LU84552A1 - MOLD COVER FOR HERMETICALLY CLOSING A CONTAINER - Google Patents

Description

The invention relates to improved closure lids for hermetically sealing containers of glass or plastic or other materials / and relates more particularly to a closure lid molded from plastic, the device for which sealing includes ribs or sealing edges molded with the cover.

Plastic covers with ribs or sealing edges are presently used to seal containers in various packaging applications. A closure of this type is placed on the threaded neck of the container and it provides a hermetic seal when its ribs or edges bear firmly against the end of the container. Such closures are commonly known as unlined closures.

Some packages require a seal that maintains a vacuum inside the closed container in order to preserve the packaged product. Although the general type of plastic closure described above maintains a certain percentage of vacuum in closed packages, the percentage of packages in which the seal fails to maintain vacuum is, in many cases, too high. high to be acceptable.

Plastic covers with ribs or sealing edges are usually molded in one piece from polyolefin materials, often a polyolefin of the polypropylene type. The sealing edges 2 are relatively rigid compared to other materials such as plastisol linings normally used for hermetically sealing containers. The polyolefin sealing edges therefore lack flexibility making it possible to establish intimate contact with the end of the container, as is necessary to maintain a vacuum, in particular during the handling of the packages. Although containers are made within specified tolerances, they do not always have perfect ends due to problems inherent in their manufacturing process.

Another problem with the materials used for the production of plastic fasteners without packing is that the adhesion of other materials to the polyolefin surfaces is very difficult.

The method of the invention for improving. sealing possibilities consists in placing a softer sealing material, for example a wax, a hot-melt material, an epoxy resin, a plastisol 20 or a softer or softer plastic material on the sealing ribs or edges closing cover. For example, a paraffin wax and a plastisol have been tried and both have improved the ability of the closure to maintain the vacuum. When a plastisol is used, it is applied in liquid form to the sealing edges, then it is heated to change to the solid state by melting or gelling. Liquid plastisol can be applied to the edges using a fixed nozzle while the cover is turned. A plastisol thickness of 0.025 to 0.5 mm, applied to the ribs or fins, has been found to be useful, as described below.

The object of the invention is to improve the ability to seal or seal airtight plastic lids without packing, in particular for maintaining a vacuum inside airtight packages. , and it therefore has for its object the production of a closure cover molded in plastic material, making it possible to obtain an acceptable percentage of packages suitably sealed under vacuum, the sealing being able to be carried out on an automatic sealing machine, at extremely high work rates.

Another subject of the invention is an improved closure without lining, made of plastic, and more particularly a closure without lining, molded in plastic, comprising a relatively thin coating of sealing material on the sealing elements of the cover. The closure may in particular comprise a relatively thin, melted or gelled sealing shutter coating applied to the shutter edges or other tight shutter elements.

The invention will be described in more detail with reference to the attached drawing by way of non-limiting examples and in which; Figure 1 is an elevation, partly in section, of a preferred embodiment of the closure cover according to the invention; Figures 2 and 3 are partial and detailed longitudinal sections, on an enlarged scale, of different embodiments of the closure cover according to the invention, hermetically sealing a container; Figure 4 is a partial and detailed longitudinal section, on an enlarged scale, of another embodiment of the closure cover according to the invention; FIG. 5 is a partial and detailed longitudinal section, on an enlarged scale, of another embodiment of the closure cover according to the invention; and FIG. 6 is an elevation, partly in section, showing a preferred method of applying the soft, hermetic sealing coating to the sealing elements of the closure according to the invention.

The closing cover 1 according to the invention comprises a top 2 and a skirt 3 mistletoe extends downwards from the top and mistletoe comprises threads 4 intended to engage with a container. The outer surface of the skirt 3 may have knurling or other gripping means 5 for fitting the closing cover 1 on a container 6 and removing it from the container. The top 2, the skirt 3 and the threads 4, as well as a hermetic obtu-ration device for the container, constitute a closure cover molded in one piece or in one piece, produced by means of a conventional cover molding machine.

