JPH0446747B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a corrugated board sheet made of plastic film liner that is inexpensive and has excellent water resistance.

[Problems to be solved by conventional technology and invention]

Normal paper cardboard has liners made of paper such as kraft paper, so cardboard sheets with liners on both the front and back, such as double-sided or multi-sided,
It is a completely plate-like material with some rigidity, and cannot be rolled up or used on a curved surface like single-sided cardboard, and the paper quality is not only water resistant, but also has good cushioning properties and scratch resistance. It was not satisfactory, and had some disadvantages, such as being limited in terms of transportation, storage, and as a packaging material. In addition, since the adhesive to the core is starch glue, it lacks water resistance and has the drawback of extremely decreasing strength due to moisture absorption.

For this reason, the inventor first conducted extensive research to form a water-resistant layer on the outer layer of the liner, and developed and provided a water-resistant corrugated board in which a plastic film layer is formed on the outer layer of a paper liner, and a method for manufacturing the same.

However, it cannot be denied that forming a plastic film layer on the surface of the conventional paper liner layer increases the amount of materials and costs.

In addition, still using starch glue for adhesive is a disadvantage for water resistance;
The use of water-resistant adhesives causes even higher costs.

The inventor of the present invention has conducted repeated research in order to provide a corrugated board with excellent water resistance at a low cost. The liner consists of a single plastic film layer that has been completely removed.
In addition, even if it is double-sided corrugated cardboard, it has been successfully produced that can be rolled up and used on curved surfaces.

[Means to solve the problem]

In other words, the corrugated board sheet of the present invention has a plastic film made of a heat-fusible resin with a low melting point on at least the inside surface, and a plastic film alone on one or both sides of the core, which is corrugated using the heat-fusibility of the inside surface. It is characterized by being adhesively bonded as a liner.

[Effect]

Conventionally, among corrugated cardboard structures, only single-sided corrugated cardboard can be used for winding or curved surfaces. This is because if the liners on both the front and back sides were made of paper, the corrugated cardboard structure would become a somewhat rigid plate-like body that could not be formed into a curved surface.

However, in the case of the cardboard sheet of the present invention,
Since at least one side is made of only a flexible plastic film liner, the plastic film liner side can be freely bent into a curved shape.

Therefore, in the corrugated cardboard sheet of the present invention, even if it is a double-sided or multi-sided corrugated structure, the corrugated cardboard sheet can be rolled up or used in a curved shape.

This has never been seen in conventional double-sided corrugated cardboard structures, and it is highly anticipated that new applications and markets will be developed using this property.

In addition, as a packaging material, the plastic film liner surface according to the present invention not only has better water resistance than the conventional paper liner surface, but since it is a liner made of plastic film alone and does not contain paper, it has good cushioning properties and contents. It is also extremely good at preventing scratches on objects. This effect is particularly noticeable at the corners of containers and the like.

In addition, the corrugated cardboard sheet of the present invention retains the characteristics of conventional cardboard due to its corrugated core, eliminates the need for adhesive by skillfully utilizing heat-fusible resin, and further maintains its shape as a liner. By using a flexible plastic film, it is possible to eliminate the paper layer from the conventional liner and provide a corrugated board sheet that is inexpensive, has excellent water resistance, and is easy to work with.

This also makes it possible to expand the application to fields where conventional water-resistant corrugated cardboard could not be used.

It goes without saying that the types of corrugated cardboard sheets include single-sided corrugated cardboard, double-sided corrugated cardboard, double-sided corrugated cardboard, multiple double-sided corrugated cardboard, etc., as long as the purpose of the present invention can be achieved.

〔Example〕

Next, the present invention will be explained based on the drawings. Fig. 1 is a perspective sectional view showing the structure of a corrugated board sheet 1 according to an embodiment of the present invention. It consists of film liners 3, 3. Further, this film liner 3 has a heat-fusible film 3a as an inner layer (on the core 2 side) and a stretched reinforced film 3b having excellent mechanical properties as an outer layer.

The most typical example of the heat-fusible film 3a is a low-melting-point polyethylene film or an ethylene copolymer film that can be easily heat-sealed. This portion is heated and melted by heat conduction, and the top of the step of the core 2 comes into contact with it and pressurizes it, joining each other.

As the stretched reinforced film 3b, a uniaxially or biaxially stretched polypropylene film is most commonly used. This stretched reinforced film 3b is a reinforcing base material laminated to the heat-welded film 3a in order to maintain the shape of the liner 3, and even after the step top of the core 2 and the heat-welded film 3a are heat-pressed, this stretched and reinforced film 3b is Liner 3 with reinforced film 3b
can maintain normal morphology.

