JP7348251B2 - newsprint - Google Patents

Description

TECHNICAL FIELD The present invention relates to newsprint printed on a rotary offset press, and particularly to supple newsprint made from neutral paper.

In recent years, offset printing paper, especially newsprint for offset printing, has rapidly become color printing, faster, and more tower-based. Printing workability is required. In addition, because large quantities of printing are done in a short period of time, problems such as blurring of the printed surface due to paper dust accumulation are considered important. Furthermore, in recent years, there has been an increasing demand for newsprint to be lighter in weight from the viewpoints of environmental protection, increased page size, portability, and the like. However, if the mass (basis weight) per unit area of paper is reduced in order to reduce the weight, the paper becomes thinner, which may result in a decrease in paper opacity and paper strength. As a result, print quality deterioration may occur, such as "bleed-through" in which images and characters on the front side of the print are seen through on the back side, and a decrease in the clarity of the printed image.

On the other hand, newsprint, which is used to read articles with the paper unfolded and turn the pages, requires flexibility and ease of turning the pages. Although newsprint with high rigidity and tension is suitable for processing such as folding after printing, it is stiff when reading a newspaper, making it difficult to turn the pages. Therefore, there is a need to develop newsprint that is pliable and easy to turn, while still being stiff enough not to impair workability during printing.

It is known that increasing the opacity, specific scattering coefficient, and oil absorption of the paper is effective as a method for reducing the bleed through of newsprint, for example.

The technology to increase opacity is to use waste paper pulp with a blending ratio of 60% by mass or more, 3 to 25% by mass of one or more fillers containing fresh calcium carbonate, and 1.5 to 4.0g on both sides. / m ² pigment coating layer is provided, and the ash content derived from the base paper and the pigment coating layer is 7 to 25% by weight (Patent Document 1), and the paper containing polyhydric alcohol and fatty acid ester compound ( A) and an ester compound (B) which is an ester compound of a polyhydric alcohol and a fatty acid and has an oxyalkylene group having 2 to 4 carbon atoms on average of more than 0 mol and less than 12 mol per mol of the ester compound. A method has been proposed in which paper is bulked up by adding a bulking agent such as an ester compound having a temperature of 100° C. or less to provide newsprint with high opacity (Patent Document 2).

As a technique for increasing the specific scattering coefficient, a method of internally adding a titanium oxide filler or a urea-formalin resin filler (Non-Patent Document 1) has been proposed.

As a technique to improve oil absorption and prevent bleed-through, for example, papermaking is performed by adding hydrated silicic acid slurry to paper stock containing pulp and calcium carbonate, and the oil absorption amount and pore volume of hydrated silicic acid are , filled paper with the average particle diameter set within a specific range (Patent Document 3), and newsprint containing mainly white carbon and calcium carbonate with the proportion of these in the ash set within a specific range (Patent Document 3). 4) etc. have been proposed.

Patent No. 5265900 specification Patent No. 3041297 specification Japanese Patent Application Publication No. 09-176985 Japanese Patent Application Publication No. 2002-201590

Paper Paper Technology Association Journal 44, (8) 865 (1990)

However, these conventional techniques have the following problems.
(1) According to the technology described in Patent Document 1, although opacity is improved by providing a pigment coating layer, during offset printing, the pigment coating layer inhibits ink absorption into the base paper, resulting in ink drying There is a possibility that printing workability may be deteriorated, such as deterioration of . In addition, pigment coating equipment is required, which is disadvantageous in terms of power and cost.
(2) According to the technology described in Patent Document 2, although the opacity is improved by the bulking effect, the bulking agent improves the paper thickness by inhibiting hydrogen bonds between the pulp fibers of the base paper, so the surface strength This causes problems such as pile-up and paper dust generation, which deteriorates printing workability.
(3) According to the techniques described in Patent Documents 3 and 4 and Non-Patent Document 1, white carbon, titanium oxide, and urea-formalin resin fillers are expensive to begin with, leading to an increase in cost. In particular, white carbon tends to generate paper dust and stain printing equipment due to its particle characteristics, so there is a limit to how much it can be added in order to maintain the strength of the paper.
(4) Regarding newsprint, although there are many technologies related to workability during printing, there has been no technology that takes into account human sensations, such as flexibility when turning pages.

