JP7323481B2 - Manufacturing method of core base paper for corrugated board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing core raw paper for corrugated board, and more particularly to a method for producing core raw paper for corrugated board having excellent lamination suitability.

The base papers that make up corrugated board are classified into exterior liner, interior liner, and core base paper. Among these, the core base paper is formed into a corrugated shape called a flute, and adhesive is applied to the corrugation tops of the core base paper. Corrugated board is manufactured by coating and laminating each liner.

Corrugated cardboard is a packaging material that can be easily used because it is inexpensive, but on the other hand, further cost reduction is demanded in recent years. In terms of raw materials, we have responded by increasing the ratio of waste paper, etc., but this has caused a reduction in paper strength, resulting in the heavy use of paper strength enhancers, especially surface strength agents, which has hit a ceiling in cost reductions.

As described above, manufacturing core base paper by limiting surface strength agents while using inexpensive raw materials and further reducing the energy used in base paper production is one of the issues that must be resolved for corrugated base paper manufacturers. It's becoming

As a method for solving this problem, for example, Patent Literature 1 discloses a method of applying an aqueous starch solution by a film transfer method.

JP 2009-114572 A

However, the method disclosed in Patent Document 1 uses two layers of paper, so there is concern about peeling, and the starch is sprayed between the layers, which increases the cost. It was suggested that the drying efficiency was down due to the fact that it was not satisfactory.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a method for manufacturing corrugating medium paper for corrugated board with high productivity and excellent lamination suitability.

Other objects and effects of the present invention will be easily understood by those skilled in the art by referring to the following description.

In order to solve the above-mentioned problems, the method for producing core raw paper according to the present invention is a method for producing corrugated board having water-soluble polymers on the front and back surfaces of a single-layered base paper for corrugated board, comprising: It has a process of coating a water-soluble polymer on one side, a drying process, a process of coating a water-soluble polymer on the other side, and a drying process, and the coating method is a film transfer method. Excellent lamination suitability.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a method for manufacturing corrugating medium paper for corrugated board with high productivity and excellent lamination suitability.

FIG. 2 is a chart showing blends of corrugating medium and evaluation results in Examples. FIG.

Next, the present invention will be described in detail with reference to embodiments, but the present invention should not be construed as being limited to these descriptions. Various modifications may be made to the embodiments as long as the effects of the present invention are achieved.

The core raw paper for corrugated board according to the present embodiment has a step of coating a water-soluble polymer on one side, a drying step, a step of coating a water-soluble polymer on the other side, and a drying step. The construction method is the film transfer method.

The core base paper for corrugated board according to the present invention is obtained by coating a water-soluble polymer on both sides of a base paper for core base paper for corrugated board (hereinafter sometimes referred to as "base paper"), and the base paper is It is desirable to use waste paper pulp as the main component. Here, the "main component" means the component with the highest content on a mass basis among the components constituting the base paper. In the present embodiment, waste paper pulp preferably accounts for 60% by mass or more of the components constituting the base paper, more preferably 90% by mass or more, and most preferably 100% by mass. . Raw material waste paper used for the base paper includes high-quality waste paper such as high-quality waste paper such as high-quality white paper, white paper, card, imitation, colored paper, Kent, white art, and milk carton, as well as newspapers, magazines, cutouts, medium-quality antiques, and brown imitation. , Corrugated cardboard, Mounting paper, Certificate of origin, Cardboard, etc. Among these, the content of unbleached softwood kraft pulp (NUKP) and unbleached hardwood kraft pulp (LUKP) is high, and the various strengths of the paper are likely to be high.

The pulp used in the combined use of waste paper pulp and other pulp is not particularly limited, but wood pulp is preferable. Such wood pulp includes chemical pulp such as softwood bleached kraft pulp (NBKP), softwood unbleached kraft pulp (NUKP), hardwood bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP), and groundwood pulp (GP). ) and thermomechanical pulp (TMP), and one or more selected from these raw material pulps can be used. Among these, NBKP and NUKP are particularly preferable because they tend to improve various strengths of paper. When NBKP or NUKP is used in combination with waste paper pulp, the content is preferably 20% by mass or less, more preferably 10% by mass or less, from the viewpoint of cost.

