Use of oxygen absorbing substances for making flexible tubes

Abstract

A metal tube for storing and distributing liquids, the tubes typically being manufactured of an aluminum alloy, comprising a cylindrical or truncated skirt having one end and another end linked to a dispensing head, the inner surface of the cylindrical skirt being covered, proximate to the open end, with an adhesive annular seal; and wherein the adhesive seal comprises an oxygen absorbing agent that is released when the tube is finally sealed; and wherein the oxygen absorbing agent is directly incorporated in the resin used for producing the seal to ensure that the oxygen absorbing agent is released only when the tube is finally sealed.

Description

TECHNICAL FIELD

[0001] The invention relates to metallic receptacles such as aluminium alloy tubes designed for storage and distribution of liquid to pasty products. These tubes form an excellent barrier to gas diffusion and are particularly suitable for containing products sensitive to oxidation.

DESCRIPTION OF RELATED ART

[0002] Aluminium alloy tubes are obtained by impact extrusion of a slug. They comprise a cylindrical or truncated skirt with one open end and one end connected to a dispensing head. The said dispensing head or collar comprises a distribution neck generally delimiting an orifice that has not yet been opened and a shoulder connecting the neck to the skirt. The inner surface of the tube is covered by a varnish and an annular seal near the open end composed of a “latex based” resin, typically an adhesive resin based on synthetic rubber or an acrylic type resin, the said resins being in suspension in an aqueous solution.

[0003] Once made, the tubes are packaged upside down with the orifice sealed and/or closed off by a cap and then sent to the packager. The packager fills them by delivering the product to be packaged through the open end. When filling is complete, the portion of the skirt close to the open end fitted with the annular seal is flattened along a diameter such that the parts of the wall facing each other can come into contact over their entire surface and be adjacent to each other. This flattened end is then folded over itself several times (usually 2 or 3 folds are made) and then compressed. Consequently, due to the adhesive seal trapped in the folds thus formed, the tube containing the product is finally sealed so as to make the said tube leak tight. The seal is self-adhesive or thermo-adhesive depending on the material used.

[0004] Until recently, this type of practice was fully satisfactory because the essential requirement was leak tightness to liquids to prevent a product contained in the tube from leaking. At the moment, aluminium alloy tubes are less frequently used for packaging products for daily consumption (such as toothpaste), but they are still particularly in demand for packaging products sensitive to degradation by ambient air, and particularly easily oxidisable products. Thus, cosmetics for which the invention is applicable include hair dyes and anti-aging creams, containing products such as retinol or vitamin C.

[0005] Formulations offered by cosmetics manufacturers are changing: they are becoming more and more efficient but they are also becoming more and more sensitive to oxidation. Under the conditions described above, the seal is perfectly satisfactory for leak tightness requirements for liquids, but not for more severe gas tightness requirements, particularly for oxygen. Therefore, it is found that the final sealing of the tube described above is no longer sufficient to preserve the packaged product, since the product is immediately oxidised by oxygen in the air trapped when the tube is being sealed or gradually oxidised by air that diffuses through the adhesive seal.

STATEMENT OF THE PROBLEM TO BE SOLVED

[0006] Therefore, the Applicant attempted to solve the problems that arise due to the appearance of these new products particularly sensitive to oxidation.

PURPOSE OF THE INVENTION

[0007] The purpose of the invention is a metal tube comprising a cylindrical or truncated skirt having one open end and another end connected to a dispensing head, the inner surface of the said cylindrical skirt being covered with an adhesive annular seal close to the said open end, characterised in that the said adhesive seal comprises an oxygen absorbing agent that is released when the tube is finally sealed.

[0008] The tube is metallic because its wall has an excellent barrier property to oxygen diffusion, significantly better than is possible with a wall made of a polymer material. Preferably, this tube will be an aluminium alloy, for practical shaping reasons. The Applicant has found that it is advantageous to release an oxygen absorbing agent previously contained in the seal close to the said pocket, to absorb oxygen contained in the residual air pocket remaining in contact with the product after the tube is sealed.

[0009] In order to be released only at the time of the final seal, the oxygen absorbing agent may be incorporated directly into the “latex based” resin from which the seal is made, in the form of a chemical that remains passive until it is brought into contact with the product to be packaged. For example, products like those described in U.S. Pat. No. 4,536,409 & U.S. Pat. No. 4,702,966 can be incorporated, which become reducing after reaction with water contained in the product with which they come into contact due to their sensitivity to humidity.

[0010] The oxygen absorbing agent can also be simply included in an envelope, or preferably in a large number of microcapsules incorporated in the said “latex based” resin used to make the seal, this envelope or these microcapsules being destroyed after the tube is filled and/or finally sealed.

[0011] The oxygen absorbing agent is packaged inside the microcapsules and is easy to mix in a liquid resin such as the resin used to make the seal. The microcapsules are simply incorporated and mixed in this aqueous suspension, then the said “latex based” resin is deposited on the internal wall of the tube when it is still in the liquid form. In general, this wall is already covered with a layer of varnish, usually a phenol epoxy type varnish. The “latex based” resin may possibly be dried at ambient temperature (self-adhesive seal) or at a high temperature (thermal adhesive seal). The microballs remain trapped in the hardened seal after drying.

[0012] These microcapsules may be destroyed mechanically, taking advantage of the operations necessary for the final seal (compression and then folding of the edges of the open end, compression of the final seal, etc). The envelope of these microcapsules can also be destroyed (or made permeable to oxygen) for example using a different type of mechanical action (for example ultrasound) or by adding external energy (addition of heat, electromagnetic radiation such as microwaves, ultraviolet or infrared radiation) or by a chemical method (addition of a solvent, water, lipids, pH of the packaged product, etc.).

