JP5359703B2 - Sealed container and manufacturing method thereof - Google Patents

Description

  The present invention relates to a sealed container sealed by laser welding and a sealing method thereof, and more specifically, a sealed container in which sealing failure due to adhesion of contents or the like of a laser welded portion is prevented and a method for manufacturing the same. About.

As a method of sealing the container with a lid, in general, an adhesive is applied to the contact surface of the container and the cover material, and the contact surface of the container and the cover material is formed from a heat-sealable resin, and heat is applied. Sealing is performed by welding with a seal, and welding by heat sealing is generally adopted because it is a simple method, but it takes time for the heat welding process and the cooling process performed thereafter. Therefore, improvement of production efficiency is desired.
Further, in a heat seal method using a general heat seal bar, a certain area is required for the welded portion, and the welded surface needs to be planar. In addition, since heat must be conducted from the outer surface of the welded part to the sealing surface, it takes time to conduct heat in a thick-walled container, and productivity is reduced. There is a problem that is low.

In addition, since it takes a certain amount of time for the heat seal part to be cooled and completely sealed, the head space that has been thermally expanded due to the seal heat, especially when filling contents with self-generated pressure or hot filling. The gas may escape from the melted seal portion to cause seal peeling.
On the other hand, laser welding is also known as a method for welding containers and lids. For example, in Patent Document 1 below, a bottom lid and an upper lid are welded to a container body by laser welding and integrated. It has been proposed.
In the welding of the members of the package by such laser welding, since the welding is performed immediately after the laser beam irradiation as compared with the case of heat sealing, the time required for welding is shortened. In addition, in the sealing method of the container and lid by laser welding, various welding locations such as the outer surface side, inner surface side, or flange portion of the container side wall can be selected depending on the irradiation direction of the laser beam, and the shape is restricted. It is possible to perform welding reliably without receiving.

JP 2000-128166 A

However, when the lid material has an annular side wall portion around the top surface like a drop lid, and the inner surface of the annular side wall portion and the container side wall portion are laser welded after filling the contents, the sealing is poor. It has been found that there is a risk of content leakage or content corruption.
That is, when the contents are filled in the container, or when the contents filled by shaking during transportation in the production line from filling to sealing adhere to the inner surface of the container side wall, or the contents are filled by hot filling In such a state, even if the laser beam is irradiated to the close contact portion of the inner surface of the container and the side wall portion of the lid material, the two are not welded well and the sealing performance cannot be secured. I understood it.
As a method for solving such a problem, it is conceivable to reduce the amount of contents and increase the head space, but it is disadvantageous in terms of economy.

Accordingly, an object of the present invention is to provide a sealed container in which a sealing failure is effectively prevented in a sealed container of a type in which the inner surface of the container side wall and the side wall of the lid member are welded after the contents are filled.
Another object of the present invention is to provide a manufacturing method of a sealed container capable of effectively removing contents adhered to the inner surface of the container side wall when the cover material is fitted.

According to the present invention, a sealed container comprising a container having at least a bottom part and a side wall part and a lid that can be fitted to the opening of the container, and being sealed and integrated by laser welding, the lid is formed of the container. A plurality of annular projections that can come into contact with the upper inner surface of the sidewall portion; and a laser welding of the annular projection other than the lowermost annular projection to the container at a position where the annular projection is in close contact with the container sidewall A sealed container is provided.
In the sealed container of the present invention,
1. The fitting between the container and the lid has the largest fitting force at the laser weld,
2. One of the container or lid is colored,
3. One of the container or the lid has a multilayer structure in which the intermediate layer is colored;
4). An opening is formed on the top surface located on the inner side of the side wall of the lid, and the opening is sealed with a sealing material,
Is preferred.

According to the present invention, there is also provided a method for producing a sealed container comprising a container having at least a bottom part and a side wall part, and a lid having a side wall formed with a plurality of annular protrusions capable of contacting the upper inner surface of the side wall part. The lid is fitted to the container opening while the lowermost annular protrusion of the annular protrusion is in contact with the inner surface of the container side wall, and the annular protrusions other than the lowermost annular protrusion of the annular protrusion are in close contact with the inner surface of the container side wall. A method for manufacturing a sealed container is provided, in which the container and the lid are laser-welded by performing laser irradiation on the position.

