JPH0218042A - Heat-sealing cover material for hermetic seal packaging container - Google Patents

Abstract

PURPOSE:To reduce a lowering in adhesive force in watery environments and enable a favorable sealed condition to be maintained for a long time by providing a heat-sealing material layer comprising a monoolefin-unsaturated carboxylic acid copolymer resin or a metallic salt thereof on one side of a metallic foil, and providing a coating layer comprising a silane coupling agent on the surface of the heat-sealing material layer. CONSTITUTION:A heat-sealing material layer 2 comprising a monoolfein- unsaturated carboxylic acid copolymer resin or a metallic salt thereof is provided on one side of an aluminum foil 1 through an adhesive layer 3 therebetween, and a coating layer5 of a silane coupling agent is provided on the surface of the layer 2. This construction provides excellent adhesion even on an adhered surface being porous and comparatively low in polarity, such as a mouth part of a glass container, increases markedly the water resistance of a heat-sealed adhered part, reduces a lowering in adhesive force in watery environments, and enables a favorable adhered condition to be maintained for a long time.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a heat-sealable lid material for a sealed packaging container.

Conventional technology Conventionally, in order to hermetically package powdered, liquid, or viscous foods in glass containers such as bottles, a metal cap is caulked to the mouth of the container after the food is filled, or a metal or synthetic resin cap is used. It was sealed by screwing on a screw cap or by putting a crown on it. Conventionally, a lid material has been coated with a thermoadhesive resin, and this lid material has been bonded to the mouth of a glass container by heat sealing.

Problems to be Solved by the Invention However, the above-mentioned caps and crowns have problems in that they are relatively difficult to open and are expensive. In addition, when heat-sealing the heat-adhesive resin coated on the lid to the mouth of a glass container, if the contents of the container are powder such as powdered milk or instant coffee, there is a gap between the mouth of the container and the lid. Although there is no decrease in the adhesive strength of the adhesive part, if the contents are liquid or viscous substances such as alcohol, juice, or jam, the heat-sealed adhesive part between the container mouth and the lid material may be damaged during storage. Water gets in and the adhesion strength decreases significantly.
In severe cases, there was a problem in that the lid material would peel off.

In particular, when directly thermally bonding a lid to the mouth of a glass container, the surface of the mouth of the glass container is porous;
Because of its relatively weak polarity and poor adhesion, in recent years the use of special ionomers with improved adhesion has been developed as heat-adhesive resins applied to lid materials (for example, JP-A-Sho [1l
(Refer to Publication No.-54587). It is true that such thermoadhesive resins have excellent thermal adhesion properties in a very short time and at relatively low temperatures, but if water enters the bonded area after heat sealing, the adhesiveness may deteriorate. There was a problem in that there was a significant decrease in the adhesive strength and the lid material was easily peeled off from the adhesive interface.

By the way, it has already been known to directly coat the mouth of a glass container with a silane coupling agent as a sealing material (for example, see Japanese Patent Publication No. 8273/1983). The work of coating the sealant is extremely troublesome, and the surface of the opening of the glass container is porous and uneven, making it difficult to apply the sealant uniformly. Therefore, if the amount of sealing material applied is not sufficient, it will be difficult to achieve a uniform seal due to the unevenness of the opening, variations in parallelism, etc., and if the amount applied is too large,
There was a problem of high cost.

Furthermore, a method is already known in which a metal salt, a silane coupling agent, etc. are used as an anchor coat layer on the opening of a glass container, and this layer is further coated with a thermoadhesive resin (for example, Japanese Patent Publication No. 81-9181) However, with this conventional method, when the container is opened, some of the resin from the lid material may remain at the mouth of the container, damaging the appearance, and the mouth of the container must be coated with thermoplastic resin in advance. Therefore, the number of steps increases accordingly,
There were problems in that the productivity of the container was poor and the cost was high.

Furthermore, conventionally, heat-sealable lidding materials (for example, JP-A-80-58
No. 549), as well as heat-sealing lid materials comprising a heat-sealing material layer made of an ionomer composition containing a silane coupling agent applied to one side of a metal foil through an ionomer layer (for example, JP-A-Sho fil- 104971) is already known, but when a silane coupling agent is mixed into the heat-sealing resin of the lid material in this way, the silane coupling agent bleeds onto the surface of the heat-sealing material layer, and the silane coupling agent bleeds onto the surface side. The silane coupling agent becomes diffused and concentrated, and therefore the amount of silane coupling agent present on the surface of the heat sealing material layer increases. There was a problem in that it was very difficult to adjust the amount of silane coupling agent present on the surface to be heat sealed because it varied depending on the time and other factors.

