JPS634504B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for manufacturing double-sided corrugated board. Double-sided corrugated board is constructed by laminating flat liners to both corrugated tops of corrugated corrugated cardboard, and is widely used as a material for packaging containers when assembled into corrugated cardboard cases. In order for the packaging melter to withstand the filling of heavy objects, the compressive strength of the cardboard itself must be improved. In order to improve the compressive strength of double-sided corrugated board, it is easy to increase the basis weight of the core or liner, but the size of the core corrugations is standardized, and the As the basis weight of the corrugated cardboard increases, its thickness and rigidity also increase, and the external force that the corrugated paper is subjected to during corrugated forming increases, making it difficult to form corrugated sheets normally, and the running speed of the corrugated board laminating machine increases rapidly. There are problems such as a decline in Another method for improving the compressive strength of the core paper is to add strength-improving agents such as polyacrylamide, polyethyleneimine, epoxidized polyamide, or urea resin internally during the manufacturing process of the core paper, or to improve the compressive strength of the pipe used. There are methods such as increasing the beating degree, and these methods improve not only the compressive strength but also the tensile strength, but on the other hand, they become brittle or the bending strength decreases, causing problems during step forming.
There are limits to the improvement of compressive strength by these methods. In addition, it is difficult for the core to which the above-mentioned strength improver is added internally to adhere to the liner using a commonly used starch adhesive. On the other hand, sodium silicate has long been used as an adhesive to the liner by being applied to the corrugated top of corrugated corrugated medium during the production of corrugated sheets. Currently, starch-based adhesives are mainly used as the adhesive between the liner and the top of the corrugated corrugated board due to limitations on running speed and problems such as contamination and discoloration of the corrugated board surface due to alkali stain. . Furthermore, sodium silicate with a concentration of 30 to 40% is applied to one side of the cardboard base paper, and the two sheets of cardboard base paper with the coated sides stacked on top of each other are glued together. A corrugated board (see Utility Model Publication No. 53-6771) is produced by hardening the material to produce a medium that has pressure resistance, and then adhering a liner to the top of the corrugated medium using a starch-based adhesive. Are known. The above-mentioned known corrugated board has a large adhesion of sodium silicate, which reduces the running speed of the corrugated cardboard during corrugation, and the manufacturing process for the corrugated cardboard is complicated because two sheets of corrugated paper are glued together. becomes. The present inventors have completed this invention as a result of intensive research into improving the strength of corrugated cardboard using relatively inexpensive sodium silicate. That is, the present invention provides a method for producing double-sided corrugated board, in which one liner is attached to the corrugated top of a corrugated corrugated medium, and the other liner is adhered to the corrugated top on the opposite side. , after applying a sodium silicate solution to either or both of the core side surface of the other liner and the core surface facing the surface, the other liner is bonded to the top of the corrugated board of the single-sided corrugated board. This is a manufacturing method for double-sided corrugated cardboard. An example of the manufacturing method of the present invention will be explained with reference to the drawings. In FIG. 1, numeral 1 indicates a corrugated core, and one liner 3 is attached to one step top 2a of the core 1. A single-sided corrugated board A is formed. A coating layer 1b, 4b of a sodium silicate solution is provided on both the surface 1a of the corrugated corrugated board 1 of the single-sided corrugated board A on the corrugated top 2b side and the surface 4a of the other liner 4 facing the surface 1a. As shown in the figure, the other liner 4 is joined to the corrugated top portion 2b of the single-sided corrugated board A to form a double-sided corrugated board B. Note that a starch-based glue is applied as an adhesive to the step tops 2a and 2b of the liner 1, and the liner 3,
4 is glued. In the example described above, a coating layer of sodium silicate solution is applied to the surface 1a of the core 1 and the surface 4a of the liner 4.
Although the coating layer of the sodium silicate solution is shown to be provided on both the inner and outer cores, the coating layer of the sodium silicate solution may be provided on either the surface 1a of the core 1 or the surface 4a of the liner 4. Sodium silicate is represented by the general formula Na ₂ O.nSiO ₂ , where n is suitably in the range of 2 to 4. JIS-
The solid content concentration of No. 3 sodium silicate specified by K1408 with n = 3 is 40% by weight, but if applied at this concentration, a strong rigid film will be formed, resulting in the durability of cardboard and cardboard cases. Although the compression properties are significantly improved, on the other hand, there are problems such as becoming brittle, causing an alkali stain phenomenon and staining, and having a high viscosity that makes it difficult to apply. Therefore, it has been found that it is preferable to dilute the commercially available sodium silicate with water and use it as an aqueous solution, and that the desired effect can be sufficiently obtained even when applied as an aqueous solution. The sodium silicate aqueous solution is preferably a mixture of 10 to 100 parts by weight of water to 100 parts by weight of No. 3 sodium silicate, that is, a solid content concentration of 20 to 36% by weight. The solid content of sodium silicate is in the range of 3 to 30 g/m ² , preferably 4 to 20 g/m ² . In addition, the solid content amount of sodium silicate is indicated by the weight relative to the plane of the liner, but
