JP2005042265A - Newsprint paper for offset printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a newsprint paper for offset printing particularly having excellent surface strength and opacity. <P>SOLUTION: The newsprint paper is produced by separating waste paper pulp originated from waste magazine into short fiber fraction and long fiber fraction by mechanical classification and mixing the long fiber fraction to newsprint paper pulp containing waste newspaper without beating the fraction and making the paper from the mixture. The newsprint paper has a surface smoothness of 20-75 sec in conformity to JIS P 8119, and the newsprint paper pulp obtained by dispersing the newsprint paper with a standard disintegrator in conformity to JIS P 8209 has the ratio of the residue on 42 mesh sieve of <50% by a pulp sieving test in conformity to JIS P 8207. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to newsprint for offset printing, and more particularly to newsprint for offset printing with a high recycled paper pulp mixing ratio excellent in color printing quality and printing workability.

  In recent years, newspaper printing has been rapidly changing from the conventional letterpress printing method to the offset printing method, and as a result, more excellent printing workability and printing suitability are required for newspaper paper as a printing medium. ing.

  Newspaper paper, on the other hand, uses paper made mainly of mechanical pulp and wastepaper pulp, and the proportion of wastepaper pulp is increasing from the viewpoint of resource conservation, and there is a demand for further reduction in the basis weight of paper. Yes. In addition, since offset printing uses fountain solution, water resistance of the paper surface is also required.

  Further, with the reduction in weight of newsprint paper, there is a demand for opacity after printing on the paper. In order to increase the opacity of paper, inorganic pigments such as white carbon, titanium oxide, and talc have been used as fillers, but these fillers tend to ooze out of the paper layer easily with dampening water. There is. Furthermore, DIP (used paper deinked pulp), which is regarded as important in terms of the environment, has a high rate of blending, and DIP has less opacity than MP (mechanical pulp) such as GP, RGP, and TMP. There was a drawback that it was very difficult to improve the transparency and re-establish a high-rate blending of DIP.

  Further, conventionally, newsprint paper for offset printing has been conventionally coated with a surface treatment agent mainly composed of starch, polyacrylamide or the like on the surface thereof. Although this external additive is effective in suppressing the generation of paper dust, it has poor water resistance, and it is difficult to cause blanket piling and nappari trouble.

In order to solve such drawbacks, Japanese Patent Application Laid-Open No. 11-247095 (Patent Document 1) describes the application of a surface treatment agent mainly composed of titanium dioxide and an adhesive on both sides of a base paper containing waste paper pulp. An offset printing newsprint provided with a layer (90 ° or more contact surface with water) is disclosed. However, although this newsprint has the advantage of being able to improve opacity, the cost is high, and the high-speed newsprint press has problems such as falling paper dust and increasing the weight per unit. .
Japanese Patent Laid-Open No. 11-247095

  An object of the present invention is to provide newsprint for offset printing having excellent printing workability and excellent color printing quality despite the high mixing ratio of recycled paper recycled pulp.

  The present inventors have conducted research and studies for obtaining newsprint paper for offset printing that satisfies the above-described characteristics required for newspaper printing even when the ratio of recycled paper pulp is increased. As a result, the newsprint paper pulp is classified into short and long fibers by mechanical classification, and the long fibers are not beaten and mixed with the newsprint pulp to produce the desired offset. I found out that I could get newsprint for printing.

  The present invention has been made based on this. According to the present invention, the following (1), (2) and (3) are provided.

(1) Waste paper pulp derived from used magazine paper is separated into short fibers and long fibers by mechanical classification, and the long fibers are mixed with newspaper raw material pulp, including used newspaper, without being beaten, and paper-made. In the newsprint we produce,
The newsprint paper has a paper surface smoothness of 20 to 75 seconds based on JIS P 8119, and the newsprint paper pulp obtained by dispersing the newsprint paper with a standard disintegrator based on JIS P 8209 is JIS P 8207. Newsprint paper for offset printing, characterized in that, in the pulp sieving test based on the ratio, the remaining 42 mesh is less than 50%.