The raw material pulp is made into a pulp slurry having an appropriate beating degree using a disintegrator and a beating machine. In the present invention, CSF is preferably 200 to 500 ml, more preferably 250 to 450 ml, in terms of Canadian standard freeness (JIS P 8121:1995 pulp freeness test method). If the CSF is less than 200 ml, the freeness at the wire part is low, and the water tightness at the press part in the next step is also poor, which may lead to poor productivity. On the other hand, if the CSF exceeds 500 ml, the strength against ring crush and the like may decrease, and desired performance may not be obtained.

A pulp slurry adjusted to an appropriate degree of beating is used as a raw material slurry, and paper is made by a paper machine to form a base paper for corrugated board. As the paper machine, known paper machines such as a Fourdrinier paper machine, a twin wire paper machine, a cylinder paper machine, a hybrid former, and a gap former can be used. Among these, a twin wire paper machine having a top wire, a hybrid former having a top wire, and a gap former are preferable. By adopting this type of paper machine, water is removed from the felt surface as well, so ash and fine fibers are suppressed in the same way as the wire surface. can be done. The upper dewatering ratio is preferably 5% or more, more preferably 10% or more, relative to the total amount of dewatering. If the upper dewatering ratio is less than 5%, the desired quality cannot be obtained in the difference between the front and back surfaces, and the productivity is low. The structure of the base paper shall be a single layer. In multi-layer paper making of two or more layers, the base paper becomes hard and it is necessary to spray starch or the like to prevent peeling from the layers, which is disadvantageous in terms of both quality and cost.

In the present invention, it is preferable to introduce a shaking device into the paper machine. This improves the formation on the paper machine and tends to form a uniform film layer when the water-soluble polymer is applied. In general, as an index showing the sliding energy of a shaking device,
Shaking number I = f^2 x s/V
is used. The shaking number range is preferably 1000-8000, more preferably 2000-5000. Here, I: shaking number, f: period [cycle/min], s: amplitude [mm], V: paper speed [m/min]. Although the shaking device to be used is not particularly limited, for example, Duo Shake 400 Nm (manufactured by Voith) can be used.

In the present invention, it is preferable to add a paper strength agent to the base paper. By adding a paper strength agent to the raw material slurry, sufficient strength is ensured even when the content of waste paper pulp is high, and cracks are less likely to occur during flute processing. The paper strength agent used here is not particularly limited, but it is preferable to use starch, modified starch, polyacrylamide-based resin, polyvinyl alcohol-based resin because it is inexpensive and easy to impart cationic groups. , cationic starch and amphoteric polyacrylamide resin are more preferable. If it has a cationic group, it will be easier to fix to the anionic pulp. The amount of the paper strength enhancer added is preferably 0.1 to 2.0% by mass, more preferably 0.2 to 1.0% by mass, based on 100% by mass of pulp. The polyacrylamide resin content is preferably 0.05 to 1.0% by mass, more preferably 0.1 to 0.5% by mass. Other papermaking additives such as internal sizing agents, fillers, retention aids, dyes, and aluminum sulfate may also be used.

Paper sludge incinerated ash may be blended into the base paper. Paper sludge incineration ash is a powder obtained by dehydrating and incinerating outflow raw materials from paper mills. Clay, calcium carbonate, talc, silica, etc., are the main ingredients of waste paper raw materials and waste from paper manufacturing. The amount of paper sludge added is preferably 20% by mass or less, more preferably 16% by mass or less, in the core raw paper. If the amount added exceeds 20% by mass, it is advantageous in terms of cost, but cracks are likely to occur during flute molding, leading to process contamination during production. Although there is no particular lower limit for the amount to be blended, 1% by mass or more is preferable in consideration of cost.

In the present invention, both the front and back surfaces of the base paper are coated with a water-soluble polymer. By coating the base paper with a water-soluble polymer, sufficient strength is ensured even when the content of waste paper pulp is high, and cracks are less likely to occur during flute processing. As the water-soluble polymer used here, one or more selected from starch, modified starch, polyvinyl alcohol resin, and polyacrylamide resin can be used. Homemade thermochemically modified starch (TCC) is preferred because it can enhance the When thermochemically modified starch is used, for example, it is preferable to use starch having a concentration of 17% by mass and a B type viscosity of 15 to 25 cps (60 rpm, 60° C.) diluted to 6 to 14% by mass. Thermochemically modified starch is prepared by cooking raw starch or acetylated starch in the presence of an oxidizing agent such as ammonium persulfate at a temperature of about 140° C. to obtain a starch paste having a viscosity that is easy to coat.

