JPS5844075B2 - Method for manufacturing paperboard containers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a paperboard container with excellent water resistance.

BACKGROUND ART Conventionally, packaging bodies made of paperboard filled with a liquid or paste-like substance and sealed with a lid have been widely used as a sales format for foods and the like.

In such paperboard containers, one method for imparting water resistance, oil resistance, etc. to the inner surface of the container is to line the inner surface of the container with a thermoplastic resin film by vacuum forming.

If the outer surface of a paperboard container is also required to be water resistant, it is possible to make the container using paperboard coated with synthetic resin in advance, with the coated surface as the outer surface, and then line the inner surface of the container with a film by vacuum forming. However, since there is a water-resistant layer on the outer surface of the container, it is impossible for air to be sucked through the paperboard, and in order to make the film adhere closely to the inner surface of the container, it is necessary to provide ventilation at the joint between the side wall and bottom wall. I have to do it.

Therefore, in order to provide air permeability and water resistance to the joint between the side wall and the bottom wall, Japanese Patent Publication No. 43-25479 discloses a method in which the side wall and the bottom wall are continuously bonded in the circumferential direction with an adhesive. Although it is stated that a non-adhesive part with a very narrow width should be formed to prevent water infiltration but still have air permeability, or that a breathable adhesive should be used as an adhesive, In the adhesive bonding method, the adhesive spreads and spreads when pressed, making it impossible to provide a non-bonded portion of a predetermined width.

If the non-adhesive area is wide, water can enter from the outside and cause the seam to separate, weakening the strength of the container and causing it to break if it is subjected to impact during distribution, or even if it is not damaged, it will damage its appearance and lose its product value. Moreover, if the non-adhesive area is narrow, air permeability is impaired, making it difficult to line the inner surface of the container with a film.

Furthermore, even with breathable adhesives, there is a drawback that lining with a film is difficult.

The present invention has been made to eliminate the drawbacks of the conventional paperboard container manufacturing method described above and to obtain a paperboard container that has excellent water resistance on both the inner and outer surfaces. A bottom wall with a thermoplastic resin water-resistant layer on the lower surface and a connecting edge formed by bending the outer periphery downward is fitted into the inner lower part of the cylindrical side wall having a resin water-resistant layer, and the water-resistant layer at the lower end of the side wall A thermoplastic resin film is applied to the inner surface of the paperboard container, which is formed by bending along the lower surface of the bottom wall and the connecting edge, and joining the side wall and bottom wall, using a vacuum forming method, a pressure forming method, or a combination of these methods. The paperboard is lined by a molding method, and then the bottom wall and the bent part along the bottom wall at the lower end of the side wall are pressed together and ultrasonic vibration is applied to fuse the two together. The problem lies in the method of manufacturing the container.

Next, the present invention will be explained with reference to the drawings.

Fig. 1 is a partially omitted sectional view showing an example of a paperboard container obtained in the present invention in a fused state, and Fig. 2 is a partially enlarged sectional view of Fig. 1, where 1 is a cylindrical side wall. , 2 is a circular bottom wall.

The side wall 1 is made of a paperboard 11 having a thermoplastic resin water-resistant layer 12 on the outer surface in a tapered cylindrical shape with a wide upper end and a narrow lower end, and the bottom wall 2 is made of a paperboard 21 having a thermoplastic resin water-resistant layer 22 on the lower surface. The connecting edge 23 is formed by bending the outer peripheral edge downward.

This bottom wall 2 is fitted into the lower part of the side wall 1, and the water-resistant layer 12 at the lower end of the side wall 1 is connected to the water-resistant layer 22 on the lower surface of the bottom wall and the connecting edge 2.
3, the side wall 1 and the bottom wall 2 are joined, and the paperboard container A is assembled.

That is, the side wall 1 and the bottom wall 2 are such that the lower end of the side wall 1 is connected to the connecting edge 2.
3 is folded back to form a folded edge 13,
It is further bent along the lower surface of the bottom wall 2, and folded back so that the water-resistant layer 12 of the side wall 1 is overlapped with the lower surface of the bottom wall 2 to form an annular ridge 14 along the bottom wall 2. The lower end of the paperboard 11 of the side wall 1 is bent and hung down along the connecting edge 23 of the bottom wall 2 to form a hanging edge 15. By bending the lower end of the side wall 1 in this way, the paperboard 11 of the side wall 1 is folded. The connecting edge 23 of the bottom wall 2 is held between the two by the repulsive force of the curved portion.

In order to bend the lower end of the side wall 1 and clamp and connect the connecting edge 23 of the bottom wall 2, the lower end of the side wall 1 is curled along the bottom wall 2 and the connecting edge 23, and the curled portion It is only necessary to press it toward the corner of the bottom wall 2 and the connecting edge 23.

In the illustrated example, the lower end of the connecting edge 23 has a raised edge 24 that is folded back inward, but if this raised edge 24 is formed, the bottom wall 2 can be attached to the side wall 1. Even if an upward lifting force acts on the rising edge 24, the upper end of the rising edge 24 hits the lower end of the hanging edge 15, and the bottom wall 2 does not come off from the side wall 1.
This is preferred because it will be firmly connected to the side wall 1.

Further, in this paperboard container A, the paperboards 11 and 21 may be those used for food packaging, but it is preferable to use ones with excellent water resistance.

In addition, as the thermoplastic resin water-resistant layer 12.22, low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acetate copolymer, etc., which are water-resistant and have good adhesion to paperboard, are preferably used alone or in mixtures. Yes, polypropylene,
Ethylene-propylene copolymers and the like can also be used.

The water-resistant layer 12.22 preferably has a thickness of at least 0.02 mm in order to be pinhole-free.

