JPS6243792Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to corrugated board that is waterproof and non-breathable. In general, cardboard is an excellent packaging material and has been used as a packaging material in many ways since ancient times. On the other hand, in recent years, with the development of refrigeration technology, the number of frozen foods has increased rapidly, and most cases for transporting these frozen foods are made of cardboard. However, since ordinary cardboard is made up of multiple sheets of paper pasted together, it has the disadvantage that its strength rapidly decreases when it absorbs moisture, making it ideal for use in extreme environments such as frozen foods. When transporting low-temperature items, when the transport case is removed from the freezer during transport and exposed to the outside air, a large amount of moisture in the air immediately condenses, and as a result of this condensed moisture permeating the cardboard, its strength decreases. There was a problem that the case was so slow that it no longer functioned as a case. In addition, such cases have a problem in that the elasticity is too high, and when fruits and vegetables are stored, the moisture in the fruits and vegetables evaporates quickly, making it difficult to maintain freshness. Therefore, in order to solve the above problems, for example,
In Publication No. 51-93771, as shown in FIG. 4, films b and b of a water-resistant resin such as polyethylene or polyester are pasted on both outer surfaces of corrugated board liners a and a; is proposed. However, such a water-resistant film b
In the case where the liner A is simply attached to the surface of the liner a, the resin film b that gives the corrugated board water resistance is exposed to the surface of the corrugated board, so this resin film b is easily damaged. In addition to the disadvantages that if this resin film is easily damaged, the waterproof and non-breathable functions are easily damaged, if such a resin film is attached to the surface of the corrugated board, it will cause damage to the surface of the cardboard. In addition, in order to attach such resin film b to the surface of liner a, the step and box manufacturing conditions (especially temperature and adhesive) must be adjusted to the usual conditions. Due to the conditions of
This resulted in a decrease in productivity, and the resulting corrugated paperboard sheets also had drawbacks such as being prone to curling. In addition, examples of products that do not have the above-mentioned drawbacks include, for example,
No. 29985, as shown in Figure 5, a polyolefin resin film c with a thickness of 0.03 to 0.3 mm is sandwiched between two pieces of kraft paper d and d and pasted on a cardboard. A corrugated board with liner paper e has been proposed, which has improved the above-mentioned drawbacks such as the ease with which the resin film is damaged and the difficulty of printing. However, the thickness of the resin film c, which is 0.03 to 0.3 mm in this product, is generally very thick for providing water resistance, so this product is made of cardboard made of cheap kraft paper, etc. However, it had the drawbacks of being considerably more expensive and weighing more. Therefore, the inventor of the present invention conducted extensive research into why a resin film c as thick as 0.03 to 0.3 mm is necessary, and found that when forming these cardboards into three-dimensional containers, ruled lines are applied to them. At the bent part,
A large external force is applied by adding ruled lines and bending the cardboard, and the cardboard is greatly deformed at the bending part. c is also significantly elongated and deformed, and for this reason, if the resin film c is thin, the resin film c will be damaged at the bending part, and water and air will escape from the bending part. distribution becomes easier, and the strength begins to deteriorate from the folded part, which is the most important part of providing strength to the container. They realized that it was necessary to apply an abnormally thick resin film. Therefore, this idea was based on the above knowledge,
Even if the resin film interposed between the paper layers is thin, the resin film will not be damaged at the bending part, and therefore the container strength will not deteriorate from the bending part, making it waterproof and non-waterproof. The aim is to provide a corrugated board with breathability, and its gist is a polyolefin resin thin film in which 0.001 to 5% by weight of fine water-insoluble inorganic substances with an average particle size of 0.8μ or less are dispersed and mixed. According to the invention, a composite sheet for bonding two sheets of paper is used as a liner or as a liner and a corrugated core;
This corrugated cardboard is characterized by its waterproof and non-breathable properties. Embodiments will be explained with reference to FIGS. 1 and 2. 1 is a composite sheet, 2 is a liner base paper for cardboard
and 40 g/m ² of kraft paper 3 are adhered with a molten low-density polyethylene thin film 4 having a thickness of 8 μm. Particle size
0.05μ fine calcium carbonate 40% by weight
Approximately 0.5% was uniformly dispersed and mixed. The above composite sheet 1 was used as a liner, corrugated core paper for corrugated board was used as the corrugated core 5, and corrugated into double-sided corrugated board under normal conditions using a corrugator to obtain corrugated board A according to the present invention. Next, in order to demonstrate the performance of the corrugated board according to this invention, as a comparative example with the embodiment constructed as described above, first, liner base paper for corrugated board and kraft paper of 40 g/m ² were mixed with a thickness of 16 μm.
