JP2003336188A - Newsprint paper for offset printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a newsprint paper for offset printing causing little web break in an offset newspaper press. <P>SOLUTION: The newsprint paper for offset printing has an anisotropy index of fracture toughness of ≤0.28 and preferably the minimum value of the fracture toughness of ≥0.2 J/m. The anisotropy index of the fracture toughness is determined in conformity to SCAN-test standard P77:95 by measuring the fracture toughness values in at least 8 directions (directions with intervals of 22.5° based on the paper-making direction) and calculating with formula 1 which is a part of a Fourier series. F(θ)=C[1+ηcos2(θ-α)]...(1) wherein θ is the fracture toughness at an angle θ based on the paper-making direction; C is the average value of the fracture toughness; α is the anisotropy angle of the fracture toughness; and η is the anisotropy index of the fracture toughness. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a newsprint paper for offset printing, which is less likely to break in a newspaper offset press.

[0002]

2. Description of the Related Art Newspaper for offset printing is generally a paper containing mechanical pulp (MP) or deinking pulp (DIP) as a main raw material, and the type of paper is classified into middle and lower grade paper. However, since newspaper companies carry out high-speed, high-volume printing with newspaper offset rotary presses to write the latest news articles, the runnability required for offset printing newsprint is more severe than that for general printing paper. Also,
Newspaper offset rotary presses have increased the printing speed and the introduction of color printing over the past few years, increased printing speed, managed printing pressure, transfer pressure, dampening water, ink roller and blanket materials, ink, printing plates, etc. Is required, and the runnability and quality required for offset printing newsprint are becoming increasingly complex and diversified.

On the other hand, due to the cost reduction and environmental awareness of paper manufacturers, the content of DIP is gradually increasing even in newsprint for offset printing, and it is not uncommon to exceed 70%. However, as the blending ratio of DIP increases, various problems may occur in the running property during offset printing, but the problem of paper breakage is one of the most important problems. This is the most important issue in many printing stations, because once a paper break occurs during running, printing efficiency decreases due to an increase in the paper threading work thereafter, an increase in waste paper, and a blanket breakage.

Causes of paper breaks include a decrease in strength, a decrease in size, scratches, and an increase in holes. A high DIP content causes a decrease in strength due to deterioration of pulp fibers and scratches and holes due to adhesive foreign matter. Since this causes an increase in the number of sheets, it is easy to lead to an increase in paper breaks. As a method of preventing paper breakage, means such as blending of high-strength pulp, addition of paper strengthening agent, and external addition of oxidized starch are used. I couldn't hold back. In addition, it was difficult to evaluate the paper break because the physical property value that correlates with the occurrence of paper break was not found.

[0005]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide an offset printing newsprint excellent in running property and printing workability without causing a paper break during offset printing. Especially.

[0006]

Means for Solving the Problems As a result of diligent examination of the factors causing the paper breakage during offset printing, the present inventors have found that
We have found that the occurrence of paper breaks is strongly influenced by the presence of scratches and holes in the paper, and that there is a correlation between the occurrence of paper breaks and the fracture toughness of the paper. . Further, as a result of intensive studies to obtain a newsprint paper for offset printing with less breakage during offset printing, it was found that the problem can be solved by setting the anisotropy index of fracture toughness to 0.28 or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, the strength of paper is often discussed by the maximum load when breaking a test piece by applying tension, that is, the tensile strength. When discussing paper breaks in 2., the easiness of paper breaks was often evaluated based on the strength of the tensile strength. However, the tension in the newspaper offset rotary press is about 0.3 to 0.8 kN per A roll width (1626 mm), that is, 0.18 to 0.49 kN / m, whereas the tensile strength of general offset printing newsprint is , 2.0-3.0kN / m in machine direction, 0.6-1.0k in cross machine direction
It is about N / m. Therefore, if the newsprint paper for offset printing has no scratches or holes, it is unlikely that paper breakage will occur in the newspaper offset press. In other words, the present inventors believe that the newsprint for offset printing will be broken in the newsprint rotary press only when the paper has scratches or holes.