(2) The newspaper for offset printing according to claim 1, wherein the newsprint raw material pulp dispersed by the standard disaggregator has a ratio of passing 150 mesh less than 7% in the pulp sieving test based on JIS P 8207. Paper.

(3) The newsprint raw material pulp obtained by dispersing the above newsprint paper with a standard disintegrator based on JIS P 8209 has a mechanical pulp ratio of phloroglucin hydrochloride of 50% or more in the projection method based on Tappi T232. 3. Newsprint paper for offset printing according to claim 1 or 2.

(4) Newsprint paper for offset printing according to any one of claims 1 to 3, wherein the newsprint paper is processed with a soft calender of 2 stacks or less comprising a metal roll and an elastic roll.

(5) Newsprint paper for offset printing according to claim 4, wherein the nip pressure of the soft calendar is 5 to 150 kg / cm and the surface temperature of the metal roll is 80 to 150 ° C.

  As is apparent from Table 1, the newsprint for offset printing of the present invention is effective in color printing because both the surface strength and the opacity are good and there is no ink absorption unevenness.

Hereinafter, the present invention will be described in more detail.
Examples of the raw material pulp for the newsprint for offset according to the present invention include waste paper pulp, chemical pulp such as LBKP and NBKP, mechanical pulp such as GP and TMP, non-wood fiber such as kenaf and bagasse, and synthetic fiber. Examples of the raw material for waste paper pulp include upper white, ruled white, card, special white, medium white, imitation, Kent, white art, newspaper, magazine and the like. Two or more of these pulps may be used.

  In the present invention, it is possible to obtain suitable printability, surface strength improvement effect, and opacity improvement effect even when 100% recycled paper pulp is used as a raw material. Therefore, it is desirable to actively use recycled paper pulp that can contribute to effective utilization of resources and environmental protection.

  In addition, if the above-mentioned waste paper pulp is used, it is particularly preferable to use waste paper pulp derived from waste magazine paper. Magazine waste paper is difficult to reuse as waste paper pulp due to the presence of foreign matter such as back glue, hot melt and vinyl bound in magazines, and most of the magazine waste paper is currently incinerated.

  The present inventors can remove most foreign substances from old magazine paper by deinking with a known deinking method and then classifying long fibers and short fibers with a known classifier. I find out what I can do.

  In addition, for the prevention of the deterioration of surface properties and texture unevenness due to containing waste paper pulp, the waste paper pulp is classified to remove short fibers, and by using waste paper pulp which is only long fibers, A decrease in paper strength can be prevented. The short fibers to be removed can be suitably used for printing paper that does not require paper strength. The average fiber length for the long fibers can be appropriately changed in consideration of the paper making method and the characteristics of the product after paper making. Preferably, classification is performed such that the freeness (CSF) of the pulp slurry of waste paper pulp is 280 ml to 350 ml. Further, the difference from the remaining fiber length is desirably at least 10%.

  On the other hand, the classification of used paper pulp may be performed using a known mechanical classifier and classification technology. For example, it can be classified by hydraulic classification with a classifier such as Johnson Frankionator, Atomizing Hall, X-Cron, etc., and it can also be classified by mechanical sieving with multi-fractor, CH-F screen, fiber craft, etc. be able to. Among the classifiers, “Multi-Fractor” (manufactured by Voith) and “CH-F screen” (manufactured by Aikawa Tekko) are particularly suitable.

  Newspaper paper pulp that has been dispersed after being dispersed by a standard disintegrator based on JIS P 8209 is adjusted and made into paper in a pulp sieving test based on JIS P 8207 so that the ratio of the remaining 42 mesh is less than 50%. Yes. Deviating from this range causes problems such as a decrease in paper density, a decrease in opacity, and a decrease in whiteness. At the same time, as shown in the examples described later, the newsprint raw material pulp dispersed by the standard disaggregator has a ratio of passing through 150 mesh in a pulp sieving test based on JIS P 8207 of less than 7% of the whole. In the projection method based on Tappi T232, it is desirable that the proportion of mechanical pulp by phloroglucin hydrochloride is 50% or more.

