JP2698809B2 - Heat sealing method for glass containers for hermetic packaging - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for heat sealing a glass container for hermetically sealed packaging.

2. Description of the Related Art Conventionally, powdery, liquid and viscous foods can be sealed and packaged in glass containers such as bottles by filling the foods with a metal cap at the mouth of the glass container, or by using a metal or synthetic material. It was sealed by screwing a resin screw cap or by covering it with a crown. Conventionally, a lid made of a metal foil on which a heat-adhesive resin is laminated is bonded to the mouth of a glass container by heat sealing.

Problems to be Solved by the Invention However, there has been a problem that the cap and the crown described above are relatively difficult to open and costly. When the heat-adhesive resin laminated on the metal foil is bonded to the mouth of the glass container by heat sealing, if the contents of the container are powder such as milk powder, instant coffee, etc., the gap between the mouth of the glass container and the lid material is used. There is no decrease in the adhesive strength of the adhesive part, but if the contents are liquid or viscous material such as sake, juice, jam, etc., heat sealing adhesion between the glass container mouth and the lid material during storage There is a problem that water invades into the part, the adhesive strength is remarkably reduced, and in severe cases, the lid is peeled off.

In particular, when a lid material is directly heat-bonded to the mouth of a glass container, the surface of the mouth of the glass container is porous.
In recent years, it has been developed to use a carboxyl-modified form of a saponified ethylene-vinyl acetate copolymer as a heat-adhesive resin to be applied to a lid material because of its relatively weak polarity and poor adhesiveness (for example, See Japanese Unexamined Patent Publication No. 60-177802).

Such a thermo-adhesive resin is excellent in thermo-adhesiveness in a short time and at a relatively low temperature, but the content of the glass container is, for example, a liquid or a viscous material such as sake, juice and jam. In such a case, the contents adhere to the mouth of the container at the time of filling or transport of the glass container containing the contents at the sealing line for filling the contents, and this becomes a foreign substance at the time of heat sealing, and originally the surface of the mouth of the glass container is contaminated. On the other hand, even if the heat-adhesive resin of the lid material has good adhesiveness, the problem that the original adhesiveness is not exhibited due to the presence of such contaminants at the time of heat sealing, resulting in poor bonding. there were. In addition, in the case of the conventional heat-adhesive resin, when water enters the bonding portion after heat sealing, there is a problem that the bonding force is remarkably reduced and the lid material is easily peeled off from the bonding interface.

Conventionally, a heat-adhesive resin layer A is provided on the upper portion of the mouth of a glass container, and a heat-adhesive resin B is also provided on a base material such as an aluminum foil for a cover material, and both resin layers are adhered by heat sealing. Materials for hermetically sealed packages adapted to be used are known. There are two types of this conventional material for a sealed package. Specifically, (I) the resin layers A and B are different, and (A) the ionomer alone or a mixture of the ionomer and another resin. When the resin layer (B) is either a resin alone or (b) polyethylene alone or a mixed resin of polyethylene and another resin (for example, see JP-A-59-103862), Polypropylene alone or a mixed resin of modified polypropylene and another resin, and the resin layer B is a mixed resin of at least one of polypropylene and modified polypropylene, or a mixture of at least one of modified polypropylene and modified polypropylene and another resin. There are some cases (for example, see JP-A-59-103863). In addition, in the case of any of the above (I) and (II), this conventional material for a sealed package is used to bond the heat-adhesive resin layer A on the glass container side to the heat-adhesive resin layer B on the lid material side. The strength was adjusted to, for example, about 0.8 to 3.0 kg / 15 mm width so as to meet the condition of easy open (easy to open), and peeled off at the bonding interface between the two. However, in this case, since the adhesive strength between the resin layer A on the container side and the resin layer B on the lid material side is relatively weak, the contents of the glass container are liquid or viscous material such as sake, juice, jam, and the like. In such a case, in the filling seal line of the contents as described above, if the contents attached to the mouth of the container are interposed as impurities at the time of heat sealing, the original adhesiveness of both resin layers AB is not exhibited, In addition, there is a problem that a bonding failure occurs, and in addition, since the thermal adhesive resin layer A on the glass container side and the thermal adhesive resin layer B on the lid material are peeled off at the bonding interface, after opening the container, Inevitably, the resin layer A remains, and the appearance of the glass container is impaired.