[0013] The substance released during final sealing absorbs residual oxygen in the air pocket trapped in the receptacle after filling with the product to be packaged and after closing the said receptacle. Preferably, this substance is provided in a sufficiently large quantity so that it can also absorb any oxygen that diffuses through the interface between the flattened, glued or folded parts of the seal while the product is being used.

[0014] This substance is chosen as a function of usage conditions of the product packaged in the tube. It may be any oxidisable compound compatible with use of the product to be distributed such as iron powder, a metallic salt such as a ferrous salt or a cobalt salt, an oxidisable compound chosen from the group containing reduced forms of quinone, or an oxidisable composition comprising an active oxygen absorbing compound chosen from among the group containing organic anti-oxidants, phosphites, phosphines and organic phosphates, hydroquinone, substituted hydroquinone, sulphates, sulphites, phosphites and metal nitrites, thiodipropinoic acid and its esters and salts, thio-bis (ethylene glycol beta-aminocrotonate), cysteine, cystine, methionine, primary, secondary and tertiary amines and derivatives of them.

[0015] The diameter of the microcapsules varies between 1 and 50 &mgr;m. Depending on the nature of the oxygen absorbing agent, the envelopes are made by drying, spray cooling, prilling), are coated with molten polymers, gelified polymers, hydrosoluble polymers in a fluidised bed, by phase separation (simple or complex coacervation), by solvent elimination, polymerisation, cross linking, polycondensation, etc.

[0016] Depending on their composition, microcapsule envelopes may be hydro or liposoluble with various natures of polymers such as agar, alginate, wax, collagen, polylactate, polyglycolate, gelatine, chitosane, ethyl-cellulose, carboxymethyl-cellulose, polysaccharide, polyvinyl alcohol, polyethylene-imine, vinyl acetate and mixes thereof.

Claims

1. Metallic tube comprising a cylindrical or truncated skirt with one open end and one end connected to a dispensing head, the inner surface of the said cylindrical skirt being covered by an annular adhesive seal near the said open end, characterised in that the said adhesive seal comprises an oxygen absorbing agent that is released when the tube is finally sealed.

2. Tube according to claim 1, in which the oxygen absorbing agent is incorporated directly into the resin used to make the adhesive seal, in the form of a chemical that remains passive until it is brought into contact with the product to be packaged.

3. Tube according to claim 1, in which the oxygen absorbing agent is included in at least one envelope incorporated in the resin used to make the said adhesive seal.

4. Tube according to claim 3, in which the oxygen absorbing agent is included in microcapsules with diameter varying between 1 and 50 &mgr;m, and incorporated in the resin used to make the said adhesive seal.

5. Tube according to claim 3, in which the envelope is selected from capsules capable of being destroyed mechanically during final sealing, by compression and then folding of the edges of the open end of the skirt.

6. Tube according to claim 3, in which the envelope is selected from capsules capable of being destroyed using ultrasound.

7. Tube according to claim 3, in which the envelope is selected from capsules capable of being destroyed or made permeable to oxygen by adding external energy, such as heat, electromagnetic radiation such as microwaves, ultraviolet or infrared radiation.

8. Tube according to claim 3, in which the envelope is selected from capsules capable of being destroyed or made permeable to oxygen by a chemical method, such as addition of a solvent, water, lipids, modification due to the pH of the packaged product.

9. Tube according to claim 1, in which the said substance absorbing the oxygen is provided in a sufficiently large quantity so that it can also absorb any oxygen that diffuses through the interface between the flattened, glued or folded parts of the seal while the product is being used.

10. Tube according to claim 1, in which the said substance absorbing the oxygen belongs to the group containing iron powder, metallic salts such as a ferrous salt or a cobalt salt, oxidisable compounds chosen from the group containing reduced forms of quinone, or oxidisable compositions comprising an active oxygen absorbing compound chosen from among the group containing organic anti-oxidants, phosphites, phosphines and organic phosphates, hydroquinone, substituted hydroquinone, sulphates, sulphites, phosphites and metal nitrites, thiodipropinoic acid and its esters and salts, thio-bis (ethylene glycol beta-aminocrotonate), cysteine, cystine, methionine, primary, secondary and tertiary amines and derivatives thereof.

11. Tube according to claim 3, in which the envelope is made of a material belonging to the group containing agar, alginate, wax, collagen, polylactate, polyglycolate, gelatine, chitosane, ethyl-cellulose, carboxymethyl-cellulose, polysaccharide, polyvinyl alcohol, polyethylene-imine, vinyl acetate and mixes thereof.

12. Tube according to claim 4, in which the microcapsules are selected from capsules capable of being destroyed mechanically during final sealing, by compression and then folding of the edges of the open end of the skirt.

13. Tube according to claim 4, in which the microcapsules are selected from capsules capable of being destroyed using ultrasound.

14. Tube according to claim 4, in which the microcapsules are selected from capsules capable of being destroyed or made permeable to oxygen by adding external energy, such as heat, electromagnetic radiation such as microwaves, ultraviolet or infrared radiation.

15. Tube according to claim 4, in which the microcapsules are selected from capsules capable of being destroyed or made permeable to oxygen by a chemical method, such as addition of a solvent, water, lipids, modification due to the pH of the packaged product.

16. Tube according to claim 4, in which the microcapsules are made of a material belonging to the group containing agar, alginate, wax, collagen, polylactate, polyglycolate, gelatine, chitosane, ethyl-cellulose, carboxymethyl-cellulose, polysaccharide, polyvinyl alcohol, polyethylene-imine, vinyl acetate and mixes thereof.