  The newsprint according to the present invention first comprises a filler (for example, inorganic pigments such as kaolin, calcium carbonate, talc and titanium dioxide; urea formaldehyde resin, etc.), sizing agent (paper strength enhancer, yield improver) in the prepared raw material pulp. , Reinforced rosin sizing agent, emulsion sizing agent, etc.), water resistance, UV protection agent and the like, after adding generally known papermaking chemicals, it can be obtained by papermaking by a known papermaking process. In addition, a coating layer can be formed on the obtained paper as a base paper (paper support). Here, when the sizing agent is added to the coating layer, the sizing agent may or may not be added to the base paper pulp. When making the raw material pulp, it may be carried out in the acidic region or in the neutral to alkaline region, but preferably in the neutral region of pH 6-8.

  In this coating solution, auxiliary agents such as a surface sizing agent, an antifoaming agent, and a thickening agent that are usually used in papermaking decomposition may be appropriately used in combination. The addition of a surface sizing agent is particularly useful because it can increase the contact angle of the paper surface.

The dry coating amount of the coating layer is 0.3 to 3 g / m ² , preferably 0.5 to ² g / m ² . If it is less than 0.3 g / m ² , sufficient surface strength cannot be obtained, and if it exceeds 3 g / m ² , the adhesiveness in the nepari wet state becomes high, sticking to a blanket, cutting paper, etc. May cause trouble.

  Although it does not specifically limit as a coating device, For example, 2 roll size press, a blade metalling size press, a rod metalling size press, a gate roll coater, a blade coater bar coater, a rod blade coater, an air knife coater etc. are suitably used. used. The coating layer can be formed not only on one side of the base paper but also on both sides.

  The newsprint for offset printing according to the present invention is finished by smoothing the surface. A calender is usually used for smoothing at that time, but a soft calender having a large smoothing effect without increasing the pressurizing condition is preferably used.

  Specifically, a soft calender of 2 stacks or less from a metal roll and an elastic roll, preferably a nip pressure of 5 to 150 kg / cm, a surface temperature of the metal roll of 80 to 150 ° C., and based on JIS P 8119 The surface smoothness of the paper is 20 to 75 seconds.

  If the surface smoothness is less than 20 seconds, the smoothness is low and the paper surface has large irregularities, causing a problem that the ink does not transfer to the concave portions after printing. On the other hand, if the surface smoothness exceeds 75 seconds, the paper will be crushed too much, leading to a decrease in stiffness, waist, opacity, etc., which is not preferable.

  In the case of a hard nip calender, the metal roll hits both sides of the paper, so only the thick part of the thick paper is crushed and the density increases. In the case of the soft calender, an elastic roll (resin roll) is used on one side of the paper. Hit and hit one side with a metal roll. On the surface where the elastic roll hits, the elastic roll also hits the thick part and the peripheral part of the paper, so that the pressure is dispersed, and the density of the thick part is less likely to be higher than the metal roll, and density unevenness can be reduced. At this time, if the hardness shore D of the elastic roll is too low, the smoothness does not increase. On the other hand, if the hardness shore D of the elastic roll is too high, the smoothness increases as in the case of the hard nip calender, but the density unevenness increases and the effect of the soft calender cannot be obtained.

  Next, the present invention will be specifically described with reference to examples. Of course, the present invention is not limited to them. In addition, the part and% here are the mass part and the mass%, respectively, unless otherwise specified.

(Example 1)
Beating or kneading pulp slurry (raw pulp) consisting of 60 parts by weight of used paper pulp and 40 parts by weight of TMP pulp using a kneader such as various known refiners, PFI mills, or dispersers, mica processors, kneaders, etc. To do. Next, the used paper pulp after beating or kneading is diluted with a large amount of water and classified by a known method. Classification conditions are not particularly limited, but a large amount of water is preferably used, and is preferably 65 times or more (pulp concentration of 1.5% or less) with respect to waste paper pulp (air-dried).