The weight of the core is expressed as the weight relative to the area obtained by dividing the entire corrugated surface by the plate repetition rate. Therefore, even if the amount of solids applied is the same, the amount of solids applied to the entire corrugated surface of the core is smaller than that of the liner. If the solid content concentration of the above-mentioned sodium silicate aqueous solution is less than 20% by weight, the aqueous solution will penetrate and disperse into the inside of the core or liner to a large extent, and the effect of improving compressive strength with the same solid content amount will be reduced. In addition, if you try to increase the amount of coating to obtain the desired effect of improving compressive strength, the moisture content of the paper will increase, which will reduce the rigidity of the paper and the temperature during the manufacturing process, which will cause problems with the corrugated board laminating machine. This will cause problems in operations. Further, if the solid content concentration of the aqueous solution exceeds 36% by weight, the same problem as described above occurs when commercially available sodium silicate is used without being diluted. If the solid content amount of sodium silicate is less than 3 g/ ^m2 , the improvement in compressive strength will be small, and the solid content amount will be less than 3 g/m2.
If it exceeds 30 g/m ² , the compressive strength will be improved, but damage will occur when the corrugated cardboard sheet is bent at the crease line, and the alkali stain phenomenon will likely occur, which is not preferable. In order to apply the above-mentioned aqueous sodium silicate solution to the inside surface of the single-sided corrugated board, it is preferable to use a mist-like coating method or a curtain-like coating method in which the inside surface is coated without applying pressure. The running speed of the corrugated board laminating machine is adjusted depending on the quality of paper used, etc., and the amount of sodium silicate aqueous solution discharged per hour can be adjusted to follow changes in the running speed of the laminating machine. The above coating method is preferable. Incidentally, mist-like coating is preferable than curtain-like coating because the coating liquid permeates and diffuses less into the paper, the coating is uniform, and the amount of coating can be small. Adhesion of the other liner to the top of the corrugated core of a single-sided corrugated board is accomplished by applying a conventional glue, such as starch, to the top of the corrugation of the corrugated board. The adhesive may be applied either before or after the application of the sodium silicate solution on the surface of the medium. When applying a glue after applying the sodium silicate solution, apply the sodium silicate solution to the surface of the core, dry it, and then apply the glue to the top of the step of the core to join the liner. In addition, when applying a sizing agent before applying the sodium silicate solution, or when applying the sodium silicate solution only to the surface of the liner to be joined, heat the liner after joining the liner to the top of the corrugated core. to solidify the sodium silicate. In this case, if the amount of sodium silicate solution applied is large, the so-called adhesion setting will be delayed and the adhesion between the top of the corrugated corrugated board and the liner will not be sufficient. When double-sided corrugated cardboard is stacked in a flat plate, it will be reset by its own weight, so there will be no problem with adhesion. When applying the sodium silicate solution to the inside or liner surface of a single-sided corrugated board, it is not necessarily necessary to apply it to the entire surface thereof. For example, it may be applied to the bottom, side surfaces, or crease lines of a cardboard case made of double-sided cardboard in an appropriate width. The location and application area of the sodium silicate solution may be appropriately set depending on the weight, shape, etc. of the packaged items to be filled in the cardboard case. Examples of the present invention will be described below. Example 1 Paper made with semi-chemical pulp, basis weight 125
g/m ² of medium paper specified as JIS-P3904 B grade and liner (JIS-P3902, B grade basis weight 220g/
m ² ) to produce A flute single-sided corrugated cardboard, then apply a starch glue to the top of the single-sided corrugated cardboard, and then apply 100 parts by weight of No. 3 sodium silicate to 100 parts by weight of water on the entire surface of the corrugated cardboard. After spraying and applying a mist of sodium silicate solution diluted by parts by weight at a liquid pressure of 40 kg/cm ² , a liner similar to the above was bonded to the top of the single-sided corrugated board, and then brought into contact with a hot plate at 160°C. This was then dried to produce double-sided corrugated board. The lamination traveling speed during the above corrugated board production was 140 m/min,
Three spray amounts of the sodium silicate solution were used: 40, 30, and 20 c.c./m ² (solid content: 9.5, 7.1, and 4.8 g/m ² ). Next, use the above-mentioned double-sided cardboard to make a 360 degree
An A-1 type glue joint case measuring 300 x 250 mm was manufactured. Table 1 shows the physical properties of the double-sided cardboard and cardboard case. For comparison, samples that were not treated with sodium silicate were also tested in the same manner, and their physical properties are also listed.