The purpose of the present invention is to solve the problems of the prior art described above, and to provide a material that has extremely excellent adhesion even to a porous and relatively weakly polar adhered surface such as the mouth of a glass container. Not only can the lidding material be heat-sealed to the mouth of the sealed packaging container in a short time, but also the amount of silane coupling agent that should be present on the surface of the heat-sealing material layer can be easily adjusted. Therefore, the adhesive force between the heat sealing material layer and the opening of the glass container is greatly strengthened, and the content of the container is a liquid or viscous substance such as alcohol, juice, or jam. Even in such cases, it is possible to reliably prevent water from entering the heat-sealed bonded area, greatly increasing the water resistance of the heat-sealed bonded area, and reducing the decrease in adhesive strength in a water environment. An object of the present invention is to provide a heat-sealing lid material for a sealed packaging container that can maintain a good adhesion state for a long period of time and has excellent sealing properties.

Means for Solving the Problems In order to achieve the above object, the heat-sealing lid material for a sealed packaging container according to the present invention has a monoolefin-unsaturated carboxylic acid copolymer resin or its metal on one side of a metal foil. It is characterized in that a heat sealing material layer containing salt is provided, and a coating layer made of a silane coupling agent is provided on the surface of the heat sealing material layer.

As the metal foil, aluminum foil is usually used, but other metal foils may be used. For aluminum foil,
Its thickness is 5-200/ff, preferably 20-60
It is p. When metal foil is used as a base material for heat sealing material,
It has excellent barrier properties and can effectively preserve the contents of desserts, cooked foods, etc. for a long period of time.

The heat sealing material may be an ionomer (for example,
1-54587).

This ionomer is composed of a monoolefin-unsaturated carboxylic acid copolymer resin or a metal salt thereof.

Here, the monoolefin-unsaturated carboxylic acid copolymer resin includes an α-monoolefin such as ethylene, propylene, 1-butene, isobutyne, 4-methyl-1-pentene, 1-hexene, and 1-heptene; α such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid,
It is based on a resin obtained by copolymerizing β-unsaturated carboxylic acid, and typical examples include ethylene-acrylic acid copolymer resin and ethylene-methacrylic acid copolymer resin. It will be done. The molecular weight of such a copolymer resin is 1,000 to 200,000, and the unsaturated carboxylic acid content in the copolymer resin is 1 to 30% by weight, preferably 2 to 20% by weight.

Examples of metal salts of the monoolefin-unsaturated carboxylic acid copolymer resin include replacing the carboxyl group of the copolymer resin with an alkali metal ion such as sodium or potassium or an alkaline earth metal such as zinc or magnesium. Examples include ionically crosslinked resins, ie, ionomer resins, obtained by neutralization with ions. The degree of neutralization by metal ions is, for example, 0.5 to 40%. In particular, it is preferable to use an ionomer resin made of a zinc salt of an ethylene-methacrylic acid copolymer resin. The carboxylic acid content of the ionomer resin is 5-18%, and the degree of ionization is several %-9.
It is 0%.

In addition, in order to prevent so-called blocking, synthetic resins other than the above-mentioned resins may be blended into the heat sealing material depending on the case.

Further, as the above-mentioned silane coupling agent, one represented by the general chemical structural formula: YR8IXa is used.

In the formula, R is an alkyl group; For example, mercapto, amino, epoxy,
Vinyl, methacrylic, etc.

As the silane coupling agent, at least one silane compound selected from the group consisting of mercaptosilane, aminosilane, epoxysilane, vinylsilane, and methacrylsilane having the above general formula is used.

Specific examples of silane coupling agents include γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane. , vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, and γ-methacryloxypropyltrimethoxysilane.

The thickness of the heat sealing material layer is usually 5 to 300 mm, preferably 20 to 100 mm, and the thickness of the coating layer made of a silane coupling agent is usually 0.01 to 10/If.
f, preferably 0.1 to 5p.

If the thickness of the coating layer made of the silane coupling agent is less than 0.017ff, it will be too thin and will not provide sufficient water resistance to the heat-sealed joint, resulting in poor adhesion in a water environment. , undesirable.

On the other hand, when the thickness of the coating layer made of the silane coupling agent exceeds 1 OJyI, it is not preferable because not only the adhesiveness does not change much in an aqueous environment, but also the cost increases.

A coating layer made of a silane coupling agent may be provided on the surface of the heat sealing material layer by, for example, a spray method or a roll coating method.

Further, the heat sealing material layer is preferably filled with an inorganic compound in order to ensure low-temperature sealability and to prevent blocking during punching by press.

Here, examples of inorganic compounds include oxides, hydroxides, carbonates, and sulfates of magnesium, calcium, aluminum, titanium, and silicon, talc, clay, feldspar powder, mica, pallite, etc., and particularly preferred. Calcium carbonate, talc is used.

