JP5008541B2 - Printing paper - Google Patents

Description

  The present invention relates to printing paper. More specifically, it is bulky and excellent in printability despite the heavy use of used paper (50% or more in the present invention), hardly generates paper dust, and can be suitably used for, for example, offset printing and rotary printing. Related to printing paper.

  In recent years, research has been conducted on the reduction in the weight of printing paper and the improvement in bulkiness for the purpose of reducing the number of pages with respect to the thickness by increasing the bulkiness of the printed matter and creating an apparent volume.

  Also, in terms of printing technology, for example, offset printing, color printing, high-speed mass printing, and automation have made great progress. With this, workability and printability of printing paper have also been improved. Improvement is required from the aspect.

  For example, various types of printing paper are used according to the type of printed matter such as advertisements, direct mail, various magazines, catalogs, manuals, and books. Among them, comic paper is mainly composed of mechanical pulp and deinked pulp. In printing on paper as well, demands for higher printing speed, color paper, automation, etc., as described above, have increased, and in conjunction with the introduction of computer systems for printing paper, the shift from letterpress printing to offset printing has rapidly progressed. Yes.

  Due to the widespread use of offset printing, for example, (1) high bulkiness, (2) high print reproducibility, and (3) no generation of paper dust are required for printing paper. Is done. Among these, the demand for excellent bulkiness and printability is particularly high.

  As measures for improving the bulkiness of printing paper, the use of bulking agents and the high blending of mechanical pulp that is rigid and easily creates voids between fibers are being studied. However, since the bulking agent is expensive and has the property of inhibiting or separating the bonds between the fibers, it has a problem of reducing not only the surface strength but also the paper quality strength in the Z-axis (thickness) direction. Moreover, although high blending of mechanical pulp makes it possible to obtain bulkiness at low cost, mechanical pulp has inherently low whiteness and a large amount of fluorescent whitening agent must be used. However, the frequent use of the fluorescent brightening agent significantly deteriorates the fading property of the printing paper over time and causes a decrease in whiteness. Furthermore, the heavy use of mechanical pulp is not only due to the above-mentioned whiteness problem, but also the paper surface flatness is impaired, causing paper dust generation during offset printing, and due to a decrease in wet paper strength due to dampening water in rotary printing. Various problems also arise in printability, such as paper breaks.

  Therefore, various techniques have been developed to provide a printing paper that is improved in bulkiness and has excellent printability without generation of paper dust or breakage.

For example, Patent Document 1 discloses a printing paper containing hardwood mechanical pulp having a density of 0.45 g / cm ³ or less of handmade paper produced using 100 ml of pulp with Canadian Standard Freeness (hereinafter referred to as CSF). (See paragraph number 0017). Such hardwood mechanical pulp is obtained by impregnating hardwood wood chips with an alkaline hydrogen peroxide aqueous solution and then subjecting to normal pressure or pressure refining treatment, and has a large Runkel ratio of 4.0 or more and is a rigid hardwood machine By including 5 to 96% by weight of pulp in the base paper, an attempt is made to obtain a printing paper that maintains optical properties such as opacity and whiteness, and is bulky and excellent in printability.

  However, since the printing paper disclosed in Patent Document 1 uses hardwood mechanical pulp, as described above, the raw pulp has a very low CSF of 100 ml. Printing paper made from such raw pulp not only breaks the paper and generates paper dust during bookbinding, but also has poor surface properties and paper dust due to its rigid hardwood mechanical pulp. Inferior, it is difficult to perform high-definition printing.

  Patent Document 2 discloses a coated printing paper containing mechanical pulp having an opacity of 89% or more, a whiteness of 65% or more, a surface roughness of less than 4.5 μm, and 90% by weight or more of the total fiber amount. Has been. In such coated printing paper, the mechanical pulp of 90% by weight or more of the total fiber amount is used to give opacity and rigidity, and within a relatively bulky range, it is adjusted to the desired volume by calendering, and is suitable for printing. In addition, the production cost is reduced by reducing the amount of chemical pulp used.