【table】

[Table] In Table 1 above, the adhesive strength of the other liner of corrugated cardboard is
JIS-Z0402, vertical compressive strength and planar compressive strength are the measured values according to JIS-Z0401, and the compressive strength and deformation of the cardboard case are the measured values according to JIS-Z0212. As seen in Table 1, the adhesive strength, vertical compressive strength, and planar compressive strength of the double-sided corrugated board are improved compared to Comparative Example 1, and the pressure resistance strength of the corrugated cardboard case is 20 to 20% higher than that of Comparative Example 1. It has improved by 30%.
Moreover, there is almost no difference in the amount of deformation of the cardboard case compared to Comparative Example 1. Example 2 Paper is made from waste paper pulp and has a basis weight of 125 g/m ² JIS-
An A-flute single-sided corrugated board was manufactured using a medium paper base paper equivalent to the P3904C grade and a liner with a basis weight of 200 g/m ² equivalent to the JISA grade of kraft pulp, and a starch glue was applied to the corrugated top of the single-sided corrugated board. after,
A sodium silicate solution made by diluting 100 parts by weight of No. 3 sodium silicate with 43 parts by weight of water was applied to the entire surface of the core at a hydraulic pressure of 6.
After spraying and applying it in a mist at Kg/ ^cm2 , a liner similar to the above was bonded to the top of the single-sided corrugated board.
Thereafter, it was dried by contacting it with a hot plate at 180°C to obtain a double-sided cardboard. The amount of sodium silicate sprayed during the above corrugated board production was 44c.c./m ² (solid content amount 15.4g/
^m2 ), and the cardboard lamination traveling speed is 130m/
The test was conducted at two speeds: minute and 200 m/min. Then,
Inner dimension 695 x 415 x 977 mm using the above double-sided cardboard
A type A-1 glue joint case was manufactured, and five handle holes of 100 x 30 mm were provided. In Comparative Example 2, the sodium silicate treatment was not performed. The performance of the above Example 2 and Comparative Example 2 was evaluated in the following second example.
Shown in the table.

[Table] As seen in Table 2 above, in Example 2, the adhesive strength and compressive strength of the cardboard were improved compared to Comparative Example 2, and even if the lamination speed was increased, the improvement was not affected much. . Especially when a handle hole is provided in the case, the pressure resistance of the case is 40% higher than that of Comparative Example 2.
It is noteworthy that this has improved by more than %.

[Brief explanation of the drawing]

1 and 2 are vertical cross-sectional views of the cardboard. A: Single-sided corrugated board, B: Double-sided corrugated board, 1: Medium cardboard, 1a: Medium cardboard surface, 1b, 4b: Sodium silicate coating layer, 2a, 2b: corrugated top, 3, 4: liner, 4a: liner surface.

Claims (1)

[Scope of Claims] 1. Production of double-sided corrugated board by bonding one liner to the corrugated top of a corrugated corrugated medium, and then adhering the other liner to the corrugated top on the opposite side of the single-sided corrugated board. In the method, after applying a sodium silicate solution to either or both of the medium side surface of the other liner and the surface of the medium facing the surface, the other liner is adhered to the corrugated top part of the single-sided corrugated board. A method for producing double-sided corrugated cardboard, which is characterized by: 2. The method for manufacturing double-sided corrugated cardboard according to claim 1, wherein a sodium silicate solution is applied to the surface of the corrugated cardboard of the single-sided corrugated cardboard, and after drying, a glue is applied to the top of the corrugated corrugated cardboard to adhere the liner. . 3. A patent claim in which a glue is applied to the corrugated top of a single-sided corrugated board, and then a sodium silicate solution is applied to either or both of the corrugated surface and the liner surface, and the liner is bonded to the corrugated top and then dried. A method for producing double-sided corrugated cardboard according to item 1. 4. The method for producing double-sided corrugated cardboard according to any one of claims 1 to 3, wherein the solid content of sodium silicate is 3 to 30 g/m ² .