In the present invention, the method of applying the water-soluble polymer is a film transfer method. Film transfer methods include, for example, a metering size press and a gate roll size press. Water-soluble polymers are more effective when they are localized on the surface. It is not preferable because the amount of The sizing liquid that has penetrated to the inside does not contribute to surface modification, and leads to an increase in subsequent drying load.

The film transfer type applicator roll used for coating the water-soluble polymer is preferably made of synthetic rubber. If polyurethane is used, the material is too hard to control the amount of transfer.

In the present invention, the coating of the water-soluble polymer is carried out in the order of coating the water-soluble polymer on one side, drying, coating the water-soluble polymer on the other side, and drying. For this reason, it is preferable to use a metering size press for single-sided coating. If both surfaces are coated and dried at the same time, the drying efficiency is poor because water vapor evaporates only from each coated surface. On the other hand, when one side is coated and dried, water vapor for one side escapes from both sides, thereby improving productivity. In addition, since the drying is completed in a short time, the size press liquid containing the water-soluble polymer hardly permeates in the direction of the paper layer and is localized on the surface, so that the effect is sufficiently exhibited. Furthermore, by coating and drying one side at a time, even if the opposite side is supported by a roll or the like, the supporting tool does not get dirty and contamination with foreign matter can be suppressed. In addition, when simultaneous coating is performed on both sides, the phenomenon of the paper fluttering easily occurs because the separation of the paper from the applicator roll is not stable. In such a case, the coating pattern becomes striped, and the quality is not stable.

In the present invention, the coating amount of the water-soluble polymer is preferably 0.2 to 2.5 g/m ² in terms of solid content per both sides of the base paper, and is in the range of 0.4 to 1.2 g/m ² . is more preferable. If the coating amount is less than 0.2 g/m ² , sufficient strength cannot be ensured even with a high content of waste paper pulp, and cracks are likely to occur during fluting. If it exceeds 2.5 g/m ² , it becomes too hard and the surface tends to crack.

Further, in the present embodiment, the base paper for corrugating medium after drying may be smoothed if necessary. The smoothing method is not particularly limited, and a machine calender, soft calender, super calender, or the like can be used as appropriate.

The basis weight of core raw paper for corrugated board is preferably 100 to 220 g/m ² , and preferably 110 to 130 g/m ² in order to enhance the effects of the present invention. Since the lower the basis weight, the lower the strength, the effect of the present invention is greatly exhibited.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, "parts" and "%" in the examples indicate "mass parts" and "mass%", respectively, unless otherwise specified. The number of parts to be added is a value in terms of solid content.

[Productivity]
The production volume of core raw paper for corrugated board per hour was evaluated in the following four stages based on the relative ratio when the production volume of Example 2, which was the most productive, was taken as 100.
A: Good productivity. Assuming that the production volume of Example 2 is 100, the following criteria are used.
○: Good productivity, 96 to 99% of the production volume of ◎.
Δ: Lower limit of productivity, production volume of 90 to 95% of ◎.
×: Poor productivity, production volume less than 90% of ◎.

[Lamination property]
The core raw papers obtained in Examples and Comparative Examples were evaluated by a corrugator in terms of laminating property to the liner according to the following four grades.
⊚: The bonding state is good over the entire surface of the corrugated cardboard sheet.
◯: Slight lamination failure is observed in the corrugated cardboard sheet.
Δ: Defective lamination is observed on the corrugated cardboard sheet, but within the adjustment range. (Practical lower limit)
x: Defective lamination is observed in a part of the corrugated cardboard sheet, and it is difficult to deal with it. (Not practical)

[Example 1]
A raw pulp slurry of 100% by mass of corrugated waste paper pulp is beaten to 380 cc of CSF, and 0.7% by mass of cationic starch (Neotac 40T, manufactured by Nihon Shokuhin Kako Co., Ltd.) is added to 100% by mass of raw pulp, and a paper strength enhancer (Hermid RB234 , manufactured by Harima Kasei Co., Ltd.) and 0.02% by mass of a yield improver (High Holder C503, manufactured by Kurita Water Industries Co., Ltd.). 1 g/m ² of homemade thermochemically modified starch was applied in a solid form and dried, then 1 g/m ² was applied to the back surface using a film transfer type sizer, dried, and then calendered to obtain corrugated cardboard. . A fourdrinier single mesh paper machine equipped with a top wire and having a paper speed of 600 m/min was used.