An object of the present invention is to solve the above-mentioned problems of the prior art,
Using a heat-sealing material containing a carboxyl-modified form of a saponified ethylene-vinyl acetate copolymer having excellent adhesion to both the mouth surface of the glass container and the surface of the metal foil of the lid, Heat sealing material layer and the heat sealing material layer on the lid material side can be very firmly and integrally bonded. When opening, the adhesive interface between both heat sealing material layers does not peel off and the glass container side Even if the heat sealing material layer is peeled off from the surface of the glass container, so that the contents of the container are liquid or viscous material such as sake, juice, jam, etc., the original adhesiveness of both heat sealing material layers is maintained. In addition to being sufficiently exhibited, it does not cause bonding failure and can reliably prevent water from entering the heat sealing adhesive portion, greatly increasing the water resistance of the adhesive portion of the heat sealing material, and Adhesive strength is small and good adhesion is maintained for a long time A glass container for hermetically sealed packaging, which has an excellent sealing property and has no heat-sealing resin remaining at the mouth of the container after opening, so that the appearance of the container is not impaired at all. It is intended to provide a heat sealing method.

Means for Solving the Problems In order to achieve the above object, a method for heat sealing a glass container for hermetically sealed packaging according to the present invention comprises the steps of: A heat-sealing material layer containing a carboxyl-modified product of the combined saponified product is provided, and a heat-sealing material layer made of the same material is provided on one surface of the lid material, and the lid material is provided at the mouth (2) of the glass container for hermetic packaging. And heat-sealing the two heat-sealing material layers to each other, and at the time of opening, the adhesive interface between the two heat-sealing material layers does not peel off between the heat-sealing material layer on the glass container side and the surface of the mouth of the glass container. The gist of the present invention is a method for heat sealing a glass container for hermetic packaging, characterized in that both heat sealing material layers are joined so as to be peeled off.

In the above description, the glass container for hermetic packaging includes, for example, a metal container, a ceramic container, or pottery in addition to the original glass container. In the case of a glass container,
It is not necessary to perform special treatment on the mouth of the glass container, and a general untreated glass container may be used. Of course, a glass container which has been subjected to a process of forming a metal oxide film on the mouth surface of the glass container in order to improve mechanical strength and chemical stability may be used.

As the metal foil which is the base material of the lid material, an aluminum foil is usually used, but other metal foils may be used. In the case of aluminum foil, its thickness is 5 to 200 μm, preferably 20 to 60 μm. When a metal foil is used as the base material of the heat sealing material, it has excellent barrier properties and can effectively preserve contents such as desserts and cooked foods for a long period of time.

A carboxyl-modified product of a saponified ethylene-vinyl acetate copolymer, which is the main component of a heat sealing material layer provided on the upper surface of the mouth of the container body and one surface of the lid material of the hermetically sealed glass container (for example, The following is used as the reference).

That is, a melt index of 1 to 300 g / 10 minutes (ASTM1
238-65T) and an ethylene-vinyl acetate copolymer having an ethylene content of 50-97 mol%, preferably 70-92 mol%, having a hydroxyl equivalent of 100-3000 g / 1 equivalent, preferably Prepares a saponified product of 200 to 1000 g / 1 equivalent, and then uses a saponified product obtained by graft polymerization of an unsaturated compound having a carboxylic acid group to the saponified product.

Here, examples of the carboxylic acid group-containing unsaturated compound include acrylic acid, methacrylic acid, crotonic acid, itaconic acid and citraconic acid. The carboxyl-modified product of the obtained graft polymer, that is, the saponified ethylene-vinyl acetate copolymer, has an acid equivalent of 50,000 g / 1 equivalent or less as a whole, preferably 1,000 to 10,000 g / 1 equivalent.