Papermaking is performed using the obtained raw material pulp, and a soft calendering process of 2 stacks or less is performed from a metal roll and an elastic roll, and the basis weight of 44 g / sq. to obtain a newsprint of m ^2.

  The newsprint was dispersed with a standard disintegrator based on JIS P 8209, and then sieved with a pulp sieving tester based on JIS P 8207, and the sieving ratio was measured. Furthermore, the blending ratio of mechanical pulp was measured by the projection method based on Tappi T232 using the dispersed raw material.

  Measurements were also made on the paper quality of the newsprint based on this example.

These measurement results are shown in Table 1.
In Examples 2 and 3, and Comparative Examples 1 and 2, raw pulps obtained by changing the time and concentration of various refiners, beating machines such as PFI mills, or kneading apparatuses such as dispersers, mica processors, and kneaders, respectively. It is the result measured using.

  The quality evaluation of the newspapers for offset printing of Examples and Comparative Examples thus obtained was performed as follows, and the results obtained are summarized in Table 1.

(Surface strength): Using a discoloration tester (Meiji Seisakusho: RI-1 type) described in JIS K 5701, the surface of the newspaper for offset printing was visually observed under the conditions of one-time printing of ink tack 18. Was judged. As for the symbol in the table, ◎ is not removed at all, ○ is slightly removed, and x is clearly removed.

(Opacity): Measured based on JIS P 8138. The symbols in the table are 90% or more, ○ is 88% to less than 90%, and x is less than 88%.
(Ink absorption unevenness): Using an offset printing press (Komori SYSTEM C-20), four color printing was performed, and the ink density unevenness of the indigo / red heavy color portion was visually determined.
A: The ink density unevenness is not seen at all, and the image is uniform and clear.
○: Ink density unevenness is hardly seen, and the image is uniform.
Δ: Ink density unevenness is recognized and the image is slightly non-uniform.
X: Ink density unevenness is obvious and the image is uneven.

(Blanket paper dust piling): Using an offset printing machine (Komori SYSTEM C-20), after performing 5000 color four-color printing, the degree of paper dust accumulation in the blanket non-image area was visually determined.
○: Generation of paper dust is not recognized.
Δ: Some generation of paper dust is observed.
X: A lot of paper dust is accumulated on the blanket.

(Neppery (Blanket Adhesive)): Cut two newspaper printing paper samples into appropriate sizes, immerse them in water for 10 seconds, quickly contact them, and pass the paper through the calendar at a linear pressure of 100 kg / cm After drying for 24 hours at room temperature, the peel strength of the two sheets of paper was measured using a tensile tester. The larger the value, the stronger the tackiness.

Claims (5)

Wastepaper pulp derived from wastepaper used in magazines is separated into short fibers and long fibers by mechanical classification, and the long fibers are mixed into newspaper stock pulp containing used newspapers without being beaten and made into paper for production. In paper
The newsprint paper has a paper surface smoothness of 20 to 75 seconds based on JIS P 8119, and the newsprint paper pulp obtained by dispersing the newsprint paper with a standard disintegrator based on JIS P 8209 is JIS P 8207. Newsprint paper for offset printing, characterized in that, in the pulp sieving test based on the ratio, the remaining 42 mesh is less than 50%. 2. The newsprint for offset printing according to claim 1, wherein the newsprint raw material pulp dispersed by the standard disaggregator has a ratio of passing through a 150 mesh in a pulp sieving test based on JIS P 8207 that is less than 7% of the total. The newsprint raw material pulp obtained by dispersing the newsprint with a standard disaggregator based on JIS P 8209 has a mechanical pulp ratio of phloroglucin hydrochloride of 50% or more in a projection method based on Tappi T232. 3. Newsprint paper for offset printing according to claim 1 or 2. The newsprint paper for offset printing according to any one of claims 1 to 3, wherein the newsprint paper is processed with a soft calender having two or less stacks comprising a metal roll and an elastic roll. The newsprint for offset printing according to claim 4, wherein the nip pressure of the soft calender is 5 to 150 kg / cm and the surface temperature of the metal roll is 80 to 150 ° C.