EP0745046B1 - Container self-sealing closing process - Google Patents

Abstract

PCT No. PCT/EP95/00415 Sec. 371 Date Aug. 14, 1996 Sec. 102(e) Date Aug. 14, 1996 PCT Filed Feb. 6, 1995 PCT Pub. No. WO95/21767 PCT Pub. Date Aug. 17, 1995A process for filling and self-sealing containers with molten materials is provided. The process comprises filling a container with a molten material and covering the surface of the molten material which is still at elevated temperature after filling with an insert consisting of a plastic film and a plastic disk. The plastic film faces the molten material and is larger than the plastic disk. The diameter of the plastic disk is slightly smaller than the internal diameter of said container.

Description

The invention relates to a method for self-sealing sealing of hobbocks and barrels, which are suitable for meltable masses, especially for moisture-reactive polyurethane hotmelts Advantage can be used.

Moisture-reactive polyurethane hotmelts are designed so that they already react with traces of moisture and cross-linked, no longer meltable polymers result. When bottling and storage of such polyurethane hotmelts are therefore very high Make moisture exclusion requirements, as below illustrated. To 1 kg of a polyurethane hot melt with an isocyanate content of 1% with the conversion of all isocyanate groups To harden completely, approx. 1 g of water is required. Skin formation on the surface of the hot melt therefore already occurs instead if only a fraction of this amount of water to the surface of the product.

When filling polyurethane hotmelts into hobbocks or barrels can therefore already traces of diffusing moisture Make entire container contents unusable due to skin formation.

To ensure that the filled polyurethane hot melt has a storage stability of 9 Reaching months or more are therefore extremely demanding to put the containers, especially with regard to the Tightness of the seal used and the dimensional accuracy. Since the tightness of the container is checked even with 100% incoming inspection insufficiently checked, it follows current state of the art more often that individual containers are recognized as leaky after the hot melt has been filled. Here it is extremely disadvantageous that the customer also defective Can not recognize containers because of the cross-linked skin Indistinguishable room temperature from the uncrosslinked reactive hot melt is. It is possible to change the surface each time the container is changed melt and judge whether there is already one Skin formation has occurred, however, this step is labor and time-consuming, especially in industrial applications in general only a very short period of time for changing containers Available. The processor notices the skin formation in the container usually only through a steep drop in through the plant amount of melted hot melt. Because the skin's flow lines can clog, are incorrect bonds and time and costly production interruptions the result.

There has been no shortage of attempts to find suitable packaging for reactive To develop polyurethane hotmelts, the ones above skin formation and hardening described are avoided can. For example, EP-A-102804 describes a cylindrical one Container that is heated in the bottom area and one in the bottom area Removal opening and a movable piston head at the upper end as a conclusion. During the removal of the hot melt adhesive the bottom area is heated, so that only in this area Hot melt adhesive is melted. The printing stamp of a barrel press presses on the movable piston head of the container so that the entire unmelted block of hot melt adhesive is pressed down and so the melted part of the Hot melt adhesive through the discharge opening to the one with the discharge opening associated application part for the hot melt adhesive presses. This solution has two major disadvantages, firstly are special containers with a lower outlet opening necessary, which are complex and therefore expensive, on the other hand it when using amorphous hot melt adhesives Difficulties in the application. While with hot melt adhesives, which are crystalline at room temperature, the strong one when solidified Shrinkage to form a narrow gap between the wall of the Container and the mass of the solid hot melt adhesive composition leads, the amorphous hot melt adhesives shrink in a lot to a lesser extent when solidifying, so that it is often only with these to a very small extent to the said gap formation between the Mass of the hot melt adhesive and the container wall comes. This However, gap formation does not favor the mobility of the melted part of the hot melt adhesive block during the Removal, so that when applying amorphous hot melt adhesives from such containers to considerable difficulties can come.

• hohe Kosten der Inliner, Standard-Inliner mit Polyethylen als innerer Schicht haben nur eine begrenzte Temperaturbeständigkeit von etwa 80°C. Polyurethan-Hotmelts werden jedoch zum Teil bei erheblich höheren Temperaturen abgefüllt, so daß teuere hitzebeständige Spezialfolien für die Herstellung der Inliner verwendet werden müssen.
• Das Auskleiden der Behälter (Fässer oder Hobbocks) mit den Inlinern vor der Befüllung sowie das Zusiegeln dieser Inliner nach der Befüllung erfordern zusätzliche Arbeitsgänge.
• In den Inlinern verbleiben nach der Entleerung erhebliche Mengen von nicht entnehmbarem Schmelzklebstoff. In feuchtigkeitsundurchlässigen Inlinern härtet dieses Restmaterial jedoch nicht aus, daher gibt es Probleme bei der Entsorgung der mit Schmelzklebstoff kontaminierten Inliner.