The average particle size of these inorganic compounds is 0.1-50/ffl, preferably 0.5-30/ffl, based on 100 parts by weight of the monoolefin-unsaturated carboxylic acid copolymer resin or its metal salt. , 30 parts by weight or less, usually 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, of the above-mentioned inorganic compound are mixed.

The above copolymer resin or its metal salt and the inorganic compound are mixed using, for example, a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader, etc., usually at a temperature of 15 to 200°C. .

The drying time varies depending on the drying temperature, but for example,
At 00°C, it takes about 30 seconds.

In addition, in order to provide a heat sealing material layer on one side of the metal foil, the above-mentioned heat sealing material is processed into a film in advance, and this film is coated on one side of the metal foil with, for example, a polyester-isocyanate two-component reaction. They may be joined through an adhesive such as a mold adhesive, or they may be joined directly by extruding a melted heat sealing material onto one side of the metal foil using an extruder.

Further, if necessary, an intermediate layer made of a resin film such as polyethylene or polypropylene may be interposed between the heat sealing material layer and the metal foil. This improves cushioning properties during heat sealing and prevents corrosion of the metal foil due to contents such as dressing and mustard.

Note that the other side of the metal foil is usually subjected to necessary printing, and furthermore, an anticorrosive coating layer is provided on this surface.

The above-described lid material having a coating layer made of a silane coupling agent is continuously stamped into a shape and size that fits the mouth of a glass container.

The hermetically sealed packaging container sealed by the heat-sealable lid according to the present invention is made of, for example, glass, metal, ceramic, or earthenware.

FIGS. 1 and 2 show specific examples of the heat-sealing lid material according to the present invention. First, the lid material shown in FIG. 1 consists of a heat sealing material layer (
2) is provided via an adhesive layer (3), and a coating layer (5) of a silane coupling agent is provided on the surface of this heat sealing material layer (2). An anticorrosive coating layer (4) is applied to the other side of the aluminum foil (1).

The heat-sealable lid shown in Figure 2 has almost the same structure as the lid shown in Figure 1, but one side of the aluminum foil (1) is coated with polyethylene to prevent corrosion of the aluminum foil (1) by the contents. An intermediate layer (7) made of a film is provided, and a heat sealing material layer (7) is applied to this intermediate layer (7) via an adhesive layer (3).
2), a coating layer (5) of a silane coupling agent is provided on the surface of the heat sealing material layer (2), and a printing layer (6) is provided on the other surface of the aluminum foil (1), Furthermore, an anticorrosive coating layer (4) is provided on the surface.

According to the heat-sealing lid material of the present invention, the coating layer (5) of a silane coupling agent is provided on the surface of the heat-sealing material layer (2) containing a monoolefin-unsaturated carboxylic acid copolymer resin or a metal salt thereof. Because of this, there is little loss of adhesion in a water environment, it can maintain good adhesion for a long time, and it has excellent sealing properties.This is due to the following reasons. Conceivable.

That is, for example, the heat sealing material applied to the lid of a glass container contains -OH groups and -CO because the upper surface of the mouth of the glass container is porous, has relatively weak polarity, and has poor adhesive properties.
Resins containing many functional groups such as OH groups, such as carboxyl modified products of saponified ethylene-vinyl acetate copolymers in which -○H groups or -COOH groups are introduced into monoolefins,
and ionomer resins are used to improve adhesion, but even when such resins are used, the heat sealing process time is very short, so the functional groups in the heat sealing resin are not bonded to the glass. It is thought that the resin does not interact with the glass component on the upper surface of the mouth of the container to form hydrogen bonds, but instead adheres to the glass surface mainly due to van der Waals forces. In particular, immediately after heat sealing, the molecular segments of the heat sealing resin undergo thermal movement and their orientation is disordered, making it difficult for hydrogen bonds to occur and adhesion is primarily due to van der Waals forces. After heat sealing, the functional groups are gradually arranged on the glass surface over time, form hydrogen bonds with the silanol groups on the glass surface, and the adhesive strength gradually increases.

However, when the contents of a glass container are liquid or viscous, the glass surface at the container mouth is hydrophilic, so water molecules tend to get wet, forming a multi-molecular layer of water molecules, which makes heat sealing difficult. The van der Waals forces at the bond are weakened and the hydrogen bonds are also broken, resulting in a significant decrease in adhesion.

In contrast, according to the heat-sealing lid material of the present invention, a coating layer made of a silane coupling agent is provided on the surface of the heat-sealing material layer containing the monoolefin-unsaturated carboxylic acid copolymer resin or its metal salt. As a result, the adhesive force between the heat-sealing resin of the lid material and the opening surface of the glass container is extremely strong, and therefore water is reliably prevented from entering the adhesive interface.
This greatly increases the water resistance of the heat-sealed bonded portion.