In view of this situation, it is an object of the present invention to provide newsprint that contains waste paper pulp, has a low basis weight and high ash content, has appropriate paper stiffness, is resistant to bleed through, and is easy to turn over. The task is to

As a result of intensive studies to solve the above problems, the present inventors found that the paper contains waste paper pulp, has a basis weight of 45 g/ ^m2 or less, and has an ash content measured by the 525°C combustion method described in JIS-P8251. is 10% by mass or more of newsprint without a pigment coating layer, contains light calcium carbonate added during papermaking, and has an ash content in the paper measured by the 525°C combustion method described in JIS-P8251 and JIS -Newspaper with a difference from the ash content in the paper measured by the 900°C combustion method described in P8252 of 2.0% by mass or more and a specific scattering coefficient of 50m ² /kg or more, so that it does not contain waste paper pulp. The present inventors have discovered that it is possible to obtain newsprint that has a low basis weight and high ash content, yet has appropriate paper stiffness, is resistant to bleed through, and is easy to turn over, leading to the completion of the present invention. As the calcium carbonate, it is preferable to use fresh light calcium carbonate. Further, it is preferable that the mechanical pulp is contained in a range of 5% by mass or more and 30% by mass or less based on the absolute dry mass of the total pulp, and the mechanical pulp is more preferably thermomechanical pulp (TMP) or refined ground pulp (RGP). Further, the bending stiffness of the newsprint is preferably 70 μN·m or less. Furthermore, using the tissue softness measuring device TSA, a bladed rotor was pressed from above with a pushing pressure of 100 mN onto the newsprint sample placed on the sample stage, and then rotated at a rotation speed of 2.0 (/sec). When the vibration of the sample stage was measured with a vibration sensor, the intensity (TS750) of the maximum peak of the first spectrum from the low frequency side, automatically acquired by the software on the TSA, was 70 dBV ² rms or less and 6500 Hz. It is preferable that the intensity (TS7) of the maximum peak of the spectrum including 130 dBV ² rms or less.

Although the newsprint of the present invention contains waste paper pulp and has a low basis weight and high ash content, it has the advantage of having appropriate paper stiffness, being difficult to bleed through, and being easy to turn over. In particular, it is characterized by being supple, soft, and easy to turn. Newspapers are usually delivered or sold in the form of a number of relatively large thin sheets of 813 x 545 mm, folded in quarters or in half. When reading a newspaper, fold it in half or unfold it unfolded and turn over each page as you read. The newsprint of the present invention is flexible and can be easily turned over. This is especially true when you are reading a newspaper in a crowded place, holding it in one hand while rolling it vertically and flipping through it with the other hand, or when you are reading the newspaper by rolling it back little by little after you have finished reading it. Are suitable.

FIG. 3 is a diagram showing the measurement principle of the tissue softness measuring device TSA. FIG. 3 is a diagram showing an example of an analysis result of the vibration frequency of a paper sample by TSA. It is a figure which shows the measuring method of the rigidity D of a paper sample sample by TSA.

As described above, in the present invention, a pigment coating containing waste paper pulp, having a basis weight of 45 g/m ² or less, and an ash content of 10% by mass or more in the paper measured by the 525°C combustion method described in JIS-P8251. Newspaper without a layer, containing light calcium carbonate added during paper making, with ash content measured by the 525°C combustion method described in JIS-P8251 and the 900°C combustion method described in JIS-P8252. The difference from the ash content ⁱⁿ the paper measured by However, it is possible to obtain newsprint that has appropriate paper stiffness, is difficult to bleed through, and is easy to turn.

<Newspaper>
1) Pulp The raw material pulp for the newsprint of the present invention contains waste paper pulp from environmental considerations, and in addition to waste paper pulp, wood such as softwood (N material) or hardwood (L material), bamboo, Mix and use chemical pulp (KP, SP, etc.), mechanical pulp (GP, CGP, RGP, PGW, TMP, CTMP, etc.), dissolving pulp, etc. obtained from non-wood fibers such as straw and hemp in any ratio. be able to. As the waste paper pulp, deinked waste paper pulp (DIP) and waste paper pulp that is not deinked can be used, but from the viewpoint of whiteness, it is desirable to incorporate a high amount of DIP, and 50 mass of DIP per absolute dry mass of the total pulp. % or more, preferably 70% by mass or more, more preferably 80% by mass or more. In addition, mechanical pulp and DIP can be used after being bleached if necessary, and the degree of bleaching can be arbitrarily determined. Furthermore, in order to produce newsprint with sufficient strength, it is preferable to contain mechanical pulp, and thermomechanical pulp (TMP) or refined ground pulp (RGP), which cause less damage to fibers during pulp production, is more preferable. Mechanical pulp can be mixed and used in any proportion, but in order to achieve both strength and flexibility of the paper, it is preferably 5% by mass or more and 30% by mass or less.