Fracture toughness is known as one of the three basic mechanical properties of an object, along with tensile strength and elastic modulus (Young's modulus), and is a physical property value that represents resistance to fracture, such as scratches and holes. It is an index to evaluate the ability to withstand the progress of. Fracture toughness is the work (energy) required for a crack to progress when a tension is applied to the object when the object has cracks such as scratches and holes.
Is defined by On the other hand, the tensile strength is the load at the time of breaking when the object is broken by writing tension regardless of the presence or absence of cracks or the like. In other words, tensile strength is the load required to break, and fracture toughness is the resistance of an object to break from a crack. So far, research on the fracture toughness of paper has been done in various forms, and research has also been done to investigate the relationship with paper breakage in the rotary press, but most of them have the fracture toughness in the paper machine direction. It was measured. However, the present inventors focused on the distribution of the fracture toughness in all directions of the paper, and the anisotropy index of the fracture toughness obtained by measuring the fracture toughness in all the directions was measured during running in the newspaper offset press. It was found to be highly correlated with the paper breaks of.

The reason why the fracture toughness in all directions correlates with the paper break is that the traveling path of the newspaper offset rotary press is complicated, and the tension is not always applied in the traveling direction, that is, the machine direction of the paper. Tension is applied diagonally in a bay window device composed of a turn bar that is a round bar for changing the traveling direction of the turn bar and a bay wind roller that is a roller for changing the stacking order of the turn bar and running paper and reversing the front and back. I think that is because there is. That is, the inventors of the present invention, the occurrence of paper breaks during offset printing is caused by a particular decrease in the strength of the part due to scratches or holes in the paper, and the ease of progress of cracks from this part. I'm guessing that. Therefore, when evaluating the breakage of newsprint for offset printing, it is necessary to measure the fracture toughness in all directions of the paper,
Furthermore, it is important that the fracture toughness in all directions is above a certain value on average, and we found that paper breaks on newspaper offset presses often occur when the fracture toughness is high or low only in one direction. .

From the above viewpoint, the newsprint for offset printing with less breakage on the newsprint rotary press according to the present invention has an anisotropy index of fracture toughness of 0.28.
It was achieved by: Further, it is desirable that the minimum value of the fracture toughness is 0.2 J / m or more. In addition, when considering paper breaks after printing, it is necessary to consider the effects of dampening water and ink adhesion, so the drip water absorption (based on Japan TAPPI No.33, measured with a dripping water volume of 1 μl) is 1 second or longer. Is preferred.

The fracture toughness in the present invention is
In accordance with SCAN-test standard P77: 95, Lorentzen &
It was measured using a Tensile Tester with Fracture Toughness manufactured by Wettre. Anisotropy index η measures the fracture toughness of offset printing newsprint in multiple directions,
The calculation was performed using the following Equation 1 which is a part of the Fourier series. This equation is known as a periodic function that can calculate the anisotropy index and the anisotropy angle of the fracture toughness from the acquired data by approximation.

F (θ) = C [1 + ηcos2 (θ−α)] (Equation 1) where F (θ) is the fracture toughness at the angle θ with respect to the paper making direction, and C is the average value of the fracture toughness, α Is the anisotropy angle of fracture toughness, and η is the anisotropy index of fracture toughness. In order to obtain the anisotropy index, considering the accuracy, it is desirable to measure the fracture toughness in more measurement directions, but at least 8 directions (2
2.5 degree spacing direction) is required. The anisotropy index indicates the state of the fracture toughness distribution, and the closer it is to 0, the closer the fracture toughness distribution is to a perfect circle.

As described above, the anisotropy index of the fracture toughness of the offset printing newsprint must be 0.28 or less in order to reduce paper breakage on the newspaper offset press. Fracture toughness anisotropy index
If it is 0.28 or less, the fracture toughness distribution is close to a perfect circle, and the fracture resistance is high in all directions. On the other hand, the fracture toughness anisotropy index is 0.
When it exceeds 28, the distribution of fracture toughness becomes a discontinuous shape far from a perfect circle, and the fracture toughness in a specific direction becomes low, resulting in low resistance to fracture.

The inventors of the present invention determined the fracture toughness of paper by complicatedly relating conditions such as pulp blending, wet press linear pressure, fiber orientation, etc., and the anisotropy thereof was particularly influenced by the fiber orientation. Found to be strong. Therefore, adjustment of the jet wire ratio (J / W ratio), slice nip opening degree, dehydration profile in the wire part, etc. is effective for controlling the anisotropy of fracture toughness, but especially adjustment of the J / W ratio. Is valid.

The paper machine used in the present invention is preferably a gap former, a hybrid former, an on-top former having a double-sided dehydration mechanism, but is not limited to this.