According to the sealed container of the present invention, it is possible to effectively prevent poor sealing that has occurred in a sealed container of the type in which the inner wall of the container side wall and the side wall of the lid are welded after filling the contents.
Further, according to the sealed container of the present invention, since the content line can be set in the vicinity of the container opening, the head space of the container can be reduced, and the amount of gas replacement in the head space can be reduced. In addition, the size of the container relative to the amount of the contents can be reduced, the cost can be reduced by reducing the amount of material used and the weight of the container, and the transportability is also excellent.
Further, according to the sealed container manufacturing method of the present invention, the contents and water droplets adhering to the inner surface of the container side wall can be removed without going through a special process, so that laser welding can be performed stably. Therefore, it is possible to provide a sealed container with good productivity and excellent sealing performance.

It is a partial expanded sectional view of an example of the sealed container of the present invention. It is a partially expanded sectional view of another example of the sealed container of the present invention. It is a partially expanded sectional view of another example of the sealed container of the present invention. It is a partially expanded sectional view of another example of the sealed container of the present invention. It is a perspective view of an example of the sealed container of the present invention. It is a perspective view of another example of the sealed container of the present invention.

(Sealed container)
FIG. 1 is a partially enlarged cross-sectional view of an example of a sealed container of the present invention, (A) is a view showing a state where a drop lid 10 is fitted to a cup-type container 1, and (B) FIG. 3 is a view showing a state where a drop lid 10 is fitted to a cup-type container 1.
The cup-type container 1 includes a bottom (not shown), a side wall 2 and a flange 3, and the side wall 2 is tapered such that the diameter decreases as the lower part 2 a goes downward, and the upper part 2 b goes upward. It has an inversely tapered shape with a decreasing diameter, and a step 4 is formed between the upper end of the lower part 2a and the lower end of the upper part 2b. The step portion 4 is a stacking position when a plurality of cup-type containers 1 are stacked.
The drop lid 10 is formed with an annular side wall portion 12 protruding upward from the periphery of the top surface 11, and a flange 13 corresponding to the flange portion 3 of the cup-type container 1 is formed from the upper end of the side wall portion 12. Yes.

An important feature of the sealed container of the present invention is that a plurality of annular projections are formed on the outer surface of the side wall portion 12 of the drop lid 10. In the specific example shown in FIG. 14b is formed. The two annular protrusions 14 a and 14 b are both formed so as to be in contact with the upper inner surface of the side wall 2 of the cup-type container 1.
The annular protrusion 14a located below is formed so that the outer diameter of the drop lid at the part is larger than the annular protrusion 14b located above. As shown in FIG. When the lid member 10 is fitted to 1, the inner surface of the side wall portion 2 of the cup-type container 1 is moved downward (in the direction of arrow P in FIG. 1A). Therefore, when the contents etc. have adhered to the upper inner surface of the side wall part 2 of the cup-type container 1, it goes down while scraping off the attached contents etc., and it will be in the fitting state shown to FIG. 1 (B). Become.
In the fitted state shown in FIG. 1 (B), laser irradiation (arrow L) from the cup-shaped container 1 side to the position of the annular protrusion 14b located above causes the annular protrusion 14b to melt and the cup-shaped container 1 and Although the drop lid 10 is welded, as described above, the welding location where the annular protrusion 14b is located has already scraped off the attached contents and the like due to the passage of the annular protrusion 14a, so that laser welding is stably performed. The sealed package can be formed without causing poor sealing.

  In the specific example shown in FIG. 1, laser irradiation is performed from the outside of the container. In this case, as will be described later, a spot (not shown) that absorbs the laser beam and generates heat is formed in the drop lid 10. However, of course, laser irradiation can also be performed from the lid member side. In this case, it is sufficient that the container 1 has a portion that absorbs the laser beam and generates heat.