  However, since the coated printing paper disclosed in Patent Document 2 is coated paper, the manufacturing cost is not only higher than that of non-coated paper, but also has a higher density due to coating.

Further, in Patent Document 3, a starch-based paper strength agent is applied to a base paper using at least hardwood mechanical pulp and bulking agent produced by chemical treatment, and the density is 0.35 to 0.50 g / cm. ^Three bulky medium printing papers are disclosed. In such a bulky medium-sized printing paper, hardwood mechanical pulp having a single fiber density index of 0.20 or more is used in an amount of 10 to 60% by weight of the total pulp, and the amount of bulking agent added is 0.1 to 1.2%. By setting the coating amount of the surface paper strength agent to 0.3 to 3.0 g / m ² , the whiteness is improved, the density is reduced, and the flexibility (low rigidity) is improved. It is intended to improve the printability and suppress the occurrence of bleeding.

However, the bulky medium-sized printing paper disclosed in Patent Document 3 contains a bulking agent, but, similarly to the printing paper disclosed in Patent Document 1, it also uses hardwood mechanical pulp, so the CSF of the raw pulp Is extremely low at 100ml and not only breaks the paper and generates paper dust during bookbinding, but also has a hard surface and paper powder, particularly poor flatness and poor printability due to its rigid hardwood mechanical pulp. It is difficult to do.
JP 2003-49386 A JP 2004-525284 A JP 2005-163253 A

  The present invention has been made in view of the background art described above, and an object of the present invention is to provide a printing paper which is excellent in printability and hardly generates paper dust despite being bulky.

  As a result of intensive investigations on printing paper that ensures bulkiness and is excellent in printability and generates almost no paper dust, the present inventors have used recovered paper pulp that has been collected and recycled many times as a main raw material. A used printing paper according to JIS P 8220 (1998), which has a disaggregation pulp freeness of 450 cc or more according to JIS P 8121 (1995) after disaggregation of the printing paper, and the raw material after disaggregation The pulp fiber roughness of the pulp is 10 to 25 mg / 100 m, and the ratio of the mechanical pulp by the dyeing method based on JIS P 8120 (1998) of the raw pulp after the disaggregation is 60% by mass or more. It has been found that the above problems can be achieved.

Therefore, as the present invention described in claim 1, the disaggregation pulp freeness according to JIS P 8121 (1995) after disaggregation of the printing paper according to JIS P 8220 (1998) is 450 cc or more, and the disaggregation The pulp fiber roughness of the subsequent raw pulp is 10 to 25 mg / 100 m, and the proportion of the mechanical pulp by the dyeing method according to JIS P 8120 (1998) of the raw pulp after the disaggregation is 60% by mass or more. Thus, the basis weight of the printing paper according to JIS P 8124 (1998) is 40 to 100 g / m ² , and the density of the printing paper according to JIS P 8118 (1998) is 0.20 to 0.30 g / cm. Printing paper is provided, characterized in that it is ³ .

As a second aspect of the present invention, there is provided the printing paper according to the first aspect, wherein the run-up ratio of the disaggregated pulp is 2.0 to 3.0.

  Although the printing paper of the present invention is bulky, it has excellent printability and hardly generates paper dust, and can be suitably used for, for example, offset printing and rotary printing.

Hereinafter, the present invention will be described in more detail.
As a raw material of the used paper pulp in the present invention, as shown in the used paper standard quality specification table of the used paper recycling promotion center, white, ruled white, cream white, card, white, medium white, imitation, fair white, Kent, white art, special upper limit, another upper limit, newspaper, magazine, etc. Specific examples include non-coating computer recording paper that is information-related recording paper, printer recording paper such as thermal paper and pressure sensitive paper, and OA waste paper such as PPC recording paper, art paper, coated paper, fine coated paper, Coated paper such as matte paper, high quality paper, color quality, notebook, notepaper, wrapping paper, fancy paper, medium quality paper, newsprint, reprint paper, supermarket paper, imitation paper, pure white roll paper, milk carton, etc. Chemical pulp paper, high-yield pulp-containing paper, etc. are used as paper such as non-coated paper and used paper, but it is not particularly limited regardless of printing, copying, printing, or non-printing.

When the waste paper pulp is contained in the raw material pulp at 50% or more, particularly 60 to 100%, the idea of the present invention becomes clearer.
The printing paper of the present invention preferably has a basis weight of 40 to 100 g / m ² . In order to obtain print quality with less bleeding, the basis weight is preferably 50 g / m ² or more, and more preferably 60 g / m ² or more. Here, the basis weight is the weight of the paper per square meter, and changes depending on the thickness and density of the paper. In particular, in recent printing paper, although high blending of used paper pulp has been promoted in response to the needs of products that are more resource-saving and environmentally friendly, the volume of the paper is increased due to deterioration of the used paper pulp itself as recycling progresses. A difficult phenomenon has occurred, and in order to obtain a hand feeling equivalent to that in the past, there are cases where the basis weight is increased.

Accordingly, although the basis weight tends to increase against the trend of weight reduction, in the present invention, in a printing paper having a basis weight of 40 to 100 g / m ^{2 that} can be suitably adapted to a known printing machine as a printing paper, Even if used paper is used as a main component, it is possible to provide printing paper that is not inferior to conventional virgin pulp.

According to the present invention, while using waste paper pulp that has been exhausted in repeated recycling, the basis weight of the printing paper is 40 to 100 g / m ² , and the density of the printing paper according to JIS P 8118 (1998) is 0.00. The present invention has found a technology that makes it possible to provide printing paper characterized by being 20 to 0.30 g / cm ³ , and the ratio of waste paper pulp is less than 50% and the basis weight is out of 40 to 100 g / m ² . And the effect which this invention aims at cannot be exhibited regretfully.

The quality of the printing paper should be evaluated in terms of the quality of the “printing paper” produced as a product. Unlike the raw material stage prior to papermaking, fine additives such as fine fibers and fillers, and various papermaking at the papermaking stage. Influenced by chemicals. In the present invention, at the stage of “printing paper” manufactured as a product, printing based on JIS P 8220 (1998) in consideration of raw pulp, various papermaking chemicals and additives so as to obtain a predetermined raw material quality. The present invention has been completed by analyzing and examining the disaggregated raw material pulp after the paper is disaggregated in detail.
That is, in the present invention, the raw pulp after disaggregation is adjusted in advance by beating treatment or classification means so that the pulp freeness according to JIS P 8121 (1995) is 450 cc or more. Particularly preferably, it is obtained by selectively using a pulp having a long fiber content or a high fiber roughness so as to be 450 cc or more by a classification means. The classification conditions are not particularly limited, but it is desirable that the classification conditions be used after being diluted to a pulp concentration of 1.5% or less. It is also possible to classify and further beat. The classification process can be performed using a washing process that is normally performed in paper and pulp mills. After diluting with a large amount of water, it is dehydrated and concentrated using a known SP filter, washer, thickener, extractor, filter press, etc. You can also get it.
Conventional papermaking technology uses papermaking pulp with a pulp drainage of 450 cc or more after disaggregation, and bulky printing paper by devising the papermaking process, such as reducing the press pressure of the paper machine or reducing the machine calender pressure However, if the percentage of waste paper pulp in the raw material pulp is large, the desired bulk cannot be obtained and the surface strength is weakened, and further, dehydration at the wire part during paper making is too early. Therefore, there is a problem that the paper becomes poorly formed.

  In the study by the present inventors, the pulp fiber roughness of the raw pulp is 10 to 25 mg / 100 m as the properties of the raw pulp having a pulp drainage after disaggregation of 450 cc or more.