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

Example 1 As shown in Figure 1, a special ionomer, that is, a monoolefin-unsaturated carboxylic acid copolymer resin, was applied to the other side of a 50 μm thick aluminum foil (1) having an anticorrosive coating layer (4) on one side. A heat-sealing film containing 5% by weight of calcium carbonate, which is a metal salt and has an average particle size of approximately 1 m, uniformly dispersed and mixed (trade name: HiSeishin 1F02, manufactured by DuPont Mitsui Polychemicals, melt index: 14 g/10 minutes, zinc ion) A heat sealing material layer (2) with a thickness of 50 JyI (type) was provided by dry lamination via an adhesive layer (3), and then an amino-based silane coupling agent ( (Product name: A1100, manufactured by Nippon Unicar Co., Ltd.) was coated using a roll coating method for 10 minutes.
By drying at 0° C. for 5 minutes, silane coupling agent coating layers (5) having various thicknesses were formed to produce lid materials (sample N (L 1 to 5)).

The various lid materials thus obtained were punched out using a punching press into a predetermined shape and size corresponding to the opening (1G) of a glass container.

Next, the glass container was filled with water at 40°C, and the lid material was placed at the mouth of the container at a temperature of 200°C and a pressure of 160 kgf.
The lids were heated and pressurized for 2 seconds under the conditions of 1000 ml/piece, and these lids were directly bonded to the mouth (10) 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 are shown in the table below.

Example 2 In this example, as shown in Fig. 1, the same heat sealing material layer (2) as in Example 1 was applied on one side of the aluminum foil (1) via an adhesive layer (3). After dry lamination, an epoxy-based silane coupling agent (trade name A-187, manufactured by Nippon Unicar Co., Ltd.) was applied to the surface of the heat sealing material layer (2) by a roll coating method.
By drying at 0° C. for 5 minutes, a silane coupling agent coating layer (5) with a thickness of 0.4 mm was formed, and a lid material (sample No. 6) was produced.

The lid material thus obtained was subjected to a sealed packaging test in the same manner as in Example 1, and the results are shown in the table below.

Comparative Example For comparison, the same heat sealing material layer (
2) was provided by dry lamination, but the lid materials were not provided with the silane coupling agent coating layer (5), and a sealed packaging test was conducted on these lid materials in the same manner as in Example 1. The results obtained are also shown in the table below.

(Hereinafter, blank space) As is clear from the above table, according to the lid material of the present invention,
Since a coating layer made of a silane coupling agent is provided on the surface of the heat sealing material layer containing the monoolefin-unsaturated carboxylic acid copolymer resin or its metal salt, the adhesive strength to the mouth surface of the glass container is extremely high. The adhesive strength of the lid material does not decrease even after a glass container filled with water is stored upside down for a long period of time, and it has good water resistance and excellent sealing performance.

On the other hand, according to a comparative example lid material using a heat sealing material that does not use a silane coupling agent, the lid material peels off when a glass container is 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 has a heat-sealing material layer containing a monoolefin-unsaturated carboxylic acid copolymer resin or a metal salt thereof on one side of the metal foil. A coating layer made of a silane coupling agent is provided on the surface of the heat sealing material layer, so it is suitable for adhered surfaces that are porous and have relatively weak polarity, such as the mouth of a glass container. It has very good adhesive properties, and not only can the lid material be heat-sealed to the mouth of the sealed packaging container in a short time, but it also has a silane coupling that must be present on the surface of the heat-sealing material layer. The shape of the agent can be easily adjusted, and the adhesive strength can be reliably increased.
For this reason, the adhesive force between the heat sealing material layer and the mouth of the glass container is greatly strengthened. Therefore, the mouth of the glass container is generally hydrophilic, and in addition, if the contents of the container are, for example, alcohol, alcohol, etc.
Even in the case of liquids or viscous substances such as juices and jams, it is possible to reliably prevent water from entering the heat-sealed area, greatly increasing the water resistance of the heat-sealed area.
There is little decrease in adhesive strength in a water environment, a good adhesive state can be maintained for a long period of time, and it has excellent sealing properties.

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.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged cross-sectional view showing a specific example of the product of the present invention;
The figure is a partially enlarged sectional view showing one specific example. (1)... Aluminum foil, (2)... Heat sealing material layer, (3>... Adhesive layer, (4)... Anti-corrosion coating layer,
(5)...silane coupling agent coating layer. Figure 1 Figure 2

Claims (1)

[Claims] A heat sealing material layer containing a monoolefin-unsaturated carboxylic acid copolymer resin or its metal salt is provided on one side of the metal foil, and a coating layer made of a silane coupling agent is provided on the surface of the heat sealing material layer. A heat-sealable lid material for a sealed packaging container, characterized by: