JP2015193972A - Inner core base paper for cardboard and cardboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inner core base paper for cardboard high in adhesive strength even to liners having low heat conductivity (e.g. thick liners) and suffering high speed lamination, i.e. having high productivity.SOLUTION: There is provided an inner core base paper for cardboard having heat conductivity of 0.222 W/(m K) or more. Especially, there is provided a cardboard having a value of heat conductivity of the inner core base paper for cardboard y satisfying 0.222 W/(m K)≤y and the value of heat conductivity of the liner x satisfying 0.221 W/(m K)≤x, and satisfying y≥-3.993x+1.139.

Description

The present invention relates to a core base paper used for corrugated cardboard and corrugated cardboard using the core base paper.

Corrugated cardboard is manufactured by adhering a liner and a core base paper with a laminating machine (corrugator). The core base paper is manufactured by corrugating with a corrugating roll provided in a laminating machine, and a solution containing an adhesive component such as starch paste is applied to the top of the wave. After this application, the core base paper and the liner are laminated and heated to about 80 ° C. with a hot plate or the like to complete the bonding. The bonded cardboard is subjected to, for example, a process for putting a crease ruled line or a process for cutting it into a predetermined size. However, if the adhesive strength between the core base paper and the liner is insufficient, the core base paper and the liner may be peeled off, and it is necessary to reduce the bonding speed. Conversely, by increasing the adhesive strength between the core base paper and the liner, it is possible to increase the production rate by increasing the speed of the bonding machine (corrugator). Therefore, the adhesive strength between the core base paper and the liner greatly affects the productivity of the corrugated cardboard sheet. Further, among liners, thick liners having low thermal conductivity have a drawback that it is difficult to bond with a core base paper under high-speed bonding because heat is not easily transmitted to the liner. In order to increase the thermal conductivity of the liner, it is necessary to make the liner thinner. However, if the liner is thinned, the strength decreases at the same time, so this problem is not simply solved by thinning the liner.

In addition, when using a core base paper or a liner produced by increasing the ratio of used paper due to cost reduction or raw material procurement, the thermal conductivity tends to be low. Adhesion between the core base paper and the liner may be difficult under high-speed bonding, but the problem of lowering productivity remains when the bonding speed is reduced. Corrugators used for processing corrugated cardboard sheets have increased in speed in recent years, and some corrugators have a processing speed of 300 m / min or more. This processability can be judged by evaluating the adhesive strength between the core base paper and the liner to determine whether the quality is satisfactory for corrugated cardboard.

  Therefore, various proposals have been made to improve the adhesive strength between the core base paper and the liner. For example, Patent Document 1 proposes a method of improving the water absorption of a liner and efficiently absorbing an aqueous solution of an adhesive component. However, with this method, problems such as a significant change in adhesive strength depending on the performance of the core base paper remain, so it cannot be said that productivity has been sufficiently improved.

JP 2014-12908 A

  The main problem to be solved by the present invention is that the core base paper for corrugated cardboard has high adhesive strength even for liners with low thermal conductivity (for example, thick liners) and can withstand high-speed bonding, that is, high productivity. Is to provide.

The invention made to solve the above problems is
This is a core base paper for corrugated board having a thermal conductivity of 0.222 W / (m · K) or more.

  The present invention also provides a corrugated cardboard comprising the core base paper and a liner.

  The thermal conductivity value y of the core base paper for corrugated board is 0.222 W / (m · K) ≦ y, and the thermal conductivity value x of the liner is 0.221 W / (m · K) ≦ x, and A corrugated cardboard having a value satisfying y ≧ −3.993x + 1.139.

  By increasing the thermal conductivity to 0.222 W / (m · K) or higher in the core base paper for corrugated cardboard, heat is transferred to the solution containing the adhesive component at a high speed, and the adhesive component contained in the solution melts quickly. To do. Thereby, even if a bonding machine (corrugator) is high-speed, the adhesive strength of a core base paper and a liner is maintained.