2) Filler The type of filler (internal filler) added in the present invention is light calcium carbonate, which has a high specific scattering coefficient, has high oil absorption, and is effective in improving printing quality such as strike-through. Preference is given to particularly "fresh" light calcium carbonate, which has not previously been incorporated into paper. Fresh light calcium carbonate has a more controlled shape than recycled fillers, so it is thought to have excellent oil absorption and light scattering properties, as well as contributing to the development of flexibility. The filler may be light calcium carbonate alone, or light calcium carbonate and one or more other fillers may be used in combination. Examples of fillers other than light calcium carbonate include, but are not limited to, known papermaking fillers such as heavy calcium carbonate, hydrated silicic acid, white carbon, talc, kaolin, clay, titanium oxide, and synthetic resin fillers. It is not something that will be done.

In the present invention, "JIS-P8251 Paper, paperboard and pulp - Ash content test method -525℃
The ash content in the paper measured by the method described in "Combustion Method" is preferably 10% by mass or more from the viewpoint of preventing strike-through. More preferably, it is 11.5% by mass or more. The upper limit of the amount of ash in the paper is not particularly limited, but considering operability during production and processing suitability during printing, it is usually about 40% by mass or less, preferably 30% by mass or less.

In the present invention, it is preferable to add light calcium carbonate as an internal filler because the opacity and whiteness of paper can be improved at a relatively low cost. Furthermore, in order to obtain supple newsprint, it is desirable that the addition rate of light calcium carbonate be high, preferably 4% by mass or more, and more preferably 5% by mass or more, based on the absolute dry mass of the total pulp. The upper limit is not particularly limited, but considering the upper limit of the ash content in paper and the ash content brought in from waste paper pulp, it will usually be about 35% by mass or less.

In the present invention, "JIS-P8251 Paper, paperboard and pulp - Ash content test method -525℃
The difference between the ash content measured by the method described in "Combustion Method" and the ash content measured by the method described in "JIS-P8252 Paper, Paperboard and Pulp - Ash Content Test Method -900℃ Combustion Method" is 2.0 mass % or more. Since newsprint contains various inorganic components (fillers and pigments), including a certain amount of ash brought in from waste paper, it is difficult to easily and directly measure the content of specific inorganic components in the paper. It is difficult. However, it is generally known that when calcium carbonate is burned at a high temperature of around 900°C, it decomposes into carbon dioxide and water. It is possible to estimate the calcium carbonate content in paper using the ash content difference in the method. That is, the larger the difference in ash content, the higher the content of calcium carbonate. In the present invention, the difference in ash content when burning newsprint at 525°C and 900°C is set to 2.0% by mass or more, and by increasing the calcium carbonate content in the paper, it is possible to effectively prevent print-through and page turning. Ease of use can be improved. The upper limit of the ash content difference is not particularly limited, but considering the upper limit of the ash content in paper, it will usually be about 35% by mass or less.

3) Paper making system The newsprint of the present invention is not particularly limited, and may be either acidic paper made by acidic papermaking or neutral paper made by neutral papermaking so that the pH of the paper surface is 6 to 9. However, in the case of neutral papermaking, it is possible to incorporate a high amount of calcium carbonate as a filler, so neutral paper is preferable in terms of quality such as show-through and flexibility.

4) Internally added chemicals, etc. The types and amounts of internally added chemicals used in acidic papermaking and neutral papermaking differ, but conventionally known internally added sizing agents, alkyl ketene dimer (AKD)-based sizing agents, alkenyl anhydride Succinic acid (ASA) based sizing agents, neutral rosin sizing agents, etc. can be used.

In addition, various conventionally used internal chemicals for paper manufacturing such as nonionic and cationic retention improvers, freeness improvers, paper strength improvers, and bulking agents can be selected as needed. can be used. Further, for example, basic aluminum compounds such as aluminum sulfate, aluminum chloride, basic aluminum chloride, and basic polyaluminum hydroxide may be internally added. Other papermaking auxiliaries include various starches, polyacrylamide, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide, polyamine resin, polyamine, polyethyleneimine, polyamide epichlorohydrin, polyamine epichlorohydrin, vegetable gum, Various compounds such as polyvinyl alcohol, latex, polyethylene oxide, hydrophilic crosslinked polymer particle dispersions, and derivatives or modified products thereof can be used. Furthermore, it is also possible to add internal chemicals for papermaking, such as dyes, optical brighteners, pH adjusters, antifoaming agents, pitch control agents, and slime control agents, as appropriate depending on the purpose.

5) Surface treatment agent In order to improve surface strength and printability, a clear coating layer can be provided by applying a surface treatment agent containing a surface strength agent, surface sizing agent, etc. onto the newsprint base paper. .

