JPH0255222B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a method for manufacturing reinforced corrugated board. In particular, one liner sandwiching the core is a paper liner, and the other liner is a so-called stretch-reinforced synthetic resin laminated paper liner (hereinafter referred to as This invention relates to a manufacturing method for preventing warping of reinforced corrugated cardboard, which is referred to as a "reinforced liner." ``Prior art'' The above-mentioned reinforced cardboard was first developed in Japanese Unexamined Patent Publication No. 57-
36647 (Special Publication No. 60-2180) (Name: Reinforced Corrugated Cardboard), JP-A No. 57-61549 (Special Publication No. 60-906) (Name: Liner for Cardboard), JP-A No. 57-131544 (Name: Durable cardboard, filing date: February 9, 1982
(Japanese), Jitsukai No. 57-138637 (Jikkoi No. 1-18349)
(Name: Cardboard Box with Strengthened Compression Resistance, Application Date: February 23, 1982), etc. By the way, when considering the uses of corrugated cardboard, it is often subjected to force from one side, so the reinforcing liner described above is used on one side sandwiching the core, and the liner on the other side is used as a liner for corrugated cardboard. It is believed that the use of paper liners that are resistant to paper is the most rational and most economical way to obtain reinforced corrugated board. The reason for this is that even if the reinforcing liners described above are used on both sides, the reinforcing liner on the convex side of the corrugated board that curves due to force will help strengthen the corrugated board, but the reinforcing liner on the concave side will not be useful for strengthening the corrugated board. This is because it only unnecessarily increases costs. Therefore, a corrugated board with a reinforced liner on only one side that bends due to external force is extremely rational. However, there are serious manufacturing difficulties in manufacturing such reasonably reinforced corrugated cardboard. That is,
When a reinforced liner is used on only one side and a normal paper liner is used on the other side, if the corrugated board is produced in the usual manner, the corrugated board will be very warped as shown in FIG. This is because the reinforcing liner 3 is made of stretched synthetic resin cloth and/or synthetic resin film, which causes heat shrinkage in the heating and pressing part of the corrugated board manufacturing equipment, resulting in strong tension reinforcement. While the liner 3 tries to pull the paper liner 2 on the other side, which has a weaker tension, outward, the paper liner 2 itself evaporates moisture due to drying and shrinks somewhat, but at outside temperature it returns to its original moisture content. Since it has the property of stretching back to its original shape at the same time as it returns to its original shape, it is thought that a large warping phenomenon as shown in Fig. 1 occurs. On the other hand, Japanese Patent Publication No. 55-23147 has been proposed as a method for reducing the general warpage phenomenon in corrugated cardboard. This is done by using heat, moisture, tension, and heating time as control parameters to determine the condition of single-sided webs and double-sided liners, and balancing them in composite double-sided webs, independent of web production speed. , a process control system for corrugated paper making machines that produces blanks that are completely warped. "Problems to be solved by the invention" However, such a control system naturally
The disadvantage is that the equipment is complex and expensive. The control system may also be suitable for reducing warpage caused by complex small variations in various manufacturing factors. However, when the materials or physical properties of both liners are extremely different, such as the above-mentioned reinforced corrugated board, where one liner is paper and the other liner is a stretched reinforced synthetic resin laminated paper liner, the above control system no longer works. Not suitable. That is, the thermal shrinkage rates of both liners in the reinforced corrugated board are significantly different, and in the heat-pressing section of the corrugated board manufacturing equipment, the reinforced liner containing the stretched reinforced synthetic resin shrinks significantly, and the paper liner on the opposite side contracts accordingly. However, attempting to prevent such warping by controlling various manufacturing factors would be a waste of time due to manufacturing conditions (manufacturing speed) that are significantly lower than normal corrugated board operating conditions. , heating amount, heating time, etc.), which not only significantly reduces manufacturing efficiency and increases the cost of the product, but also does not provide a satisfactory solution to the warpage itself. be. ``Means for Solving the Problems'' Therefore, the inventors of the present invention have developed a reinforced corrugated board with the above-mentioned structure by making only slight changes to the corrugating machine in the field without adopting an expensive control system as described above. As a result of intensive research to find a simple and inexpensive manufacturing method that is virtually warp-free, we discovered that before bonding both the paper liner and the reinforced liner to the core, the humidification state of the paper liner and It has been discovered that by adjusting the residence time, it is possible to produce the above-mentioned reinforced corrugated board that is substantially free from warping. That is, the structure of the present invention is such that one liner sandwiching the core is a paper liner, and the other liner is a so-called stretch-reinforced liner in which paper and a stretch-reinforced synthetic resin cloth and/or a stretch-reinforced synthetic resin film are laminated. In the method for manufacturing reinforced corrugated board that is a synthetic resin laminated paper liner;
The above-mentioned paper liner is humidified to a moisture content of 35%, and an aging (residence) time of at least 20 seconds is provided to stretch the paper liner with that moisture content by a predetermined amount, and then a stretch-reinforced synthetic resin laminated paper liner is added. The invention is characterized in that it is configured to undergo a heat-pressing drying process in which the adhesive is bonded to the adhesive. Therefore, the question arises as to whether such a humidified state of the paper liner is possible only by controlling the moisture content of the control system described above. However, when looking at the moisture supply means in the control system, it is assumed that warpage occurs due to internal stress due to non-uniform humidity between the single-sided web and the double-sided liner, and in order to reduce the warpage, one-sided web It merely provides a means for providing a substantially constant amount of moisture to the web and double-sided liner. In fact, humidifying the paper liner to a moisture content of 15% or more has never been considered in the past. Moreover, providing a residence time (aging time) of 20 seconds or more in a humidified state to allow the paper liner to stretch is a novelty that has never been found in the control system or conventional moisture supply means. It's an idea. This is due to the fact that the target corrugated cardboard is reinforced corrugated cardboard with the above-mentioned special structure. That is, the main cause of warpage is that the stretched and reinforced synthetic resin cloth and/or stretched reinforced film that constitute the reinforced liner shrinks in the heat and pressure bonding section of the corrugating machine and does not expand to its original state even after returning to room temperature. The purpose of the method of the present invention is to prevent shrinkage at the heated and compressed portion of the reinforced liner by creating a reaction force on the paper liner on the opposite side to counteract the shrinkage, thereby balancing the shrinkage forces on both sides and preventing warpage. It is an attempt to prevent this. To this end, the paper liner needs to be in a mature state where it has expanded by a predetermined amount before being inserted into the heat-press bonding section, and it is necessary that the paper liner undergoes a predetermined shrinkage action at the same time as drying in the heat-press bonding section. The method of the present invention adopts the above-described structure for this purpose, but the humidification of the method of the present invention can be applied regardless of whether the paper liner is left in a mature state in which it has been stretched by a predetermined amount, or is contracted by a predetermined amount as it is heated and dried. Conditions and humidification are the most effective. The amount of humidification applied to the paper liner is preferably set so that the moisture content of dry paper is 15 to 35%.
Hitherto, it has never been considered to humidify a paper liner to a moisture content of 15% or more. However, in the reinforced cardboard according to the present invention, if the degree of humidification is less than 15%, warping cannot be suppressed. In addition, if the degree of humidification is 35% or more, the paper liner may break during the bonding process, poor adhesion between the paper liner and the core may occur, and in some cases, the product may warp, which is the opposite of what would occur without humidification. This is not desirable as it may occur. Furthermore, drying excess moisture consumes more thermal energy than necessary. Therefore, in reality, the optimum humidification amount within the above range depends on the paper liner, core, type of reinforced liner, material and form of the elements that make up the reinforced liner, type of adhesive, bonding conditions, etc. Since it differs depending on the situation, it is preferable to determine it appropriately through a preliminary test. In the present invention, after humidifying the paper liner,
The time required for the next bonding step is also an important essential requirement, and in order to effectively carry out the method of the present invention, the time from humidification to bonding is preferably at least 20 seconds or more. This time is the elongation time (referred to as "aging time" in the industry) for the paper liner that has been humidified to a predetermined amount to expand by a predetermined amount as described above.もIt is the time to stay or leave it alone. Since this time is also affected by the thickness of the paper liner, it is determined based on appropriate preliminary tests. As mentioned above, in order to suppress the thermal shrinkage of the reinforced liner, the paper liner on the opposite side undergoes drying shrinkage, but in order to do so, the paper liner itself must stretch a certain amount before drying. No. This cannot be achieved by mere humidification, but is achieved by a combination of a predetermined amount of humidification and a predetermined elongation time (ripening time) under that humidified state. However, if the standing time after humidification before the next bonding is too long and the humidified moisture essentially evaporates to the moisture content of ordinary paper (approximately 5 to 9%), the method of the present invention No effect will be obtained. Next, the change in elongation over time with respect to the water content of the paper liner is shown in a table. Moreover, FIG. 3 shows this in a graph. The reference paper liner before humidification is made of C220g, moisture content 8.0%, and length 1307m/m.
I used the one from According to this table and FIG. 3, it can be seen that the paper liner almost reached the target moisture content 20 seconds after humidification. Further, the paper liner gradually expands over time, but after 3 minutes or more, the expansion slows down. In addition, the higher the moisture content, the greater the elongation.
It can be seen that the growth rate with respect to elapsed time is also large. The amount of humidification and residence (aging) time are determined by preliminary tests, assuming such elongation of the paper liner, using a reinforced liner and other conditions.

[Comparative example 1]

In Example 1, the paper liner was moistened at 20% and approx.
Corrugated board was produced in the same manner as in Example 1, except that the residence time of seconds was not provided. The cardboard showed significant warpage, causing serious trouble in the feeding device for secondary processing in Example 1, and making it impossible to mechanically assemble the box. [Example 2] As a reinforced liner, a reinforced liner was used, which was made by laminating paper and a cross of stretch-reinforced polypropylene flat yarn with a polyethylene hot melt adhesive, and further laminating a stretch-reinforced polypropylene film on the surface of the flat yarn. . A paper liner that had been humidified to a moisture content of 35% in advance and left for about 25 seconds, and the paper side of the reinforced liner,
Starch glue was applied by hand to both sides of the core almost simultaneously under heat and pressure and allowed to dry. No warpage was observed in the reinforced corrugated cardboard sheet after drying. [Comparative Example 2] Corrugated board was produced in the same manner as in Example 2, except that a non-humidified paper liner with a moisture content of 7.3% was used instead of the humidified paper liner in Example 2, and no particular residence time was provided. This cardboard has a width of 1m.
It showed a warpage of 30 cm. [Example 3] As a reinforcing liner, a material obtained by laminating paper and stretch-strengthened polypropylene film with a polyethylene hot melt agent was used. The paper side of this reinforced liner is first bonded to the core to form a single-sided corrugated board, and then the paper liner, which has been moistened to a moisture content of 20%, is left for 20 seconds and then bonded to the top of the core of the single-sided corrugated board for reinforcement. Manufactured cardboard. In the reinforced corrugated board manufactured in this way, the warpage had completely disappeared when the moisture content reached 9% after air drying. [Comparative Example 3] Instead of using a humidifying paper liner, the moisture content was 8%.
Corrugated board was produced as in Example 3, except that a conventional paper liner was used and no residence time was provided. The resulting cardboard showed significant warping.

[Brief explanation of the drawing]

FIG. 1 is a perspective view illustrating a deformed state of reinforced corrugated cardboard manufactured by a conventional method. FIG. 2 is a block diagram of an apparatus for carrying out the method according to the present invention. Third
The figure is a graph showing changes in elongation over time with respect to moisture content of paper liner. 1... Core, 2... Paper liner, 3... Reinforced liner, 4
... core base paper, 5 ... corrugated roll, 6, 11 ... glue roll, 7 ... press roll, 8 ... single-sided corrugated board, 9 ...
Spray device, 12... rider roll, 13... mill roll stand, 14... heating section, 15... corrugating belt, 16... cooling section, 17... cutter, 18... hot plate.

Claims (1)

[Claims] 1. One liner sandwiching the core is a paper liner, and the other liner is a so-called stretch-reinforced synthetic resin laminated paper liner made by laminating paper with a stretch-reinforced synthetic resin cloth and/or a stretch-reinforced synthetic resin film. In the method for manufacturing reinforced corrugated board; humidifying the paper liner of the single-sided corrugated board to which the paper liner and core are bonded so that the moisture content of the paper liner is 15 to 35%, and the paper liner having that moisture content, Manufacture of reinforced corrugated cardboard, characterized in that it is configured such that a maturing time of at least 20 seconds or more is provided as the time for stretching it by a predetermined amount, and then a heat-pressing drying process is performed in which it is bonded to a stretched reinforced synthetic resin laminated paper liner. Method.