Caps with safety function for prevention of excessive pressure

Abstract

The invention relates to a cap for closing containers comprising at least one mesh, one foamed polymer and at least one further polymer, and to containers equipped with the cap of the invention.

Claims

1. Cap (1) with screw thread (2) for closing a container (3), comprising at least one mesh (4) applied in the cap to the internal wall (5) of the cap, and comprising at least one foamed polymer layer (6) applied to the mesh (4) and comprising at least one further polymer layer (7) which has been applied on the foamed polymer layer (6) and which closes the container aperture (8).

2. Cap according to claim 1, wherein within the mesh (4) the diameter of the mesh filaments, which are in essence round, is 0.2 mm to 5 mm.

3. Cap according to claim 1, wherein the foamed polymer layer (6) comprises at least one polymer selected from the group consisting of polypropylene, polyethylene, high-density polyethylene (HDPE), low-density polyethylene (LDPE), high-density polypropylene (HDPP), low-density polypropylene (LDPP), polyethylene terephthalate, polystyrenes, polyurethane, polycarbonate, ethylene-propylene-diene rubber (EPDM), or fluorinated foamed polymers, such as preferably fluororubber (FKM) in accordance DIN ISO 1629 and fluororubber in accordance with ASTM D1418, polytetrafluoroethylene (PTFE), and other foamed partially fluorinated or perfluorinated hydrocarbons based on vinylidene (di)fluoride or mixtures of these foamed polymers.

4. Cap according to claim 1, wherein the density of the foamed polymer layer (6) is 45 to 450 kg/m.sup.3.

5. Cap according to claim 1, wherein the polymer layer (7) consists of polytetrafluoroethylene.

6. Cap according to claim 1, wherein an adhesive is used to connect the foamed polymer layer (6) to the polymer layer (7).

7. Cap according to claim 6, wherein adhesives used are based on at least one of cyanoacrylates, methylmethacrylates, unsaturated polyesters, epoxy resins, phenolic resins, polyimides, polysulfides, bismaleimides and 1-component and 2-component condensation-crosslinking silicones and glutine glue or mixtures of these adhesives.

8. Cap according to claim 1, wherein the mesh (4) consists of polypropylene (PP) or polyethylene (PE) or mixtures of these polymers.

9. Cap according to claim 1, wherein a polyethylene seal is used as seal on an edge (12) of the container aperture (8).

10. Cap according to claim 1, wherein the cap (1) consists of polyethylene terephthalate (PET), polypropylene (PP) or polyethylene (PE) or mixtures of these polymers.

11. Container comprising the cap according to claim 1.

12. Container according to claim 11, wherein the container has been at least partially filled with liquid dimethyldicarbonate.

13. Container according to claim 1, wherein the maximal tightening torque M used to close the cap is 4 Nm≤M≤8 Nm.

14. Container according to claim 11, wherein the aluminium content of the container is ≥95% by weight, based on the total weight of the container without cap.

Description

[0041] The invention is explained in more detail below with reference to the figures, without restriction of the general concept of the invention.

[0042] FIG. 1 shows a general structure of the cap of the invention.

[0043] FIG. 1 here shows a cap (1) of the invention with screw thread (2) for closing a container (3), comprising at least one mesh (4) applied in the cap to the internal wall (5) of the cap, and comprising at least one foamed polymer layer (6) applied to the mesh (4) and comprising at least one further polymer layer (7) which has been applied on the foamed polymer layer (6) and which closes the container aperture (8).

[0044] The container (3) is preferably closed by pressing, onto the same, the cap (1) with the mesh (4), the foamed polymer (6) and the further polymer layer (7).

[0045] FIG. 2 shows a further embodiment of the invention, where a seal (9) is used which additionally seals the container aperture (8) at the edge (12) of the aperture. In this embodiment, the polymer layer (7) is placed onto the seal (9). It is preferable that the polymer layer (7) and the seal (9) are connected to one another. This is preferably achieved by adhesion.

[0046] By virtue of the pressure, the foamed polymer layer (6) can move into the open regions of the mesh (4). The further polymer layer (7) follows the motion of the foamed polymer layer (6) and thus releases regions at the edge (12) of the bottle aperture which permit release of pressure by way of the gap (13) between container aperture and cap.

