JP2845285B2 - Newsprint paper for offset printing consisting of multiple layers - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to newsprint, particularly newsprint for offset printing having excellent surface strength.

[Prior Art] Offset printing is increasingly used in newspaper presses in place of conventional letterpress printing, and in recent years color pressurization and the addition or remodeling of web offset presses due to the establishment of a newspaper factory as a distributed factory have become almost offset presses.

In offset printing, the ink tackiness is higher than in letterpress printing due to the need to impart water resistance to the ink, and newspaper paper for offset printing requires a correspondingly high surface strength.If the surface strength is low, paper powder accumulates on blankets and guide rolls However, this may cause deterioration of print quality or a problem in running property.

Generally, newsprint contains mechanical pulp such as groundwood pulp (hereinafter abbreviated as GP), thermomechanical pulp (hereinafter abbreviated as TMP), chemical pulp such as kraft pulp (hereinafter abbreviated as CP) and waste paper pulp (hereinafter abbreviated as DIP). Have been. The properties of these pulp have advantages and disadvantages, and GP has excellent opacity but low strength. Although TMP has a somewhat excellent opacity, depending on the chip used, the radiation-sensitive cells tend to turn into paper powder and have poor surface strength. CP is strong, but
Opacity decreases. DIP has high density and low bulk,
Although suitable for increasing the number of stations (extending the winding length), opacity and rigidity are reduced. As described above, these pulp have reciprocal properties, and the quality of the conventional newsprint is controlled by uniformly mixing the pulp and changing the pulp composition.

Under such circumstances, measures have been taken to increase the surface strength of newsprint, such as increasing the distribution of CP with strong pulp strength, or avoiding excessively crushing the paper with a calendar or breaker stack to avoid a decrease in strength. . However, if the paper is not crushed by a calender or the like, the winding diameter increases, so that the limitation of the winding diameter due to the increase in the number of stations is exceeded, and the problem is that the smoothness of the paper is reduced and the printing quality is reduced. . The surface strength can also be increased by increasing the distribution of chemical pulp, but there are problems such as a decrease in opacity, an increase in cost, and resource saving. Furthermore, assuming that the chemical pulp content is increased, it is necessary to increase the mixing ratio of other virgin pulp in balance due to the reciprocity of the pulp described above. The rate decreases.

As a means of improving the surface strength without changing the pulp composition, a method of applying starch or the like to the paper surface by a size press has been proposed. However, such a paper is difficult to absorb water and an offset printing machine without a dryer. In this case, there are many adverse effects such as a loss of the balance between the ink and the dampening solution, and the printing of the ink is slow because the ink dries slowly.

In any case, a person skilled in the art has not found any satisfactory means for obtaining the surface strength required for newsprint for offset printing.

[Problems to be Solved by the Invention] In view of the above-mentioned situation, the present invention is indispensable because of the strength required for newsprint that does not break during high-speed printing and the basis weight is lighter than general printing paper. It is an object of the present invention to provide newsprint paper for offset printing which has a high surface strength while satisfying the quality such as opacity so that printed characters cannot be seen through from the back, despite its thinness.

[Means for Solving the Problems] The above-mentioned problem is solved by a plurality of layers in which an outer layer mainly composed of chemical pulp is formed on both sides of an inner layer including waste pulp and mechanical pulp in a wire part of a paper machine as newsprint for offset printing. A solution to this problem is to provide a newsprint for offset printing, and an offset printing newsprint consisting of a plurality of layers in the wire part of a paper machine, in which an inner layer and an outer layer having a higher proportion of fine fibers than the inner layer are formed on both sides of the inner layer. Was done.

That is, the first invention of the present invention arranges DIP, GP, TMP with low surface strength in the inner layer as newsprint for offset printing,
The structure is such that chemical pulp having strong surface strength is arranged on the outer layer on both sides thereof.

KP is a typical chemical pulp, but other chemical pulp may be used in the present invention.

The proportion of each pulp used is the same as that of conventional newsprint, and is generally 15% to 30% for CP, 10 to 25% for GP, 15 to 35% for TMP, DIP2
0 to 55%. Conventional newsprints are formed by uniformly mixing these pulp.The most preferable form in the present invention is that a predetermined ratio of waste pulp such as DIP, GP, TMP and the like to mechanical pulp is uniform. Into a raw material for the inner layer,
Chemical pulp such as KP is used as the raw material of the outer layer and formed into three layers by the wire part of the paper machine. However, the present invention is not limited to this form, and may be formed by mixing a small amount of chemical pulp in the inner layer and a small amount of waste paper pulp or mechanical pulp in the outer layer in consideration of the properties and required quality of the pulp.

