JP2000225658A - Preparation of corrugated board and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent warpage from being generated by a simpler method by separately controlling water contents of the back liner and the surface liner. SOLUTION: In a corrugated board preparing process, on the upstream part of an inlet of a heating part for laminating a one face corrugated board and a surface liner and heating and drying them, a back liner water content measuring means 24 for measuring water content of the back liner and a surface liner water content measuring means 25 for measuring water content of the surface liner are arranged. Based on these measured values, the water contents of the back liner and the surface liner are adjusted by actuating moistening nozzles 27 and 29 or heating means 28 and 30 arranged on their upstream side in such a way that combination of the water contents of the surface liner and the back liner does not generate warpage after lamination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cardboard manufacturing method and apparatus, and more particularly to a cardboard manufacturing method and apparatus for preventing cardboard warpage.

[0002]

2. Description of the Related Art A corrugated cardboard is manufactured by laminating a back liner made of a hygroscopic paper material, a stepped core, and a front liner and bonding them together with glue. Warpage is likely to occur due to imbalance in the water content of the liner, and minimizing or eliminating warpage in cardboard manufacturing technology has become a major technical problem, and various solutions have been proposed so far. However, no complete solution has yet been found. As a conventionally proposed solution, for example, a water difference between the peripheral portion and the central portion of the corrugated cardboard is controlled until the double-faced corrugated cardboard reaches equilibrium moisture (Japanese Patent Laid-Open No. 10-80962).
No.) In order to prevent warpage of the bonded double-faced cardboard due to aging, the transfer path of the cooling unit provided downstream of the heating unit of the double facer is cooled to run the cardboard in a low temperature state. (See Japanese Patent Application Laid-Open No. H10-166478), or a high-pressure air collides with the corrugated cardboard to forcibly cool the corrugated cardboard. There is one that controls the tension applied to the liner and the back liner (Japanese Patent Laid-Open No. 10-128881).

[0003]

Among the above-mentioned proposals, any of those proposed to adjust the moisture as a countermeasure against the occurrence of the warp are intended to prevent the occurrence of the warp due to the change with time by adjusting the moisture of the cardboard after the lamination. Is what you do. However, according to the experiment of the present inventor, the occurrence of warpage is largely affected by the difference in moisture content between the front liner and the back liner at the time of lamination. Since the difference between the moisture content of the back liner and that of the back liner is bonded without being corrected, a difference occurs in the amount of expansion and contraction of both liners after the bonding, and warpage occurs. For example, if one of the liners is bonded in a state of shrinking with a low water content and the other liner is bonded in a state of swelling with a high water content, in the conventional method, the water content of each liner is adjusted after bonding and both liners are adjusted. Since it is difficult to balance the water content of the two liners, there has been a problem that the amount of expansion and contraction of both liners cannot be corrected, and the occurrence of warpage cannot be completely prevented.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a cardboard manufacturing method capable of preventing warpage by a simpler method by individually adjusting the water content of the back liner and the front liner. It is an object to provide a method and an apparatus.

[0005]

In order to solve the above-mentioned problems, the present inventor conducted various experiments and found that the moisture content of the front liner and the back liner in the laminating heat drying step of laminating the front liner to the single-sided cardboard. Have been found to vary with some correlation to each other. Therefore, it is difficult to adjust both the back liner and the front liner to a desired moisture content in the bonding heating drying process in the heating unit, but in consideration of the correlation, each moisture content is adjusted at the entrance of the heating unit. If individually adjusted, the water content of both at the outlet of the heating unit can be adjusted to a desired value. Therefore, if the water content of the front liner and the back liner (single facer) is individually adjusted by the entrance of the heating unit so that the difference in expansion and contraction of both liners does not appear in the bonded state, it is more effective. Warpage can be prevented from occurring.