In general, polyester films and biaxially oriented polypropylene films are difficult to heat-bond, especially heat-seal, so they are laminated with polyethylene films that have low heat resistance and can be heat-sealed, creating a so-called laminate film that has heat-sealable properties. It is commercially available. In this embodiment, this laminate film can be used as the film liner 3.

Alternatively, for example, polyethylene raw material may be heated and melted in an extruder, extruded into a film having a constant thickness, laminated on the stretched and reinforced polypropylene film 3b, and simultaneously welded to the top of the step of the core 2.

In the above embodiments, the case where the film liner 3 is formed by laminating the thermofusible film 3a using the stretched reinforced film 3b as a plastic base material has been described, but the plastic base material is not necessarily limited to the stretched reinforced film. In short, any plastic film that has a high melting point and is difficult to thermally bond can be used. Therefore, for example, polyester film, cellophane film, acetate film, etc. can also be used as the base material for laminating the heat-fusible film 3a.

In this way, in the corrugated board sheet of the present invention, the film constituting the liner 3 itself is directly adhered to the corrugated top of the core 2 due to its thermal weldability, so it can be used with starch glue used in ordinary corrugated board or with conventional water-resistant corrugated board. There is no need for hot melt agents or water-resistant adhesives to be used.

FIG. 2 shows an embodiment in which the film liner 3 is not a laminate film as shown in FIG. 1, but is made of a slightly thick heat-weldable polyethylene film 3a alone. As described above, the slightly thicker heat-fusible film 3a can be bonded to the step top of the core 2 under heating conditions that melt only the inner surface thereof, and can also maintain its shape as a liner. can. Note that the other liner 4 is a normal paper liner.

In this embodiment, since there is a large difference in thermal shrinkage rate between the film liner 3 and the paper liner 4, the film liner 3 tends to warp greatly. However, if this property is utilized, it is suitable for wrapping highly hygroscopic products by wrapping them on the film liner 3 side.

Fig. 3 shows another embodiment, in which the plastic reinforcement material for the outer layer is a cloth 5 made of a plain-woven fabric made of medium-low pressure polyethylene film or polypropylene film flat yarn (stretched tape) or split yarn, or a cloth 5 obtained by laminating and bonding vertically and horizontally. It uses non-woven fabric.

A film liner 3 made of such a cloth 5 or a nonwoven fabric as a base material and a heat-welded film 3a laminated thereon has much higher mechanical strength such as bursting strength and tearing strength than the laminated film liner shown in FIG. Because it has excellent properties, it can be used in the field of fishing boxes, which have traditionally been made of wood.

Note that in all of the above examples, heat weldability is imparted using a heat fusible film, but the heat weldability imparted to the base film is not limited to the above examples, and PVC/PVC This can also be achieved by coating with a coating resin such as a copolymer or styrene-butadiene rubber, with similar effects and results.
It is something that can exhibit effects.

FIG. 4 is a configuration diagram of an embodiment of the apparatus for manufacturing the corrugated sheet 1 of the present invention, which has the advantage that, compared to conventional corrugating machines, it does not require any adhesive device using adhesives such as starch glue. The difference is that a band sealer method using an endless belt is used in the heating section of the double facer section.

That is, the paper core base paper 2a is heated with a preheater and then placed between the corrugating rolls 6, 6, and the laminate film 3c for the front liner, which has a heat-fusible film laminated on the inner surface, is placed on the press roll in an unheated state. 7, one corrugated top of the core 2 and a heat-welding film are pressed together and heat-welded at the same time to form a single-sided corrugated board 8.

In this instant bonding process using the corrugating roll 6 and press roll 7, the heat to melt the heat-welded film is applied from the corrugating roll 6 side, and the press roll 7 is not heated, so the reinforcing film of the outer layer hardly changes. .

The single-sided corrugated cardboard 8 is fed as is into the heating section 9 of the double facer section. At the same time, the laminate film 3d for the back liner is fed into the heating section 9 in order to thermally weld its heat-welded film layer to the top of the other corrugated board of the single-sided corrugated board 8.

In this heating section 9, unlike the instantaneous heat and pressure bonding between the corrugated roll 6 and the press roll 7, the contact pressure between the core and the heat-welded film is relaxed to the extent that the core is not crushed. The thermal welding of the thermal welding film on top takes time.

Further, since heating is applied from the hot plate 10 on which the laminate film 3d is placed, the outer layer of the laminate film, that is, the film reinforcing base material, which needs to maintain the liner shape, must be protected from the heating of the hot plate 10.

In this embodiment, a buffer film 11 is interposed in the form of an endless belt between the laminate film 3d and the hot plate 10 to protect the film reinforcing base material from the hot plate 10, and to appropriately apply melting heat to the heat-welded film. It is conducted to Furthermore, the buffer film 11 is constructed in the shape of an endless belt for economical use, and the corrugated cardboard sheet 1 is transported smoothly by utilizing the appropriate frictional resistance on the surface of the buffer film 11.

