NZ250882A

NZ250882A - Tube, typically for toothpaste: polyolefin layers on internal face of barrier layer have total thickness of 40 to 150 micrometers, for flavouring or scent preservation

Info

Publication number: NZ250882A
Application number: NZ250882A
Authority: NZ
Inventors: Michel Rebeyrolle; Jacques Benquet
Original assignee: Cebal
Priority date: 1993-02-22
Filing date: 1994-02-15
Publication date: 1995-09-26
Also published as: AU673399B2; HU9400468D0; FI940816A; BG61335B1; CA2115705C; IL108682A0; RO113447B1; PL302323A1; CZ40194A3; IL108682A; HK1001042A1; BR9400628A; TNSN94015A1; ATE152040T1; CA2115705A1; BG98497A; KR0127770B1; MX9401227A; MA23117A1; JPH06297599A

Abstract

The subject of the invention is a storage and dispensing (distribution) tube (C) for a product, for example a water-containing product which may be flavoured or perfumed, comprising a dispensing head which is fixed onto a flexible multilayer skirt, this skirt essentially containing an intermediate polymer layer (20) which has a barrier effect with respect to oxygen and flavours or perfumes, the said layer being sensitive to humidity, as well as, on each face of this intermediate layer, one or more polymer layers (1; 12,14,10) based on polyolefins, all of the said layers being bonded together in a continuous manner, characterised in that the set of layers situated on the inner face of the said intermediate layer having a barrier effect (1,21) has a total thickness of between 40 and 150 micrometres, so as better to conserve the flavour or the perfume which is or may be contained therein. This tube preferably includes one or two means which render the dispensing of the contained product easier and more complete. It applies to the industries for packaging products which are, for example, liquid, creamy or pasty. <IMAGE>

