JP2012132134A - Newsprint paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a newsprint paper that is light and has high brightness and opacity.SOLUTION: The newsprint paper contains at least one selected from purple pigment, blue pigment, purple dye and blue dye. As to the paper hue measured by a method according to JIS P 8150 of the newsprint paper, a bvalue is -10 or more and less than 4 in the measurement with wavelength including that of ultraviolet ray. The newsprint paper has a brightness of 60% or more and an opacity measured by a method according to JIS P 8149 is 88% or more.

Description

  The present invention relates to a newspaper printing paper, and more particularly, to a newspaper printing paper 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 basis weight is often used higher than that of normal newspaper.

  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. Therefore, an object of the present invention is to provide a newspaper printing paper that is lightweight and has high whiteness and opacity.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have made white by including any one or more color materials having purple and blue colors in the components constituting newspaper printing paper. It has been found that newspaper printing paper having a high degree of transparency and high opacity can be obtained, and the present invention has been completed.

Specifically, the present invention relates to a newsprint paper containing at least one selected from a violet pigment, a blue pigment, a violet dye, and a blue dye, and is a method for measuring paper measured by the method of JIS P 8150 for newsprint paper. The b ^* value is −10 or more and less than 4 in the measurement including the ultraviolet ray, the whiteness is 60% or more, and the opacity measured by the method of JIS P 8149 is 88% or more. It relates to newspaper printing paper.

  According to the present invention, there is a remarkable effect that a newspaper printing paper of a quality that is lightweight but has high whiteness and excellent opacity can be obtained. In particular, the newspaper printing paper of the present invention has a strong white appearance, and the whiteness appears more conspicuous than the whiteness measured by the instrument. In addition, there is a remarkable effect that an excellent quality newspaper printing paper having a small amount of back-through at the time of offset printing and having good ink deposition property can be obtained while being lightweight. In particular, according to the present invention, a high white newsprint can be obtained as a newsprint for an offset rotary press.

L ^* a ^* b ^* Hue change after colorant addition in hue system

  The newspaper printing paper of the present invention includes a pigment coating layer mainly composed of a pigment and an adhesive, and a clear coating layer mainly composed of an adhesive (hereinafter sometimes referred to as a size press layer in the present specification). 1 or more layers are provided (hereinafter, the pigment coating layer and the clear coating layer may be collectively referred to as “coating layer” in this specification). Newspaper printing paper consists of a base paper (hereinafter sometimes referred to as “base paper” or “base paper layer” in this specification), or at least one coating layer on one or both sides of the base paper. It has newspaper printing paper.

  The newspaper printing paper obtained by the present invention can be printed by printing methods such as planographic printing such as cold offset printing and heat offset printing, intaglio printing such as gravure printing, and letterpress printing.

Color Material In the present invention, a color material is contained in newspaper printing paper. In the present invention, the color material means a colored pigment or dye other than white. The pigment is a white or colored powder that is insoluble, hardly soluble or dispersed in water, oil, an organic solvent or the like, and includes inorganic and organic powders. In the present invention, either inorganic or organic materials may be used. A dye is an organic dye that absorbs or reflects visible light and has a unique color, and is dyed onto fibers or pigments by an appropriate dyeing method. It can be used as a solvent (water, organic solvents, etc.). It is melted. In the present invention, for the base paper layer, mainly colored dyes are used, and for the clear coating and the pigment coating layer, mainly from the viewpoint of being excellent in light resistance and preventing discoloration and coloring over time of the paper. It is preferable to use colored pigments. However, in the case of clear coating, it is also preferable to use a colored dye.

[Coloring material (pigment)]
The pigment as the color material of the present invention may be one or more of blue or purple, and examples of the blue pigment include EMT-Blue DS-18 manufactured by Toyo Ink Manufacturing Co., Ltd. Examples of purple pigments include SA Violet C12896 made by Gokoku Color Co., Ltd. The pigment may be blue alone, purple alone, or a combination of both, but in order to improve opacity, it is preferable to use a purple pigment. In the present invention, color materials other than blue and purple, such as black, red, and yellow, may be added as necessary.