Since the bottom wall 2 of the paperboard container A is simply joined by bending the lower end of the side wall 1, there remains a gap between the bottom wall 2 and the side wall 1 that communicates with the inside of the container and the outside. Therefore, the inner surface of the container A can be lined with a thermoplastic resin film 3 by a vacuum forming method, a pressure forming method, or a forming method using both of these methods.

The thermoplastic resin film 3 may be any film made of vacuum-formable resin, such as polyethylene,
Polypropylene, polystyrene, ethylene-vinyl acetate copolymer, ethylene-ethyl acetate copolymer, ionomer resin, polyvinyl chloride, polyvinylidene chloride, ABS
It is a single-layer or multi-layer film made of resin, acrylonitrile resin, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate copolymer, polyamide, etc., and is used depending on the purpose.

For these films that do not adhere well to paperboard, a heat-sensitive adhesive layer such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, or ethylene-acrylic acid ester copolymer may be applied as a surface layer. Preferably.

After lining the paperboard container A with a thermoplastic resin film 3, the bottom wall 2 and the bent portion along the lower surface of the bottom wall 2 at the lower end of the side wall 1, that is, the ridge 14 in the figure, are pressed together and subjected to ultrasonic vibration. By giving , the two are fused together.

In the figure, 4 is a fixed type, and 5 is a vibrating type.

The fixed mold 4 and the vibrating mold 5 have a cylindrical shape, and are adapted to clamp the projecting edge 14 and the bottom wall 2 between their tips.

The vibration mold 5 is fixed to a vibration part (not shown) of an ultrasonic vibration generator, and serves as a tool horn in an ultrasonic welder.

The vibrating part and the vibrating die 5 are configured such that the end surfaces of the vibrating die 5 are in contact with and away from the bottom wall 2 applied to the fixed die 4 using an air cylinder or the like.

Then, the downward protrusion 14 of the bottom wall 2 of the paperboard container A, whose inner surface is lined with the film 3, is applied to the fixed mold 4, and the vibrating mold 5 is pressed against the bottom wall 2 inside the container A. is pressed between the fixed mold 4 and the vibrating mold 5, and then ultrasonic vibrations are reflected on the vibrating mold 5 by the vibrating section.

When ultrasonic vibration is applied to the vibrating mold 5, ultrasonic heat generation occurs at the overlapping interface between the downward water-resistant layer 22 of the bottom wall 2 and the water-resistant layer 12 of the flange 14, and the two-needle water layer 22 and 12 are melted, and the ultrasonic vibrations are stopped and the parts are cooled under pressure and fused together.

In the figure, 6 indicates this fused portion. By thus fusing the water-resistant layers 12 and 22 between the projecting edge 14 and the lower surface of the bottom wall 2, the space between the side wall 1 and the bottom wall 2 is sealed, resulting in a container with excellent water resistance. At the same time, the side wall 1 and the bottom wall 2 are integrated to form a strong container.

Note that the paperboard containers obtained in this way are often used with a lid placed on them and sealed after being filled with the contents, so the top surface should be at the opening edge to ensure a good seal with the lid. It is best to form a flat tsuba.

To form such a tsuba, curl the opening edge,
What is necessary is to press and dip to form a triple-layered tsuba, and then fuse this tsuba using ultrasonic vibration.

The method for manufacturing the paperboard container of the present invention is as described above, in which the lower end of the side wall is bent and the side wall and the bottom wall are joined, so that air permeability is maintained between the two. Therefore, it is possible to easily line the inner surface of the container with a water-resistant thermoplastic resin film in close contact with the inner surface of the container by a vacuum forming method, a pressure forming method, or a molding method that uses both of these methods.

In other words, the lower end of the side wall is bent so that its water-resistant layer follows the water-resistant layer downward from the bottom wall, and the bent part τ'a between the bottom wall and the bottom wall at the lower end of the side wall is the same. Since they are on two flat surfaces, they can be compressed uniformly when they are compressed and fused by applying ultrasonic vibrations, and heat is generated uniformly only between the water layers of both needles to fuse the entire circumference. A strong paperboard container with excellent water resistance is obtained.

In addition, since heat is generated only between the water layers of both needles, the water-resistant layers on the inner and outer surfaces of the container are not melted and damaged, making it possible to manufacture paperboard containers with reliable water resistance on the inner and outer surfaces. There is no need to use adhesives or adhesives, making manufacturing easy and efficient.

[Brief explanation of the drawing]

FIG. 1 is a partially omitted sectional view showing an example of a paperboard container obtained in the present invention in a fused state, and FIG. 2 is an enlarged sectional view showing the main part of FIG. 1. 1: Side wall, 2: Bottom wall, 11, 21: Paperboard, 12゜22:
Thermoplastic resin water-resistant layer, 13: folded edge, 14: projecting edge, 15
: hanging edge, 23: connecting edge, 24: rising edge, 3: thermoplastic resin film, 4: fixed type, 5: vibrating type, 6: fused part.

Claims (1)

[Claims] 1. A bottom wall having a thermoplastic resin water-resistant layer on the lower surface and having a connecting edge formed by bending the outer peripheral edge downward is fitted into the inner lower part of the cylindrical side wall having a thermoplastic resin water-resistant layer on the outer surface, The water-resistant layer at the lower end of the side wall is bent along the lower surface of the bottom wall and the connecting edge, and a thermoplastic resin film is applied by vacuum forming or compressed air to the inner surface of the paperboard container where the side wall and bottom wall are joined. Lining is performed by a molding method or a molding method that uses both of these methods, and then the bottom wall and the bent portion along the bottom wall at the lower end of the side wall are pressed together and ultrasonic vibration is applied to cause fusion between the two. A method for manufacturing paperboard containers.