There are a number of suitable devices for hermetically sealing containers, made in one piece with the lid and having the usual-. The shape of edges, ribs or rings which project downwards from the underside of the closure cover. A hermetic sealing device of this general type is described in prior patents such as US patent 3,815,771. This patent and also other issued patents describe projecting ribs or ridges , molded with the closure cover and arranged to bear against the edge of the container. The edges or ribs come into contact with the edge of the container and provide hermetic sealing intended for the contents of the closed container.

As shown, the closure edges 7 are inclined both relative to the top 2 of the closing neck and to the edge 8 of the container so as to flex and adapt by itself against the adjacent edge. 8 of the container ensuring sealing.

The refinement of the invention comprises the application of a thin layer 9 of softer or softer sealing material 35 to the edges 7. Suitable sealing layers 9 comprise layers of material which can be easily applied, for example waxes, hot-melt materials, epoxy resins, plastisols or other soft plastic materials applied in the form of a thin layer on the edges 7.

Layers of these materials have been tried and shown to significantly increase the possibilities of hermetic sealing of molded closures, and in particular to increase the ability of hand closures to maintain a vacuum inside the containers. hermetically closed.

When a plastisol is used, it is applied by spraying or otherwise on the sealing edges 7, and is then heated and melted or gelled to form a continuous elastic sealing layer on the edges. Layers of plastisols having a thickness of 0.025 to 0.5 mm have been tried and found to be effective in providing the improved sealing action.

20 The molten or gelled plastisol substantially follows the shape of the plastic sealing edges and is retained in the closure, not only because of its own qualities of adhesion, but also because of the physical engagement which takes place. produced between the layer 9 and the sealing edges 7. Even if. hermetically sealed packages with the edges coated as described above are subjected to high temperatures such as those resulting from the use of water vapor by the sealing and production apparatus 30 vacuum, no significant loss of the improved sealing action of the layers appeared.

Preferred plastisols consist of a suitably dispersed mixture of ingredients such as dispersing resins, resins for mixing, plasticizers, stabilizers, lubricants, wetting agents, viscosity reducing agents , pigments, fillers, etc. The resin may be a homopolymer of polyvinyl chloride or copolymers of vinyl chloride such as a copolymer of vinyl acetate and vinyl chloride.

When a molded polyolefin closure is subjected to sufficient heat, it can shrink or melt. To avoid these effects, the heat used to bring the liquid plastisol, by fusion or gelling, to a solid form should be relatively moderate.

Tests have shown that certain copolymer dispersion resins, designed to melt at relatively low temperatures, are particularly suitable for this application. Temperatures of 150-165 ° C and times of 3 to 4 minutes have been used successfully.

Butyl benzyl phthalate (PBB) uti-. Read as a plasticizer appeared to significantly lower the required heating cycle.

A preferred plastisol composition comprising copolymers of vinyl chloride and other plastisol ingredients, which melts or gels at low temperatures, is as follows:

Formulation (PCR) 1 2 3 Resin 100 100 100 25 Plasticizer (P.D.O. or P.B.B.) 60 100 100

Stabilizing agent (Ferro (707X)). 2 1 2

Pigment (Horsehead A-410) - 2 2 30 Lubricant (Crodamide OR) 555

Lubricant (Crodamide ER) - - 7 P.D.O. = dioctyl phthalate -v 7

Description of the Supplier Description _resin_ _ _

Homopolymer of Hooker chloride FPC-605 vinyl Tenneco 1759 5 Copolymer of Hooker chloride FPC-6338 vinyl and Stauffer acetate SCC-40 vinyl Stauffer Scc-52

Diamond Shamrock PVC-7401 Tenneco 0565 10 Copolymer of vinyl chloride and vinyl ester B.F. Goodrich Geon 138 special

The six copolymer resins listed above have been found to be generally superior to homopolymer resins because they require less heat to melt or gel. In particular / the copolymer resins SCC-40, PVC-7401, Geon 138 and FPC 6338 exhibit physical properties by requiring less heat than that required by the homopolymer resins FPC-605 or Tenneco 1759. In addition, the copolymer resins reach a maximum tensile load higher than that of the homopolymer resin, as indicated below: Resin Breaking stress _ (kPa) _ 25 PVC-7401 7245

Geon 138 6965 FPC-6338 6790 SCC-40 6720 SCC-52 6580; 30 0565 5950 1759 5495 FPC-605 5285

These data show that not only copolymer resins such as SCC-40, Geon 138, PVC-7401 and 35 FPC-6338 have physical properties, under more moderate heating conditions than those used for polymer resins, but that they are by their nature 8 more resistant than homopolymer resins similar to FPC-605 and Tenneco 1759.