The second invention for achieving the object of the present invention is made by paying attention to the fact that the pulp properties are different depending on the length of the fiber length of the pulp. Is based on the finding that the surface strength is superior to that of a small amount of paper. The CP has the highest effect on the surface strength of the fine fibers of each pulp, but the paper layer formed by the fine fibers of the mechanical pulp also has a stronger surface strength than the paper layer of the whole pulp. Therefore, the type and composition of the pulp used as the inner layer are not particularly limited, and may be those used for composing conventional newsprint. In the most preferred form of the present invention, the pulp to be blended is sieved in advance, and a portion having a large amount of fine fibers is used as an outer layer paper material, and a small portion is used as an inner layer paper material. By forming the outer layer higher than the inner layer, the surface strength can be improved without changing the pulp composition.

As equipment for forming the multilayer paper of the object of the present invention by the wire part of a paper machine, a multi-layer head box has been developed by BELOIT, VALMET-KMW, and the like, and this multi-layer head box is now used as a simple unit. The above-described multilayer paper can be formed by replacing the head box with a mechanism for discharging one raw material layer.

[Operation] In the present invention, since CP having high surface strength is used as the outer layer and GP and TMP having excellent opacity are arranged in the inner layer, offset newsprint having excellent printing strength without impairing the strength and opacity can be obtained. By forming an outer layer having many fine fibers having a high surface strength on both sides of the inner layer, newsprint paper for offset printing having excellent printing strength can be obtained.

[Examples] Representative examples of the present invention will be described below, but the present invention is not limited to the scope of the following examples.

Example 1 Chemical pulp for outer layer, raw material for inner layer consisting of premixed GP, TMP, DIP, raw material for outer layer, and chemical pulp for outer layer again sequentially supplied by ORIENTED SHEET FORMER manufactured by Kumagaya Riki Kogyo Co., Ltd. at a wire speed of 750 m / min. Forming a paper layer, dehydrating,
By drying, a three-layer paper comprising different raw material layers in the thickness direction was produced, and the surface strength by printing and other paper quality were evaluated.

Printing is performed using a Prüfbau printability tester, 50 x 200m
Toyo Ink Web Z on blanket plate with m plate surface
Immediately after supplying 200 == ET LF black ink and supplying 10 == 10% isopropanol as dampening solution, printing pressure 600N, speed 2.
Printing was performed in a room conditioned at 22 mC and 55% at 0 m / s.
The surface strength was measured by sensory evaluation of the state of the dampness of the fibers in the wet printed portion, and the other paper quality was measured by JIS standards. The surface strength is graded as 1 when no marks are seen, and as 5 when the surface is almost uniformly stained,
Those with an evaluation of 3 or more are not practical and are outside the scope of the present invention.

Table 1 shows the pulp composition of the inner layer and the outer layer of the prepared sample and the basis weight ratio thereof. Freeness in the table is CANADIAN S
TANDARD FREENESS.

Comparative Example 1 A mixed raw material having the same pulp mixing ratio as in Example 1 was prepared, and as in Example 1, ORIENTED SHEET FORMER manufactured by Kumagaya Riki Kogyo Co., Ltd.
The mixed raw material was supplied at a speed of 750 m / min, dewatered, and dried to produce a single-layer paper, and the surface strength and other paper quality by the same printing as in Example 1 were evaluated.

The results are shown in Table 1. The papers produced in this example and the comparative example have anisotropy in fiber orientation as in the actual paper machine, and the quality such as tearing, pulling, and stiffness depends on the papermaking direction. (Mschine Direction MD) and its orthogonal direction (Cross
Since there is anisotropy in s-machine Direction CD), these qualities were evaluated by the square root of MD × CD. Example 1, which is a three-layered paper of the present invention, has the same strength, opacity, and equal or higher whiteness and rigidity as Comparative Example 1, which is considered to have the physical properties of standard newsprint, and is printed. The surface strength was excellent.

Example 2 The inner layer pulp was DIP, and the outer layer pulp was NBKP and LBKP as shown in Table 2 in the same manner as in Example 1.
, And the same test as in Example 1 was performed. Table 2 shows the materials of the outer layer and the inner layer and the basis weight ratio. All papers were prepared total basis weight 60 g / m ² as a target.