The basis weight of the printing paper according to JIS P 8124 (1998) is such that the ratio of the mechanical pulp by the dyeing method according to JIS P 8120 (1998) of the raw pulp after the disaggregation is 60% by mass or more. 40-100 g / m ² , JIS P 8121 of raw pulp after disaggregation, characterized in that the density of the printing paper according to JIS P 8118 (1998) is 0.20-0.30 g / cm ^3. Even when the pulp freeness according to 1995) is 450 cc or more, it is possible to obtain a printing paper that is excellent in bulkiness and printability, hardly generates paper dust, and can be suitably used for, for example, offset printing and rotary printing. it can.

  In the printing paper of the present invention, a raw material in which the pulp fiber roughness of the raw pulp after disaggregation is in the range of 10 to 25 mg / 100 m is obtained in order to obtain characteristics that are excellent in bulkiness and printability and hardly generate paper dust. Use.

  Waste paper pulp used as the main raw material in the present invention has a tendency that the fiber wall is worn away and the fiber roughness is reduced by repeated recycling treatment, and the hard paper pulp-derived waste paper raw material frequently used for printing paper is the original. Even if the fiber roughness is as low as less than 10 mg / 100 m, the absolute value of the fiber roughness can be obtained by using waste paper pulp using waste paper such as magazine waste paper containing a lot of long fibers represented by conifers. By means such as improving, including mechanical pulp derived from conifers with high fiber roughness originally, further reducing fiber roughness by promoting fluffing of the fiber wall by beating treatment, classification treatment, etc. The fiber roughness can be adjusted to 10 to 25 mg / 100 m.

  In recent years, it has become possible to produce 100% waste paper pulp from magazine waste paper through progress in efforts to clarify and sort waste paper collection routes. 100% waste paper pulp from magazine waste paper has high fiber roughness and is bulky despite being waste paper. It is possible to use 100% of the used paper pulp in the magazine used paper pulp because it becomes easy to obtain recycled paper pulp. However, if the content of the mechanical pulp contained in the product exceeds 90%, the printability is good. Since the problem of paper dust may occur, it is preferable to adjust the blending so that the ratio of mechanical pulp in the product is 90% or less.

  Although the higher fiber roughness tends to be bulky, if it exceeds 25 mg / 100 m, the formation is deteriorated and the printability is lowered, and if it is less than 10 mg / 100 m, the present invention is a solution. , Bulk is difficult to obtain.

  More preferably, 14-20 mg / 100m is preferable. A bulky product can be easily obtained in synergy with the preferred range of the Runkel ratio of the disaggregated pulp described later, and is particularly suitable.

  As an important element for achieving the present invention, the proportion of the mechanical pulp by the dyeing method according to JIS P 8120 (1998) of the disaggregated pulp after disaggregating the printing paper according to JIS P 8220 (1998) is 60% by mass. It is suitable to contain above. Mechanical pulp is produced by mechanical grinding of wood raw materials, so there are more fiber walls of pulp fibers compared to kraft pulp, and the fiber outer surface is fibrillated variously by mechanical grinding, resulting in fluffy fine fibers. Therefore, it is frequently used as a raw material pulp for obtaining bulkiness. However, mechanical pulp in recycled paper pulp recycled from waste paper loses fine fibers on the fiber surface due to repeated regeneration treatment, and the fiber wall is worn away and thinned. There is little improvement contribution to bulkiness. In the study by the present inventors, at least 60% by mass of mechanical pulp is contained in the disaggregated pulp, and the disaggregated pulp freeness according to JIS P 8121 (1995) after disaggregating the printing paper is 450 cc or more. In addition, it has been found that it is necessary to use a raw material pulp having a pulp fiber roughness of 10 to 25 mg / 100 m after the disaggregation in order to further exert the effects of the present invention. When the ratio of mechanical pulp is less than 60% by mass, when used paper is used as the main raw material, the bulkiness is hardly exhibited, printability and paper dust generation problems appear, and the printing paper that the present invention seeks is obtained. I can't.