Incidentally, in order to prevent so-called blocking, a synthetic resin other than the above resins may be blended in the heat sealing material in some cases.

The heat sealing material layer is preferably filled with an inorganic compound in order to ensure low-temperature sealing performance and to prevent blocking during punching by a press.

Here, as the inorganic compound, for example, magnesium,
Oxides, hydroxides, carbonates and sulfates of calcium, aluminum, titanium and silicon, or talc,
Clay, feldspar powder, mica, barite and the like can be mentioned, and it is particularly preferable to use calcium carbonate and talc. The average particle size of the inorganic compound is 0.1 to 50 μm, preferably 0.5 to 30 μm.

When the heat sealing material contains an inorganic compound, the inorganic compound is mixed in an amount of 30 parts by weight or less, usually 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin.

The heat sealing material layer may be provided on the surface of the glass container by, for example, a spray method, a brush coating method, a roll coating method, or the like.

Further, in order to provide a heat sealing material layer on one side of a metal foil, the above heat sealing material is processed in advance into a film shape, and this film is formed on one side of the metal foil by, for example, a polyester-isocyanate two-liquid reaction type. What is necessary is just to join directly through bonding | bonding via adhesives, such as an adhesive agent, or extruding the melted material of a heat sealing material to one side of a metal foil using an extruder.

The thickness of the heat-sealing material layer provided on the upper surface of the mouth of the container body of the hermetically sealed glass container and one surface of the lid material is 20 to 200.
μm, preferably 50-100 μm.

If necessary, a resin film such as polyethylene or polypropylene may be interposed between the upper surface of the mouth of the container body of the hermetically sealed glass container or the metal foil of the lid and the heat sealing material layer. Thereby, the cushioning property at the time of heat sealing is improved, and when the content is dressing, mustard or the like, corrosion of the metal foil on the lid material side can be prevented.

In addition, the other surface of the metal foil of the cover material is usually printed as required, and a corrosion coat layer is provided on the surface of the metal foil.
The lid material composed of the metal foil and the heat sealing material layer is continuously punched and formed into a shape and a size covering the mouth of the glass container.

1 and 2 show a specific example of the method of the present invention. First, as shown in FIG. 1, the method of the present invention includes a carboxyl-modified form of a saponified ethylene-vinyl acetate copolymer on the upper surface of the mouth (2) of the container body (1a) of the glass container (1). In addition to providing the heat sealing material layer (3), a heat sealing material layer (13) made of the same material is provided on one side of the aluminum foil (11) of the lid material (10) via an adhesive material layer (12). , Cover material (1) on the mouth (2) of the glass container (1)
0) and heat-sealing the two heat-sealing material layers (3) and (13) to each other. The other surface of the aluminum foil (11) of the lid (10) is provided with an anticorrosion coat layer (14).

Thus, the heat sealing material layer (3) on the glass container (1) side
And the heat-sealing material layer (13) on the side of the lid material (10) are made of the same heat-sealing material containing the same carboxyl-modified saponified ethylene-vinyl acetate copolymer. Even when the time is very short, the heat sealing material layer (3) on the glass container (1) side and the heat sealing material layer (13) on the lid material (10) side are very strong and integrated. When the lid material (10) is peeled off after the bonding and therefore the heat sealing material, as shown in FIG. 2, the adhesive interface between the heat sealing material layers (3) and (13) is not peeled off, and the glass container (1) is removed. Between the heat sealing material layer (3) on the side and the surface of the mouth (2) of the glass container.

For this reason, when the content of the container is a liquid or a viscous material such as alcohol, juice, jam, or the like, the container main body ( 1a) mouth (2)
When the contents adhere to the surface and become contaminants at the time of heat sealing, the original adhesiveness of both heat sealing material layers (3) and (13) is sufficiently exhibited, and no bonding failure occurs.

