the temperature is constant, the final pH after addition of sulfuric acid is 8.0, and the total sulfuric acid addition time is 240 minutes. Added. This slurry was separated into coarse particles at 100 mesh nodes, filtered through a belt filter, and redispersed to about 10% to obtain an average particle size and a sample for paper analysis. The sample for oil absorption and BET specific surface area was redispersed in ethanol so that the sample was about 10%, filtered, dried in a dryer at 105 ° C., and made into a powder sample. As a result, the average particle size was 3.4 μm and the oil absorption amount was 159 ml / 100 g. The average particle diameter of the rosetta type light calcium carbonate used for the core is 3.0 μm and the oil absorption is 119 ml / 100 g.

<Manufacture of newsprint>
[Example 1]
As raw material pulp, LKP (freeness CSF = 400 ml, whiteness 86%), newspaper bleach DIP (freeness CSF = 230 ml, whiteness 67%), cedar TMP (freeness CSF = 80 ml, whiteness 72%) ), NKP (freeness CSF = 570 ml, whiteness 82%) mixed with a slurry of 35: 5: 30: 30 light calcium carbonate (average particle size 4.3 μm, whiteness 95) as a filler %) Was added so that the ash content in the target paper would be 16% by weight, and the newsprint base paper was made using a gap former type paper machine at a paper making speed of 1000 m / min and a basis weight of 57 g / m ^2. did. Next, hydroxyethylated starch was applied with an on-machine gate roll coater so that the coating amount was 0.5 g / m ^{2 on} both the felt surface and the wire surface. Newspaper paper was obtained by performing the treatment so as to obtain 0.73 g / cm ³ .

[Example 2]
Newspaper was obtained in the same manner as in Example 1 except that paper was made so that the basis weight was 59 g / m ² .
[Example 3]
Newspaper was obtained in the same manner as in Example 1 except that paper was made so that the basis weight was 61 g / m ² .

[Comparative Example 1]
Newspaper was obtained in the same manner as in Example 1 except that paper was made so that the basis weight was 55 g / m ² .
[Comparative Example 2]
Example except that cedar TMP (freeness CSF = 80 ml, whiteness 72%) was used instead of bleached TMP (freeness CSF = 80 ml, whiteness 72%) made of radiata pine wood chips. Newspaper was obtained in the same manner as in 1.

[Comparative Example 3]
As raw material pulp, LKP (freeness CSF = 400 ml, whiteness 86%), newspaper bleach DIP (freeness CSF = 230 ml, whiteness 67%), cedar TMP (freeness CSF = 80 ml, whiteness 72%) ), Bleached TMP (freeness CSF = 80 ml, whiteness 72%), NKP (freeness CSF = 570 ml, whiteness 82%) 35: 5: 10: 20: 30 A newsprint was obtained in the same manner as in Example 1 except that mixing was performed at a blending ratio of.

[Comparative Example 4]
As raw material pulp, LKP (freeness CSF = 400 ml, whiteness 86%), newspaper bleach DIP (freeness CSF = 230 ml, whiteness 67%), cedar TMP (freeness CSF = 80 ml, whiteness 72%) ), TMP (freeness CSF = 80 ml, whiteness 72%), NKP (freeness CSF = 570 ml, whiteness 82%) 35: 5: 20: 10: 30 A newsprint was obtained in the same manner as in Example 1 except that mixing was performed at a blending ratio of.
[Comparative Example 5]
Newspaper was obtained in the same manner as in Example 1 except that paper was made so that the basis weight was 64 g / m ² .

[Example 4]
As a filler, 5% by weight of the above calcium carbonate-silica composite is added to the pulp slurry, and light calcium carbonate (average particle size 4.3 μm, whiteness 95%) is added so that the target paper ash content is 16% by weight. Newspaper was obtained in the same manner as Example 1 except for the addition.
[Example 5]
Newspaper was obtained in the same manner as in Example 4 except that paper was made so that the basis weight was 59 g / m ² .

[Example 6]
Newspaper was obtained in the same manner as in Example 4 except that the paper was made so that the basis weight was 61 g / m ² .

[Comparative Example 6]
Newspaper was obtained in the same manner as in Example 4 except that the basis weight was 55 g / m ² . [Example 7]
Example 1 except that the above calcium carbonate-silica composite was added as a filler in place of light calcium carbonate (average particle size 4.3 μm, whiteness 95%) so that the target paper ash content was 16% by weight. The newspaper was obtained in the same way.

[Example 8]
Newspaper was obtained in the same manner as in Example 7 except that paper was made so that the basis weight was 59 g / m ² .
[Example 9]
Newspaper was obtained in the same manner as in Example 7 except that paper was made so that the basis weight was 61 g / m ² .

[Comparative Example 7]
Newspaper was obtained in the same manner as in Example 7 except that paper was made so that the basis weight was 55 g / m ² .

[Example 10]
As raw material pulp, LKP (freeness CSF = 400 ml, whiteness 86%), newspaper bleach DIP (freeness CSF = 230 ml, whiteness 67%), cedar TMP (freeness CSF = 80 ml, whiteness 72%) ), L-TMP (freeness CSF = 150 ml, whiteness 79%) and NKP (freeness CSF = 570 ml, whiteness 82%) using eucalyptus globulous wood chips as 25: 5: 20: Newspaper was obtained in the same manner as in Example 1 except that the mixture was mixed at a mixing ratio of 20:30.

[Example 11]
Newspaper was obtained in the same manner as in Example 10 except that paper was made so that the basis weight was 59 g / m ² .
[Example 12]
Newspaper was obtained in the same manner as in Example 10 except that paper was made so that the basis weight was 61 g / m ² .

[Comparative Example 8]
Newspaper was obtained in the same manner as in Example 10 except that paper was made so that the basis weight was 55 g / m ² .

[Example 13]
As a filler, 5% by weight of the above calcium carbonate-silica composite is added to the pulp slurry, and light calcium carbonate (average particle size 4.3 μm, whiteness 95%) is added so that the target paper ash content is 16% by weight. Newspaper was obtained in the same manner as Example 10 except for the addition.

[Example 14]
Newspaper was obtained in the same manner as in Example 13 except that paper was made so that the basis weight was 59 g / m ² .
[Example 15]
Newspaper was obtained in the same manner as in Example 13 except that paper was made so that the basis weight was 61 g / m ² .

[Comparative Example 9]
Newspaper was obtained in the same manner as in Example 13 except that paper was made so that the basis weight was 55 g / m ² .

[Example 16]
Example 10 except that the calcium carbonate-silica composite was added so that the ash content in the target paper was 16% by weight instead of light calcium carbonate (average particle size 4.3 μm, whiteness 95%) as a filler. The newspaper was obtained in the same way.

[Example 17]
Newspaper was obtained in the same manner as in Example 16 except that paper was made so that the basis weight was 59 g / m ² .
[Example 18]
Newspaper was obtained in the same manner as in Example 16 except that paper was made so that the basis weight was 61 g / m ² .

[Comparative Example 10]
Newspaper was obtained in the same manner as in Example 16 except that paper was made so that the basis weight was 55 g / m ² .

From Table 1, the following can be said.
(A) From the comparison of Examples 1 to 3 and Comparative Example 1, by blending 30% by weight of cedar TMP, the basis weight of newsprint while maintaining the quality of whiteness 78% or more and opacity 90% or more. It can be seen that the weight can be reduced to 58 g / m ² .
(B) missing opacity and back of newsprint and lightweight to a basis weight of 58.2 g / ^{m 2} of Example 1, equivalent to the newsprint of Comparative Example 5 having a basis weight of 64 g / ^{m 2} of cedar TMP-free formulation Thus, a weight reduction of about 6 g / m ² is possible.
(C) From the results of Comparative Examples 2 to 4, when the cedar TMP composition is less than 30% by weight, it is impossible to reduce the weight while maintaining the opacity at 90% or more and maintaining the showthrough. .
(D) In Example 4 in which light calcium carbonate as a filler in Example 1 was partially replaced with a light calcium carbonate-silica composite, and in Example 7 in which the entire amount was replaced, 30 wt. It can be seen that the weight of newspaper paper can be reduced to 58 g / m ² while maintaining the quality with whiteness of 78% or more and opacity of 90% or more.
(E) When blending cedar TMP and broad-leaved tree TMP (eucalyptus bleached TMP), blending cedar TMP at 20% by weight or more and blending broad-leaved tree TMP at 20% by weight or more in the same manner as in Example 1. It can be seen that the basis weight of the newsprint can be reduced to 58 g / m ² while maintaining the quality with whiteness of 78% or more and opacity of 90% or more.
(F) From the comparison between Example 1 and Example 10, the comparison between Example 4 and Example 13, and the comparison between Example 7 and Example 16, the composition of cedar TMP was 20% by weight, and It can be seen that the newsprint containing 20% by weight of L-TMP has improved smoothness and good ink deposition compared to newsprint containing 30% by weight of cedar TMP.
(G) It can be seen that the newspaper papers of Examples 13 and 16 using light calcium carbonate-silica composite and Eucalyptus Globulus L-TMP have a further improved see-through than Example 10.

Claims (4)

Newsprint paper for offset printing with clear coating on the surface of the base paper,
Contains 30% by weight or more of thermomechanical pulp, the raw material of which is Cryptomeria japonica, with a whiteness of 68% or more, and a basis weight of 58 g / m ² or more and 64 g / m with respect to the total pulp solid content. less than ^2, and a whiteness of 78% or more and an opacity of 90% or more, offset printing newsprint, wherein the paper in ash content is 15% solids by weight or more. Newsprint paper for offset printing with clear coating on the surface of the base paper,
20% by weight or more of thermomechanical pulp whose raw material is Cryptomeria japonica, 20% or more of its whiteness, and 20% of thermomechanical pulp whose raw material is hardwood with respect to the total pulp solid content In a paper having a whiteness of 75% or more, a basis weight of 58 g / m ² or more and less than 64 g / m ² , a whiteness of 78% or more and an opacity of 90% or more. Newsprint paper for offset printing, wherein the ash content is 15% by weight or more . The newsprint for offset printing according to claim 1 or 2 , wherein the filler contains at least one of light calcium carbonate or light calcium carbonate-silica composite. 4. Newsprint paper for offset printing according to claim 3 , wherein the newsprint paper is processed by a high-temperature soft nip calender after clear coating.