The pulp material for the newsprint for offset printing produced by the present invention is not particularly limited, and ground pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTM).
P), deinked pulp (DIP), softwood kraft pulp (NKP) and the like, which are generally used as a raw material for papermaking. Further, papermaking may be carried out by either acid papermaking or neutral papermaking. The physical properties of the obtained newsprint paper for offset printing may be at least a level having an opacity, a friction coefficient, and the like of ordinary newsprint paper for offset printing.

[0017]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

<Measurement of Fracture Toughness> In the present invention, the fracture toughness is the SCAN-test standard.
Lorentzen & Wettre Tensile T in accordance with P77: 95
It measured using ester with Fracture Toughness. 8 directions of newsprint for offset printing (22.
The fracture toughness (at intervals of 5 degrees) was measured, and the anisotropy index η was calculated using the following equation (1), which is a part of the Fourier series. This equation is known as a periodic function that can calculate the anisotropy index and the anisotropy angle from the acquired data by approximation. F (θ) = C [1 + ηcos2 (θ-α)] (Equation 1) F (θ) is the fracture toughness at an angle θ with respect to the paper making direction, C is the average value of the fracture toughness, and α is the anisotropic fracture toughness. The sex angle, η, is an anisotropy index of fracture toughness.

<Measurement of water absorption by drip> Japan TAPPI No.33
In accordance with the above, the drip water absorption was measured at a dropping water amount of 1 μl.

<Evaluation Method of Paper Breakage> Using a Toshiba offset rotary press, four-color printing was performed at a printing speed of 700 rpm, and the number of paper breaks during 180,000 copies was measured. Fountain solution film thickness is 0.7 μm
And

Example 1 As raw material pulp for papermaking, newspaper deinking pulp (freeness 150 ml), thermomechanical pulp (TMP, freeness 80 ml), softwood kraft pulp (NKP, freeness 500 ml) 65 A white paper was prepared by adding 1.0% by weight of white carbon as a filler to a pulp slurry mixed in a mixing ratio of 20:15 as a filler. Using this stock material, a gap former type paper machine was used, the paper making speed was 1000 m / min, the J / W ratio was 0.98 and the basis weight was 43
A g / m ² newsprint base paper is made into paper, and then oxidized starch (trade name: SK-2 is used with an on-machine size press coater.
0, Nippon Corn Starch Co., Ltd. coating amount is 0.5 g / m ^{2 on} both felt surface and wire surface, and external additive sizing agent (trade name: Polymarlon NS25, Arakawa Chemical Industry Co., Ltd.) coating amount The felt surface and the wire surface were coated so as to be 0.05 g / m ² to obtain a newsprint for offset printing. Fracture toughness and its anisotropy and drip water absorption of the newsprint for offset printing were measured by the methods described above, and the paper breakage during offset printing on an offset rotary press was evaluated. The results are shown in Table 1. It was

[Example 2] The coating amount of the externally added sizing agent was 0.1.
A newsprint for offset printing was manufactured in the same manner as in Example 1 except that g / m ² was used. Fracture toughness and its anisotropy and drip water absorption of the obtained newspaper for offset printing were measured, and paper breakage during offset printing was evaluated. The results are shown in Table 1.

[Example 3] The coating amount of the externally added sizing agent was 0.2.
A newsprint for offset printing was manufactured in the same manner as in Example 1 except that g / m ² was used. Fracture toughness and its anisotropy and drip water absorption of the obtained newspaper for offset printing were measured, and paper breakage during offset printing was evaluated. The results are shown in Table 1.

Comparative Example 1 A newsprint for offset printing was manufactured in the same manner as in Example 1 except that the J / W ratio was 1.04. Fracture toughness and its anisotropy and drip water absorption of the obtained newspaper for offset printing were measured, and paper breakage during offset printing was evaluated. The results are shown in Table 1.

Comparative Example 2 A newsprint for offset printing was manufactured in the same manner as in Example 2 except that the J / W ratio was 1.04. Fracture toughness and its anisotropy and drip water absorption of the obtained newspaper for offset printing were measured, and paper breakage during offset printing was evaluated. The results are shown in Table 1.

Comparative Example 3 A newsprint for offset printing was manufactured in the same manner as in Example 3 except that the J / W ratio was 1.04. Fracture toughness and its anisotropy and drip water absorption of the obtained newspaper for offset printing were measured, and paper breakage during offset printing was evaluated. The results are shown in Table 1.

