JPH04201864A - Heat-sealable lid material for sealed packaging container - Google Patents

Abstract

PURPOSE:To obtain a lid material which has a satisfactory adhesive property for a porous, hydrophilic surface and which can effectively prevent the intrusion of water into adhesive surface, even when a container is filled with liquid or viscous contents, by providing a heat-sensitive adhesive layer having a predetermined water content on one side of metal foil. CONSTITUTION:The subject heat sealable lid material for use on sealed packaging container is provided on one side of its metal foil with the heat-sensitive adhesive layer having at most 2% water content. In the case of aluminum foil, its thickness is 5-200mum. The use of the metal foil as the base material of the heat-sealable material offers an outstanding barrier character and permits an effective preservation of contents such as food for a long period of time. The heat-sensitive adhesive layer provided for the purpose of heat sealing plays the part of a cushioning layer upon heat sealing and its thickness is 5-300mum. As the heat-sealable material, polyethylene, ethylene-vinyl acetate copolymer or ethylene-unsaturated carboxylic acid copolymer is used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat-sealable lid used for a sealed packaging container, particularly a surface-untreated glass bottle, etc., in which a liquid or viscous substance is sealed inside. It is related to materials.

Conventional technology Conventionally, when powder, liquid, or viscous foods are hermetically packaged in containers such as glass bottles, heat-sensitive adhesive resin coated on the lid material is directly adhered to the mouth of the glass container by heat sealing. This has already been done, but the surface of the glass container is porous and has relatively weak polarity, is easily compatible with water, and does not melt during heat sealing, resulting in poor adhesion.

Conventionally, after food is filled into a glass container, the mouth of the container is sealed by screwing a metal or synthetic resin screw cap, caulking an aluminum cap, or placing a crown on top of the container. But it was done.

Furthermore, conventionally known methods include (1) coating the mouth of a glass container with a silane coupling agent as a sealing layer, or (2) coating the mouth of a glass container with a heat-adhesive resin.

Problems to be Solved by the Invention However, in the case of (2) above, if the contents of the container are powder such as powdered milk or instant coffee, there is no decrease in the adhesive strength of the adhesive between the container opening and the lid. When the contents are liquid or viscous, such as alcohol, juice, or jam, the surface of the glass container is porous and has relatively low polarity, and is easily compatible with water, as described above. Because it does not melt during heat sealing, water easily enters the glass/resin interface, breaking the bond at the glass/resin interface, significantly reducing adhesive strength, and in severe cases, causing the lid material to peel off. There was an interlude.

In addition, in the case of (2) above, there is a problem that the cap or crown is relatively difficult to open and is expensive.

Furthermore, in the case of (2) above, if the coating amount of the sealing layer made of the silane coupling agent was not sufficient, it was difficult to achieve uniform sealing due to irregularities in the mouth of the container, variations in parallelism, etc.

In addition, in the case of (2) above, the mouth of the container is coated with thermoplastic resin in advance, which increases the number of steps, lowers the productivity of the container, and increases costs. There was a problem in that some of the resin remained and the appearance was impaired.

The purpose of the present invention is to solve the problems of the prior art described above, and to provide a material that has good adhesion even to porous and hydrophilic surfaces such as the mouth of glass containers, and which also has good adhesive properties. Even when the content is a liquid or viscous substance such as alcohol, juice, or jam, it can effectively prevent water from entering the adhesive interface, and the adhesive strength is less likely to decrease in an aqueous environment. Therefore, water resistance is greatly increased, a good adhesive state can be maintained for a long period of time, and it has excellent sealing properties, and can be easily opened with moderate force. An object of the present invention is to provide a heat-sealing lid material for a sealed packaging container that has both easy-peel functions.

Means for Solving the Problems In order to achieve the above object, the present invention provides a container for sealed packaging, in which a heat-sensitive adhesive layer with a moisture content of 2% or less is provided on one side of a metal foil. This article focuses on heat-sealing lid materials.

As the metal foil, aluminum foil is usually used, but other metal foils may be used. For aluminum foil,
Its thickness is 5-200/I! 777° preferably 20~
It is 60 sh. When metal foil is used as a base material for a heat sealing material, it has excellent barrier properties and can effectively preserve contents such as foods for a long period of time.

The heat-sensitive adhesive layer is provided for heat sealing and to function as a cushion layer during heat sealing, and its thickness is 5 to 300 Iy!
, preferably 20-100/1171! It is.

Specifically, the heat sealing material constituting this heat-sensitive adhesive layer includes polyethylene, ethylene-vinyl acetate copolymer, ethylene-unsaturated carboxylic acid copolymer, and ethylene-vinyl acetate copolymer. Modified product obtained by graft polymerizing a carboxyl group-containing unsaturated compound to a partially saponified product, ionomer, water-dispersed polyolefin, mixture of water-dispersed polyolefin and epoxy resin, polyester, modified polypropylene, polyvinyl chloride, polyvinyl butyral, polymethacrylic acid At least one thermoplastic synthetic resin selected from the group consisting of esters and polyacrylic esters is used.

In addition, as a heat sealing material for a glass container, it is preferable to use an ethylene-vinyl acetate copolymer, an ionomer, polyvinyl butyral, and polymethacrylic acid ester.

Furthermore, in order to improve water-resistant adhesive properties, silane monomers, silane coupling agents, rosins, water repellents, etc. may be added to these heat-sensitive adhesive layers. Such a heat-sensitive adhesive layer may include, for example, 55 to 99 parts by weight of a heat-sensitive adhesive resin whose main component is a partially saponified ethylene-vinyl acetate copolymer or (and) an acid-modified product thereof, and 1 to 99 parts by weight of a rosin. It is preferable to use one containing 45 parts by weight.