Further, the heat sealing material layer (3) on the glass container (1) side and the heat sealing material layer (13) on the lid material (10) side are very firmly and integrally bonded, so that heat sealing adhesion is achieved. Intrusion of water into the part can be reliably prevented. Of course, on the upper surface of the mouth (2) of the container body (1a) of the glass container (1), a heat sealing material layer (3) containing a carboxyl modified product of a saponified ethylene-vinyl acetate copolymer, for example, Since the body film can be heated and melted and bonded for a sufficient time, water can enter between the upper surface of the mouth (2) of the glass container (1) and the heat sealing material layer (3). There is no occurrence of peeling, and therefore, the water resistance of the bonded portion of the heat sealing material is greatly increased, the adhesive strength in a water environment is less reduced, and a good bonded state can be maintained for a long time. It is very excellent in hermeticity.

Next, examples of the present invention will be described together with comparative examples.

EXAMPLE First, as shown in FIG. 1, acrylic acid was graft-polymerized to a saponified ethylene-vinyl acetate copolymer on the upper surface of a mouth (2) of a container body (1a) of a glass container (1). A heat-sealing material layer made of a heat-sealing material film having a thickness of 50 μm in which 5% by weight of calcium carbonate having an average particle size of about 1 μm is uniformly dispersed and mixed in the obtained modified product (Dumilan®, manufactured by Takeda Pharmaceutical Co., Ltd.). (3) Adhesive layer (2)
Through dry lamination. On the other hand, a 50 μm thick aluminum foil (11) having an anticorrosion coating layer (14) on one side, and a 50 μm thick
The heat-sealing material layer (13) made of the heat-sealing material film of No. m was joined by dry lamination via the adhesive layer (12) to form a cover material (10).

The lid material thus obtained was punched into a predetermined shape and size corresponding to the mouth (10) of the glass container by a punch press.

Then, the glass container (1) is filled with water at 40 ° C., and the lid (10) is heated at the mouth (2) of the container (1) at a temperature of 200 ° C. and a pressure of 160 kgf / piece for 2 seconds. The container (1) was sealed by pressurizing and thermally bonding the heat sealing material layers (3) and (13) to each other.

When the lid material (10) is peeled off after the heat sealing, as shown in FIG. 2, the adhesive interface between the heat sealing material layers (3) and (13) is not peeled off, and the heat sealing material on the glass container (1) side is not peeled off. The peeling strength between the layer (3) and the surface of the glass container mouth (2), and the peel strength of the lid (10) immediately after heat sealing, and the sealed glass container (1)
Was left standing at 40 ° C. for 30 days, and the peel strength of the lid member (10) was measured. The results are shown in the following table.

COMPARATIVE EXAMPLE For comparison, the same heat sealing material layer (13) as in Example 1 above was joined to one side of an aluminum foil (11) via an adhesive layer (12) by dry lamination, and a lid material ( I made 10).

Then, the lid (10) was directly joined to the surface of the mouth (2) of the glass container (1), and the container (1) was sealed.

After heat sealing, a peeling test of the lid material (10) was performed in the same manner as in the example, and the obtained results are shown in the table below.

As is clear from this table, according to the method of the present invention, the heat sealing material layer (3) on the glass container (1) side and the heat sealing material layer (13) on the lid material (10) side are the same. Since it is made of a heat sealing material containing a carboxyl modified product of a saponified ethylene-vinyl acetate copolymer, even if the heat sealing processing time is as short as 2 seconds, the glass container (1) side The heat sealing material layer (3) and the heat sealing material layer (13) on the side of the lid material (10) are very firmly and integrally bonded, and when the lid material (10) is peeled off, the two heat sealing material layers (3) The adhesive interface of (13) does not peel off, and the heat sealing material layer (3) on the glass container (1) side
And the surface of the glass container opening (2) is peeled off, and after sealing water in the glass container (1) and storing it in an inverted state for a long time, the heat sealing material layers (3) (13) ) Does not decrease in adhesive strength, has good water resistance, and has extremely excellent sealing properties.

On the other hand, on the surface of the mouth (2) of the glass container (1),
According to the comparative example in which the heat sealing material layer (13) of the lid material (10) was directly joined and the container (1) was sealed, the lid material (10) was peeled off when the glass container was stored in an inverted state for a long time. It was inferior in water resistance.