Surface paper strength agents include starch, enzyme-modified starch, thermochemically modified starch, oxidized starch, esterified starch, etherified starch, hydroxyethylated starch, cationized starch, etc., and polyvinyl alcohol (PVA). , polyvinyl alcohol-based products such as carboxyl-modified polyvinyl alcohol and cation-modified polyvinyl alcohol, polyacrylamide-based products such as polyacrylamide, cationic polyacrylamide, amphoteric polyacrylamide, and nonionic polyacrylamide, cellulose-based products such as carboxymethyl cellulose, hydroxyethyl cellulose, and methyl cellulose, etc. Various copolymers (latex) such as water-soluble polymers such as styrene/butadiene, styrene/acrylic, ethylene/vinyl acetate, butadiene/methyl methacrylate, and vinyl acetate/butyl acrylate may be mentioned. These may be used alone or in combination of two or more.

As the surface sizing agent, in the case of neutral papermaking, a cationic surface sizing agent is preferable, such as a styrene/(meth)acrylic acid copolymer ("(meth)acrylic acid" refers to "acrylic acid and/or methacrylic acid"). ), styrene/(meth)acrylic acid ester copolymer, styrene/(meth)acrylic acid/(meth)acrylic acid ester copolymer, styrene/maleic acid copolymer, styrene/maleic acid semipolymer Ester copolymer, styrene/maleic acid ester copolymer, ethylene/(meth)acrylic acid copolymer, isobutylene/(meth)acrylic acid copolymer, n-butylene/(meth)acrylic acid/(meth)acrylic acid Examples include, but are not limited to, acid ester copolymers, propylene/maleic acid copolymers, ethylene/maleic acid copolymers, α-olefin-maleic acid copolymers, and the like. These copolymers may be used as sodium, potassium or ammonium salts. In addition, a nonionic surface sizing agent, an alkyl ketene dimer type sizing agent, etc. can be used in combination as long as the desired quality is not impaired.

In addition, Neppari inhibitor, wet paper strength agent, polyethylene glycol, preservative, antifoaming agent, ultraviolet inhibitor, optical brightener, dye, antifading agent, viscosity stabilizer, anti-slip agent, lubricant, polyethylene wax, ink Auxiliary agents such as fixing agents and metal salts can be used as appropriate.

6) Paper-making method There is no particular limitation on the type of paper-making machine, and paper-making can be performed using a publicly available paper machine such as a Fourdrinier paper machine, a gap former, or a hybrid former (on-top former). Press line pressure is used within normal operating ranges. A surface treatment agent may or may not be applied. When forming a clear coating layer using a surface treatment agent, there are no particular limitations on the components of the surface treatment agent, and there are no limitations on the type of size press. A membrane transfer type size press or the like can be used as appropriate.

7) Paper quality and others The newsprint of the present invention is manufactured to have a basis weight of approximately 30 g/m ² or more and 50 g/m ² or less, but the effects of the present invention, such as improved bleed-through and flexibility, are In order to achieve higher expression, newsprint with a low basis weight of 45 g/m ² or less is preferable. More preferably, it is 43 g/m ² or less. In addition, when applying a surface treatment agent (clear coating layer), the coating amount is not particularly limited, but is 0.1 g/m ² or more per side and 5.0 g/m ² or less per side. It is desirable that there be. As a method for drying the clear coating layer, various methods such as a steam heating cylinder, a heated hot air air dryer, a gas heater dryer, and an electric heater dryer may be used alone or in combination. Further, smoothing treatment may be performed using a machine calender, a super calender, a high temperature soft nip calender, etc., or non-calender treatment may be performed. In addition, if the smoothness is too high, sufficient paper thickness cannot be obtained and the paper becomes weak. On the other hand, if the smoothness is too low, poor ink adhesion occurs when printing, so in the present invention, JIS-P8119: It is desirable to carry out the calendering treatment so that the Bekk smoothness measured in accordance with 1998 is 30 to 70 seconds, preferably 35 to 60 seconds. The moisture content of newsprint is approximately 1.0% or more and 9.0% or less from the viewpoint of printing workability and ink receptivity.

The newsprint of the present invention does not have a pigment coating layer. The pigment coating layer refers to a layer containing a pigment and a binder that is coated on the surface of the base paper after the base paper is made.

The newsprint of the present invention has a specific scattering coefficient of 50 m ² /kg or more. The specific scattering coefficient can be calculated based on the formula specified in TAPPI T425 (ISO 9426). If the specific scattering coefficient is high, even if the opacity is the same, the paper will be less likely to show through. The upper limit of the specific scattering coefficient is not limited, but considering the upper limit of 40% by mass of the ash content in the paper, it will usually be about 80 m ² /kg. From the viewpoint of balance with ash content and strength such as bending stiffness, it is more preferable that the weight is 70 m ² /kg or less. The specific scattering coefficient can be adjusted mainly by the type and amount of filler used.