In the above, there are the following three methods for controlling the moisture content of the heat-sensitive adhesive layer to 2% or less.

(1) After creating a heat-sensitive adhesive layer on one side of the metal foil, this is stored in a dry atmosphere to prevent water absorption.

(2) Immediately before heat sealing, perform hot air drying to dehydrate.

(3) Immediately before heat sealing, contact with a hot roll to dehydrate.

The moisture content of each heat-sensitive adhesive layer was measured at 110°C.
x10 minutes, determined from the difference in weight before and after drying.

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

Example 1 A partially saponified ethylene-vinyl acetate copolymer with a vinyl acetate content of 33% (saponification degree 50
5% by weight of calcium carbonate and ethylene bisstearic acid, which is a modified product (registered trademark Dumilan, manufactured by Takeda Pharmaceutical Company Limited) obtained by graft polymerizing acrylic acid to (mol%) and having an average particle size of about 1 mm. Amide 0.05
5% by weight of dibasic acid-modified rosin ester (trade name Louisol 28, manufactured by Rika Vercules Co., Ltd.) and 5% by weight of a heat-sensitive adhesive film obtained by uniformly dispersing and kneading. The layers were dry laminated together via an adhesive layer to create a lid. Then, the lid material immediately after lamination was used as a sample. The moisture content of the heat-sensitive adhesive layer of this lid material was 1.0%.

Example 2 The lid material having the heat-sensitive adhesive layer used in Example 1 was stored for one month in an atmosphere with a temperature of 20 to 25° C. and a humidity of 60% or less, and then used as a sample.

The moisture content of the heat-sensitive adhesive layer of this lid material was 1.8%.

Example 3 The lid material having the heat-sensitive adhesive layer used in Example 1 above was heated to
When stored for a month, the moisture content of the heat-sensitive adhesive layer of the lid material was 3%. Next, blow warm air (50℃) over this lid material.
After drying for 1 hour in a drying atmosphere, it was used as a sample. The moisture content of the heat-sensitive adhesive layer of this lid material is 1. 3911+
Met.

Example 4 The lid material having the heat-sensitive adhesive layer used in Example 1 above was heated to
When stored for a month, the moisture content of the heat-sensitive adhesive layer of the lid material was 3%. Next, the protective film side of this lid material was brought into contact with a hot roll (100° C.) for 1 minute, and then used as a sample. The moisture content of the heat-sensitive adhesive layer of this lid material is 1.
It was 5%.

Comparative Example The lid material having the heat-sensitive adhesive layer used in Example 1 above was heated to
After being stored for a month, it was used as a sample. The moisture content of the heat-sensitive adhesive layer of this lid material was 3%.

The various lid materials obtained as described above were punched out using a punching press into a predetermined shape and size corresponding to the opening of a glass container.

Next, a glass container (capacity 100 cc) was filled with water at 40°C, and the lid material was placed at a temperature of 200°C over the mouth of the container.
Then, the lids were heated and pressurized for 2 seconds at a pressure of 160 kgr/c-, and the lids were directly bonded to the mouth of the glass container by heat sealing to seal the container.

Then, the peel strength of the lid material immediately after heat sealing and the peel strength of the lid material after the sealed glass container was left in an inverted state at 40°C for 30 days were measured, and the obtained results are summarized in the table below. Indicated.

(Hereinafter, blank space) As is clear from the above table, according to the heat-sealable lid material of the present invention, if the moisture content of the heat-sensitive adhesive layer is 2% or less,
The adhesion to the mouth surface of the glass container is very good, and even after a glass container filled with water is stored upside down for a long time, the adhesion of the lid material does not decrease, and the water resistance is good and the seal is sealed. Excellent quality.

On the other hand, according to the lid material of the comparative example in which the moisture content of the heat-sensitive adhesive layer was 3%, the lid material peeled off if the glass container was stored upside down for a long time, resulting in poor water resistance. Met.

Effects of the Invention As described above, the heat-sealing lid material for a sealed packaging container according to the present invention is one in which a heat-sensitive adhesive layer with a moisture content of 2% or less is provided on one side of a metal foil. It has good adhesion even to porous and hydrophilic surfaces such as the mouths of glass containers, and even if the contents are liquids or viscous substances such as alcohol, juice, or jam. Even in such cases, it can effectively prevent water from entering the adhesive interface, reducing the decrease in adhesive strength in a water environment, thereby greatly increasing water resistance and maintaining a good adhesive state for a long time. It can be maintained, has excellent sealing properties, and can be opened easily with a moderate amount of force, making it extremely convenient.

Further, according to the heat-sealing lid material of the present invention, after filling food with food as in the past, a metal cap can be caulked to the mouth of the container, a metal or synthetic resin screw cap can be screwed, or a crown can be screwed onto the mouth of the container. Since the container is not covered or sealed, it is easy to open, and the sealing cost of the hermetically sealed packaging container is reduced because no cap or crown is used.

Furthermore, there is no resin left at the container mouth when the container is opened, so the appearance of the container mouth is clean after opening, and heat sealing can be performed at a relatively low temperature, making it easy to install filling and sealing equipment. This has the effect of reducing costs and operating costs, and improving the workability of filling and sealing.

that's all

Claims (1)

[Claims] A heat-sealable lid material for sealed packaging containers, which has a heat-sensitive adhesive layer with a water content of 2% or less on one side of metal foil.