The printing paper obtained by the present invention has a very high bulkiness of 0.20 to 0.30 g / cm ³ in accordance with JIS P 8118 (1998).
As described above, the printing paper mainly composed of waste paper obtained by the prior art has a thin fiber wall and almost no fuzz even if it contains mechanical pulp that is highly effective in exhibiting bulkiness. For this reason, the fiber is easily squashed and flattened by a press and flattening process at the paper making stage, so that the bulk does not come out. In accordance with JIS P 8124 (1998) manufactured using waste paper pulp as a main raw material according to the present invention. The basis weight is 40 to 100 g / m ² , and the pulp freeness according to JIS P 8121 (1995) after disaggregating the printing paper according to JIS P 8220 (1998) is 450 cc or more, after the disaggregation The raw material pulp has a pulp fiber roughness of 10 to 25 mg / 100 m, and JIS P 81 of the disaggregated pulp after disaggregating the printing paper according to JIS P 8220 (1998). By using 60% by mass or more of the mechanical pulp by the dyeing method based on 0 (1998), more preferably, the disaggregated pulp having a Runkel ratio of 2.0 to 3.0 is used. A printing paper having a density in accordance with P 8118 (1998) of 0.20 to 0.30 g / cm ³ can be obtained.

The density is highly related to the type of used paper pulp, Runkel ratio, and fiber roughness. The type of used paper pulp, Runkel ratio, and fiber roughness are adjusted as appropriate, and the density is 0.20 to 0. It is important to configure the raw material pulp so as to be .30 g / cm ³ . In particular, when waste paper pulp having deteriorated is used, a density exceeding 0.30 g / cm ³ tends to be exhibited, and when waste paper pulp which has not been recycled is used, bulky low density printing paper having a density of less than 0.20 g / cm ^3. However, the problem of printability and paper dust becomes obvious.

  In this invention, it is preferable to use the raw material pulp whose Runkel ratio of disaggregated pulp is 2.0-3.0.

  Although it is a raw material pulp mainly composed of waste paper, it constitutes a raw material pulp mixed with various pulps, but the quality of the used paper pulp as a starting material is an important factor. The disaggregation pulp freeness according to JIS P 8121 (1995) after disaggregating the printing paper is 450 cc or more, and the pulp fiber roughness of the raw pulp after disaggregation is 10 to 25 mg / 100 m. The ratio of the mechanical pulp by the dyeing | staining method based on JISP8120 (1998) of the subsequent raw material pulp is 60 mass% or more, and also the Runkel ratio of disaggregated pulp is set to the range of 2.0-3.0. By adjusting the raw material pulp, it is possible to obtain a printing paper which is excellent in printability and hardly generates paper dust despite being bulky.

  The Runkel ratio can be adjusted by using raw pulp or waste paper pulp having a known Runkel ratio, or by beating the raw pulp in a sticky manner to make the fiber wall fluffy and making the fiber wall thinner.

  When the fiber wall is fluffed and fluffed, and the fiber wall thickness is lowered to less than 2.0, the cell wall becomes thin and brittle, resulting in a problem that the quality of both bulk and paper powder deteriorates. Raw material pulp having a Runkel ratio of more than 3.0 requires selection of used paper with a relatively large amount of virgin pulp, and the need to use a large amount of virgin pulp, which is a reality when using raw material pulp mainly composed of used paper pulp in the present invention. Not right.

  In general, it can be said that the fiber with a larger Runkel ratio is a stiffer fiber, and when such a fiber is used, it becomes easier to produce a low-density paper. The general theory is not applied to the above, and in the examination by the present inventors, the disaggregation according to JIS P 8121 (1995) after disaggregating the printing paper according to JIS P 8220 (1998) described above. The pulp freeness is 450 cc or more, the pulp fiber roughness of the raw pulp after the disaggregation is 10 to 25 mg / 100 m, and the ratio of mechanical pulp by the dyeing method according to JIS P 8120 (1998) is Combined with the condition of 60% by mass or more, the printing paper is excellent in printability and hardly generates paper dust despite being more effective and bulky. It is possible to obtain.