A composite sheet (not shown) bonded with a thin film of low-density polyethylene in a molten state was prepared. In this low density polyethylene, fine inorganic substances such as calcium carbonate were not dispersed and mixed as in the case of the previous example. This composite sheet was used as a liner, corrugated cardboard was used as the corrugated core, and corrugation was carried out under the same conditions as in the previous example to obtain corrugated board B. Therefore, the double-sided corrugated cardboard A of the present invention obtained as described above and the double-sided corrugated cardboard B of the known example were respectively made into a box under the same conditions, and the A
-1 type of cardboard cases P and Q were manufactured, and in order to test the waterproofness and non-breathability of these two types of cases, case P and case Q were each sealed in an H shape with adhesive tape, and After applying adhesive tape to each joint part of the case, a long-term water sprinkling test was conducted on the entire surface, and the case was opened at predetermined intervals to observe the wet state of the folded part inside the case. The table summarizes the results.

[Table] The symbols used in the table are: ◎ No water exposure at all 〇 Very little water exposure △ Some water exposure × Quite a lot of water exposure ×× Extremely a lot of water exposure. We also compared the peeling state of the craft paper 3 on the case surface, and found that container P had less peeling than case Q, which was better. As is clear from the above test results, the composite sheet 1 used for the cardboard A of case P has a low density polyethylene thin film 4 with a thickness of 8μ.
Compared to the thickness of the low-density polyethylene thin film of the composite sheet used for the cardboard B in case Q, which is 16 μm,
Although the composite sheet 1 is extremely thin, at about half the thickness, the waterproof performance is far superior to that of the composite sheet of the comparative example. This is due to the difference in whether the fine inorganic substance of calcium carbonate is dispersed and mixed in the low-density polyethylene thin film 4 or not. The calcium carbonate fine particles 40 are dispersed in the low-density polyethylene thin film 4.
It is presumed that if an appropriate amount of low density polyethylene is mixed and dispersed in the low density polyethylene thin film 4, when an external force such as tension is applied, the intermolecular shear stress in the low density polyethylene thin film 4 is relaxed, and as a result, it becomes easier to cause a larger deformation under a certain external force. Due to this action, even if the low density polyethylene thin film 4 used to form the composite sheet 1 is very thin, the thin film 4 will not be damaged at the bending portion for forming the case, and therefore it is considered that sufficient waterproofing can be exhibited even under severe wet conditions. In the above embodiment, the resin thin film 4 is formed from low density polyethylene, but this resin thin film 4 is not limited to low density polyethylene, and in other embodiments, it may be a polyolefin resin such as linear low density polyethylene, high density polyethylene, isotactic, or unoriented thin film of polypropylene, and it is not limited to the use of only one type, and in other embodiments, two or more types of resins may be mixed and used. In any embodiment, according to the present invention, the thickness of the resin thin film 4 does not need to be 0.03 to 0.3 mm as in the conventional example, and it is possible to use a thickness of 5.
In the above embodiment, the calcium carbonate fine particles 40 are dispersed and mixed in the low-density polyethylene thin film 4, but the water-insoluble inorganic material constituting this invention is not limited to calcium carbonate. In other embodiments,
One or more water-insoluble inorganic substances such as barium carbonate, magnesium carbonate, aluminum carbonate, calcium oxide, barium oxide, magnesium oxide, and aluminum oxide may be used in combination.