FIG. 2 is a partially enlarged cross-sectional view showing another example of the sealed container of the present invention, showing a mode in which the basic structure is the same as the specific example shown in FIG. is there.
That is, in the embodiment shown in FIG. 2, the annular protrusions 14a and 14b are formed as flexible annular protrusions whose thickness decreases toward the tip.
In this embodiment, since the annular protrusions 14a and 14b adhere to the inner surface of the side wall 2 of the cup-type container like a wiper and proceed downward, the contents attached to the inner surface of the container side wall can be effectively scraped off. it can.

The container used for the sealed container of the present invention is not limited to the cup-shaped container shown in FIGS. 1 and 2, and various types such as a tray type having a quadrangular or elliptical cross-sectional shape can be used. The shape can be adopted.
Also, as shown in FIGS. 1 and 2, the side wall of the container is not only tapered at the upper part and tapered at the lower part, but the upper part is reversely tapered and the inner diameter of the lower part is the same from the bottom part to the opening part. Various shapes such as a straight shape, a tapered shape whose inner diameter decreases as the entire side wall portion goes downward, or a straight shape where the entire side wall portion is straight, can be adopted. It is particularly preferable that the upper portion has a reverse taper shape in terms of ease of scraping off the attached contents.
The upper taper angle is not limited to this, but is preferably in the range of 8 to 12 ° with respect to the axis.

The lid used for the sealed container of the present invention is not limited to the drop lid shape shown in FIG. 1 and FIG. 2, but may be various as long as it has a side wall that can form an annular protrusion that can contact the inner surface of the side wall of the container. Shape can be adopted.
For example, although not limited to this, as shown in FIG. 3, the side wall portion hangs down from the top surface, and is a type that is in close contact with the inner surface of the container side wall as a so-called inner ring, or from the top surface as shown in FIG. Examples include a plug type in which a cylindrical side wall portion hangs down.
The shape of the ring-shaped protrusion formed on the side wall of the lid may be a quadrilateral shape in addition to a semicircular shape, a triangular shape, or the like, as shown in FIG.

The number of the annular protrusions may be at least two, that is, the annular protrusion located at the lowermost position for scraping off the contents attached to the inner surface of the container side wall and the upper annular protrusion serving as the laser welding portion.
When three or more annular protrusions are provided, and there is a large amount of contents adhering to the inner surface of the container side wall, a pocket is formed between the lowermost annular protrusion and the annular protrusion immediately above the annular protrusion. Thus, since the contents that could not be scraped off can be stored, it is possible to completely prevent the contents from adhering to the laser welding portion.
Further, the plurality of annular protrusions may be continuous ones at the roots of the upper and lower annular protrusions, or may be ones having a space between the roots of the upper and lower annular protrusions.
In order to improve the sealing performance of the sealed container by laser welding, it is preferable that the annular protrusion has the largest fitting force in the portion that becomes the laser welding portion in the fitting state of the container and the lid. It is preferable that the relationship between the inner diameter D1 of the container in the part and the outer diameter D2 of the upper annular projection part serving as the laser welding part is D2> D1, and particularly D2-D1 is in the range of 0.5 to 2.0 mm. It is preferable to adjust the protrusion amount of the annular protrusion or the taper angle of the container.
From the viewpoint of scraping off the contents attached to the inner surface of the container side wall, it is important that the relationship between the inner diameter D1 of the container serving as the laser welded portion and the outer diameter D3 of the lowermost annular projection is D1 ≦ D3. is there.

  Further, in the sealed container of the present invention, the portion sealed by laser welding cannot be easily opened by hand. Therefore, when providing easy-opening performance to the sealed container, other parts having easy-openability are available. It is desirable to form an opening. For example, as shown in FIGS. 5 and 6, the top surface 11 of the drop lid 10, a part of the top surface 11 in the specific example shown in FIG. 5, and a part other than the outer peripheral edge of the top surface 11 in the specific example shown in FIG. It is desirable to form the opening 15 and to seal the opening 15 with a sealing material 16 bonded with a sealing strength that can be opened by hand.