Effect of the Invention The method for heat sealing a glass container for hermetic packaging according to the present invention comprises, as described above, a carboxyl modified product of a saponified ethylene-vinyl acetate copolymer on the upper surface of the mouth of the container body of the glass container for hermetic packaging. A heat sealing material layer including the same material is provided on one side of the lid material, and the lid material is placed over the mouth of the glass container for hermetic packaging. The two heat-sealing material layers are heat-bonded to each other, and when opened, the two heat-sealing material layers are separated so that the adhesive interface between the two heat-sealing material layers does not peel off between the heat-sealing material layer on the glass container side and the surface of the glass container mouth. According to the present invention, according to the present invention, the heat sealing material containing the carboxyl modified product of the saponified ethylene-vinyl acetate copolymer is excellent in both the surface of the mouth of the glass container and the surface of the metal foil of the lid. With good adhesion In addition, both the heat sealing material layer on the glass container side and the heat sealing material layer on the lid material side are made of the same heat sealing material containing the same carboxyl-modified saponified ethylene-vinyl acetate copolymer. The two heat-sealing material layers have very good compatibility, and therefore, even if the processing time of the heat-sealing is very short, the two heat-sealing material layers are very firmly and integrally bonded, When the lid material is peeled off after the heat sealing, the adhesive interface between the two heat sealing material layers does not peel off, and the heat sealing material layer on the glass container side and the surface of the glass container mouth part are peeled off. For this reason, the content of the container is a liquid or a viscous material such as sake, juice, jam or the like, and the content is inserted into the mouth of the container body at the time of filling or transporting the glass container containing the content in the sealing line for filling the content. Is attached,
Even when foreign substances are formed during heat sealing, the original adhesiveness of both heat sealing material layers is sufficiently exhibited, and bonding failure does not occur.

In addition, the heat sealing material layer on the glass container side and the heat sealing material layer on the lid material side are very firmly and integrally bonded,
Water can be reliably prevented from entering the heat sealing material layer,
The water resistance of the bonded portion of the heat sealing material is greatly increased, the adhesive strength in a water environment is hardly reduced, a good bonded state can be maintained for a long time, and the sealing property is very excellent. Moreover, since the heat sealing material layer on the glass container side and the glass container mouth surface are peeled off at the time of opening, the heat sealing material resin does not remain at the mouth of the container, so that the appearance of the container is impaired. There is an effect that there is not at all.

[Brief description of the drawings]

FIG. 1 shows a specific example of the method of the present invention, and is a partially enlarged sectional view of a glass container and a lid member, and FIG. 2 is a partially enlarged sectional view showing a state where the lid member is peeled off in FIG. (1) ... hermetically sealed glass container, (1a) ... container body, (2) ... mouth, (3) ... heat sealing material layer, (10) ...
... lid material, (11) ... aluminum foil, (12) ... adhesive layer, (13) ... heat sealing material layer.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hirokazu Takenaka 6, 224, Kaiyama-cho, Sakai-shi, Osaka Showa Aluminum Co., Ltd. (56) References JP-A-60-1778042 (JP, A) 59-103862 (JP, A) JP-A-61-244705 (JP, A) JP-A-49-33783 (JP, A)

Claims (1)

(57) [Claims] 1. A heat sealing material layer containing a carboxyl modified product of a saponified ethylene-vinyl acetate copolymer (3) on the upper surface of the mouth (2) of the container body (1a) of the hermetically sealed glass container (1). In addition, a heat sealing material layer (13) made of the same material is provided on one side of the lid material (10), and the lid material (10) is attached to the mouth (2) of the hermetically sealed glass container (1). The heat sealing material layers (3) and (13) are heat-bonded to each other, and the adhesive interface between the heat sealing material layers (3) and (13) is not peeled off at the time of opening. Bonding the heat sealing material layers (3) and (13) so as to peel off between the heat sealing material layer (3) and the surface of the glass container mouth (2).
Heat sealing method for glass containers for hermetic packaging.