The average particle size of these inorganic substances is preferably 0.8 μm or less, and the amount used is preferably 0.001 to 5% by weight. As for the paper used to form the composite sheet 1, in addition to liner paper for corrugated board and kraft paper, various papers such as corrugated board core paper, tissue paper, coated paper and the like can be used. Furthermore, the waterproof and non-breathable corrugated board according to the present invention is one in which the liner of a single-faced corrugated board is made of the composite sheet 1, one or both of the two liners of a double-faced corrugated board is made of the composite sheet 1, and
Needless to say, this includes those in which one, two or three of the three liners in a double-sided corrugated board are the composite sheet 1, those in which one, two or three of the three liners are the composite sheet 1, and those in which the composite sheet 1 is used not only as a liner but also as a corrugated core. The step of bonding two sheets of paper with a thin polyolefin resin film can be easily performed by using an extrusion laminator, so when a composite sheet according to this invention is produced using an extrusion laminator, for example, before bonding the cardboard liner base paper 2' and the kraft paper 3' with the polyolefin resin film 4, if the bonding surfaces of the cardboard liner base paper 2' and the kraft paper 3' are oxidized with a strong oxidizing flame or the like to form thin layers 20, 30 of cellulose oxide on the surfaces and then bonded, the adhesive strength between the cardboard liner base paper 2' and the kraft paper 3' and the resin film 4 is increased,
The composite sheet 10 for forming corrugated board according to the present invention can be obtained, which has the added advantage that the two sheets of paper 2', 3' are less likely to peel off from the resin film 4 even under severe humid conditions. The waterproof and non-breathable corrugated board according to the present invention has been described above as an embodiment, and as can be understood from the above, the waterproof and non-breathable corrugated board according to the present invention does not require any special conditions when making corrugated boards and boxes, and can be made into corrugated boards and boxes at high speed like normal corrugated boards, and can be easily printed on its surface, and the resin thin film for achieving excellent waterproofness and non-breathability is extremely thin compared to conventional ones, so that it can be obtained at low cost. Therefore, the corrugated board according to the present invention can provide packaging containers with excellent strength at low cost for products used under humid conditions, such as marine products, fruits and vegetables, and frozen foods, and products that require prevention of permeation of water vapor, air, and various other gases.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing one embodiment of the present invention, Fig. 2 is an enlarged sectional view of the main part, Fig. 3 is a partial enlarged sectional view showing another embodiment, and Fig. 4 is a conventional example. FIG. 5 is a longitudinal sectional view showing another conventional example. DESCRIPTION OF SYMBOLS 1... Composite sheet, 2... Liner base paper for cardboard, 3... Kraft paper, 4... Polyolefin resin thin film, 40... Water-insoluble inorganic substance, 5...
Corrugated core.

Claims (1)

[Claims for Utility Model Registration] 1. A composite sheet that adheres two sheets of paper using a polyolefin resin thin film containing 0.001 to 5% by weight of fine water-insoluble inorganic substances with an average particle size of 0.8μ or less, A waterproof and non-breathable corrugated board characterized by its use as a liner or as a liner and corrugated core. 2 The thickness of the polyolefin resin thin film is 5 to 5.
20μ, and the polyolefin resin is low-density polyethylene, the waterproof and air-impermeable corrugated board according to claim 1 of the utility model registration. 3 The polyolefin resin film has a thickness of 5 to 20 μm.
The waterproof and non-breathable corrugated board according to claim 1, which is made of linear low-density polyethylene. 4 The polyolefin resin film has a thickness of 5 to 20 μm.
The waterproof and non-breathable corrugated board according to claim 1 of the utility model registration claim, which is made of high-density polyethylene. 5 The polyolefin resin film has a thickness of 5 to 20 μm.
isotactic polypropylene,
A corrugated board having waterproofness and non-breathability as set forth in claim 1 of the utility model registration claim. 6 Utility model registration claims Paragraphs 1 to 6, wherein the paper forming the composite sheet is cardboard base paper
The waterproof and non-breathable corrugated board according to any of Item 5. 7. The waterproof and air-impermeable corrugated board according to any one of claims 1 to 5, wherein the paper forming the composite sheet is kraft paper.