Since the container and the lid constituting the sealed container of the present invention generate heat by laser irradiation and weld and seal them together, they are transparent or capable of transmitting the laser beam at least on the laser beam incident side of the welded portion. It is necessary to be translucent, and in order to convert the laser beam into heat, it is necessary to provide a heat generating part in the vicinity of the interface of the welded part, and each of the welded parts of the container and the lid These resins are preferably the same type of resin.
As a resin capable of forming a transparent or translucent layer capable of transmitting a laser beam, a thermoplastic resin conventionally used in packaging containers can be used, but the laser transmittance is 70% or more, particularly 80% or more. These thermoplastic resins are suitable, and examples of such thermoplastic resins include olefin resins and polyester resins. The laser transmittance can be obtained by measuring the transmittance of light corresponding to the wavelength of the laser light to be used using a spectrophotometer.
In addition, even if it is the same thermoplastic resin, a laser transmittance changes with thickness of a layer, and in this invention, in the range of the thickness which the container or lid | cover (including an annular protrusion) mentioned later can take. It means having a transmittance of 70% or more.

Further, among the above-mentioned resins capable of transmitting the laser beam, the laser welded portion includes low-, medium-, and high-density polyethylene, isotactic polypropylene, propylene / ethylene copolymer, polybutene-1, and ethylene / propylene copolymer. It is desirable to use an olefin resin such as a polymer, an ethylene / butene-1 copolymer, a propylene / butene-1 copolymer, an ethylene / propylene / butene-1 copolymer, and the melting point is particularly 160 ° C. or less. It is preferable to use a thermoplastic resin because it can be easily welded.
Although the heat generating part should just be formed in any one of a container or a lid | cover, it is preferable from the point of the welding efficiency that it is formed in the interface vicinity of the annular protrusion of a container and a lid | cover. The heat generating part can be composed of a metal such as a metal foil or a metal plate, a coating film made of a colored paint such as black, or a resin containing an oxygen absorbent such as iron powder or carbon black, or a welded part itself. May be a polyamide resin, a polyester resin, a polyurethane resin, etc. capable of self-heating by laser irradiation, but a colored layer made of a thermoplastic resin is preferable from the viewpoint of productivity.

As the material having the heat generating portion, it is necessary to form a heat generating portion separately from a laminate having at least two layers consisting of a thermoplastic resin layer capable of transmitting a laser beam and capable of laser welding and a layer serving as a heat generating portion. Since it does not exist, it can be used suitably. Although not limited thereto, for example, an outer layer or an inner layer made of a thermoplastic resin that can transmit a laser beam and can be laser-welded, and an intermediate layer that becomes a heat generating portion such as a polyamide resin, an iron-based oxygen absorbent-containing resin, or an aluminum foil. It is particularly preferable to have a multilayer structure such as a three-layer structure. Of course, it is also possible to form a separate heat generating part only on the welded part, such as forming a black coating film on the welded part.
In addition, either the container or the lid may be formed from a resin-coated metal plate, and the other member to be combined may be made of a resin that can transmit a laser beam.

The thickness of the layer capable of transmitting a laser beam is preferably in the range of 5 to 500 μm, particularly 20 to 100 μm. If the thickness is less than the above range, reliable welding cannot be performed. On the other hand, if the thickness is thicker than the above range, it becomes difficult to make the laser beam reach the heat generating part under normal conditions. After all, reliable welding cannot be performed.
Other than the layer that can transmit the laser beam, it can be set as appropriate depending on the laminated structure of the container and the lid, the form of the package, or the application, and cannot be specified in general. For example, the container can transmit the laser beam. Consisting of a single layer of olefinic resin, and the lid is composed of a laminate of olefinic resin (laser transmission welded part) / colorant-containing olefinic resin (heat generating part) / olefinic resin (outer layer) in order from the inner surface side, When laser irradiation is performed from the container side, the thickness of the container is in the range of 200 to 1500 μm, the thickness of the lid welded portion (including the annular protrusion) is 5 to 500 μm, the thickness of the heat generating portion is 10 to 500 μm, The thickness of the outer layer is preferably in the range of 10 to 500 μm. The container is composed of a laminate of olefin resin (laser beam transmission welded portion) / colorant-containing olefin resin (heat generating portion) / olefin resin (outer layer) in order from the inner surface side, and the lid can transmit the laser beam. When made of olefin resin and laser irradiation from the lid side, the thickness of the welded part of the container is 5 to 500 μm, the thickness of the heat generating part is 10 to 500 μm, and the thickness of the outer layer is 10 to 500 μm, The thickness of the welded portion of the lid is preferably in the range of 200 to 1500 μm.

