JPH0358298B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is a lid material for sealed packaging containers made of glass, ceramic, etc., and exhibits excellent sealing performance over a long period not only for powder contents but also for liquid contents. The present invention also relates to a lid material for a sealed package that allows boil sterilization or retort sterilization with the contents sealed inside the container, is easy to open when taking out the contents, and has a beautiful opening.

Conventionally, liquid or fluid contents such as alcoholic drinks, juices, dressings, mayonnaise, jams, etc. are mainly stored in glass containers and sealed with metal or plastic screw caps, which are difficult to open. It has the drawbacks of being difficult and expensive. Another method is to caulk an aluminum plate to the opening of the glass container and seal it, but this method is also difficult to open and is also expensive. Some glass containers for storing powders such as instant coffee and powdered cream are heat-sealed and sealed using a laminated material such as aluminum foil or paper that has been coated with a heat-sealing agent. When the container is used as a sealed package for a liquid or fluid, there is a drawback that the adhesive strength of the heat-sealed portion decreases significantly within a short period of time due to contact with the contents, resulting in peeling. Tokuko Showa 53
Publication No. 8273 discloses a technique of coating the open end surface of a glass container with silane as a heat sealing material, but this method also has problems. In other words, if the sealing material is not applied thick enough, uniform heat sealing will be difficult due to irregularities in the opening of the glass container, variations in parallelism, etc., and if the application thickness is made sufficiently thick, the cost will be significant. It gets expensive. Furthermore,
After filling the contents into a glass container and sealing it, boil sterilization or retort sterilization is performed, but even in this case, it is difficult to find a combination of glass container and lid material that can sufficiently withstand sterilization treatment at high temperatures. is the current situation.

The present inventor has completed a material for sealed packaging bodies in which different thermoplastic resin layers are formed on the open end surface of a glass container and the base material for the lid, and has already applied for a patent (Japanese Patent Application No. 57-210338). ). The hermetically sealed package consisting of the combination of the glass container and the lid material has excellent heat-sealability, shows no decrease in adhesive strength even when it comes into contact with liquid contents, is easy to open, and has a It has the excellent effect of making the container opening look beautiful. However, since it requires a step of forming a thermoplastic resin layer on the open end surface of the glass container, there is room for improvement from an economic standpoint.

Therefore, the present inventor has conducted various studies in order to achieve an effect comparable to that of the invention described in the above-mentioned Japanese Patent Application No. 57-210338 without forming a thermoplastic resin layer on the open end surface of a glass container. When a heat sealing agent layer containing a polyolefin resin into which a carboxyl group has been introduced (hereinafter referred to as a carboxyl group-containing polyolefin resin) and a silane coupling agent is formed on a lid base material such as aluminum foil, the purpose We found that it is possible to achieve this.

That is, the present invention provides a sealed package characterized in that (i) a heat sealing agent layer containing 100 parts by weight of a carboxyl group-containing polyolefin resin and 0.1 to 20 parts by weight of a silane coupling agent is formed on one side of a base material. (hereinafter referred to as the first invention of the present application) and (ii) on one side of the base material, (a) an intermediate layer made of a polyolefin resin, and (b) 100 parts by weight of a carboxyl group-containing polyolefin resin and 0.1 to 0.1 to 0.1 parts by weight of a silane coupling agent. 20
The present invention relates to a lid material for a sealed package (hereinafter referred to as the second invention of the present application), characterized in that heat sealing agent layers containing parts by weight are successively formed.

The base material of the lid material of the present invention can be aluminum foil, plastic film, paper, or a laminate of these materials, which are the same as those conventionally used as the base material of lid materials for sealed packages for powder. Although not described in detail, specific examples include aluminum foil, polyester film, paper, and laminates thereof.