EP-B-354650 therefore proposes to line the adhesive container from a heat-resistant film before filling it with an inner bag, so that the hot melt adhesive cannot adhere to the container wall. If these inner bags, also called "inliners", consist of moisture-proof aluminum composite film and are sealed after filling, there is even additional moisture protection for the hot melt adhesive. However, these inliners have several disadvantages, so that they have so far hardly been successful on the market. The main disadvantages of these inliners are:

• high costs of inliners, standard inliners with polyethylene as the inner layer have only a limited temperature resistance of about 80 ° C. However, polyurethane hotmelts are sometimes filled at considerably higher temperatures, so that expensive heat-resistant special films have to be used for the production of the inliners.
• Lining the containers (barrels or hobbocks) with the inliners before filling and sealing these inliners after filling require additional work steps.
• After emptying, considerable amounts of non-removable hot melt adhesive remain in the inliners. However, this residual material does not harden in moisture-impermeable inliners, so there are problems with the disposal of the inliners contaminated with hot melt adhesive.

Because the two methods described above despite their effort not always leading to satisfactory results would be a lot easier solution is obvious: The surface of the melt is after filling the polyurethane hot melt into the container with a dimensionally accurate, moisture-blocking film covered by the user immediately before processing from the then solid surface of the hot melt is withdrawn. That simple solution would be inexpensive and easy to produce with little additional effort to realize. The later disposal of the film did not prepare Problems because they are peeled off the product without any buildup can. Compared to the solution with inliners described above however, this approach has a major disadvantage. At the Cooling of the polyurethane melt in the hobbock occurs a thermal Shrinkage occurs, with crystalline hot-elts there is an additional one Shrink through crystallization. This shrinkage leads to that the hot melt is usually more or less different from the Replaces the container wall. This creates a depth Gap between the container wall and the mass of the hot melt composition. Moisture caused by any container leaks diffused into the container, or in the upper one There is air space between the filled hot melt mass and the lid cannot reach most of the surface of the hot melt, since this is protected by the flat cover, due to the gap on the container wall, however, the moisture in penetrate the depth and there to skin formation, and thus to malfunctions during the application of the hot melt.

So the task was to find a sealing process with the moisture sensitive meltable masses, in particular Polyurethane hotmelts that can be packaged and used for a long time are stable in storage.

According to the invention the object was achieved by the characterizing features of the claim 1 solved. As a rule, they have for Containers, hobbocks or barrels used a meltable mass circular cross section, so that the cover sheet and the Plastic disc are cut in a circle.

The invention also relates to a hot melt adhesive packaged by this method according to claim 10.

To seal the film cut is concentric on the Plastic disc placed and the protruding part of the film around the bent around the outer circumference of the plastic disc. Immediately after filling the container with the polyurethane hot melt adhesive the plastic disc covered with the film is inserted into the container and lightly pressed onto the melting material so that the product rises about 1 to 4 mm in the edge area, the one with the The film-covered side of the disc faces the melting material. The Plastic discs have two important functions: firstly As a centering aid, it facilitates the precise positioning of the Covering film on the melting material, especially in the edge area. Surprised an additional effect was found, that of the one described above Disadvantage of a surface covering according to the previous one Allows to overcome the state of the art, this effect is therefore to be seen as the main function of the plastic disc. If the plastic disc made of a thermoplastic material with high specific Thermal expansion is established, it expands as soon as the heat of the melting material flows into the disc. This creates over a period of several hours in which the hot melt cools, a radial pressure that is perpendicular to the top Part of the cover sheet presses against the container wall. The one in these Hot melt adhesive that has risen to the edge now creates an intimate and tightly sealing bond between the film edge and the Inside of the container wall. The plastic disc expands arched upwards in the middle. By pressing this Covering film over the entire cooling phase is ensured that the film adheres firmly to the edge and one in the Deep gap between the container wall and the melt material mass can bridge, so that the entire melting material moisture-proof is sealed.

The film material must have a high water vapor barrier effect, in addition, it must be thermally so stable that it can high temperatures of the cooling melt are not damaged becomes. As a rule, only multilayer composite films are used for this suitable. Although two-layer composite films are also used have found films with at least three layers Structure proven to be particularly suitable. The one facing the melt Side of the composite film should have anti-adhesive properties if possible have so that the composite film from the end consumer before Application can be easily removed from the solidified melting material can. This inner layer is therefore preferably the same as the solidified one Hot melt adhesive facing, made of polyethylene, Polytetrafluoroethylene (PTFE) or especially polypropylene. The middle layer of the three-layer composite film consists of a Aluminum foil as a water vapor barrier. The outside of the composite film the overall composite should have a sufficiently high mechanical strength therefore, polyamide foils or especially preferred polyester films. The suitable according to the invention Composite films must be laminated so that the film composite the high temperature load during the cooling phase of the hot melt adhesive, the films are therefore preferred with a laminating adhesive such as Liofol (RTM, company Henkel) laminated.

Plastic panes to be used according to the invention consist of polyvinyl chloride (PVC), polystyrene, polyethylene, polypropylene, polymethyl methacrylate or Polyoxymethylene.

As mentioned above, the linear thermal expansion of the plastic disc is intended to bring about radial pressure on the protruding edge region of the cover film against the inner wall of the container. For this reason, thermoplastics with a linear expansion coefficient of at least 6x10 ^-5 / K measured at room temperature are suitable. This coefficient of linear expansion should preferably be even higher at higher temperatures. This is ensured in particular in the case of branched polyethylene or also in the case of polypropylene, so that polyethylene and, in particular, polypropylene are suitable as the material for the plastic pane. The outer dimensions of the plastic disc depend on the container to be sealed. The thickness of the plastic disc is not critical as long as sufficient mechanical stability is guaranteed. The thickness of the disc can be between 0.1 and 5 mm, but the notes preferably have a thickness of 1 to 3 mm.

In a particularly preferred embodiment, the plastic disc has an inner circular section that shows the handling of the insert when inserting after filling and when removing relieved before removing the hot melt adhesive.

The dimensions of the plastic film and the plastic disc depend on the container to be sealed. At an industry-standard Hobbock with an inner diameter of 280 mm for example, a three-layer composite film cut into a circle with a diameter of 310 mm used as a plastic film.

A polypropylene disc with a plastic disc is used Use diameter of 275 mm and a thickness of 2 mm, whereby the polypropylene disc has an inner circular section of approximately 125 mm.

Different dimensions apply to containers with different dimensions for the film and for the plastic pane.

To give the processor even greater security against skin formation The hot melt adhesive can ensure after filling of the melting material and the sealing with that described above Insert consisting of a foil and a plastic disc be placed on the insert with a molecular sieve. The molecular sieve removes the gas space between the insert and the container lid the residual moisture in it. In addition, the Processor through a simple functional test of the molecular sieve Check whether the container was tight by checking it before application moistened the bag with molecular sieve. If the molecular sieve strongly warmed up by this moistening, it had to this At the time still large adsorption capacities for water, so this a sure sign of sufficient tightness of the container is.

The processor opens the to apply the hot melt adhesive Hobbock, removes the plastic disc and can remove the sealing film without great effort from the solidified hot melt adhesive pull it off. Because the plastic disc is not dirty , it can be reused for the same purpose. Of the Hot melt adhesive can now be used with any conventional barrel press can be removed with a heated follower plate.

In this way, the container can be left down to very small quantities empty completely so that usually recycling or disposal of the container is not a problem. This can be further facilitated by the fact that the container bottom also before filling with the polyurethane hot melt adhesive is covered with a suitable composite film blank. After Discharge of the hot melt can be the little remaining in the floor area The rest of the hot melt adhesive can be easily removed after cooling, so that the container in the bottom area is bare metal and accordingly is easy to reuse or dispose of.

Figur 1 zeigt in halbperspektivischer Darstellung das Einlegeteil bestehend aus der Verbundfolie 1 mit dem im Randbereich über die Kunststoff-Folie umgebogenen Teilbereich 4 sowie der Kunststoffscheibe 2 mit ihrem zentrischen kreisförmigen Ausschnitt 3.

Figur 2 zeigt das mit dem Schmelzklebstoff befüllte und fertig versiegelte Gebinde. Dabei liegt die Verbundfolie 1 mit der antiadhäsiven Seite zum Schmelzklebstoff 6. Auf der Verbundfolie 1 liegt die Kunststoffscheibe 2 und preßt während der Abkühlphase den nach oben umgebogenen Randbereich 4 der Verbundfolie 1 fest gegen die Behälterwand 5 des Gebindes. Nicht dargestellt ist in Figur 2 die geringe Menge Schmelzklebstoff, die sich zwischen dem nach oben umgebogenen Randbereich 4 der Verbundfolie und der Innenseite der Behälterwand 5 befindet. Ebenfalls dargestellt ist der in den Bodenbereich eingelegte zusätzliche Verbundfolienzuschnitt 7 sowie das mit Molekularsieb gefüllte Säckchen 8 und der das Gebinde abschließende Deckel 9.