[0006] However, the change in the water content of the front liner and the back liner in the heating section is completely different depending on the heating method. When the heating means is a hot plate, for example, when the moisture content at the entrance of the heating section is high and the back liner is low, the moisture content of both during passing through the heating section, the front liner gradually decreases, and conversely The back liner increases and the water content of both reverses halfway, and after exiting the heating section, both increase substantially in parallel and then decrease to a steady state. On the other hand, when the heating means is dielectric heating, the water content of the front liner and the back liner changes in a substantially parallel state even in the heating section, and after exiting the heating section, both increase substantially in parallel and then decrease to a steady state. State. The reason why the change in the moisture content of the front liner and the back liner is different depending on the heating means is that in the case of a hot plate, both the liner and the paste are heated, so that the moisture generated from the liner and the paste is absorbed by the back liner. As a result, the front liner gradually dries, while the water content of the back liner increases. On the other hand, in the case of dielectric heating, only the glue is heated, so that the moisture generated from the glue moves to the liners on both sides.

The amount of warpage of corrugated cardboard is largely influenced by the difference or ratio of the water content of the front liner and the back liner at the entrance of the heating section. In the case of dielectric heating, the water content of both at the entrance of the heating section is made uniform. Although we thought that it should be kept, as a result of various experiments, warpage does not necessarily occur if the water content of the front liner and the back liner are equal, and various conditions, for example, the degree of the water content, It is affected by line speed, ambient temperature, humidity, etc. However, even with these fluctuating factors, the amount of warpage always changes following the change in the difference in water content, and it has been found that the difference between the two water contents and the change in the amount of warpage have a correlation. Therefore, under predetermined conditions (for example, line speed, liner width, water content of the front liner or back liner, etc.), the change in the amount of warpage with respect to the difference in water content is determined in advance as experimental data, and is tabulated. Is stored as control data in the control device, and the difference between the two water contents at which the amount of warpage becomes zero under predetermined conditions is determined. The water contents of the front liner and the back liner are determined so as to be the difference between the two. By adjusting, the warpage of the cardboard can be eliminated.

On the other hand, when the heating means is a hot plate, the change in the water content of the front liner and the back liner is reversed in the heating section. By adjusting the water content of the front liner and the back liner at the entrance of the heating section, it is possible to obtain a cardboard free from warpage. The present invention has been achieved based on the above findings, and comprises the following technical means.

In order to achieve the above object, a method for producing corrugated cardboard according to the present invention comprises a single-sided corrugated cardboard manufacturing step of laminating a stepped core and a back liner to form a single-sided corrugated cardboard, and adjusting the water content of the back liner. The adjusting step and the table liner moisture content adjusting step of adjusting the moisture content of the table liner, the laminating and drying step of laminating and heating and drying the single-sided corrugated cardboard and the table liner, the laminating heating and drying step includes a heating means. Is carried out through the arranged heating section,
The step of adjusting the moisture content of the front liner and the step of adjusting the moisture content of the back liner are characterized in that the moisture content of the back liner and the front liner at the entrance of the heating unit is adjusted to a predetermined value.

The heating means is preferably a dielectric heating means, but may be a conventional hot plate. When the heating means is a dielectric heating means, the water content (%) of the front liner is represented by X, and the water content (%) of the back liner is represented by orthogonal coordinates by Y. When the water content of the liner is straight line Y = 0.5X + 0.4
It is desirable that the coordinates be adjusted so as to be coordinate points within a range located above the straight line Y and below the straight line Y = 0.5X + 2.8. As another control target value, focusing on the difference between the moisture content of the back liner and the moisture content of the front liner at the entrance of the heating section, the difference p between the moisture content of the back liner and the moisture content of the front liner is -2 <p < It may be adjusted so as to be 2. Further, the bonding heating and drying step is performed by heating in a state in which the stepped core coated with the paste and the liner are overlapped, and by providing an air laminar flow on the liner surface to be bonded, the paste in the heating unit is removed. The generated moisture can be efficiently removed.