The bending stiffness of the newsprint of the present invention is preferably 70 μN·m or less. The bending stiffness can be measured as the bending stiffness in the MD direction (paper making direction) in accordance with ISO2493. Appropriately low bending stiffness improves flexibility and softness, making the paper easy to turn. The lower limit of the bending stiffness is not limited, but will usually be about 30 μN·m, taking into account the suitability of processing and workability in a printing machine (particularly a folding machine). In order to achieve both ease of turning and processability at a high level, it is desirable that the resistance is 45 μN·m or more and 65 μN·m or less.

In addition, in the present invention, it has been found that the ease of turning a newspaper correlates with a value measured by a tissue softness measuring device TSA (Tissue Softness Analyzer), and this measured value can be used as an index. TSA is used for quantitative evaluation of hand feel in the field of tissue paper products and sanitary thin paper rolls, and is described in, for example, JP-A No. 2013-236903 and JP-A No. 2014-233363. It is something.

In the present invention, a bladed rotor is pressed into the sample from above with a pushing pressure of 100 mN, using printed newsprint as a sample, and then rotated at a rotation speed of 2.0 (/sec). When the vibration of the sample stage is measured with a vibration sensor, the intensity of the maximum peak of the first spectrum from the low frequency side (TS750) automatically acquired by the software on the TSA must be 70 dBV ² rms or less. is preferable, more preferably 67 dBV ² rms or less, still more preferably 65 dBV ² rms. The lower limit is 50 dBV ² rms or more. TS750 represents smoothness and roughness; if TS750 is too high, the smoothness is poor, and if it is too low, only the smoothness becomes noticeable and a good tactile sensation may not be obtained.

Further, the intensity (TS7) of the maximum peak of the spectrum including 6500 Hz, automatically acquired by software on the TSA, is preferably 130 dBV ² rms or less, more preferably 125 dBV ² rms or less, and most preferably 120 dBV 2 rms ^{or less} . rms or less. The lower limit is 90 dBV ² rms or more. TS7 indicates a soft feel (surface softness and bulk softness); if TS7 is too high, sufficient softness cannot be obtained, and if TS7 is too low, only the softness stands out, and a good tactile sensation may not be obtained. .

Further, in the present invention, the rigidity (D) measured by TSA is preferably 0.75 to 0.85 mm/N, more preferably 0.78 to 0.80 mm/N. If this measured value is too low, the overall pliability of the newsprint will be poor, and if it is too high, the pliability will be noticeable and the overall balance may be lost. Rigidity (D) is measured when a bladed rotor is pressed from above with a pushing pressure of 100 mN and 600 mN, respectively, on a sample placed on a sample stage, without rotating it. It is expressed as the amount of deformation displacement in the direction.

The details of the measurement method are as shown in FIG. 1. The tissue softness measuring device TSA110 collects vibration data detected by various sensors when a rotating bladed rotor 104 is pressed against a paper sample 106. The software is used to quantitatively evaluate the softness (feel to the touch) of paper by analyzing vibration and converting it into parameters (TS value). Emtec Electronic GmbH (Germany) It is the product name of the manufacturer.

Specific measurements using TSA are as follows:
(i) A sample 106 (a sample processed into a circular shape with a diameter of approximately 112.8 mm using an emtec sample punch) is installed so as to cover the circular sample stage 105 from the outside, and a sample fixing ring is attached to the outer periphery of the sample 106. hold at 108;
(ii) After pushing the bladed rotor 104 onto the sample 106 with a pushing pressure of 100 mN, the rotor 104 is rotated at a rotation speed of 2.0 (/sec),
(iii) The vibration of the sample stage 105 is measured by the vibration sensor 103 installed inside the sample stage 105, and the vibration frequency is analyzed.

(iv) Next, the amount of deformation displacement (mm/N, rigidity D) in the vertical direction is measured when the sample 106 is deformed at a pushing pressure of 100 mN and 600 mN, respectively, without rotating the rotor 104.

According to the above procedure, one sample is measured five times and averaged.

Note that the sample stage 105 is installed on the base plate 101, and the force sensor 102 is arranged between the sample stage 105 and the base plate 101. Then, the pushing pressure of the bladed rotor 104 is controlled based on the detected value of the force sensor 102. Further, the bladed rotor 104 is rotated by a motor 109.

Furthermore, emtec measurement system is used as software for analyzing vibration and creating parameters (TS values). This software is equipped with various algorithms (for example, Base Tissue, Facial, TP, etc.) to automatically obtain TS750, TS7, D (rigidity) on the software, and calculate the TS750, TS7, D, and basis weight. The HF (hand feel) value is calculated from the , thickness, number of Ply, etc. using various algorithms. In the present invention, only TS750, TS7, and D are specified, not the HF value. Any algorithm may be used as long as the above measurement conditions are satisfied, and the values of TS750, TS7, and D may vary depending on the type of algorithm. Nothing will change.