[0047] FIG. 3 shows the mesh (4) with the mesh filaments (10) and (11).

[0048] The invention permits incorporation of excessive-pressure prevention at extremely low cost and without any structural change to the cap, merely by insertion of a mesh and of two polymers differing from one another or of a composite of these polymers. There is no need to implement any structural measures on the cap; considerable costs and resources are thus saved.

[0049] The design can provide reliable avoidance of excessive pressure, without at any juncture sacrificing the integrity of the packaging.

EXAMPLES

Inventive Example 1

[0050] A round mesh made of polyethylene (diameter 6.6 cm, diameter of mesh filaments 2 mm, separation between the mesh filaments in the square mesh: 10 mm) and a composite made of foamed polyethylene (PE) (thickness: 3 mm, density: 194 kg/m.sup.3, diameter: 6.6 cm) and of a polytetrafluoroethylene layer (PTFE) with a thickness of 0.5 mm (diameter: 6.6 cm) were inserted into a commercially available polyethylene closure cap of diameter 6.6 cm with screw thread. The cap moreover bore a safety ring to indicate absence of damage prior to opening.

[0051] An empty aluminium bottle with a volume of 6 l was then closed by the above cap with a tightening torque of 6.7 Nm, and the pressure within the bottle was slowly increased to 1.5 bar by adding compressed air. The pressure within the bottle was measured by a manometer integrated within the bottle. When 1.5 bar was reached, a release of pressure was observed; by virtue of the pressure, the foamed polymer layer (6) was able to move into the open regions of the mesh. The polytetrafluoroethylene layer (7) follows the motion of the foamed polymer layer (6) and thus releases regions at the edge (12) of the bottle aperture which permit release of pressure by way of the gap (13) between container aperture and cap. Within 15 minutes, the pressure decreased from 1.5 bar to 1.2 bar.

[0052] Once appropriate release of pressure has been achieved, the polymer layers again provide closure.

Inventive Example 2

[0053] A round mesh made of polyethylene (diameter 6.6 cm, diameter of mesh filaments 2 mm, separation between the mesh filaments in the square mesh: 10 mm) and a composite made of foamed polyethylene (PE) (thickness: 3 mm, density: 194 kg/m.sup.3, diameter: 6.6 cm) and of a polytetrafluoroethylene layer (PTFE) with a thickness of 0.5 mm (diameter: 6.6 cm) were inserted into a commercially available polyethylene closure cap of diameter 6.6 cm with screw thread. The cap moreover bore a safety ring to indicate absence of damage prior to opening.

[0054] An aluminium bottle with a volume of 6 l was then closed by the above cap with a tightening torque of 6.7 Nm The bottle contained 6 kg of dimethyldicarbonate (Velcorin, Lanxesss Deutschland GmbH, batch CHWV5547, purity >99.8%). After filling and closure, the bottle was stored for 12 months at room temperature. The bottle was then stored for 6 months at 50° C. The bottle was then opened. On opening, the bottle was free from damage, and no pressure increase ≥1.2 bar could be detected. The purity of the DMDC was by this stage only 90%. By virtue of the cap of the invention, the CO.sub.2 formed during the partial decomposition of the DMDC was able to escape.

[0055] The experiment was repeated with a 3 l glass bottle containing 3 kg of dimethyldicarbonate. Again in this case no pressure increase ≥1.2 bar could be observed on opening, and the bottle remained undamaged.

Comparative Example 1

[0056] An aluminium bottle with a volume of 6 l was closed by a commercially available cap with screw thread, with a torque of 6.7 Nm; compressed air was used to produce a pressure of 1.5 bar, and any pressure decrease that might occur was observed over a period of 3 days. The pressure within the bottle was measured by a manometer integrated within the bottle. No release of pressure was measured.

Comparative Example 2

[0057] The cap with inserted composite comprising foamed polyethylene (PE) (6) and polytetrafluoroethylene layer (PTFE) (7), from Inventive Example 1, but without the additional mesh (4), was used to close a 30 litre glass bottle containing 3 litres of dimethyldicarbonate and 1 litre of water, with a torque of 6.7 Nm. After 24 h of pressure increase, the glass shattered at a pressure of 10 bar.