The preferred embodiment of the insert to be used for the method according to the invention for sealing containers is to be explained in more detail below with reference to the descriptions for FIGS. 1 and 2.

FIG. 1 shows a semi-perspective representation of the insert consisting of the composite film 1 with the partial area 4 bent over the plastic film in the edge area and the plastic disk 2 with its central circular cutout 3 .

Figure 2 shows the container filled with the hot melt adhesive and sealed. The composite film 1 lies with the anti-adhesive side to the hot melt adhesive 6 . The plastic disc 2 lies on the composite film 1 and, during the cooling phase, presses the upwardly bent edge region 4 of the composite film 1 firmly against the container wall 5 of the container. The small amount of hotmelt adhesive which is located between the upwardly bent edge region 4 of the composite film and the inside of the container wall 5 is not shown in FIG. Also shown is the additional composite film blank 7 inserted into the base area, as well as the sachet 8 filled with molecular sieve and the lid 9 closing the container.

The above-described embodiments for sealing containers, which contain meltable masses are the preferred ones Embodiments of the invention, any person skilled in the art however, recognize that the invention is available in other embodiments can be used advantageously. For example, the Plastic disc after the melting material has cooled down before the final one Close the container with the container lid from the Foil can be removed because the foil is reliable Edge bonding / sealing even without the plastic pane adequate protection against moisture penetration during the Storage of the container guaranteed. In this case the Plastic disc at the adhesive manufacturer / filler and can immediately be returned to the filling process.

The application of the sealing method according to the invention is not limited to use with reactive hot melt adhesives, other meltable masses that are protected from moisture, Air access or even pollution are safely protected can be sealed in containers in this way, provided they can only be filled at sufficiently high temperatures. In the Usually the surface temperature of the mass to be sealed should at least 50 ° C, preferably 80 ° C, so that the plastic disc due to their thermal expansion a sufficiently large one Contact pressure is generated on the film in the edge area. If it is the masses to be sealed are not hot melt adhesives, the edge area of the film that seals / glues to the inside wall of the container should be, preferably with a heat sealable coating, e.g. a hot melt adhesive coated be. In this way, even with these masses reliable sealing / bonding in the edge area guaranteed.

Claims (10)

1. A process for filling and self-sealing a container filled with a molten material (6), characterized in that the surface of the melt which is still at elevated temperature after filling is covered with an insert consisting of a plastic film (1) and a plastic disk (2), the plastic film (1) facing the melt (6) and being larger than the internal diameter of the container (5), the diameter of the plastic disk (2) being slightly smaller than the internal diameter of the container and the linear thermal expansion of the plastic disk causing that part of the film which projects vertically upwards to be pressed radially against the inner wall of the container.
2. A process as claimed in claim 1, characterized in that the plastic film (1) is an at least two-layer composite film and in that the plastic disk (2) consists of a plastic with a linear expansion coefficient of at least 6·10^-5/K.
3. A process as claimed in claim 2, characterized in that the plastic film (1) is a three-layer composite film of a polypropylene film, polyethylene film or PTFE film as the inner layer, an aluminium foil as the water vapor barrier and a polyester film or polyamide film as the outer layer.
4. A process as claimed in claim 2, characterized in that the plastic disk (2) consists of PVC, polystyrene, polyethylene, polypropylene, polymethyl methacrylate or polyoxymethylene and has a thickness of 0.1 to 5 mm and preferably 1 to 3 mm.
5. A process as claimed in at least one of claims 1 to 4, characterized in that the plastic disk (1) has an inner, preferably circular cutout.
6. A process as claimed in at least one of claims 1 to 5, characterized in that the material (6) to be sealed has a temperature of at least 80°C when the cover is applied.
7. A process as claimed in at least one of claims 1 to 6, characterized in that, after the fusible material (6) has been sealed, a small bag filled with a molecular sieve (8) is placed on the insert as a water absorber and the container is subsequently closed with a lid (9).
8. A process as claimed in at least one of claims 1 to 7, characterized in that the insert is pressed onto the still warm surface of the fusible material (6) in such a way that the melt rises about 1 to 4 mm at its periphery (4).
9. A process as claimed in at least one of claims 1 to 8, characterized in that, after the fusible material (6) has cooled to ambient temperature, the plastic disk (2) is removed and the container is subsequently closed with a lid (9).
10. A packed hotmelt adhesive, characterized in that the pack consists of a container (5), a plastic film (1), of which the diameter is larger than the internal diameter of the container, and a plastic disk (2) of which the diameter is slightly smaller than the internal diameter of the container, the container having been filled and sealed by the process claimed in at least one of claims 1 to 8.

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