In the first invention of the present application, a heat sealing agent layer containing 100 parts by weight of a carboxyl group-containing polyolefin resin and 0.1 to 20 parts by weight of a silane coupling agent as essential components is formed on one side of the base material.
As the carboxyl group-containing polyolefin resin, one or two types of ionomer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, carboxylated polyethylene, carboxylated polypropylene, carboxylated ethylene-vinyl acetate copolymer, etc. Use the above. Carboxylated polyethylene, carboxylated polypropylene, carboxylated ethylene-vinyl acetate copolymer, etc. are polyolefin resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, etc., and maleic acid, fumaric acid, crotonic acid, acrylic acid, methacrylic acid. A carboxyl group is introduced by copolymerizing an acid, an unsaturated carboxylic acid such as maleic anhydride, itaconic anhydride, or an anhydride thereof. Silane coupling agents include γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris-β-methoxyethoxysilane, γ-methacryloxypropyltrimethoxysilane, β-3,4-epoxy Cyclohexylethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N
-β-aminoethoxy-γ-aminopropyltrimethoxysilane and the like are exemplified. If the amount of the silane coupling agent per 100 parts by weight of the carboxyl group-containing polyolefin resin is less than 0.1 parts by weight, the adhesive strength of the heat sealing agent layer to the glass or ceramic container will not be sufficient; If the amount exceeds 100%, the adhesion to the container and substrate will be significantly reduced.

In addition, in order to prevent blocking and improve the slipperiness of the heat sealing agent layer, one or more of polyolefin resins such as polyethylene and polypropylene, vinyl resins, acrylic resins, and polyester resins may be carboxylized. A maximum of about 100 parts by weight may be added to 100 parts by weight of the group-containing polyolefin resin.

The thickness of the heat sealing agent layer is preferably 1 μm or more in order to obtain a uniform seal, and for economic reasons, the upper limit is preferably about 50 μm.

The heat sealing agent layer is formed by applying the above-mentioned resin mixture in the form of a solution or emulsion to a substrate, and drying or hot-melt extrusion onto the substrate.

In the second invention of the present application, an intermediate layer made of polyolefin resin is formed between the base material and the heat sealing agent layer. As the polyolefin resin forming the intermediate layer, any resin that has excellent adhesion to the base material and the heat sealing agent layer can be used, including polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, etc. Coalescence, ionomer, polypropylene, silane-modified polyethylene,
Examples include silane-modified polypropylene, carboxylated polyethylene, carboxylated polypropylene, carboxylated ethylene-vinyl acetate copolymer, and the like. The formation of such an intermediate layer prevents the risk of corrosion that can occur when using aluminum foil as a substrate and also improves the cushioning properties during heat sealing operations. The thickness of the middle layer is 10
It is preferable to set it to about 50 μm.

In addition, a printing layer, an overcoat, etc. can be provided as necessary on the surface of the lid material of the present invention opposite to the surface on which the heat sealing agent layer is provided, according to a conventional method.

Incidentally, the glass container used in combination with the lid material of the present invention may be coated with a metal oxide film in a conventional manner. That is, in the normal glass container manufacturing process, a solution of a metal compound such as tin tetrachloride is poured into the glass container immediately after leaving the molding station, that is, at the hot end, at a temperature of about 300 to 600°C. By spraying, an extremely thin film of metal oxide, such as tin oxide, is formed into the network structure of the glass, improving the mechanical strength and chemical stability of the glass container. According to the research of the present inventor, when the contents of the sealed package are liquid, the presence of such a metal oxide film significantly improves the water resistance of the adhesive part between the glass container and the lid material. It has been found.

In order to produce a sealed package using the lidding material of the present invention, the above-mentioned glass container or ceramic container is sterilized and filled with the contents, and then the lidding material is heated to a temperature of 170° C. to It is sufficient to heat seal at 220°C for 1 second. Filling methods include aseptic filling, 90~
A hot pack method of filling jam, alcohol, etc. at about 95°C can be arbitrarily adopted. When the hot pack method is employed, the effect of lowering the heat sealing temperature and shortening the heat sealing time is also achieved. Heat sealing of the container and the lid material can be performed by a known heating method such as heating with a hot plate or high frequency induction heating. The sealed package after heat sealing is subjected to high temperature sterilization treatment such as boil sterilization or retort sterilization, if necessary.