FIG. 2 shows an example of the analysis results of the vibration frequency of a paper sample by TSA. Let the intensity of the maximum peak A of the first spectrum from the low frequency side be TS750, and the intensity of the maximum peak B of the spectrum including 6500 Hz (before and after 6500 Hz) be TS7. Maximum peak B is typically located at about 6500 Hz.

FIG. 3 shows a method for measuring the stiffness D of a paper sample by TSA.

The vibration frequency of the paper sample depends on the paper structure and the rotation speed of the rotor 104, and the amplitude (intensity of the spectrum) depends on the height of the paper structure, such as the crepe height. The frequency at which TS7 appears (in the range of 5,000 to 8,000 Hz, usually around 6,500 Hz) is the resonant frequency of the rotor 104, and when it becomes a horizontal vibration and travels on the paper surface, it is momentarily interrupted by the paper fibers and due to the vibration of the rotor 104. to cause.

The opacity of the newsprint of the present invention is preferably 93% or more, since it is difficult to see through if it is high. Opacity can be measured according to JIS-P8149:2000. The upper limit of the opacity is not limited, but considering the low basis weight of newsprint, it is about 96%. Further, in the present invention, it is preferable that the strike-through value is 85% or more. Here, the strike-through value is determined by printing so that the density of the printed surface is 1.15 as measured by a Macbeth reflection densitometer, and leaving it for 24 hours under controlled humidity conditions of 23°C and 50RH%. The reflectance of the back side is measured and is the value obtained by dividing the reflectance of the printed back side by the reflectance of the unprinted back side. It is shown that the larger this value is, the less the strike-through is.

In the present invention, if the coefficient of friction is too high, pages will stick to each other when reading a newspaper, making it difficult to turn them, and if the coefficient of friction is too low, slipping will occur, making it difficult to turn them. Therefore, the static friction coefficient measured by the ISO horizontal method according to JIS-P8147:2010 is preferably 0.62 to 0.69, and the dynamic friction coefficient is also preferably 0.59 to 0.62. By setting the coefficient within these ranges, it is possible to obtain a newspaper that is easy to turn and read.

The newsprint of the present invention is usually wound into a paper tube to form a newsprint roll, but the invention is not limited thereto. There are no particular limitations on the method of winding up the manufactured newsprint to make it into a newsprint roll, and the newsprint of the present invention can be wound up with a winder (winding machine). The winding speed and tension (tensile strength) may be adjusted as appropriate depending on the desired characteristics of the newsprint.

In addition, the paper tube to be rolled up when making the newsprint of the present invention into a newspaper roll is not particularly limited, but since it can be made into a pliable news roll that suppresses the occurrence of wrinkles, it is preferable to use corrugated cardboard as the main material. A paper tube base paper may be used, in which a paper tube base paper and a liner are wound together, the outermost layer is formed by wrapping the liner one or more times, and the other layers are formed by wrapping the paper tube base paper 19 times or more. Preferably, the combined number of turns of the paper tube base paper and liner is 24 or more. Wrapping a highly smooth liner on the outside makes the surface of the paper tube smooth and prevents wrinkles and bumps in the newsprint that occur along the shape of the surface of the paper tube. Further, the obtained paper tube is seasoned at normal temperature (room temperature) for 5 days or more to adjust the moisture content of the paper tube to 6.5 to 9.0%. Adjustment using this method is preferable because it reduces the moisture difference between the inside and outside of the paper tube, thereby suppressing the occurrence of wrinkles in newspaper rolls and printing due to deformation and dimensional changes in the paper tube.

The present invention will be described below with reference to Examples, but the present invention is not limited thereto. In addition, unless otherwise specified, parts and % in the examples indicate parts by mass and % by mass, respectively, and numerical ranges are described as including the end points thereof.

(1) Measurement of basis weight Measurement was carried out in accordance with the "Basic weight measurement method" described in JIS-P8124.

(2) Measurement of paper thickness Measurement was carried out in accordance with "Paper and paperboard - Test method for thickness and density" described in JIS-P8118.

(3) Opacity Measured in accordance with JIS-P8149:2000.

(4) Specific scattering coefficient Calculated based on the formula specified in TAPPI T425 (ISO 9426).

(5) ISO bending stiffness The bending stiffness in the MD direction (paper making direction) was measured in accordance with ISO2493.

(6) JIS Friction Coefficient Static friction coefficient and dynamic friction coefficient were measured in accordance with the ISO horizontal method described in JIS-P8147:2010.