[0027]

[Table 1] As shown in Table 1, in the newsprint for offset printing having an anisotropy index of fracture toughness of 0.28 or less, the number of paper breaks was significantly reduced. Further, the higher the drip water absorption, the smaller the number of paper breaks.

[Example 4] As the raw material pulp for papermaking, newspaper deinking pulp (freeness 150 ml), TMP (freeness 80 m)
l) and NKP (freezing degree 500 ml) were mixed at a ratio of 30: 65: 5 to a pulp slurry, and calcium carbonate was added as a filler to 0.8% by weight of the dry weight of the pulp to prepare a paper stock. . Using this stock material, a gap former type paper machine was used to make a newsprint base paper with a paper making speed of 800 m / min, a J / W ratio of 1.00, and a basis weight of 41 g / m ² , and a size press for on-machine machines. Oxidized starch (trade name: SK-20, manufactured by Nippon Corn Starch Co., Ltd.) was coated with a coater so that the coating amount was 0.5 g / m ^{2 on} both the felt surface and the wire surface, and an external sizing agent (trade name) : Polymaron NS
No. 25, manufactured by Arakawa Chemical Industry Co., Ltd. was coated on both the felt side and the wire side so as to be 0.1 g / m ² to produce a newsprint for offset printing. Fracture toughness and its anisotropy were measured for the obtained newsprint paper for offset printing, and the paper breakage during offset printing was evaluated. The results are shown in Table 2.

[Embodiment 5] Newspaper deinking pulp (freeness 150 ml), TMP (freeness 80 ml),
Except that the NKP (freeness 500 ml) was set to 30:60:10,
A newsprint for offset printing was manufactured in the same manner as in Example 2. About the obtained newsprint paper for offset printing,
Fracture toughness and its anisotropy were measured, and paper breaks during offset printing were evaluated. The results are shown in Table 2.

[Example 6] A deinked pulp for newspaper (freeness 150 ml), TMP (freeness 80 ml),
Except that the NKP (freeness 500 ml) was set to 30:55:15,
A newsprint for offset printing was manufactured in the same manner as in Example 4. Fracture toughness and its anisotropy were measured for the obtained newsprint paper for offset printing, and the paper breakage during offset printing was evaluated. The results are shown in Table 2.

Comparative Example 4 A newsprint for offset printing was manufactured in the same manner as in Example 4 except that the J / W ratio was 1.05. Fracture toughness and its anisotropy were measured for the obtained newsprint paper for offset printing, and the paper breakage during offset printing was evaluated. The results are shown in Table 2.

Comparative Example 5 A newsprint for offset printing was manufactured in the same manner as in Example 5 except that the J / W ratio was 1.05. Fracture toughness and its anisotropy were measured for the obtained newsprint paper for offset printing, and the paper breakage during offset printing was evaluated. The results are shown in Table 2.

Comparative Example 6 A newsprint for offset printing was manufactured in the same manner as in Example 6 except that the J / W ratio was 1.05. Fracture toughness and the anisotropy of the obtained newsprint newspaper for offset printing were measured, and the paper break during offset printing was evaluated. The results are shown in Table 2.

[0034]

[Table 2] As shown in Table 2, in the newsprint for offset printing having an anisotropy index of fracture toughness of 0.28 or less, the number of paper breaks was remarkably reduced. There was no particular correlation between the compounding ratios of NKP. In addition, the lower the minimum fracture toughness, the more paper breaks occurred.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazushi Nagao             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Technical Research Institute Co., Ltd. (72) Inventor Hideki Fujiwara             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Technical Research Institute Co., Ltd. F-term (reference) 4L055 AA02 AC03 AC06 AC09 AG48                       AH13 AJ02 BD03 BE08 EA07                       EA09 EA10 FA11 FA23 FA30                       GA16

Claims (4)

[Claims] 1. An anisotropy index of fracture toughness is 0.
Newsprint for offset printing characterized by being 28 or less 2. The minimum value of fracture toughness is 0.2J.
/ M or more, The newsprint for offset printing of Claim 1 characterized by the above-mentioned. 3. The newsprint for offset printing according to claim 1, wherein the drip water absorption (according to Japan TAPPI No. 33, measured with a dropping water amount of 1 μl) is 1 second or more. 4. A method of predicting the degree of breakage of newsprint for offset printing by the anisotropy index of fracture toughness.