The above-described laminate can be produced by a conventionally known method such as a co-extrusion method, a thermal bonding method, or a dry lamination method using an adhesive.
Containers and lids used for the sealed container of the present invention are containers such as cups or trays formed by thermoforming such as vacuum forming, pressure forming, plug assist forming, film forming and sheet-like laminated materials, draw forming, injection forming. It can shape | mold by etc.

(Sealing method)
In the sealing method of the present invention, the above-described container and lid are fitted together while scraping off the contents attached to the inner surface of the container side wall with an annular projection formed on the side wall of the lid, and the annular projection located at the top By irradiating the abutting portion of the portion with the laser beam from the container side or the lid side, the abutting surfaces of the container and the annular protrusion are fused and adhered.
In the present invention, as described above, since the contact surfaces of the annular protrusions formed on the container and the lid are pressed against each other in the fitted state, a special fixture is used for laser irradiation. Although it is not necessary to use it, of course, a fixing tool can be used to further strengthen the fitting.

As the laser beam used in the present invention, a gas laser, a solid-state laser, a semiconductor laser, or the like can be used, and among these, a semiconductor laser can be preferably used.
The output of the laser oscillator is preferably 20 to 150 W, particularly 30 to 100 W, and the wavelength of the laser beam is preferably 200 nm to 20 μm, particularly 400 nm to 15 μm. This is commercially determined by the permeability of the resin, the nature of the substance that generates heat by absorbing the laser beam, and the output, price, and safety of the laser oscillator.
In the present invention, the spot diameter of the laser beam is preferably in the range of 0.2 to 3 mm, particularly 0.5 to 2 mm, from the viewpoint of hermeticity of the package.
Further, the focal length of the laser beam is preferably in the range of 10 to 200 mm, particularly 50 to 150 mm, and the thickness of the layer capable of transmitting the laser beam is in the range of +30 to 70 mm, while ensuring hermeticity by welding, It is preferable in preventing deterioration of the resin.
The laser beam sweep speed is preferably in the range of 50 to 300 mm / second, particularly 100 to 200 mm / second, from the viewpoint of preventing the deterioration of the resin while ensuring the sealing property by welding.

  As for the welding conditions, welding can be performed under various conditions as long as a calorific value at which the welded portion is equal to or higher than the melting point can be obtained. For example, if the welding time is to be shortened, the laser output is increased to rotate. It is sufficient to increase the speed, and in a situation where a high-power laser cannot be used, the irradiation time to the welded portion may be lengthened. In the case of a container, the rotation speed of the container may be decreased. Furthermore, if a laser output that can be sufficiently melted is obtained, the laser beam diameter can be increased to increase the welding width.

[Evaluation]
The burst strength test was conducted based on JIS Z0238, which is a test method for sealed soft packaging and containers.
Further, regarding the burst strength, 0.02 Mpa or more of the burst strength required for the retort sterilization container or the like in the test was used as a criterion for determining the sealing performance.

[Laser welding conditions]
Laser oscillator: made by Jena Optic
Semiconductor (GaAs) laser
Wavelength 807 ± 3nm
Maximum output 140W
Laser irradiation conditions: output 50W
Spot diameter 1mm
Irradiation time 4 seconds (irradiation linear velocity 118mm / second)
The cradle was rotated at 0.5 revolutions / second and irradiated for two revolutions.
Irradiation method: Irradiation was performed horizontally from the container side to the lid side.

[Example 1]
(Outside surface) 450 μm polypropylene / 30 μm adhesive layer / 90 μm EVOH (ethylene / vinyl alcohol copolymer resin) / 30 μm adhesive layer / 400 μm polypropylene (melting point: 160 ° C.) By the method, the flange portion shown in FIG. 1 having a reverse taper shape (taper angle: 10 degrees) whose diameter decreases as the upper portion of the side wall portion goes upward is formed with an opening outer diameter of 75 mm and an inner volume of 150 ml. A cup-shaped container was molded.
On the other hand, 500 ppm of carbon black is added to polypropylene resin (melting point: 160 ° C.), the thickness is 0.8 mm by injection molding, and the outer diameter of the side wall portion protruding upward from the peripheral edge of the top surface is 75 mm. Was molded.
The drop lid was provided with an upper annular projection having a semicircular cross section at a position 4 mm from the upper end of the side wall, and a lower annular projection was provided at an interval of 1 mm below.
The outer diameter of the upper annular protrusion was 63.5 mm, the outer diameter of the lower annular protrusion was 64.5 mm, and the inner diameter of the container at the portion to be the laser welded portion was 62.4 mm.
Fill the container with 130 g of water, support the flange part of the container with a cradle, push the lid, perform laser welding from the container side to the lid side under the above conditions, and the strength of the welded part is ruptured When evaluated by the strength test, no bursting occurred even when the pressure was increased to 0.1 Mpa, and sufficient sealing properties were obtained.

[Comparative Example 1]
In Example 1, except that the lower annular projection of the side wall portion of the drop lid was not provided, the burst strength was less than 0.02 Mpa when evaluated in the same manner, and sufficient sealing performance was obtained. I couldn't.

  From this result, even when water is attached to the side wall of the container, the container is formed by the lower annular protrusion by forming a plurality of annular protrusions on the side wall of the lid that can come into contact with the upper inner surface of the container. The water adhering to the side wall portion of the lid is removed, so that no water remains on the upper annular projection portion of the side wall of the lid and the side wall portion of the container which become the laser welding portion. For this reason, it can be seen that laser welding is reliably performed at the laser welding portion, and sufficient sealing performance is obtained.

Since the sealed container of the present invention is sealed by effectively removing the contents adhering to the inner surface of the container side wall and water vapor released from the contents, the contents need to be hot filled, or carbonic acid. It can be suitably used for contents having self-generated pressure such as beverages.
Further, since the head space of the container can be reduced, the size of the container relative to the amount of gas replacement in the head space and the amount of contents can be reduced, and the cost can be reduced by reducing the amount of material used and the weight of the container. In addition, it has excellent transportability.
Moreover, according to the sealing method of the sealed package of this invention, since the cooling process like the welding by the heat seal using the conventional hot plate is unnecessary, productivity can be improved. Further, even a relatively thick member can be sealed at high speed and stably, and at low cost and efficiently.

  DESCRIPTION OF SYMBOLS 1 Container, 2 side wall part, 3 flange part, 4 level | step difference part, 10 drop lid, 11 top surface, 12 side wall part, 13 flange, 14 annular protrusion, 15 opening part, 16 sealing material.

Claims (6)

In a sealed container comprising at least a container composed of a bottom part and a side wall part and a lid that can be fitted to the opening part of the container, and hermetically integrated by laser welding,
The lid has a side wall formed with a plurality of annular projections that can come into contact with the upper inner surface of the side wall portion of the container, and the annular projections other than the lowermost annular projection among the annular projections are in close contact with the container side wall. A sealed container characterized by being laser welded to the container at a position where   The sealed container according to claim 1, wherein the fitting of the container and the lid has the largest fitting force at the laser welding portion.   The sealed container according to claim 1, wherein one of the container and the lid is colored.   The sealed container according to claim 1, wherein one of the container and the lid has a multilayer structure in which an intermediate layer is colored.   The sealed container according to any one of claims 1 to 4, wherein an opening is formed in a top surface located inside the side wall of the lid, and the opening is sealed with a sealing material.   A method for manufacturing a sealed container comprising a container having at least a bottom part and a side wall part, and a lid having a side wall formed with a plurality of annular projections capable of contacting the upper inner surface of the side wall part of the container. The lowermost annular protrusion of the protrusion is fitted into the container opening while contacting the inner surface of the container side wall, and laser irradiation is performed at a position where the annular protrusion other than the lowermost annular protrusion is in close contact with the inner surface of the container side wall. Thus, a sealed container manufacturing method, wherein the container and the lid are laser-welded.

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