As described above, the core base paper for corrugated board of the present invention has high thermal conductivity and excellent bonding properties. Therefore, according to the core base paper for corrugated cardboard, even when a liner having low thermal conductivity is used, corrugated cardboard that can withstand high-speed bonding and has excellent strength and productivity can be formed.

Hereinafter, embodiments of the core base paper for corrugated board of the present invention will be described in detail.

  The core base paper for corrugated board of the present invention has a thermal conductivity of 0.222 W / (m · K) or more. Even if it sticks with a liner with low heat conductivity by making heat conductivity 0.222 W / (m * K) or more irrespective of basic weight, this can express high adhesive force. Preferably, the thermal conductivity value y of the core base paper for corrugated cardboard is 0.222 W / (m · K) ≦ y, and the thermal conductivity value x of the liner is 0.221 W / (m · K) ≦ x. And a value satisfying y ≧ −3.993x + 1.139, more preferably, the value of the thermal conductivity of the core base paper for corrugated board is 0.222 W / (m · K) ≦ y, and the thermal conductivity of the liner By making the value of the range satisfying 0.221 W / (m · K) ≦ x and y ≧ −3.993x + 1.139, a corrugated board having higher adhesive strength and strength can be formed. it can.

In order to increase the thermal conductivity, it is generally attempted to make the paper as thin as possible. However, as the paper becomes thinner, the strength decreases at the same time. The core base paper for corrugated cardboard requires, for example, a compression index (horizontal) of 90 N · m ² / g or more at a minimum and a tensile strength of 3.3 kN / m or more in the longitudinal direction. There is a shortage.

  Therefore, for example, it is desirable to improve the strength of the paper by adjusting the beating degree (freeness) of the pulp slurry to 200 to 500 ml.

The basis weight of the corrugating medium in a said cardboard, 80 g / ^{m 2} or more 180 g / ^{m 2} or less, 100 g / ^{m 2} or more 160 g / ^{m 2} or less.

Further, the tension in the core base paper for corrugated cardboard is preferably 0.5 g / cm ³ or more and 0.7 g / cm ³ or less.

In the core base paper for corrugated cardboard, it is preferable to reduce the thickness and reduce the density as described above, because the structure has a physically improved thermal conductivity.
However, the thermal conductivity of the core base paper for corrugated cardboard is not limited to this method because it is influenced by factors other than thickness and density.

On the other hand, when the thermal conductivity of the core base paper for corrugated cardboard is less than 0.222 W / (m · K), the adhesive strength is weak, the core base paper and the liner are peeled off, and the pasting speed of the pasting machine needs to be reduced. Occurs.

The core base paper for corrugated cardboard can be formed by papermaking of pulp slurry containing pulp as a main component. Examples of the pulp include hardwood bleached kraft pulp, softwood bleached kraft pulp, hardwood unbleached kraft pulp, conifer unbleached kraft pulp, hardwood sulfite pulp, and conifer sulfite pulp. The main raw materials containing wood fibers are mechanically treated pulp and chips that are chemically treated with non-wood fibers such as kenaf, hemp, and straw, which are chemically processed pulps, and non-wood fiber materials. Virgin pulp, such as ground pulp, pulp that has been mechanically pulped while adding chemicals to wood or chips, and semi-chemical pulp that has been pulped with a refiner after cooking the chips until soft In addition to used paper pulp such as corrugated cardboard, newspaper, and leaflets, magazine used paper including various types of bleach-resistant paper such as coated paper, non-coated paper, ground paper, color printed paper, black and white printed paper, etc. Waste paper pulp such as can be used.

From the viewpoint of recyclability, it is preferable to use waste paper pulp. The amount of waste paper pulp used relative to the total pulp is preferably 50% by mass or more, and more preferably 80% by mass or more.

  In addition to the above pulp, rayon fibers, acrylic fibers, polyamide fibers, other synthetic fibers, glass fibers, carbon fibers and the like may be used as components of the paper layer.