As the buffer film 11, a material having a high melting temperature, excellent strength, and appropriate thermal conductivity, and having an appropriate thickness is used. The simplest method is to use kraft paper or ordinary corrugated paper sheets formed into an endless belt. However, it is preferable to use a sheet of heat-resistant film such as Teflon or heat-resistant inorganic fiber whose surface has been treated with Teflon as a buffer film and form it into an endless belt.

As the roller 13 for the belt 12 shown in the figure, an idle roller or a driven roller is used depending on the degree of friction between the belt 12 and the film liner 3d. The temperature of the hot plate 10 is determined based on the material, thickness, moving speed, etc. of the belt 12 so that the heat conducted through the belt 12 heats and melts only the inner heat-sealing film.

The corrugated cardboard sheet 1 in the heating section 9 is pressed against the endless belt 12 by the corrugating belt 14, and in the process of being conveyed together with the belt 12, the amount of heat required for thermal welding of the back side film liner and the core is transferred to a hot plate. Receive from 10.

Note that if the endless belt 12 did not have the buffer film 11, the corrugated sheet 1 would not move on the hot plate 10 due to friction between the outer layer film of the back side film liner and the top surface of the hot plate 10, and if there was even a slight movement, The outer layer film rubs against the top surface of the hot plate and is damaged.

The buffer film 11 prevents this and also relieves the heat from the hot plate 10 and transmits it to the back liner, thereby preventing the outer layer film of the back liner from melting. Moreover, while passing over the hot plate, the temperature and time are given to melt the inner layer of heat-sealed film. By taking this time appropriately, melt bonding can be completed at an appropriate temperature.

In the heating section 9, the corrugated board sheet 1 whose core and back side film liner have been completely bonded passes through the next cooling section 15, and is cut into a predetermined size by a cutter 16.

〔Effect of the invention〕

The corrugated board sheet of the present invention produced in this way has a liner made only of plastic film and is also bonded to the core using a heat-fusible resin, so it can be used for packaging products that require water resistance, such as packaging for products that require water resistance. It can also be used as a fishing box.

Conventionally, among corrugated cardboard structures, only single-sided corrugated cardboard can be used for winding or curved surfaces. This is because if the liners on both the front and back sides were made of paper, the corrugated cardboard structure would become a somewhat rigid plate-like body that could not be formed into a curved surface.

However, in the case of the cardboard sheet of the present invention,
Since at least one side is made of only a flexible plastic film liner, the plastic film liner side can be freely bent into a curved shape.

Therefore, in the corrugated cardboard sheet of the present invention, even if it is a double-sided or multi-sided corrugated structure, the corrugated cardboard sheet can be rolled up or used in a curved shape.

This has never been seen in conventional double-sided corrugated cardboard structures, and it is highly anticipated that new applications and markets will be developed using this property.

In addition, as a packaging material, the plastic film liner surface according to the present invention not only has better water resistance than the conventional paper liner surface, but since it is a liner made of plastic film alone and does not contain paper, it has good cushioning properties and contents. It is also extremely good at preventing scratches on objects. This effect is particularly noticeable at the corners of containers and the like.

Furthermore, since paper materials and adhesives are rationalized in this film liner, it can be manufactured at a lower cost than ordinary corrugated cardboard sheets.

As described above, the corrugated board sheet of the present invention is highly practical, expanding the uses of corrugated board and helping to reduce costs.

The core shown in the above embodiments was made of paper alone, but the core may be made of a plastic sheet, a film laminated on both sides with paper, or a thicker plastic sheet alone. By configuring, the water resistance of the corrugated cardboard sheet of the present invention can be further improved,
It is possible to provide so-called completely waterproof packaging materials.

[Brief explanation of drawings]

1 to 3 are perspective sectional views showing the structure of a corrugated board sheet according to an embodiment of the present invention, respectively, and FIG. 4 is a configuration diagram of an embodiment of an apparatus for manufacturing the same corrugated board sheet. 1... Corrugated cardboard sheet, 2... Core, 3... Film liner, 3a... Heat-fusible film, 3
b...Stretched reinforced film, 4...Paper liner, 5
...Film cloth.

Claims (1)

[Claims] 1. Utilizing the heat-fusibility of a plastic film whose inner surface is made of a heat-fusible resin with a low melting point, the plastic film alone is attached to one or both sides of a corrugated core. A corrugated cardboard sheet that is glued together as a film liner. 2. The corrugated board sheet according to claim 1, wherein the plastic film is a laminate film made by laminating a heat-fusible film on a stretched reinforced film as a base material.