Comparative Example 2 The inner layer pulp was DIP, and the outer layer pulp was GP, TMP, DIP as shown in Table 2 in the same manner as in Example 1;
To 6, and the same test as in Example 1 was performed. Table 2 shows the materials of the outer layer and the inner layer and the basis weight ratio. All papers were prepared total basis weight 60 g / m ² as a target. Third result
As shown in the table, Sample Nos. 1 to 3 in which KP was arranged in the outer layer irrespective of softwood (N) or hardwood (L) were excellent in surface strength and equivalent to Comparative Example 1 based on other paper quality. Yes,
It was suitable as newsprint for offset printing.

Example 3 GP (Freeness 58) TMP (Freeness 100) DIP (Freenes
s 175) GP = 15 pulp of NBKP (Freeness 660)
%, TMP = 30%, DIP = 35%, NBKP = 20% by weight, and the mixed pulp is passed through a 80-mesh on and 80-mesh pass using a sieving tester established in JIS-P-8207. It was divided into two. In the following, this 80 mesh on is used for long fiber, 8
The 0 mesh pass will be called the fine fiber component. At this time, the weight ratio of the long fiber component to the fine fiber component was 63:37.

Therefore, the total basis weight was 45 g / m2 and the basis weight of ^both outer layers was 8.5 g / m2.
^As No. ² , the weight ratio of the fine fiber in the outer layer is larger than the original mixed pulp (37%), and the fiber composition of the whole paper is the same as the original mixed pulp. Three types of three-layer papers were produced in the same manner as in Example 1, and the same tests as in Example 1 were performed.

Comparative Example 3 The weight ratio of the fine fibers in the outer layer was equal to or less than the original mixed pulp (37%), and the fiber composition of the whole paper was the same as the original mixed pulp. The three types of three-layer papers shown in Nos. To 6 were produced in the same manner as in Example 1 to obtain paper of Comparative Example 3, and an evaluation test was performed in the same manner as in Example 1.

The results are shown in Table 5. As the fine fiber content of the outer layer increases, the breaking length and opacity are slightly lower than the standard sample number 4, but the quality is practically acceptable and the surface strength is strong. It has excellent suitability as newsprint for offset printing.

Comparative Example 4 First, LBKP (Freeness 300) and TMP (Freeness 17
0) and GP (Freeness 72) were JIS in the same manner as in Example 3.
-Separated into 80-mesh long fiber and 80-mesh pass fine fiber by a sieving tester established in P-8207.

Subsequently, a double-layered paper as shown in Table 6 was prepared in the same manner as in Example 1 by using the above-mentioned fine fiber component as the inner pulp and DIP as the outer pulp, and subjected to the same printing test as in Example 1. . The results are shown in Table 6. The presence of fine fibers having a basis weight of 2 g / m ² increased the surface strength during printing, and the effect was greatest for KP-derived fine fibers.

[Effect] The present invention provides an offset printing newsprint by forming an outer layer mainly made of chemical pulp on both sides of an inner layer mainly made of DIP and mechanical pulp on a wire part of a paper machine, and By forming an inner layer and an outer layer with a higher ratio of fine fibers than the inner layer on both sides of the inner layer in the wire part of the machine, it has excellent surface strength and can withstand high-speed offset printing, as well as excellent whiteness and rigidity. Newspaper was able to be obtained. In particular, with the same composition as the pulp composition to make conventional single-layer paper,
The fact that newsprint having better whiteness, stiffness and surface strength than single-layered paper is obtained has a great effect in promoting offset printing and colorization of newsprint.

Continuation of the front page (72) Inventor Etsushi Itaya 5-21-1, Oji, Kita-ku, Tokyo Jujo Paper Co., Ltd. Central Research Laboratory (56) References JP-A-63-303199 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) D21F 11/00

Claims (2)

(57) [Claims] 1. A newsprint for offset printing comprising a plurality of layers, wherein an outer layer mainly composed of chemical pulp is formed on both surfaces of an inner layer containing waste paper pulp and mechanical pulp in a wire part of a paper machine. 2. Newspaper for offset printing comprising a plurality of layers in a wire part of a paper machine, wherein an inner layer and an outer layer having a higher ratio of fine fibers than the inner layer are formed on both surfaces of the inner layer.