(Method for producing the core raw paper for corrugated cardboard)
The core base paper for corrugated cardboard can be obtained by making a paper pulp slurry as described above. The core base paper for corrugated cardboard can be manufactured by a system generally used for papermaking. Specifically, for example, a papermaking system including a wire part, a press part, a predryer part, a coater part, a calendar part, a reel part, etc. Can be used. In addition to this, a paper making system comprising an off-machine coater in which the paper machine and the coater part are separated may be used, and a paper making system comprising an off-machine calendar in which the paper machine and the soft calendar are separated may be used.

  Known additives can be internally added to the raw pulp slurry. Known additives include, for example, polyacrylamide, polyvinyl alcohol polymer, urea / formalin resin, melamine / formalin resin, paper strength enhancer such as starch, fixing agent such as sulfate band, polyacrylamide, acrylamide / amino. Methyl acrylamide copolymer salts, cationized starch, polyethyleneimine, polyethylene oxide, acrylamide / sodium acrylate copolymer, etc. Illustrative examples include fillers, dyes, slime control agents, antibacterial agents, anti-ultraviolet agents, anti-slip agents, lubricants, oil-proofing agents, oil-repellents, and light / weather resistance-imparting agents. In addition to the above, a sizing agent can be added as an additive.

(Manufacturing method of the liner)
The corrugated liner can be obtained by papermaking the raw pulp slurry as described above. The liner can be manufactured by a system generally used for papermaking. Specifically, for example, a papermaking system including a wire part, a press part, a predryer part, a coater part, a calendar part, a reel part, or the like can be used. it can. In addition to this, a paper making system comprising an off-machine coater in which the paper machine and the coater part are separated may be used, and a paper making system comprising an off-machine calendar in which the paper machine and the soft calendar are separated may be used. As the raw material fibers and additives, those similar to the core raw paper for corrugated board can be used.

(Method for producing cardboard using the core raw paper for cardboard)
The method for producing the corrugated board using the corrugated core base paper is not particularly limited. For example, the corrugated core base paper is formed into a wave shape with a single facer. After applying a bonding adhesive (adhesive solution) to the cardboard, it is bonded to the cardboard liner to create a single-sided corrugated cardboard. Apply the adhesive for bonding (adhesive solution) and send it to the double facer. At the heating part, paste the corrugated liner on the other top of the core base paper, heat it with a hot plate, etc. Corrugated cardboard can be obtained by cooling at.

  Examples of the adhesive for pasting include starch and the like. Specifically, the adhesive is composed of water, gelatinized starch (α-modified starch), non-gelatinized starch (β-starch), alkali compound, boron compound and the like. The As non-gelatinized starch (β starch) as the main component, for example, corn starch, wheat starch, potato starch, tapioca starch and other raw starches, phosphate esterified starch, aminated starch and other cationic groups Various chemically modified starches such as modified cationized starch, oxidized starch hydrolyzed with acid to adjust molecular weight, and enzyme-modified starch hydrolyzed with α-amylase to adjust molecular weight can be used. Examples of gelatinized starch (α-modified starch) include processed starch such as acid-hydrolyzed starch, cationized starch, and enzyme-modified starch, and high amylose starch. In addition, for a water-resistant corrugated cardboard requiring water resistance, for example, a synthetic resin such as acrylic or SBR, or an adhesive mixed with starch and a synthetic resin can be used.

  In the present invention, the liner to be bonded to the core base paper is not particularly limited and a known one can be used. Even if the thermal conductivity of the liner is low, it can be satisfactorily bonded to the core base paper of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these. Unless otherwise specified, the paper made was processed according to JIS P-8111 and then subjected to a test.

  In addition, each measured value in a present Example is a value measured with the following method.

