DE1586288B2 - PROCEDURE FOR SEALING STERILIZABLE CONTAINERS - Google Patents

Description

The invention relates to a method for closing sterilizable containers made of metal with metal lids by heat sealing using a thermoplastic intermediate layer in the Area of an edge flange of the container. The invention further relates to according to this method closed, sterilizable containers with lids made of metal, in particular made of aluminum.

It is known to use packaging of any kind, such as. B. bags, cans and wrappings, by heat sealing close (cf. e.g. magazine "Kunststoffe", Volume 46, 1956, pp. 244 to 249, or Volume 53, 1963, pp. 551 to 554). In the known method, this is made of a thermoplastic or with such a plastic-coated packaging material by applying pressure and heat to the Seam welded When using packaging films coated with a thermoplastic material it is important for a proper closure that both of the facing sides of the Packaging film are coated with thermoplastic plastic. Only in isolated cases, if namely a weld of low strength is sufficient, it is possible to use a coated one to seal uncoated material.

• From FR-PS 11 26 311 it is also known at insert a thermoplastic wire between the lid and the container receiving part for small containers and by heating the wire, pressing the container cover onto the container and then cooling it to achieve a hermetic sealing of this container.

Are also known cans, which are deep-drawn from polyethylene-coated aluminum foil and with a are also closed with polyethylene-coated cover film, the cover film on one after the outer edge flange of the lower part of the can is sealed (cf. magazine »Kunststoffe«, volume 53/1963, page 554). In order to be able to open such cans or containers particularly easily, in the FR-PS 12 93 533 proposed between the cover film and the edge flange of the lower part of the can in addition one Interlayer containing thermoplastic material for producing a particularly good when opened and to arrange an easily destructible intermediate layer.

However, all of these types of packaging are unsuitable for filling goods, especially foods that contain one Must be subjected to high temperature sterilization. Because the ones applied to the aluminum Thermoplastic layers are generally insufficient to withstand the effects of sterilization temperatures resistant. If you still carry out sterilization with them, which is possible with certain material pairings is, then there is always the risk that it will be due to the subsequent storage of such containers Inadequate durability of the thermoplastic layers used leads to undesirable peeling phenomena these layers come from the aluminum foil. Because of this, it was used for sealing from Z. B. Containers filled with food that are to be sterilized hot, such as sterilization-proof tins, uses a process in which you place these tin cans on the inside with a Baked enamel, i.e. a plastic hardened by baking, coated. Closing these cans then took place by flanging the lid with the can rim with the interposition of a sealing compound, which was mostly chosen based on rubber. Although such packaging creates more resistant to sterilization Containers made it possible for them to be filled with food for longer storage afterwards are suitable for sterilization, however, such containers or cans can be sealed Beading the lid and using special sealing layers cumbersome, time-consuming and expensive.

Proceeding from this prior art, the invention is based on the object of providing a method find, in which the sealing of sterilizable metal containers, which are on the inside with a Enamel finish is provided, is made possible by heat sealing. According to the invention this is at a generic method achieved in that for sealing with a stoving lacquer layer coated inner surfaces of the container and lid a copolymer of ethylene and vinyl acetate with a Vinyl acetate content of 18 to 40% is used. It has been shown that the inventively used

The copolymer has particularly good adhesion to stoving enamels and is easy to heat-seal the inner surface of the container and lid, which is coated with the stoving lacquer layer. That Copolymer can either by applying a solution with subsequent. Drying or through Applying the molten mass, e.g. B. be applied by spraying.

In an advantageous embodiment of the invention, the copolymer is only one of the to each other sealing parts applied, e.g. B. only on the lid. It turns out to be very special Advantage if the heating during sealing is only from the side not coated with the copolymer takes place here.

But it is also possible to work without prior application of the heat sealing compound, to be precise such that the copolymer is in the form of a ring immediately before the container is closed is introduced between the surfaces to be sealed. For this ring can preferably be the shape a round wire with a cross-sectional diameter of 0.8 to 1.2 mm or the shape of a band with Select a rectangular cross-section, preferably 0.05 to 0.50 mm thick and 3.0 to 0.5 mm wide. That Welding is then carried out in a known manner by applying pressure and heat.