When the heating means is a heating element such as a hot plate, the water content (%) of the front liner is represented by X, and the water content (%) of the back liner is represented by Y, and the heating unit is represented by rectangular coordinates. The water content of the back liner and the front liner at the inlet is located above the line Y = X-2, and the line Y = X + 1.
It is advisable to adjust the coordinates so that the coordinates are within the range located below 5.

Further, the corrugated cardboard manufacturing apparatus of the present invention comprises a single-sided corrugated cardboard manufacturing means for bonding a stepped core and a back liner to form a single-sided corrugated cardboard, a back liner water content adjusting means for adjusting the water content of the back liner, Back liner moisture content adjusting means for adjusting the moisture content of the liner, back liner moisture content measuring means for measuring the moisture content of the back liner, front liner moisture content measuring means for measuring the moisture content of the front liner, moisture content of the back liner A control device for controlling the drive of the back liner moisture content adjusting means and the surface liner moisture content adjusting means based on the measurement values of the measuring means and the surface liner moisture content measuring means, laminating the single-sided cardboard and the front liner. It is characterized by comprising a lamination heating drying means for heating and drying.

When the laminating heating and drying means has a dielectric heating means, the dielectric heating electrode is provided on an insulating plate provided with a number of small holes on the side facing the front liner, and an air flow is provided from the small holes. Is desirably designed to be discharged.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG. The illustrated apparatus shows a corrugated cardboard manufacturing line, and is composed of a single facer section A, a double facer section B, and a stacker section C. In the single facer portion A, the core 1 is preheated by the preheater 10, then is stepped by the step roll 11, and is glued by the glue machine 12 to the step top serving as the bonding surface with the back liner 2, and the press roll The back liner 2 preheated by the preheater 13 is bonded between the step 14 and the step roll 11. Thereby, the core 1 and the back liner 2
Are laminated to form a single-faced cardboard 3, which is continuously sent to the double facer section B via the accumulate conveyor 15.

In the double facer section B, the center of the single facer is preheated by the heat roll 16 and, if necessary, steam is sprayed by the spray nozzle 19, and an adhesive is applied to the top of the single-faced cardboard by the glue machine 17. And apply
After being superimposed on the surface liner 4 which is preheated and sent by the heat roll 18 and sent to the laminating / heating / drying unit 20, the surface liner and the single-sided cardboard are bonded together. Street, cutter 22
Then, the sheet-shaped double-faced corrugated cardboard 5 is manufactured by cutting into a predetermined size, and is stacked on the stacker 23. The above is the same as the conventional double-faced cardboard manufacturing process, but has the following features in the present embodiment.

In this embodiment, a back liner moisture content adjusting means and a front liner moisture content adjusting means are provided, and the moisture content of the back liner and the front liner at the entrance of the laminating heating and drying unit 20 are respectively adjusted to predetermined values. It can be controlled. For this purpose, a back liner moisture content measuring means 24 for measuring the moisture content of the back liner and a front liner moisture content measuring means 25 for measuring the moisture content of the front liner are arranged at the entrance of the laminating and drying section 20. Any means can be used as the moisture content measuring means as long as it can measure the moisture content. For example, an infrared sensor that measures the moisture content by an infrared measurement method can be suitably employed.

The back liner moisture content adjusting means includes a glue machine 17 and a back liner moisture content measuring means 24.
A humidifying nozzle 27 for spraying water or steam on the back liner and a heating means 28 such as a hot-air fan for heating the back liner are disposed between them. As the moisture content adjusting means of the surface liner, a humidifying nozzle 29 for spraying water or steam on the surface liner and a hot air fan for heating the surface liner are provided between the heat roll 18 and the surface liner moisture content measuring means 25. The heating means 30 is similarly arranged. The measured values of the back liner moisture content measuring means 24 and the front liner moisture content measuring means 25 are sequentially read into the control means 31, and no warping is generated based on the measured values and the control data stored in the control means in advance. Appropriate water content of the front liner and the back liner is calculated, and a control signal is applied from the control means to the back liner water content adjustment means and / or the front liner water content adjustment means based on the calculated value, and the bonding heat drying unit At the inlet of 20, the water content of the back liner and the front liner is adjusted to a predetermined value. When the moisture content is low, the moisture content is adjusted by controlling the humidifying nozzles 27 and 29 and spraying a predetermined amount of moisture to each liner. When the water content is high, the heating is performed by heating each liner by the heating means 28, 30.

The means for adjusting the water content of the back liner and the front liner is not limited to the above. For example, the means for adjusting the water content of the back liner may be such that the humidifying nozzle 27 is not provided and the spray nozzle 19 is Moisture content measuring means 24
It is also possible to substitute the spray nozzle by controlling the temperature, and to measure the temperature of the heat roll 16 or the contact angle between the heat roll and the single-sided cardboard instead of the heating means 28 from the back liner moisture content measuring means 24. It is also possible to control according to the result. Similarly, the moisture content adjusting means of the front liner controls the temperature of the heat roll 18 or the contact angle between the heat roll and the single-sided cardboard in accordance with the measurement result from the moisture content measuring means 25 of the front liner instead of the heating means 30. It is also possible.

Further, the bonding heating and drying section 20 is configured as follows in the present embodiment. A heating device 35 as shown in an enlarged manner in FIGS. 2 to 4 is disposed along the front liner side of the conveyance path where the single-sided cardboard and the front liner overlap and pass, and the back liner side has an endless shape extending to a cooling portion. A cotton belt 36 having a number of small holes formed therein is disposed, and the cardboard is sandwiched between the heating device and the cotton belt 36 to be conveyed while being pressed. Reference numeral 45 denotes a weight roll, which presses the cotton belt so as to make appropriate frictional contact with the cardboard.

In this embodiment, as shown in FIGS. 2 and 4, a heating device 35 employs a dielectric heating electrode 37 and an insulating plate 39 provided with a large number of small holes 38, as shown in FIGS.
Grooves are formed at an equal pitch in parallel to the direction of travel, and positive electrodes 40 and negative electrodes 41 are alternately arranged in the grooves facing the front liner passing therethrough. The inclination of each of the electrodes is such that the front end of one electrode and the rear end of the adjacent electrode are the same line in the liner traveling direction so that at least the entire surface of the front liner passing over the upper surface can pass over the electrode without leakage. It is arranged so that it may be located in a shape.

The back side of the insulating plate 39 is
An air supply duct 43 is connected to the closed chamber, and air supplied to the closed chamber flows out of a small hole formed in the insulating plate and passes through the upper surface thereof. By applying air to the liner surface, a laminar air flow is formed on the liner surface, and moisture generated from the glue by dielectric heating is effectively released from the liner to the outside.

The corrugated cardboard manufacturing apparatus of this embodiment is configured as described above, and is a single-faced corrugated cardboard 3 manufactured by laminating the back liner 2 and the core 3 at the single facer portion A.
Is preheated by the heat roll 16 in the double facer section B, glued to the top of the core by the glue machine, and reaches the entrance of the bonding heating and drying section 20, while the front liner 4 and the preheater 18 are also preheated. Reaching the entrance of the lamination heating and drying unit 20, the two are superposed and enter the lamination heating and drying unit 20,
An electric field generated from the dielectric electrode concentrates only on the glue and gels the glue by sandwiching and feeding at a predetermined pressure between the insulating plate 39 on which the dielectric electrode to which the high frequency alternating voltage of the predetermined frequency is applied and the cotton belt 31 is fed. -Drying is promoted to produce double-sided cardboard. In the above process, the back liner moisture content measuring means 24
The water content of the back liner and the surface liner is measured by the surface liner water content measuring means 25. Based on the measurement result, for example, when the moisture content of the back liner is lower than a preset moisture content set in the control device, the moisture content is adjusted by spraying moisture with the spray nozzle 27. Conversely, if the water content of the back liner is higher than the set value, the heating means 28 applies hot air of, for example, a predetermined temperature to the back liner surface to evaporate water from the back liner and adjust the water content. In a similar manner, the moisture content of the front liner is adjusted.

It takes a considerably long time for the water sprayed on the liner surface to penetrate into the liner and become stable. Therefore, the water content measured at the inlet of the heating unit is higher than the true water content of the liner because the water sprayed by the humidifying nozzle upstream does not reach the inside of the liner and is not in a stable state. State. For example, when the water content immediately after spraying is 12%, the water content in a stable state drops to just over 4%. Therefore, the spray amount from the humidifying nozzle for adjusting the water content needs to be determined based on the converted water content after spraying, when the water content is not sprayed.

By the way, the water content of the back liner and the front liner for preventing the cardboard from warping is not necessarily limited to the same as described above, and varies depending on various conditions. FIG. 5 shows how the moisture content of the back liner and the front liner at the entrance of the heating section changes to the amount of warpage in the steady state formed on the double-faced cardboard under various conditions when the dielectric heating means is employed. This is a state in which the moisture content of the front liner and the back liner is plotted on orthogonal coordinates in a case where a warp that has a substantial effect does not occur during various experiments to show the effect. In the graph of FIG.
The axis represents the moisture content (%) of the front liner, and the Y axis represents the moisture content of the back liner. As a result, under various conditions, the combination of the water content of the front liner and the back liner where substantially no warping occurs is located above the straight line Y = 0.5X + 0.4, and the straight line Y = 0.5X + 2 .8 was found to be included in the range located below.

A similar experiment was conducted when a heating plate was used as the heating means. The results are shown in the graph of FIG. As a result, when the heating means is a hot plate, the combination of the water content of the front liner and the back liner that does not cause warping is located above the straight line Y = X−2 and the straight line Y =
It was found to be included in the range located below X + 1.5. It is found that the coordinates are included in the range located at the coordinates point.

Further, in the case where the heating means is a dielectric heating means, the warpage of the double-faced cardboard was measured under various conditions, focusing on the difference in water content between the back liner and the front liner. As a result, the difference between the water content of the back liner and the surface liner was -2% in either the upward warpage or the downward warpage.
10% when the amount of warpage is stable when it is in the range of
Could be kept within. Therefore, in order to keep the warpage within 10 mm, the difference between the water content of the front liner and the back liner at the entrance of the heating section may be controlled so as to be within 2% in absolute value.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various design changes can be made within the scope of the technical idea. For example, as the heating device, a dielectric heating device is desirable, but a heating element such as a conventional heating plate or a heating box, or a suitable heating device such as a microwave heating device can be adopted. In the above embodiment, the case of the double-faced cardboard was shown, but it is needless to say that the present invention is not limited to the bonding of the double-faced cardboard, but can be applied to the bonding of the double-sided cardboard or the double-sided cardboard.

[0028]

As described above, according to the present invention, the water content of the front liner and the back liner can be individually adjusted before lamination, and any combination of the water content of the front liner and the back liner can be adjusted. Since the difference in water content between the front liner and the back liner after lamination can be adjusted to a value that does not cause warpage, warpage of the double-faced cardboard can be reliably prevented. Further, since the configuration is simple, it can be easily applied to a conventional cardboard manufacturing apparatus.

Further, a dielectric heating device is adopted as the heating device,
In addition, the dielectric electrode is provided on an insulating plate having a large number of small holes, and a laminar air flow is generated on the surface of the front liner, so that only the glue is rapidly heated and the moisture generated from the glue is rapidly removed by blowing. Therefore, it is easier to adjust the water content of the cardboard and to operate at a higher speed than before.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cardboard laminating apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a heating device.

FIG. 3 is a front view of the heating device.

FIG. 4 is a sectional view taken along line AA in FIG. 2;

FIG. 5 is a graph showing the relationship between the combination of the water content of the front liner and the back liner in the double facer and the warpage in the case of dielectric heating.

FIG. 6 is a graph showing the relationship between the combination of the water content of the front liner and the back liner in the double facer and the warpage in the case of heating the heating element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Core 2 Back liner 3 Single-sided cardboard 4 Front liner 5 Utilized surface cardboard 5, 8, 16,
Reference Signs List 18 Heat roll 19 Spray nozzle 20 Lamination heating and drying unit 21 Cooling unit 24 Back liner moisture content measuring means 25 Front liner moisture content measuring means 27, 29
Humidifying nozzle 28, 30 Heating means 31 Control means 35 Heating device 36 Cotton belt 37 Dielectric heating electrode 38 Small hole 39 Insulating plate 42 Closed chamber 43 Air supply duct

Claims (9)

[Claims] 1. A one-sided corrugated cardboard manufacturing process in which a stepped core and a back liner are bonded to form a one-sided corrugated cardboard, a back liner water content adjustment step for adjusting the water content of the back liner, and a table for adjusting the water content of the front liner. Liner moisture content adjustment step, a lamination heating drying step of laminating the single-sided cardboard and the front liner and heating and drying, the lamination heating and drying step is performed by passing through a heating unit in which heating means is arranged, The method for producing corrugated cardboard, wherein the water content adjustment step for the front liner and the water content adjustment step for the back liner are performed so that the water content of the back liner and the front liner at the entrance of the heating unit is a predetermined value. 2. The method according to claim 1, wherein said heating means is a dielectric heating means. 3. When the water content (%) of the front liner is represented by X and the water content (%) of the back liner is represented by orthogonal coordinates by Y, a combination of the water content of the back liner and the surface liner at the entrance of the heating section. 3. The method of manufacturing a corrugated cardboard according to claim 2, wherein the coordinate is adjusted to be a coordinate point within a range located above the straight line Y = 0.5X + 0.4 and below the straight line Y = 0.5X + 2.8. Method. 4. The corrugated cardboard according to claim 2, wherein the water content of the back liner and the front liner at the entrance of the heating section is adjusted so that the difference in water content between the back liner and the front liner is in the range of -2 to +2. Manufacturing method. 5. The bonding heating and drying step, wherein heating is performed in a state where the stepped core coated with the paste and the liner are superimposed, and at the same time, an air laminar flow is provided on the surface of the liner to be bonded. Item 5. The method for producing a cardboard according to any one of Items 1 to 4. 6. When the heating means is a heating element and the water content (%) of the front liner is represented by X and the water content (%) of the back liner is represented by orthogonal coordinates by Y, the back surface at the entrance of the heating section is provided. The water content combination of the liner and the surface liner is represented by a straight line Y = X
2. The method for manufacturing corrugated cardboard according to claim 1, wherein the adjustment is performed such that the coordinate points are located within a range located above -2 and below a straight line Y = X + 1.5. 7. A single-sided corrugated cardboard manufacturing means for laminating a stepped core and a back liner to produce a single-sided corrugated cardboard, a back liner water content adjusting means for adjusting the water content of the back liner,
Back liner moisture content adjusting means for adjusting the moisture content of the front liner, back liner moisture content measuring means for measuring the moisture content of the back liner, front liner moisture content measuring means for measuring the moisture content of the front liner, the back liner moisture content Control means for controlling the back liner moisture content adjustment means and the surface liner moisture content adjustment means based on the measurement values of the water content measurement means and the surface liner moisture content measurement means, laminating the single-sided cardboard and the front liner An apparatus for manufacturing corrugated cardboard, comprising: a lamination heating / drying means for heating / drying. 8. The corrugated cardboard manufacturing apparatus according to claim 7, wherein the bonding heating and drying means has a dielectric heating means. 9. The dielectric heating electrode of the dielectric heating means is provided on an insulating plate provided with a number of small holes on the side facing the front liner, and allows air to flow out from the small holes. The cardboard manufacturing apparatus according to claim 8.