JPH07229082A - Paper board - Google Patents

Abstract

PURPOSE:To obtain a paper board having high rigidity and good ply bond strength and surface strength. CONSTITUTION:This paper board is produced by laminating two or more wet paper layers produced by using pulp as main raw material. The pulp is incorporated with 0.5-20wt.% of fine fibrous cellulose substance having a water-retention of 210-550% measured in conformity to JAPAN TAPPI No.26-78 and an average fiber length of 0.01-0.4mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to paperboard, and more particularly to paperboard which has high rigidity, excellent interlaminar strength and surface strength, and produces little paper powder.

[0002]

2. Description of the Related Art As an important quality required for paperboard, it is required that rigidity (strength of the waist) is required, and that from the viewpoint of workability, the interlaminar strength and surface strength are strong and less paper dust is generated. Not only when the paperboard is used as a sheet, but when it is processed and used, for example, when it is processed into a box, and when the contents are filled and stacked, the boxes are crushed,
It is the quality related to the blistering of the box when packed with powder and the like. Further, the generation of paper dust significantly reduces workability.

The method for increasing the rigidity of paperboard is (1)
There are methods such as increasing the thickness of the paper layer, (2) using pulp with high rigidity, (3) adjusting the beating degree of pulp, etc., but there is a limit to the improvement in rigidity with these methods, Problems such as deterioration of other important qualities such as surface properties may occur. In addition, as a method of increasing the surface strength of paperboard, (1)
Increasing the amount of chemical pulp having high strength, (2) adding paper strength enhancer such as starch or polyacrylamide to paper internally or externally. However, in these methods, there is a limit to the improvement of the surface strength, and in the case of external addition of chemicals, there is a problem that a device for newly coating chemicals on paper is required.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of conventional paperboard, and provides a paperboard having high rigidity, high interlaminar strength and surface strength and less generation of paper dust. It is a thing.

[0005]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present invention have conducted intensive studies by paying attention to pulp for paperboard, and as a result, arrived at the present invention. That is, the paperboard according to the present invention is a paperboard produced by combining two or more paper layers of a wet paper whose main raw material is pulp.
Water retention value specified by TAPPI No. 26-78 is 210% ~ 550%
And 0.5 to 20% by weight of a fine fibrous cellulosic material having an average fiber length of 0.01 to 0.4 mm.

The water retention value for the present invention is a value that is linked to the degree of miniaturization of the fine fibrous cellulosic material, and was used as an index for the miniaturization. The water retention value for the present invention is 210
% Or more of the fine fibrous cellulosic material is, for example, when a slurry of pulp obtained from the cellulosic material in a vibration type pulverizer is wet pulverized and observed with an optical microscope, the fiber has a water retention value of 210 to 250%. A part of the pulp fiber having a width of 20 to 30 μm is broken, and a fine fiber having a fiber width of 3 to 5 μm starts to be produced. Furthermore, as the water retention value rises, the fiber cell wall is broken, and the number of fibrils with a fiber width of 3 to 5 μm increases.
It has a shape that is partly connected or entangled. When the fibers are observed with a scanning electron microscope, fine fibers with a fiber width of 0.5 μm or less are also observed. The water retention value changes depending on the cellulosic substance, the type of pulp, the grinding method, and the like.

When the fine fibrous cellulosic material is added to the pulp, the rigidity, interlayer strength and surface strength of the paperboard are improved. This is because the fiber width of the fine fibrous cellulosic material is thin as described above, which contributes to an increase in the fiber surface area and the formation of an interfiber network, and strengthens the interfiber bond of pulp. It is estimated that the surface strength is improved. In addition, it is presumed that the fine fibrous cellulosic material on the surface of the paper layers greatly contributes to the binding when the paper layers of the wet paper are combined. Regarding the length of the fine fibrous cellulosic material used in the present invention, those having an average fiber length of 0.01 to 0.4 mm have a greater effect as described above,
If the fiber length exceeds 0.4 mm and is too large, or too small, such as less than 0.01 mm, the effect is small. It is conceivable that the way of forming a network between fibers differs depending on the difference in fiber length.

If the addition ratio of the fine fibrous cellulosic material to the pulp is less than 0.5% by weight, the effect of the addition is not seen, and if it is added in excess of 20% by weight, the raw material is filtered during papermaking in a paper machine. Since the water quality becomes poor and the wire cannot be dehydrated, it becomes difficult to make coated paper base paper. On the other hand, the addition ratio of the fine fibrous cellulosic material is also related to the water retention value of the fine fibrous cellulosic material, the higher the water retention value to obtain the same effect of addition,
The addition ratio can be reduced, but the upper limit of the water retention value that can be used is
It is about 550%.

It is known that the used paper pulp deteriorates and the strength decreases as the number of times of recycling increases,
In addition, since pulp is easily broken into paper powder with deterioration, quality problems are serious when raw materials containing a large amount of waste paper pulp are used. For this reason, when the amount of used paper pulp is large, especially when the amount is 70% or more based on the total raw material pulp, the effect of adding fine fibrous cellulosic material is great.

The fine fibrous cellulosic material used in the present invention is a slurry of pulp fibers from the cellulosic material, vibrating type pulverizer, "Micros pulverizer" manufactured by Nara Machinery Co., Ltd., high pressure homogenizer, media agitation type pulverizer. It is obtained by treating with a device, a colloid mill or the like.

The vibrating crushing device is a crushing device in which a crushing container is vibrated at a high speed to exert a force such as impact, friction or shear on the sample between beads, balls or rods filled in the container. is there. Nara Machinery's Micros crushing device consists of a crushing container, a main shaft that rotates in it, and several sub-shafts that revolve around the rotation of the main shaft.
A large number of ring-shaped grinding media are attached to each counter shaft,
It is a device that processes the sample between the orbiting and rotating ring and the wall of the crushing container. The high-pressure homogenizer is a device for pulverizing the cellulose fiber slurry by passing it through a small diameter orifice at a high speed with a pressure difference of at least 3000 psi. The media agitation type wet pulverization device rotates the agitator inserted in the fixed pulverization container at high speed to agitate the media (eg, glass beads, alumina beads, etc.) and the sample filled in the pulverization container and shear stress, It is a device for crushing a sample by generating a force such as an impact force, and there are a tower type, a tank type, a flow pipe type, an annular type, etc., but any device can be used as long as it is a media stirring method. Examples of the colloid mill include a supermass colloider manufactured by Makoto Sangyo Co., Ltd., which processes a sample between rotating disc-shaped grinders in which abrasive grains are hardened with a resin.

The processing method may be either a batch type or a continuous type, and several devices may be connected in series,
It is also possible to perform rough treatment in the first stage and fine treatment in the latter stage. It is also possible to process with different types of devices in the first and second stages. Raw materials to be used for the fine fibrous cellulose of the present invention include softwood pulp, hardwood pulp, waste paper pulp, mixed pulp thereof, and also non-wood pulp such as hemp,
Fibrous cellulose such as cotton, and further cellulose fine powder or particles can be used.

The papermaking pulp slurry in the present invention includes
If necessary, starch, a starch derivative, or a wet paper strength enhancer such as carboxymethyl cellulose, polyvinyl alcohol, or polyacrylamide may be contained. Furthermore, additives used in ordinary papermaking, such as sizing agents, defoamers, dyes, slime control agents,
Fillers, retention aids and the like can be included as necessary.

The conditions partially changed in the method for measuring the water retention value according to JAPAN TAPPI No. 26-78 used in the present invention are the conditions such as a centrifugal centrifuge with a glass filter of G3 and a hole in the lower part. Put the sample in a tube, dehydration treatment by applying centrifugal force at 3000 G for 15 minutes, measure the weight of this centrifugally dehydrated wet sample, and further dry at 105 ° C for at least 5 hours to obtain the dry weight. It means a value obtained by measuring, subtracting the dry sample weight from the wet sample weight after centrifugal dehydration treatment, dividing this by the dry sample weight, and multiplying this by 100.

Regarding the test sample to be subjected to centrifugal dehydration treatment, since the water retention value of the product after the pulverization treatment is high, dehydration becomes difficult if the water retention value is measured as it is, and the aqueous phase remains on the upper part of the sample. Therefore, as a pretreatment, preliminary dehydration was performed by filtration to obtain a solid content concentration of 8 to 12% by weight, and then the water retention value was measured.

The average fiber length is KAJAAN in Finland.
Since the number average fiber length value measured by the FS-200 type fiber length measuring device manufactured by Company I and the FS-200 type fiber length measuring device are difficult to measure less than 0.05 mm, those with a shorter fiber length are manufactured by Shimadzu SALD
-1100 is a value measured by a particle size distribution analyzer.
In the present invention, a paperboard having high rigidity, excellent interlaminar strength and surface strength can be obtained by adding the fine fibrous cellulosic material to pulp as described above.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In addition, all "%" in an Example and a comparative example is "solid content weight%."

Examples 1-2 and Comparative Examples 1-4 Freeness (csf) 410 ml corrugated cardboard waste paper pulp and Table 1
The pulp slurries prepared by mixing the fine fibrous cellulosic material having the water retention value and the average fiber length shown in Table 1 in the ratio shown in Table 1 were prepared.
In accordance with 209, use a square-type laboratory paper machine to obtain an absolute dry basis weight of 10
The paper was made to have a weight of 0 g / m ^2, and two wet papers were superposed on each other to obtain a sheet having an absolute dry basis weight of 200 g / m ² and then subjected to a wet press. At this time, when pressing the wet paper web, the press pressure was changed to produce a paper board having the same tenacity.

The fine fibrous cellulose used in Examples 1 to 2 and Comparative Examples 2 to 4 was prepared by using a vibration type pulverizer (MB-1 type) manufactured by Chuo Kakoki Co., Ltd. and having a diameter of 5 mm and a zirconia bead capacity of 200.
Crush container (3400m
It was obtained by wet-grinding in l), changing the number of revolutions, amplitude conditions, and the type of pulp under test.

The methods of measuring rigidity, interlaminar strength and surface strength used in the present invention are as follows. (1) Stiffness measurement method According to JIS P 8125, it was measured using a Taber stiffness tester. (2) Method of measuring interlaminar strength It was measured using an internal bond tester manufactured by Kumagai Riki Kogyo. (3) surface strength of the measuring methods paper RI printing tester on the surface of the sample was printed with (manufactured by Akira Seisakusho) to measure the number of white spots trace fibers per paper surface 10 cm ² was peeled off (white spots).

Example 3 and Comparative Example 5 Freeness (csf) 410 ml corrugated cardboard waste paper pulp (freeness) and freeness (csf) 470 ml hardwood bleached pulp and fine fibrous cellulose having water retention value and average fiber length shown in Table 2. To prepare pulp slurries containing them in the proportions shown in Table 2 and then adding these pulp slurries to J
According to IS P 8209, paper is made to have an absolute dry basis weight of 200 g / m ² using a laboratory square-type hand machine, and two wet paper sheets are stacked to form an absolute dry basis weight of 400 g / m ² . The paper was subjected to a wet press. At this time, when the wet paper web was pressed, the press pressure was changed to produce a paper board having the same tenacity, and the paper board was evaluated.

For the fine fibrous cellulose used in Example 3, 2% by weight of pulp slurry was prepared by MIC manufactured by Nara Machinery Co., Ltd.
It was obtained by wet pulverization using an RO-2 type pulverizer (using zirconia ring).

Example 4 and Comparative Examples 6 to 7 Freeness (csf) 360 ml corrugated cardboard waste paper pulp and Table 3
A pulp slurry was prepared by mixing the water retention value and the fine fibrous cellulosic material having the average fiber length shown in Table 3 in the proportions shown in Table 3. Then, these pulp slurries were prepared according to JIS P 8
In accordance with 209, use a square-type laboratory paper machine to obtain an absolute dry basis weight of 10
The paper was made to have a weight of 0 g / m ^2, and two wet papers were superposed on each other to obtain a sheet having an absolute dry basis weight of 200 g / m ² and then subjected to a wet press. At this time, when the wet paper web was pressed, the press pressure was changed to produce a paper board having the same tenacity, and the paper board was evaluated.

The fine fibrous cellulosic material used in Example 4 was a cellulose fine powder (KC Flock manufactured by Nippon Paper Industries,
Using a vibration type pulverizer (MB-1 type) made by Chuo Kakoki Co., Ltd., with an average diameter of 25 μm and a water retention value of 62%), 200 ml of zirconia beads having a diameter of 5 mm and a cellulose fine powder having a concentration of 4% by weight 1
It was obtained by putting 000 ml in a crushing container and performing wet crushing treatment.

Comparative Example 8 Untreated cellulose fine powder not subjected to wet crushing treatment (KC floc made by Nippon Paper Industries, average diameter 25 μm, water retention value 62%)
5%, cardboard waste paper pulp (freeness, csf360ml) 9
A paperboard was prepared in the same manner as in Example 4 except that the content was 5%, and the paperboard was evaluated. In Table 1, Examples 1-2 and Comparative Examples 1-
4, Table 2 shows the values of the stiffness, interlayer strength and surface strength of the paperboard at the tightness of 0.5 g / cm ³ obtained in Example 3 and Comparative Example 5 and Table 3 in Example 4 and Comparative Examples 6 to 8. Show.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

As is clear from the results shown in Tables 1 to 3, the paperboard of the present invention has high rigidity, strong interlaminar strength, and strong surface strength (Examples 1 to 4), whereas it is used in the present invention. Paperboard containing no fine fibrous cellulosic material (Comparative Examples 1, 5,
6) and fine fiber cellulose material having an average fiber length of 0.01 mm or less or 0.4 mm or more, and a fine fibrous cellulose material having a water retention value of 210% or less are used for paper stiffness, interlayer strength,
There is little or no effect of improving the surface strength (Comparative Examples 2, 4,
7). When the known cellulose fine powder is used, the rigidity, interlaminar strength and surface strength are rather worse than those of unblended paperboard (Comparative Examples 6 and 8). Further, as shown in Comparative Example 3, when a large amount of the fine fibrous cellulosic material used in the present invention was used, the drainage property was deteriorated and the papermaking was difficult.

From these results, it was found in the present invention that the paperboard containing a predetermined amount of fine fibrous cellulosic material having an average fiber length and a water retention value not within the above-mentioned numerical ranges is excellent in stiffness, interlayer strength and surface strength. It turns out that this is an essential requirement for obtaining a paperboard having

[0031]

As described in detail above, the present invention has high rigidity and excellent interlaminar strength by adding a specific fine fibrous cellulosic material to the raw material pulp of paperboard,
A board having high surface strength and free of paper dust can be obtained, which is of high practical value.

Claims (1)

[Claims] 1. A paperboard produced by combining two or more paper layers of a wet paper containing pulp as a main raw material, wherein the pulp contains:
Water retention value specified by JAPAN TAPPI No.26-78 is 210%
A paperboard characterized by containing 0.5 to 20% by weight of a fine fibrous cellulosic material having an average fiber length of 0.01 to 0.4 mm in an amount of 550%.