The copolymer can also contain certain amounts of resins, plasticizers, Stabilizers, wax and paraffin can be added. For coating the container with the hardenable Plastic come in particular the known stoving enamels, z. B. based on phenolic and / or epoxy resins in question.

However, the invention also relates to a sterilizable one produced by the method according to the invention Containers with lids of metal, in particular of aluminum. According to the invention, this container rt characterized in that the inner surfaces of the container and lid are coated with a layer of stoving varnish are coated, and that between the edge flange of the container and the lid is a layer of one Copolymer of ethylene and vinyl acetate is located, which has a vinyl acetate content of 18 to 40% having.

The following are two examples of the practical

Implementation of a method according to the invention given at the same time for a more detailed explanation serve the invention shown in FIGS. 1 to 3 by way of example.

example 1

An aluminum tape 0.1 mm thick was coated with a conventional can lacquer (epoxy-modified Phenolic resin) varnished and baked in. The thickness of the varnish was 5/1000 to 7/1000 mm. the end A container 1 was produced from this material by deep drawing and a lid 2 was punched out.

At the edge of the lid, a xylene solution of a copolymer of ethylene and vinyl acetate with a content of 28% of the latter was applied to the paint side and dried in warm air, so that a coating 4 with a thickness of 200/1000 to 400/1000 mm was formed (F. i g. 1). This cover was welded onto the flange 3 of the container 1, specifically at a mold ^{temperature of 200 to 230 °} C., a specific pressure of 30 kp / cm ² and a sealing time of 2 seconds. Even better results were achieved if the heat was only supplied from below, from the side of the flange 3 of the container 1. The container closed in this way (FIG. 3) was sterilized for 30 minutes at 121 ° C., and the strength of the sealing seam was then tested by drilling into container 1 and printing. The container did not burst until the internal pressure was 2.5 to 3.3 atm.

Example 2

Container 1 and lid were produced as in Example 1, but not coated with heat sealant; this was rather in the form of a wire 5 with a diameter of 1.2 mm between the lid 2 and the container - Flange 3 brought (Fig. 2). Sealing temperature and pressure and time were chosen to be the same as in example 1, the heat being supplied from both sides.

Testing of the container (FIG. 3) was carried out in the manner described in Example 1 and showed the same result.

1 sheet of drawings

Claims (7)

Patent claims: 1. Method for closing sterilizable metal containers with metal lids Heat sealing using a thermoplastic intermediate layer in the area of an edge flange the container, characterized in that for sealing with a stoving lacquer layer coated inner surfaces of the container and lid a copolymer of ethylene and Vinyl acetate with a vinyl acetate content of 18 to 40% is used. 2. The method according to claim 1, characterized in that the copolymer is only applied to one of the is applied to each other to be sealed parts. 3. The method according to claim 2, characterized in that the heat supply during the Sealing takes place only from the side not coated with the copolymer. 4. The method according to any one of claims 1 to 3, characterized in that the copolymer in Form of a ring is introduced between the surfaces to be sealed. 5. The method according to claim 4, characterized in that the ring is in the form of a round wire (5) with a cross-sectional diameter of 0.8 to 1.2 mm. 6. The method according to any one of claims 1 to 3, characterized in that the copolymer in Shape of a tape with a rectangular cross section, preferably 0.05 to 0.50 mm in thickness and 3.0 to 0.5 mm width is introduced between the surfaces to be sealed. 7. After the method according to any one of claims 1 to 6 closed, sterilizable Container with a lid made of metal, in particular made of aluminum, characterized in that the inner surfaces of container (1) and lid (2) are coated with a stove-enamel finish, and that a layer made of a copolymer between the edge flange of the container and the lid Ethylene and vinyl acetate is located, which has a vinyl acetate content of 18 to 40%.