  When the Runkel ratio of the disaggregated pulp is less than 2.0, since the raw pulp fiber itself is in a state of being soft (flexible), the bulk is difficult to obtain and the rigidity is low, and the suitability as a printing paper is lowered. If the Runkel ratio of the disaggregated pulp exceeds 3.0, the fibers become stiff and the bulk and rigidity are improved. However, on the other hand, there is a problem that the printability is deteriorated and fine printing tends not to be obtained.

  In the present invention, a bulking agent can be used as a means for assisting bulkiness. The use of the bulking agent is an already known and commonly used technique, but the bulking agent is an expensive chemical, and easy use should be avoided due to problems of product cost and paper strength.

However, in the configuration of the present invention, the pulp pulp freeness in accordance with JIS P 8121 (1995) after stripping the printing paper in the system environment exhibiting high anionic property of the raw material pulp mainly composed of waste paper pulp. 450cc or more, the pulp fiber roughness of the raw pulp after the disaggregation is 10 to 25 mg / 100 m, and the mechanical pulp of the raw pulp after the disaggregation by a dyeing method according to JIS P 8120 (1998) Under the condition of using raw pulp having a ratio of 60% by mass or more and a predetermined Runkel ratio, although the reason is not clear, the bulkiness improving effect by the bulking agent is high. The bulking agent has a function of separating the fibers, and in the case of high blending, it is preferable to refrain from the amount of use because it lowers the paper strength mainly by the Z-axis strength of the paper. It has been found that by adding 0.2 to 0.5% of an active ingredient per an absolute dry weight of pulp, it is possible to obtain a higher bulkiness improving effect than before.

  The raw material pulp suitably used in the present invention is not particularly limited in the present embodiment except that the printing paper is mainly used waste paper pulp as described above, and mechanical pulp can be suitably used. As a mechanical pulp that can be suitably used in the embodiment, in order to obtain a bulky printing paper, for example, pine, spruce, fur, and the like, which are softwood materials, are used as raw materials. There are conifer mechanical pulps such as refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), pressurized groundwood pulp (PGW), among which TMP and PGW are particularly bulky. High, high opacity, high whiteness, and high strength printing paper Masui.

  In the present embodiment, when, for example, the mechanical pulp is used as the raw pulp, the paper, board and pulp-fiber composition test method described in JIS P 8120 is used for the raw pulp after disaggregation according to JIS P 8220. The proportion of mechanical pulp by the dyeing method can secure the bulkiness by the rigidity of the fiber while suppressing the paper dust caused by the mechanical pulp, and can reduce the weight compared with the printing paper of the same thickness. In view of the above, it is preferably 60% by mass or more, and more preferably 70% by mass or more. In addition, in order to prevent paper dust caused by mechanical pulp from becoming difficult, or to prevent the printing paper itself from becoming brittle and reducing bookbinding processing suitability, the proportion of the mechanical pulp is 90% by mass or less, and further 80 It is preferable that it is below mass%.

  In order to obtain the printing paper according to the present embodiment, the pulp slurry composed of the raw material pulp, if necessary, various kinds of fillers, internally added sizing agents, fixing agents, yield improvers, cationizing agents, paper strength enhancing agents, etc. For example, a method of adding an additive as appropriate and adjusting a condition such as a pH value and making paper with a normal paper machine such as a long net paper machine or a twin wire paper machine can be employed.

  Examples of fillers include light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, silica White inorganic pigments such as magnesium acid, synthetic silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, magnesium hydroxide; styrene plastic pigment, acrylic plastic pigment, polyethylene, microcapsule, urea resin, melamine resin, etc. And organic pigments.

  Examples of internally added sizing agents include rosin sizing agents for acidic papermaking, modified rosin sizing agents for neutral papermaking, alkenyl succinic acid sizing agents, alkyl ketene dimer sizing agents, alkenyl succinic anhydride sizing agents, and wax sizing agents. Styrene resin sizing agent, olefin resin sizing agent, styrene-acrylic resin sizing agent, higher fatty acid sizing agent, cationic polymer sizing agent, oxidized starch and the like.

  In addition to the above-mentioned various additives, a method of adding a bulking agent to the raw pulp slurry and improving the bulk of the resulting printing paper has been tried, but the bulking agent is mainly based on the Z-axis strength of the paper. In order to reduce the paper quality strength, it is preferable to refrain from the use thereof, but preferably, the ash content measured in accordance with JIS P 8251 is added to 0.2 to 0.5% by mass, In the present invention, it is preferable to obtain a printing paper that is excellent in printability and hardly generates paper dust despite being bulky.

  Note that when the printing paper according to the present embodiment is applied to, for example, offset printing in particular, since dampening water is used in such offset printing, it is preferable to appropriately impart size characteristics (water absorption resistance) to the printing paper. . By maintaining such sizing properties satisfactorily, it is possible to more sufficiently suppress fears such as an increase in the amount of dampening water transfer, paper elongation, poor wet inking, and color misregistration.

  In order to control the sizing property, the internal sizing agent as described above is added to the raw pulp slurry, and the internal sizing agent is added to the inside of the printing paper at the same time as paper making, or after paper making, a two-roll size press, gate It is preferable to apply a surface sizing agent to the surface of the printing paper using a coating machine such as a roll coater, or at least one of them. As the surface sizing agent, for example, those exemplified as the internal sizing agent can be used.

  For example, in the case of using the internal additive sizing agent, in order to impart sufficient sizing properties to the resulting printing paper and to further improve the moisture resistance and water resistance, 0.1 parts by mass or more with respect to 100 parts by mass of the raw material pulp, It is preferable to be 0.3 parts by mass or more, and in order to prevent the absorption and drying properties of the ink on the surface of the printing paper from being lowered and the printing operability from being deteriorated, the amount of the raw material pulp is 100 parts by mass. It is preferably 1 part by mass or less, more preferably 0.8 part by mass or less.

  For example, when the surface sizing agent is used, in order to impart sufficient sizing properties to the obtained printing paper and to further improve the moisture resistance and water resistance, the coating amount on the printing paper is 0.04 g / m 2 per side. In addition, it is preferably 0.06 g / m 2 or more. In order to prevent the ink from drying and drying on the surface of the printing paper from being deteriorated and the printing operability from being deteriorated, the printing paper should be used. The coating amount per side is preferably 0.20 g / m 2 or less, more preferably 0.18 g / m 2 or less.

The density of the printing paper according to the present embodiment measured in accordance with “Test method for thickness and density” described in JIS P 8118 is 0.20 to 0.30 g / cm ^3. Stiffness (longitudinal) measured in accordance with “Paper Clark stiffness tester” described in JIS P 8143 gives good printing workability and feel to the touch. and also from the viewpoint of maintaining sufficient printability, it is preferably about 20 to 30 cm ^3/100.
As described above, the printing paper according to the present embodiment is excellent in printability despite being lightweight and bulky.

Next, examples and comparative examples of the present invention will be shown to clarify the effects of the present invention.
Raw material pulp was blended at the ratio shown in Table 1, and raw material pulp slurry, fiber roughness, and Runkel ratio were prepared. After adding 1 part by mass of clay to 100 parts by mass of pulp solids, 0.1 g of oxidized starch as a surface sizing agent is used as a surface sizing agent in a gate roll coater using a long net type paper machine. / M ² coating was performed to obtain a printing paper.

  In the table, the CSF based on JIS P 8121 of the raw pulp after disaggregation based on JIS P 8220 is also shown. Further, the content of mechanical pulp in each raw material pulp in the table is determined by a dyeing method based on JIS P 8120.

  Each physical property of the obtained printing paper was measured by the following method. These results are shown in Table 2. Further, a commercially available printing paper having an actually measured basis weight of 69 g / m 2 was used as Comparative Example 6, and each physical property was measured in the same manner. The raw pulp and CSF of this commercially available printing paper are as shown in Table 1.

  In this example, Examples 1 to 15 and Comparative Examples 1 to 3 used magazine waste paper pulp having a mechanical pulp content of 60% as DIP, and TMP was used for mechanical pulp. In Comparative Example 4, kraft waste paper mixed with kraft paper is used. In Comparative Example 5, medium-sized waste paper used mainly for printing paper is used. The shape was beaten and adjusted. The fiber roughness was adjusted by the amount of raw pulp obtained as a result of classifying raw pulp with holes and slit screens and accepting and rejecting.

(A) Density The density was measured in accordance with “Test method of thickness and density” described in JIS P 8118.
(B) Basis weight It measured based on the "basis weight measuring method" as described in JISP8124.
(C) Thickness Measured according to “Test method of thickness and density” described in JIS P 8118.
(D) Stiffness (vertical)
It was measured in accordance with “A stiffness test method using a paper Clark stiffness tester” described in JIS P 8143.

(1) Test example 1 (printability)
Using an RI printing test machine (Ishikawajima Industrial Machinery Co., Ltd.), 1.0 g of ink for offset printing (trade name: TK High Echo Black, manufactured by Toyo Ink Co., Ltd.) was developed and printed. After 5 minutes from the start of printing, the coated paper was adhered to the printing surface with a constant pressure, the state of ink transfer to the coated paper was examined, and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: The set is very fast, can be used for high-speed printing with offset sheet-fed printing, and there is no problem of set-off.
○: Level is fast and there is no problem of set-off.
Δ: Standard level.
×: Level of setting is slow and unusable for offset printing.
(2) Test example 2 (generation of paper dust)
Using an offset color printer (model number: LITHRONE44, manufactured by Komori Corporation), continuous 5000 copies of indigo, red, yellow, and black ink were printed. Thereafter, the accumulation state of the paper powder in the blanket non-image area was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: Paper dust is not recognized.
○: Paper dust is slightly recognized, but there is no problem in actual operation.
(Triangle | delta): Paper dust is recognized and there exists a problem in actual operation.
X: A lot of paper dust is deposited on the blanket.

<Discussion>
From the results shown in Table 1, each of the printing papers of Examples 1 to 15 has high whiteness, bulkiness, and the time required until the dynamic water absorption test value reaches 50%. It can be seen that it is long and excellent in water resistance. Further, it is found that the printability is excellent, paper dust is hardly generated, and excellent characteristics suitable for printing such as offset printing are provided.
In contrast, the printing papers of Comparative Examples 1 to 6 have insufficient whiteness, low bulkiness, and a short time required until the dynamic water absorption test value reaches 50%. It turns out that it has a problem of being inferior. In addition, it can be seen that it does not have excellent characteristics suitable for printing such as offset printing, such as poor printability and significant generation of paper dust.

  The printing paper of the present invention can be suitably used for, for example, offset printing and rotary printing.

Claims (2)

Printing paper manufactured using waste paper pulp as the main raw material,
In accordance with JIS P 8220 (1998), the pulp pulp freeness in accordance with JIS P 8121 (1995) after disaggregation of the printing paper is 450 cc or more,
The pulp fiber roughness of the raw pulp after the disaggregation is 10 to 25 mg / 100 m,
The ratio of the mechanical pulp by the dyeing | staining method based on JISP8120 (1998) of the raw material pulp after the said disaggregation is 60 mass% or more,
The basis weight of the printing paper according to JIS P 8124 (1998) is 40 to 100 g / m ² , and the density of the printing paper according to JIS P 8118 (1998) is 0.20 to 0.30 g / cm ³ . Printing paper characterized by that.   The printing paper of Claim 1 whose Runkel ratio of the said disaggregated pulp is 2.0-3.0.