[Method of measuring thermal conductivity]
The thermal conductivity was measured using GTM-T3 manufactured by Kyoto Electronics Industry. The method is a hot-wire probe method. Six sheets of core base paper for corrugated cardboard are laminated on a silicone rubber (thermal conductivity 0.238 W / (m · K)) plate (thickness of about 1.00 mm), and the probe is applied to the sheet surface to conduct heat. The rate was measured.

[Cardboard processing method]
Using a corrugator (Mitsubishi Heavy Industries, Ltd. cardboard sheet making machine), special Tokai Paper TPK (basis weight 280 g / m ² thermal conductivity 0.233 W / (m · K) or less, sheet X), commercially available Product 1 (basis weight 210 g / m ² thermal conductivity 0.232 W / (m · K) or less, sheet Y) and commercial product 2 (basis weight 280 g / m ² thermal conductivity 0.230 W / (m · K) ) Hereinafter, the sheet Z) is used as the liner base paper, the core base paper A (thermal conductivity 0.250 W / (m · K)), and the core base paper B (thermal conductivity 0.225 W / (m · K). )), Core raw paper C (thermal conductivity 0.222 W / (m · K)), core raw paper D (thermal conductivity 0.220 W / (m · K)), core raw paper E (thermal conductivity 0) .201W / (m · K)) as corrugated core base paper, and corrugating with starch paste as adhesive ( Degree 350m / min) do, was to create a cardboard.

[Cardboard processing suitability evaluation method]
The degree of adhesion was confirmed by a cardboard adhesion test (JIS Z 0402). A single facer-side adhesive strength of 320N or higher was marked with ◯, an adhesive strength of 270-320N was marked with Δ, and a thickness of 270N or lower was marked with ×.
In addition, all of the samples with the edge peeled off when visually confirmed were marked with x.

<Example 1>
A sulfuric acid band and a sizing agent were added to the pulp raw material, and paper was made with a long paper machine to produce a core base paper A having a thermal conductivity of 0.230 W / (m · K). Furthermore, corrugated board was manufactured using this core raw paper A and the sheet | seat X, and various evaluation was performed. Details are as shown in Table 1.

The raw materials for the core paper for corrugated cardboard are as follows.

(Pulp raw material)
A blend of 80% corrugated waste paper pulp and 20% kraft waste paper pulp was used.

(Sulfuric acid band)
A liquid sulfuric acid band (solid content 28%) manufactured by Asahi Chemical Industry Co., Ltd. was used.

(Starch glue)
A low cons made by Nippon Starch Co., Ltd. was used.
Coating amount (front side 3.2 g / m ² , back side 5.0 g / m ² ), concentration (front side 3.2%, back side 3.0%).

<Examples 2-9 and Comparative Examples 1-6>
Each corrugated core base paper was obtained in the same manner as in Example 1 except that the thermal conductivity of the core base paper and the liner to be bonded were changed as shown in Table 1.

  The results of the corrugated board processing suitability evaluation of each example and comparative example are shown in Table 1.

As a result of Table 1, from Examples 1 to 9, if the thermal conductivity is 0.222 W / (m · K) or more, even if pasted with a liner having a low thermal conductivity, the corrugated board is suitable for processing and good results. was gotten.

  In Comparative Examples 1 to 6 in which the thermal conductivity of the core base paper is lower than 0.222 W / (m · K), the bonded portion was easily peeled off, and the evaluation was x.

  The core base paper for corrugated cardboard of the present invention is useful for increasing the production efficiency by being able to cope with the high speed of the corrugated cardboard processing machine and the diversification of liners.

Claims (3)

  Corrugated core base paper having a thermal conductivity of 0.222 W / (m · K) or more.   A corrugated board comprising the core base paper for corrugated board according to claim 1 and a liner.   The thermal conductivity value y of the core base paper for corrugated board is 0.222 W / (m · K) ≦ y, and the thermal conductivity value x of the liner is 0.221 W / (m · K) ≦ x, and The cardboard according to claim 2, wherein a value in a range satisfying y ≧ −3.993x + 1.139 is satisfied.