According to the present invention, the following effects can be obtained.

(i) It has become possible to heat seal the container and the lid material without any pretreatment such as resin coating on the open end of the container made of glass, ceramic, etc.

(ii) Since the seal portion has good water resistance, the sealed package containing liquid and fluid materials can be used for a long period of time. In addition, especially when forming an intermediate layer, regardless of the unevenness of the opening end of the container,
Uniform sealing is possible.

(iii) The seal formed between the container and the lid is
Since it has excellent heat resistance, high temperature sterilization treatments such as boil sterilization and retort sterilization of sealed packages can be easily performed.

(iv) When the sealed package is opened, destruction occurs at the interface between the container and the resin layer on the lid side, so opening is easy and the appearance of the container opening is smooth and beautiful.

Example 1 γ-Glycidoxypropyltrimethoxysilane was added to a solution in which ethylene-acrylic acid copolymer (EAA) containing 20% acrylic acid was dispersed in aqueous ammonia, and EAA/silane = 100/2.5 (solid A heat sealing agent liquid was prepared with a weight ratio of 1.

The above heat sealing agent liquid was applied at a rate of 3 to 5 g/m ² (as solid content) to the other side of a 50 μm thick aluminum foil with a printing layer and an overcoat layer on one side, and then heated in a hot air dryer. Use 15 at 180℃
By drying for seconds, the lid material of the present invention was obtained.

On the other hand, a glass container with high-temperature end treatment with tin tetrachloride
After adding hot water of 90-95℃, use the above lid material.
Heat sealing was performed under the conditions of 200°C x 1 second x 4Kg/cm ² .

The thus obtained sealed package was left in an inverted position at room temperature for 3 months, but no water leakage due to a decrease in adhesive strength or deterioration in sealing performance occurred. Furthermore, the container was easy to open, and no so-called "stiff mouth" was observed at the opening of the container.

Comparative Example 1 A lidding material was produced in the same manner as in Example 1 except that γ-glycidoxypropyltrimethoxysilane was not used, and a glass container was sealed.
After a few days, the heat seal strength decreased to almost zero and water leaked.

Examples 2 to 5 Low-density polyethylene with a thickness of 20 μm (Example 2) on a base material made of aluminum foil similar to Example 1,
10 μm thick low density polyethylene + 20 μm thick ethylene-vinyl acetate copolymer (Example 3), 30 μm thick ethylene-acrylic acid copolymer (Example 4) and 30 μm thick ionomer (Example 3) 5) to form respective intermediate layers.

Aqueous ammonia dispersion of EAA containing 20% acrylic acid, emulsion of low density polyethylene and γ-glycidoxypropyltrimethoxysilane were mixed to form EAA/polyethylene/silane=90/
A heat sealing agent liquid having a solid content weight ratio of 10/2.5 was prepared.

Next, 3 to 5 times of the above heat sealing agent liquid is applied onto the intermediate layer formed on the above aluminum base material.
g/m ² (as solids) and at 180°C.
Dry with hot air for 15 seconds.

Next, using the four types of lid materials obtained, Example 1
A sealed package was obtained in the same manner as above.

Each of the sealed packages thus obtained was left inverted at room temperature for 3 months, but no water leakage occurred in any of them. Also, the container is easy to open.
The appearance of the opening of the container was also smooth and beautiful.

Claims (1)

[Claims] 1. A lid for a sealed package, characterized in that a heat sealing agent layer containing 100 parts by weight of a carboxyl group-containing polyolefin resin and 0.1 to 20 parts by weight of a silane coupling agent is formed on one side of a base material. Material. 2. On one side of the base material, (a) an intermediate layer made of a polyolefin resin and (b) 100 parts by weight of a carboxyl group-containing polyolefin resin and a silane coupling agent.
A lid material for a sealed package, characterized in that a heat sealing agent layer containing 0.1 to 20 parts by weight is sequentially formed.