Consequently, copolymer resins such as SCC-40, Geon 138 and PVC-7401 have appeared particularly well suited to this application.

The ability of this formulation to melt at relatively low temperatures protects the shell of the molded plastic cover from deterioration during the coating, melting or gelling operation.

2 shows a coating according to the invention, of average thickness, the material 9 of the coating filling the space between the two sealing edges 7. In this case, it appears that the coating 15 makes the sealed contact between the closure 2 and the container 6.

- Figure 3 shows a similar closure, but applied to a container 6 and using a coating 1 of thinner thickness which appears to conform more closely to the shape of the sealing edges 7. However, such coatings, the thickness of which is close to the lower limit of the range of thicknesses, provides better sealability under vacuum.

FIG. 4 illustrates the use of a coating of the type described above on a closing cover 11 comprising a different sealing device which comprises three sealing edges 12 having different lengths and forming a more angle large with the top 13 of the cover 11. This coating operates in a similar manner to that described above to improve the sealability.

FIG. 5 represents another embodiment in which the closure 14 is in leaktight contact with a container 19 and in which also a coating 16 forms a seal between the inclined edges 15 and the 9 edges 18 of the end of the container.

FIG. 6 illustrates a preferred method for applying these coatings to determined thicknesses. The covers are arranged in rotating housings of a typical machine for applying a gasket. A spray nozzle, arranged to direct a spray of coating material onto the sealing members, works for a sufficient time to apply the desired thickness of coating. After application of the coating, in the case where a plastisol or other material requiring maturation has been used, the cover is transferred to a suitable heating device for the maturation or gelation stage.

It therefore appears that an improved closure cover is obtained without a lining by the addition of an advantageous soft coating providing the ability to. vacuum tightness. The covers are manufactured in the same way as the covers currently known, with, in addition, the steps of coating application.

It goes without saying that many modifications can be made to the closure cover described and shown without departing from the scope of the invention.

Claims (9)

10 1. Molded closure cover, comprising a sealing device molded, intended to hermetically seal a container (6), characterized in that it comprises a coating (9 or 10) relatively thin in * softer material than the material of the molded cover, this coating covering the surfaces of the closure sealing device. 2. Lid according to claim 1, characterized in that it comprises one or more sealing elements (7 or 12), similar to edges, constituting the sealing device intended to be applied against the container, the coating being applied to the surfaces of these elements. 3. Lid according to claim 2, charac terized in that the coating has a thickness. from about 0.025 to 0.5 mm. 4. Lid according to claim 3, characterized in that the coating is chosen from group 20 comprising waxes, hot-melt materials, epoxy resins or plastisols. 5 Plasticizer (P.D.O. or P.B.B.) 60 100 100. Stabilizing agent (Ferro (707X)) 2 1 2 Pigment (Horsehead A-410) 2 2 10 Lubricant (Crodamide OR) 555 Lubricant (Crodamide ER) - - 7 5. Lid according to claim 4, characterized in that the plastisol resin is a homopoly-mother or a copolymer of vinyl chloride. „25 6. Lid according to claim 5, charac terized in that the resin is a copolymer of vinyl acetate and vinyl chloride. 7. Lid according to claim 6, characterized in that the copolymer resin is chosen from the group comprising SCC-40, Geon 138, PVC-7401 or FPC-6338. 8. Cover according to claim 6, characterized in that the coating composition is chosen from a group comprising the following ingredients, in the proportions indicated: 11 Formulation (PCR) 1 2 3 Resin (vinyl chloride copolymer) 100 100 100 parts parts parts 9. Lid according to claim 5, characterized in that the plasticizer is butyl benzyl phthalate and the resin is a copolymer of vinyl chloride.