  As the blue pigment / purple pigment, both inorganic pigments and organic pigments can be used. Specific examples of blue pigments include, for example, ultramarine, azurite, prussian blue, ultramarine, smalto, cobalt blue (cobalt aluminate), cerulean blue (cobalt stannate), cobalt chrome blue, cobalt, aluminum, and silicon. Examples thereof include oxide, cobalt / zinc / silicon oxide, manganese blue, and phthalocyanine. Specific examples of purple pigments include, for example, cobalt violet (cobalt arsenate, cobalt phosphate, cobalt lithium phosphate, hydrous ammonium phosphate, cobalt borate, etc.), purple ultramarine blue, iron oxide purple, manganese violet, mineral Examples thereof include inorganic pigments such as violet, indigoid, quinacridone, oxazine, anthraquinone, carbonium, and xanthene organic pigments.

  In a preferred embodiment of the present invention, by containing a certain amount of blue / purple pigment, the hue is within the range described below, thereby making the surface color of newspaper printing paper pale, enhancing the whiteness of appearance, and opacity. Can be prevented, and the show-through during printing can be prevented.

The blue and purple pigments in the present invention are color materials that change the color of the printing paper when it is contained in the printing paper. When each color material is added, the hue of the paper can be changed in the direction shown in FIG. FIG. 1 shows changes in the hue of paper that does not contain the color material of the present invention and paper that has been incorporated, based on the L ^* a ^* b ^* color system. When the hue is expressed as 0 ° in the (+) direction of the a ^* value, 180 ° in the (−) direction, b ^* (90) in the (+) direction, and 270 ° in the (−) direction, Assuming that the position of the origin is zero, when a blue color material is added, the hue of the paper after the addition changes to the portion of 210 ° or more and less than 280 ° shown in FIG. When it is added, it indicates that the hue of the paper after the addition changes to a portion of 280 ° to less than 335 ° shown in FIG. 1 as “purple”.

[Content of pigment (pigment)]
The content of the violet pigment and / or blue pigment in the present invention is not particularly limited, but the total of these pigments is preferably 0.05 to 3.5 mg per 1 m ^{2 of} newspaper printing paper, preferably 0.1 mg to More preferably, it is 2.0 mg. In general, when the amount is less than 0.05 mg, light absorption by the pigment is small, so that the concealability contributing to opacity is insufficient, which is not preferable. In general, if the amount is more than 3.5 mg, the amount of light absorbed by the pigment is large, which greatly contributes to the improvement in opacity, but the hue is greatly deviated from 0 and it is not preferable to feel white. . The pigment content can be appropriately adjusted within the above range depending on the whiteness of the raw material or raw paper. In the present invention, the numerical range includes its end points.

Further, as described later, in the present invention, the hue can be adjusted by adding a dye to the base paper. In this case, the total amount of the purple and blue pigments contained in the printing paper layer other than the base paper layer is 0. 0.05 to 2.5 mg / m ² is preferable, and 0.05 to 2.0 mg / m ² is more preferable.

[Coloring material (dye)]
In the present invention, blue, purple or red dyes can be used. Examples of the blue dye include Eisen Basic Paper Blue RH Liquid manufactured by Hodogaya Chemical Co., Ltd., and examples of the red dye include those manufactured by Astraphloxin G Liquid Chemilla (both bases). Dyes).

  There are direct dyes, acid dyes, basic dyes, vat dyes, disperse dyes, reactive dyes, and other types of dyes. Basic dyes, direct dyes, and vat dyes are often used for cellulosic fibers. Can be mentioned. The basic dye binds to the object to be dyed by Coulomb force between ions, hydrogen bond, van der Waals force, etc., and the direct dye binds to the object to be dyed by hydrogen bond, van der Waals force, etc. . Of these, basic dyes having a high dyeing power and a vivid color tone are preferred. Examples of basic dyes include azo dyes, diphenyl and triphenylmethane dyes, azine dyes, oxazine dyes, and thiazine dyes. Examples of direct dyes include azo dyes from ditolidine and dianisidine. The vat dyes include those classified into indigo / thioindigo, anthraquinone, and phthalocyanine.

Blue and purple dyes have the same effect as blue and purple pigments, making the color of newspaper printing paper a specific range, enhancing the apparent whiteness of the surface color of newspaper printing paper, and improving opacity and printing. Prevents time breakthrough. On the other hand, the red dye has an effect of lowering the b ^* value, although slightly. In addition, since the a ^* value shifts in the minus direction only with the blue dye, that is, the hue may shift to green, the red dye can easily suppress this and make the a ^* value in the range of −1 or more and 7 or less. To do.

  In the present invention, blue, purple, or red dyes may be used alone or in combination. However, from the viewpoint of increasing opacity, it is preferable to use a blue dye. The base paper layer may contain a color material other than blue and red, such as black and yellow, as necessary.

[Contents of coloring materials (pigments and dyes)]
The total amount of the color material is determined by adding the amounts of the blue pigment and the purple pigment, and the blue dye and the purple dye contained in each layer. For example, when newspaper printing paper consists of a base paper layer and a size press layer, it is calculated by the following formula.

[Layer containing color material]
The color material of the present invention may be contained in any layer of newspaper printing paper. In a preferred embodiment, the newspaper printing paper can be produced relatively easily by allowing the pigment of the present invention to be present in any one of the layers constituting the newspaper printing paper.

  The violet pigment, blue pigment, violet dye, and blue dye, which are the color materials of the present invention, may be contained in the base paper, in the size press solution, or in a newspaper provided with a pigment coating layer. If it is printing paper, it may be contained in the pigment coating layer. Moreover, when there are two or more base paper layers and / or coating layers, they may be contained in any layer or in all layers. From the viewpoint of easy production, it is preferable to contain it in the base paper layer. When the same layer (for example, a coating layer provided on both sides) is present on both sides of the base paper, the presence of a color material in one layer means that the coating layer on both sides contains a color material, or both sides Among the coating layers, one coating layer includes a color material.

  In general, newspaper printing paper is coated with an aqueous solution (size press solution) of a water-soluble polymer binder such as starch, polyacrylamide, or polyvinyl alcohol on a base paper as necessary to provide a clear (transparent) coating layer. . Therefore, the newsprint paper of the present invention may be provided with either or both of a clear coating layer and a pigment coating layer on one side or both sides of the base paper.

  Therefore, in one embodiment, the newspaper printing paper of the present invention is a coated paper having a base paper layer and a pigment coating layer, and the color material is present in both or one of the base paper layer and the pigment coating layer. In another aspect, the newspaper printing paper of the present invention is a newspaper printing paper having a base paper layer, a clear coating layer, and a pigment coating layer, and the coloring material is a base paper layer, a clear coating layer, and a pigment coating layer. It exists in one layer or a plurality of layers selected from. In yet another aspect, the newspaper printing paper of the present invention is a newspaper printing paper having a base paper layer and a clear coating layer, and the color material is present in both or one of the base paper layer and the clear coating layer.

  Opacity and whiteness are affected by light reflection within the paper surface or within the paper layer and absorption within the paper layer. The opacity defined in JIS P 8149 is the value expressed by the ratio of the single sheet luminous reflectance R0 to the intrinsic luminous reflectance R∞ in the same sample, and is the Z-axis direction (thickness direction) of the coated paper Even if violet and blue pigments are present in this area, they are hardly affected. On the other hand, the whiteness defined in JIS P 8148 is the reflectance (inherent reflectance) of a sample in which a sufficient number of samples are stacked so that there is no change in the measured reflectance, and is affected by the pigment contained in the outermost layer. Receive. Therefore, when the purple / blue pigment is present in a plurality of layers, the effect of the present invention can be obtained efficiently by increasing the ratio of the pigment present in the outermost coating layer. However, if the coating layer, which is the outermost layer, contains a large amount of violet / blue pigment, the bluish white becomes stronger and the apparent white may be lowered.

  Also, when the proportion of deinked pulp contained in the base paper is high, it contains a lot of mechanical pulp derived from deinked pulp, so the opacity of newspaper printing paper is high, but it will turn yellowish as it is. End up. Therefore, in the present invention, the base paper layer may contain a violet / blue pigment and / or a colored dye such as a blue dye, a violet dye, or a red dye. By doing so, excessive blueness can be suppressed, yellowing color caused by containing a lot of mechanical pulp can be efficiently suppressed, and high opacity and high whiteness can be achieved. preferable.

Production of Newspaper Printing Paper The newspaper printing paper of the present invention can be produced by a known method. For example, the newspaper printing paper of the present invention can produce the base paper by making the papermaking raw material described below in the wire part, then subjecting it to the press part and the pre-dryer part, and will be described later in the coater part. After coating the coating liquid on the base paper, it can be used for after-dryer part, calendar part, reel part, winder part and the like. In addition, the papermaking raw material is made in the wire part, then used in the press part and the pre-dryer part to produce the base paper, and a pigment coating layer is provided on the base paper, or the water-soluble polymer (binder) is clear coated Can be manufactured.

[Base paper]
The newspaper printing paper of the present invention has at least a base paper layer. The base paper used in the present invention may be single-layer paper or multilayer paper. When the base paper of the present invention has a multilayer structure, a color material may be contained in any one or more of a plurality of layers constituting the base paper. In order for the coloring material to be present in the base paper layer, the base paper may be made from a papermaking raw material containing a violet pigment and / or a blue pigment or a colored dye such as a blue dye, a violet dye, or a red dye. The method for producing the base paper of the present invention is not particularly limited, and can be performed by a known method using known raw materials.

  In the present invention, the base paper or the size press layer may contain a blue dye, a purple dye, or a red dye. In order for these dyes to be present in the base paper layer, the base paper may be made from a papermaking raw material containing these dyes. As described above, since the dye is dyed on fibers, pigments, and the like, the base paper is easily dyed. Moreover, although a dye may cause discoloration with time, such discoloration can be suppressed by including the dye in the innermost base paper layer. Furthermore, when many deinked pulps are used in the present invention, even if discoloration occurs due to a dye, the apparent whiteness does not decrease so much. The base paper layer may contain either the dye or the violet / blue pigment, or may contain both the dye and the violet / blue pigment.

  Therefore, in one embodiment, the newsprint paper of the present invention is a newsprint paper in which the base paper layer contains the dye and the other layer contains a violet / blue pigment or a violet / blue dye. In another embodiment, the newsprint paper of the present invention is a newsprint paper in which the base paper layer contains the dye and the purple / blue pigment, and the other layer contains the purple / blue pigment or the purple / blue dye.

  The content of the dye or the amount of the color material in the newspaper printing paper is obtained in the same manner as the purple / blue pigment.

In the present invention, the hue of the base paper is measured with the dye and / or the violet / blue pigment, and the b ^* value is −10 or more and less than 4, more preferably −6.0 or more in the measurement including ultraviolet rays according to the method of JIS P 8150. When adjusted to less than −0.5, the effects of the present invention are more easily achieved. Therefore, newsprint paper including a base paper whose hue is adjusted to the above range and a coating layer provided on the base paper is excellent even if the amount of purple / blue pigment used in the newsprint paper is reduced. It has whiteness and opacity.

  On the other hand, when a base paper having a hue outside the above range is used, it is necessary to increase the amount of purple / blue pigment contained in the coating layer or the like in order to obtain a desired whiteness. For this reason, the pigment in the coating liquid tends to remain in the pipe when changing the brand, and the operation loss tends to increase. However, this can be avoided by using a base paper having a hue within the above range. Furthermore, when using a base paper whose hue is outside the above range and adjusting the hue to a desired whiteness mainly by a layer other than the base paper layer, when the blueness of newspaper printing paper becomes too strong, the apparent whiteness There is a possibility that reduction and whiteness may be reduced, and adjustment tends to be relatively difficult. However, using a base paper having a hue in the above range makes it easy to avoid such a situation.

Even if the base paper has a hue within the above range, a base paper having a relatively low b ^* value can be used to obtain a desired hue even if the amount of purple / blue pigment contained in the coating layer is small. Therefore, the above operation loss is less likely to occur.

The a ^* value of the base paper layer is not particularly limited because it does not greatly contribute to the whiteness and opacity of the printing paper, but is usually preferably −3 to less than 7, more preferably −3 to less than 5, More preferably less than 3. If it is out of the range, the color of the newspaper printing paper may not appear white, which is not preferable.

  The addition amount of the dye in the base paper is not particularly limited. For example, the basic dye is 0.0005 to 0.01% by weight and the direct dye is 0.001 to 0.05 based on the absolute dry weight of the whole pulp. % By weight.

[Basis weight]
The newspaper printing paper of the present invention is a lightweight one having a basis weight of less than 55 g / m ² , preferably a basis weight of 30 g / m ² or more and less than 53 g / m ² . If the basis weight is less than 30 g / m ² , desired whiteness and opacity cannot be obtained, and if it is 55 g / m ² or more, it is difficult to say that the weight is reduced. In the newsprint paper of the present invention, the whiteness can be 60% or more and the opacity can be 88% or more.

[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.

[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. In addition, recycled fillers made from papermaking sludge, deinking floss, etc. can also be used. Among these, light calcium carbonate is preferable because it is inexpensive and excellent in optical properties.

  In particular, in the present invention, since the opacity and whiteness of paper can be improved at a relatively low cost, it is preferable to blend calcium carbonate as an internal filler. From the viewpoint of increasing opacity and whiteness, the paper of the present invention preferably has a calcium carbonate content of 5% by weight or more, more preferably 6% by weight or more when no pigment coating layer is provided. More preferably, it is 7% by weight or more. When the pigment coating layer is provided, the calcium carbonate content of the base paper is preferably 5% by weight or more, more preferably 6% by weight or more, and further preferably 7% by weight or more.

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.

  In the present invention, if the blending amount of the filler is too small, the whiteness and opacity of the resulting paper are not sufficiently improved, so the light calcium carbonate is contained and the ash content in the paper is 15% by weight or more. It is preferable to add such that.

  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, ash components in DIP are washed out to some extent in a washing process, and calcium carbonate, light calcium carbonate-silica composite, etc. are newly used as a fresh filler. Is added so that the ash content in the paper falls within 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.

[Internal additives]
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 newspaper printing paper of the present invention is preferably made by a neutral paper making 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 newspaper printing paper of the present invention can be clear coated on the base paper made as described above by off-machine or on-machine. The clear coating refers to applying a coating liquid not containing a pigment to a pigment (pigment) coating using a coating liquid containing a pigment. Clear coating can cover the base paper surface 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.

  As a 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. .

  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.

  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.

  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.

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.

[Pigment coating]
The newspaper printing paper of the present invention can also be provided with a pigment coating layer by pigment coating. The pigment coating layer in the newspaper printing paper of the present invention may be a single layer or multiple layers. When the pigment coating layer of the present invention has a multilayer structure, a purple pigment and / or a blue pigment may be contained in any one or more of a plurality of layers constituting the pigment coating layer. In order for the purple pigment and / or blue pigment to be present in the pigment coating layer, the pigment coating may be performed using a paint containing a purple pigment and / or a blue pigment. In the present invention, the coating method is not particularly limited, and can be performed by a known method using known raw materials. Of course, in the present invention, such pigment coating need not be applied. When pigment coating is applied, the ash content of the paper is higher due to the inorganic substance contained in the pigment coating layer, and therefore, in an embodiment of the present invention, about 10 wt% to 50 wt% is preferable, and 20 wt% to 45 wt%. % Is more preferable.

  The newspaper printing paper of the present invention can be provided with a coating layer on the base paper obtained as described above by coating and drying a coating liquid mainly composed of a pigment and an adhesive. The coating may be on one side or both sides of the base paper, but double-sided coating is preferred because it does not curl and the physical properties of the front and back sides do not differ.

  In the case of pigment coating, the pigments other than the purple and blue pigments used in the coating layer of the present invention include kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate. Inorganic pigments such as talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, and satin white; organic pigments such as plastic pigments can be appropriately selected and used. In the present invention, these pigments are sometimes referred to as “white pigments” in order to distinguish them from purple and blue pigments.

  The adhesive (binder) used in the present invention is not particularly limited. For example, preferable adhesives include styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, and vinyl acetate / butyl. Synthetic adhesives such as acrylate-based copolymers and polyvinyl alcohol, maleic anhydride copolymers, acrylic acid / methyl methacrylate copolymers; proteins such as casein, soy protein, synthetic proteins; oxidized starch, positive One or more ordinary adhesives for coated paper such as starch, urea phosphated starch, etherified starch such as hydroxyethyl etherified starch, starch such as dextrin; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose Select as appropriate It can be used.

  As the adhesive, synthetic adhesives such as styrene / butadiene latex and polyvinyl alcohol; starches, cellulose derivatives and the like can be conveniently selected and used. The ratio of the pigment and the adhesive can be used within a public range.

  In the coating liquid used in the present invention, various auxiliary agents such as a dispersant, a thickener, a water retention agent, an antifoaming agent, and a water resistance agent can be appropriately used as needed in addition to the pigment and the adhesive.

[Adjustment of coating solution]
In the present invention, the method for preparing the coating liquid is not particularly limited and can be appropriately adjusted depending on the type of coater. When a blade type coater is used, the solid content concentration of the coating liquid is preferably 40 to 70% by weight, more preferably 60 to 70% by weight. The viscosity of the coating liquid is preferably in the range of 500 to 2000 mPa · s as measured by the B-type viscosity measured at 60 rpm.

[Coating method / coating machine]
In the present invention, any commonly used coater may be used. An on-machine coater or an off-machine coater may be used, and if it is an on-machine coater, a coater such as a roll coater such as a size press coater or a gate roll coater, a blade coater, or a blade metering size press coater can be used. The coating speed is not particularly limited, but it is preferably 500 to 1800 m / min for a blade coater and 500 to 3000 m / min for a size press coater in the current technology.

The coating amount of the coating liquid in the present invention is preferably ² to 15 g / m ² , more preferably 5 to 12 g / m ² , and even more preferably 5 to 10 g / m ² in terms of solid content on one side. In the present invention, the effect of improving the opacity can be exhibited even if the coating amount is small.

  In the present invention, the method for drying the wet coating layer is not limited, and various methods such as a steam superheated cylinder, a heated hot air air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer may be used alone or in combination. it can.

In the present invention, the paper surface can be calendered, but the type and processing conditions of the calender device are not particularly limited, and a regular calender made of a metal roll, a soft nip calender, a high-temperature soft nip calender, etc. Devices may be selected as appropriate, and conditions may be set within the controllable range of these devices according to the quality target value.
Newspaper printing paper [ash]
The ash content of the newspaper printing paper of the present invention is preferably 8% by weight or more. In particular, the ash content is preferably 10% by weight or more, more preferably 12% by weight or more, and further preferably 15% by weight or more. There is no particular upper limit on the ash content, but it is preferably 40% by weight or less in consideration of the strength and operability of the paper.

  In general, the ash content indicates the amount of inorganic substances contained in the paper, and thus basically reflects the amount of filler contained in the paper. The ash content of paper is composed of those derived from fresh fillers added to the stock and those brought in by pulp raw materials such as DIP (waste paper pulp, deinked pulp). The amount of ash brought in by DIP is relatively high in calcium carbonate, but inorganic components other than calcium carbonate are also included. The ratio of calcium carbonate to other inorganic components depends on the type and collection of used paper such as used newspaper and magazine used paper. It depends on the situation. In the present invention, the ash content is measured by a method in which the combustion temperature is set to 525 ± 25 ° C. in accordance with the ash test method for paper and paperboard specified in JIS P 8251.

  If the ash content of the newspaper printing paper is less than 5% by weight, the opacity may not be sufficiently improved.

[Hue]
The hue of the printing paper of the present invention has a b ^* value of −10 or more and less than 4 in the measurement including ultraviolet rays specified in JIS P 8150, but it is more preferable that the b ^* value is −6 or more and less than −1. . By making the b * value relatively low in this way, it is possible to enhance the whiteness of the appearance of newspaper printing paper, improve the opacity, and prevent show-through during printing. Further, the a ^* value in the same measurement is not particularly limited because it does not greatly contribute to the whiteness and opacity of the printing paper, but is usually preferably −3 to less than 7, more preferably −3 to less than 5. -1 or more and less than 3 is more preferable. If it is out of the range, the color of the printing paper may not appear white, which is not preferable.

[Opacity]
The opacity of the newspaper printing paper of the present invention is preferably 88% or more, more preferably 90% or more.

[Whiteness]
The whiteness of the newsprint paper of the present invention is preferably 60% or more, and more preferably 65% or more.

[density]
Density of newsprint paper of the invention is preferably ^{0.5~0.80g / cm 3, 0.60~0.70g / cm} 3 is more preferable.

  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) Evaluation of back-through Using a Toshiba web offset press, four-color printing (black, indigo, red, 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 observed from the back side. Evaluation was made according to the following criteria.

Using a Toshiba offset rotary press ◎: No problem at all ○: No problem △: Slightly see-through is seen ×: See-through is noticeable

<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%), NKP (freeness CSF = 570 ml, whiteness 82%) ) To the pulp slurry mixed at a mixing ratio of 45:45:10, light calcium carbonate (average particle size 4.3 μm, whiteness 95%) as a filler is added so that the target paper ash content is 19% by weight. Eisen Basic Violet 64 (Hodogaya Chemical Co., Ltd.), which is a blue dye, is added as a coloring material, and Astrafloxin G Liquid (manufactured by Chemilla) is added as a red dye. Then, a newsprint base paper was made so as to have a basis weight of 52 g / m ² . 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. Processing was carried out to obtain 0.69 g / cm ³ to obtain newspaper printing paper.

[Example 2]
In addition to adding 0.03 part of a purple pigment (SA Violet C12896, Gokoku Color Co., Ltd.) to the hydroxyethylated starch and 100 parts of the hydroxyethylated starch by an on-machine gate roll coater. Produced newspaper printing paper in the same manner as in Example 1.

[Comparative Example 1]
As raw material pulp, newspaper bleached DIP (freeness CSF = 230 ml, whiteness 67%), TMP (freeness CSF = 80 ml, whiteness 72%), NKP (freeness CSF = 570 ml, whiteness 82%) Is added to the pulp slurry mixed at a blending ratio of 25/45/30 with light calcium carbonate (average particle size 4.3 μm, whiteness 95%) as a filler so that the ash content in the target paper is 11% by weight, Eisen Basic Violet 64 (Hodogaya Chemical Co., Ltd.), which is a blue dye, is added as a coloring material, and Astrafloxin G Liquid (manufactured by Chemilla) is added as a red dye. A newsprint base paper was made so that the basis weight was 52 g / m ² . 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. Processing was carried out to obtain 0.65 g / cm ³ to obtain newspaper printing paper.

  As is apparent from the table, the newspaper printing paper of the present invention containing at least one of a blue pigment, a violet pigment, a blue dye, and a violet dye has both high whiteness and high opacity, and is particularly offset during printing. It is an excellent newsprint paper that does not stand out when printed and has a wide color reproduction range. On the other hand, the comparative example in which the hue does not satisfy the scope of the present invention was inferior to the embodiment of the present invention in terms of apparent whiteness, strike-through during printing, and the like.

Claims (6)

A newspaper printing paper containing at least one selected from a purple pigment, a blue pigment, a purple dye, and a blue dye, wherein the hue of the paper measured by the method of JIS P 8150 of the newspaper printing paper includes ultraviolet rays The newspaper printing paper has a b ^* value of −10 or more and less than 4, whiteness of 60% or more, and opacity measured by the method of JIS P 8149 of 88% or more. The newspaper printing paper of Claim 1 whose basic weight of the said newspaper printing paper is 55 g / m < ² > or less.   The newspaper printing paper according to any one of claims 1 to 2, comprising light calcium carbonate as a filler.   The newspaper printing paper according to any one of claims 1 to 3, wherein the ash content in the paper is 15% by weight or more.   The newspaper printing paper according to any one of claims 1 to 4, wherein the newspaper printing paper is treated with a high-temperature soft nip calender after clear coating. The newspaper printing paper according to any one of claims 1 to 5, wherein the newspaper printing paper is treated with a high-temperature soft nip calender after pigment coating.

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