[Example 2]
A core raw paper for corrugated board was obtained in the same manner as in Example 1, except that the coating weight of the sizer of the film transfer system was changed from 1 g/m ² to 0.2 g/m ² for solid on both the front and back surfaces.

[Example 3]
A core raw paper for corrugated board was obtained in the same manner as in Example 1, except that the amount of coating by a film transfer type sizer was changed from 1 g/m ² to 2.5 g/m ² for solid on both the front and back surfaces.

[Example 4]
Corrugated board was made in the same manner as in Example 1 except that 1% by mass of a paper strength enhancer (ST5000, modified polyacrylamide resin, manufactured by Seiko PMC) was added to 10% by mass of homemade thermochemically modified starch coated by a film transfer method. A corrugating medium was obtained.

[Example 5]
10% by mass of homemade thermochemically modified starch coated by film transfer method was changed to 5% by mass, and 2% by mass of a paper strength enhancer (ST5000, modified polyacrylamide resin, manufactured by Seiko PMC) was added. In the same manner as in Example 1, core raw paper for corrugated board was obtained.

[Example 6]
Corrugated cardboard core in the same manner as in Example 1, except that the home-made thermochemically modified starch was not used and 3% by mass of a paper strength agent (ST5000, modified polyacrylamide resin, manufactured by Seiko PMC) was applied by a film transfer method. I got the original paper.

[Comparative Example 1]
Corrugating medium paper for corrugated board was obtained in the same manner as in Example 1, except that both the front and back sides were simultaneously coated using a film transfer type sizer and then dried.

[Comparative Example 2]

Since the absorption into the base paper is large, the concentration of the home-made thermochemically modified starch was changed from 10% by mass to 5% by mass (diluted with the sizing liquid), and the coating amount was 1 g/m ² in terms of solids per side. Corrugating core paper was obtained in the same manner as in Example 1, except that the machine was changed from a film transfer type sizer to a pound type size press to simultaneously coat both the front and back surfaces, followed by drying.

As shown in FIG. 1, each of the corrugating medium papers obtained in Examples 1 to 3 had high productivity and excellent lamination suitability, and was at a level of practically no problem.

On the other hand, the core raw paper for corrugated board obtained in Comparative Example 1 was coated with the aqueous starch solution on both sides at the same time. We had to slow down production. In addition, since both sides were coated at the same time, water vapor could not pass through the base paper to the opposite side during drying, resulting in evaporation only from the coated surface, increasing the drying load. Since the water-soluble polymer in the corrugating medium paper obtained here was striped, the absorption of the paste during lamination was unstable, and it is thought that the lamination was weak in some areas. Also, in areas where the coating amount of water-soluble polymer is small, the corrugated corrugated core paper cracks after flute processing, and the glue-coated roll fibers are easily removed from the surface, causing roll stains, resulting in lamination. A weak portion is generated, and troubles such as frequent cleaning of the glue coating roll occur.

The core raw paper for corrugated board obtained in Comparative Example 2 was coated with a water-soluble polymer using a pound type size press, so that the amount of water-soluble polymer absorbed into the base paper increased sharply, and the desired amount of coating per solid content was obtained. Therefore, it was necessary to halve the concentration of the water-soluble polymer. As a result, the amount of moisture applied to the corrugating medium increased, and the drying load also increased, resulting in a decrease in productivity. In addition, the increased water content in the aqueous solution made it easier for the water-soluble polymer solution to permeate in the direction of the paper layer. Later, corrugated corrugated core paper cracked and its surface strength decreased, and cleaning of the glue coating roll occurred frequently, causing trouble.

Claims (1)

A method for producing a corrugated core base paper having a water-soluble polymer on both front and back surfaces of a base paper for a corrugated core base paper made by making a single layer, the method comprising the steps of:
a first surface coating step of applying a water-soluble polymer to one surface of the base paper for corrugated board and drying ; a second surface coating step of applying a water-soluble polymer to the other surface and drying the corrugated cardboard core, wherein the water-soluble polymer is applied by a film transfer method. The manufacturing method of base paper.

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