(7) Measurement of TS750, TS7, and D values Measurement was carried out using the tissue softness measuring device TSA described above. The measurement conditions were also as described above.

(8) Strike-through value Single-sided printing was performed using an RI printing machine using offset newspaper ink so that the stamp surface density as measured by a Macbeth reflection densitometer was 1.15. After printing, the paper was left in an atmosphere of 23° C. and 50 RH% and the humidity was controlled for 24 hours, and then the reflectance of the back side of the printed surface was measured using a Macbeth reflection densitometer, and the strike-through value was calculated using the following formula:
Strike-through value (%) = (reflectance of printed back side/reflectance of unprinted back side) x 100.

(9) Ash content (525℃)
It was measured in accordance with "Paper, paperboard and pulp - Ash content test method - 525°C combustion method" described in JIS-P8251.

(10) Ash content (900℃)
It was measured in accordance with "Paper, paperboard and pulp - Ash content test method - 900°C combustion method" described in JIS-P8252.

(11) Show-through (visual evaluation)
Printing was performed using an offset rotary press (Toshiba offset rotary press: OA-4B2T-600) using high-viscosity AF ink, which is an eco-ink for offset manufactured by Toyo Ink Mfg. Co., Ltd. The printed paper was left in an atmosphere of 23° C. and 50 RH%, and 24 hours after being left, the printout was visually evaluated based on the following criteria.
◎: Ink did not penetrate into the back side of the print.
○: Almost no ink penetrated into the back side of the print.
△: Ink slightly penetrated into the back side of the print.
×: The ink penetrated into the back side of the print.

(12) Ease of flipping After printing with the above-mentioned rotary offset printing press, the sheets were cut to a size of 545 x 813 (mm) so that the short side was in the papermaking direction, and 10 sheets were stacked and folded in half. Newspaper that had been folded in half was folded into four, which is the size to be delivered. The ease with which the pages could be turned was evaluated using the following criteria when the newsprint unfolded in half was turned over one by one while held in the hand.
◎: Very flexible and easy to turn over.
○: Flexible and easy to turn.
△: Stiff and difficult to turn.
×: Very stiff and difficult to turn.

(13) Average particle diameter of filler Using a laser diffraction/scattering particle size distribution analyzer (manufactured by Malvern Co., Ltd., device name: Mastersizer 2000), the 50% point of the volume cumulative distribution was defined as the average particle diameter.

(Example 1)
<Manufacture of newsprint>
The filler was added to a pulp slurry prepared by mixing newspaper deinked pulp (freeness: 150ml CSF), TMP (freeness: 80ml CSF), and NKP (freeness: 500ml CSF) at a blending ratio of 80:15:5% by mass as pulp for papermaking. A paper stock was prepared by adding 4.0% by mass of light calcium carbonate (average particle size: 4.1 μm) based on the bone-dry mass of the pulp. Using this stock, newsprint base paper was made using a gap former type twin wire paper machine at a paper speed of 1000 m/min, and then hydroxyethylated starch was applied to the felt using an on-machine gate roll coater. Both the surface and the wire surface were coated to give a coating weight of 0.2 g/m ² to obtain newsprint for offset printing with a basis weight of approximately 42 g/m ² (42.3 g/m ² ). The paper quality, ash content, bleed through, and ease of turning were measured, and the results are shown in Table 1.

(Example 2)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that the filler addition rate was 5.0% and the basis weight was approximately 44 g/m ² .

(Example 3)
Newspaper for offset printing was obtained in the same manner as in Example 1, except that the filler addition rate was 5.0% and the basis weight was approximately 43 g/m ² .

(Examples 4 to 8)
The same procedure as in Example 1 was carried out except that the filler addition rates were 5.0%, 6.0%, 7.0%, 10.0%, and 11.0%, respectively, and newsprint for offset printing was prepared. Obtained.

(Example 9)
Newspaper for offset printing was obtained in the same manner as in Example 1, except that the filler addition rate was 11.0% and the basis weight was 37.5 g/m ² .

(Example 10)
Newspaper for offset printing was obtained in the same manner as in Example 1, except that the blending ratio of newspaper deinked pulp, TMP, and NKP was 65:30:5% by mass, and the filler addition rate was 6.0%. .

(Example 11)
Newspaper for offset printing was obtained in the same manner as in Example 1, except that the blending ratio of newspaper deinked pulp, TMP, and NKP was 85:10:5% by mass, and the filler addition rate was 6.0%. .

(Example 12)
Newspaper for offset printing was obtained in the same manner as in Example 1, except that the blending ratio of newspaper deinked pulp, TMP, and NKP was 92:3:5% by mass, and the filler addition rate was 6.0%. .

(Example 13)
Newspaper for offset printing was obtained in the same manner as in Example 1, except that the blending ratio of newspaper deinked pulp, TMP, and NKP was 95:0:5% by mass, and the filler addition rate was 6.0%. .

(Comparative example 1)
The same procedure as in Example 1 was carried out except that the blending ratio of newspaper deinked pulp, TMP, and NKP was 65:30:5% by mass, the filler addition rate was 0%, and the basis weight was about 44 g/ ^m2 , and the offset was Newsprint for printing was obtained.

(Comparative example 2)
The process was carried out in the same manner as in Example 1, except that the blending ratio of newspaper deinked pulp, TMP, and NKP was 70:25:5% by mass, the filler addition rate was 0%, and the basis weight was approximately 44 g/ ^m2 , and the offset was Newsprint for printing was obtained.

(Comparative example 3)
The process was carried out in the same manner as in Example 1, except that the blending ratio of newspaper deinked pulp, TMP, and NKP was 75:20:5% by mass, the filler addition rate was 0%, and the basis weight was approximately 44 g/ ^m2 , and the offset was Newsprint for printing was obtained.

(Comparative example 4)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that the filler addition rate was 0% and the basis weight was approximately 45 g/m ² .

(Comparative example 5)
Newspaper for offset printing was obtained in the same manner as in Example 1, except that the filler addition rate was 0% and the basis weight was approximately 43 g/m ² .

(Comparative example 6)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that the filler addition rate was 0% and the basis weight was approximately 41 g/m ² .

(Comparative example 7)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that the filler addition rate was 1.0%.

(Comparative example 8)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that the filler addition rate was 3.0%.

(Comparative example 9)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that heavy calcium carbonate (average particle size 3.8 μm) was used as the filler and the filler addition rate was 5.0%.

(Comparative example 10)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that heavy calcium carbonate (average particle size 3.8 μm) was used as the filler and the filler addition rate was 11.0%.

(Comparative Example 11)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that kaolin (average particle size 6.2 μm) was used as the filler and the filler addition rate was 5.0%.

(Comparative example 12)
Newspaper for offset printing was obtained in the same manner as in Example 1 except that kaolin (average particle size: 6.2 μm) was used as the filler and the filler addition rate was 11.0%.

As shown in Table 1, the newsprint of the present invention has a high wastepaper pulp content, a low basis weight of 45 g/ ^m2 or less, and a high ash content of 10% by mass or more (ash content at 525°C). , it can be seen that bleed through is difficult to occur and it is easy to turn over. The newsprint of the present invention has both appropriate paper stiffness and pliability (softness), and is ideal for newspaper applications where relatively large sheets of thin paper are read while being turned over one by one.

101 Base plate 102 Force sensor 103 Vibration sensor 104 Bladed rotor 105 Sample stand 106 Sample 108 Fixing ring 109 Motor 110 Tissue softness measuring device TSA

Claims (5)

Newspaper that contains waste paper pulp, has a basis weight of 45 g/m ² or less, and has an ash content of 10% by mass or more as measured by the 525°C combustion method described in JIS-P8251,
The blending ratio of deinked waste paper pulp is 70% by mass or more based on the absolute dry mass of the total pulp,
The opacity is 94.4% or more, and the number of rotations is determined by the tissue softness measuring device TSA after pushing a bladed rotor from above with a pushing pressure of 100 mN into the newsprint sample placed on the sample stage. When rotating at a speed of 2.0 (/sec) and measuring the vibration of the sample stage with a vibration sensor, the intensity of the maximum peak of the first spectrum from the low frequency side ( TS750) is 70 dBV ² rms or less, and the intensity of the maximum peak of the spectrum including 6500 Hz (TS7) is 125.8 dBV ² rms or less. Claim 1, wherein the difference between the ash content in the paper measured by the 525°C combustion method described in JIS-P8251 and the ash content in the paper measured by the 900°C combustion method described in JIS-P8252 is 2.0% by mass or more. newsprint. The newsprint according to claim 1 or 2, characterized in that the blending ratio of the deinked waste paper pulp is 80% by mass or more based on the absolute dry mass of the total pulp. Newspaper according to any one of claims 1 to 3, containing thermomechanical pulp (TMP) or refined ground pulp (RGP). Printing was performed so that the density of the printed surface was 1.15 as measured by a Macbeth reflection densitometer, and after conditioning the humidity for 24 hours in an environment of 23°C and 50RH%, the reflection of the back side of the printed surface was measured by a Macbeth reflection densitometer. When measuring the rate, the following formula:
Strike-through value (%) = (Reflectance of printed back side/Reflectance of unprinted back side) x 100
The newsprint according to any one of claims 1 to 4, characterized in that the print-through value calculated by is 85% or more.