Description

<div class="application article clearfix" id="description"> 250 8 82 No.: m'arity Oaie(s): Complete Specification Filed: ^.3.^.. Class: <CftJ I Publication Date: -2- S SEP-1995- LI P.O. Journal No: NEW ZEALAND PATENTS ACT, 1953 Z. PATENT OFFICE I 15 FEB 99* . RECEIVED Date: COMPLETE SPECIFICATION TUBE FOR THE STORAGE AND DISTRIBUTION OF A PRODUCT WHICH IS FOR EXAMPLE FLAVOURED OR SCENTED AND WHICH CONTAINS WATER We, CEBAL SA, a French company, of 98 boulevard Victor Hugo, 92115 Clichy, France hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - - 1 -(followed by page la) 5 10 15 20 250 8 82 The invention concerns a tube for the storage and distribution of a product which is typically liquid, creamy or pasty, the tube making it possible for the flavour or scent of the product contained therein to be satisfactorily preserved. EP-A-0 084 922 = US-A-4 626 456 discloses a tube for the storage and distribution of a product which is for example flavoured or scented and which contains water, the tube comprising a distribution head which is fixed on a flexible multi-layer skirt, which skirt essentially comprises an intermediate layer with a barrier effect relative to oxygen and flavourings or scents, said layer being sensitive to moisture, and on each face of said intermediate layer one or more polymeric layers based on polyolefins, all said layers being joined together. The product contained in the tube is for example toothpaste and the intermediate layer with the barrier effect is for example of E\OH (copolymer of ethylene and vinyl alcohol). The structure of the skirt without metallic intermediate layer and comprising layers essentially of polypropylene which are filled with powders for example of Ca cart>onate, mica or talc makes it possible to achieve good retention of the folds produced when the tube is squashed. Such a skirt has been observed to suffer frcm two disadvantages. On the one hand, and is known for example from US-A-4 407 897, EMDH is highly sensitive to moisture. A toothpaste generally contains 20 to 30% by mass of moisture and substantial losses of flavour of such a paste have been found with multi-layer tubes with a barrier layer of EWDH. In addition it has been found that retention of the local squeezing phenomena of the tubes made it difficult to empty the tube. In addition patent application GB-A-2 048 209 discloses a tube for a product such as toothpaste, in which the skirt of multi-layer 250 8 82 plastics materials is of suitable deformability for successive pressings and has a high level of resistance to interlaminar separation phenomena. That skirt comprises at least one barrier layer in relation to oxygen, comprising EVOH or PA (polyamide), a layer of olefin and an 5 adhesive layer of modified olefin interposed between the two preceding layers. Interlaminar separation of those layers is avoided by virtue of the adhesive layer having an elastic limit which is lower than that of the barrier layer and higher than that of the olefin layer. At the same 10 time the olefin layer is of greater thickness than the sum of the thicknesses of the barrier layer and the adhesive layer and the product of the elastic limit by the thickness of the olefin layer is frcm 9 to 170 kg/cm; those means improve deformability and restoration of the tube, each time it has been pressed. That document does not indicate 15 how the losses of flavour which are found in the absence of interlaminar separation of the skirt of the tube are to be avoided. The applicants sought to develop a tube which can provide for improved preservation of the flavour or scent of a product contained therein. The applicants further sought to provide that the tube permits 20 easier and more complete distribution of the product. first The invention concerns a tube as is known frcm tne^quoted document, characterised in that the assembly of the layers which are disposed on the internal face of said intermediate barrier-effect layer is of a total thickness of between 40 and 150 micrometres so as better 25 to preserve the flavour or the scent of a product which is or may be fl. contained therein. The applicants1 interpretation on this subject is as follows: when the thickness of the layers disposed on the internal face of the barrier-effect layer is smaller than 40 micrometres, the moisture in 30 the product which passes through those layers causes a rapid degradation in terms of the barrier qualities in relation to oxygen and • 250882 3 the flavours or scents of the barrier-effect layer, and the flavours or scents of the product can progress beyond that layer and even escape frcm the tube. When the thickness of the layers in question is greater than 150 5 micrometres, the moisture does not reach the intermediate barrier-effect layer in a sufficient amount to cause a deterioration in its qualities, but the flavours or scents are absorbed and retained in a substantial amount by said layers. Those flavours or scents are typically compounds in solution in the water contained in the product, 10 and evaporation and absorption thereof in a first approximation follow evaporation and absorption of the water forming the moisture in the product. GB-A-2 048 209 does not make it possible to foresee such effects, in spite of the magnitude thereof, and it affords no direct 15 or indirect indication relating to the thickness of the layers disposed on the internal face of the barrier layer. Even better results in terms of preserving the flavours or the scents of the product contained in the tube are achieved when the total thickness of the layers on the intermediate barrier-effect layer is 20 between 55 and 140 micrometres and still more preferably betweei 65 and 130 micrometres, with an optimum value of 70 to 120 micrometres. The foregoing conditions permit the use for the structure of the tube of economic polyolefins, giving excellent welding of the layers to each other, namely the family of polyethylenes. The applicants are 25 thus interested in a tube in which the polymeric layers based on polyolefins of the skirt consist on the me hand of an internal ft; surface layer of low or very low or linear low density polyethylene, 3 of a specific mass of between 0.86 and 0.93 g/cm , and on the other hand, other layers which are respectively either of low density 30 polyethylene (LDPE), of a specific mass of between 0.90 and 0.93 3 g/cm , or high density polyethylene (HDPE), of a specific mass of 250 8 82 between 0.935 and 0.97 g/cm^. Wishing then to make distribution of the product stored in the tube of the invention easier and more complete, which tube better preserves the flavour or scent of said product, the applicants 5 ascertained that it was possible to avoid local crushing effects due to the tube being pressed, by enhancing the elastic resistance to depression of said skirt. For that purpose the polyethylene layers of the skirt of the tube contain one or more layers of HDPE of a total thickness of greater than or equal to 90 micrcmetres. Tests show that, 10 when the total thickness of HDPE goes from 84 to 125 micrometres, the elastic reaction force of the skirt in response to depression thereof is more than double. When the thickness of the skirt is between 260 and 380 micrcmetres, for example in the case of a toothpaste tube, the total thickness of the HDPE layers is preferably between 100 and 140 15 micrcmetres, the surface layers preferably being of LDPE, or else for the internal layer linear low density PE. In fact, the properties sought for those surface layers are good ductility with good aptitude to impress ion in regard to the exterior of the tube and good resistance to micro-cracking phenomena in the interior of the tube. 20 The ranges of total thickness in respect of the HDPE which are set out above are to be transposed into relative values with respect to the thickness of the skirt if the latter is outside the specified range. For that increase in elastic reaction of the skirt to being depressed, account can be taken of the influence of the intermediate barrier-25 effect layer which has more elevated characteristics than the HDPE of the same thickness. For the skirt thickness specified above, the sum of twice the thickness of said barrier layer and the total thickness of the HDPE layers is preferably between 130 and 180 micrcmetres, in which case the foregoing condition relating just to the total 30 thickness of the layers of HDPE may or may not be satisfied. To facilitate manufacture, having surface layers of the nature specified above, that is to say typically of LDFE, it is preferable, to obtain the desired total thickness of HDPE, to use: 25088? - either a first layer of HDPE which is inserted between said internal surface layer and a first intermediate layer of LDPE which is itself disposed outside the intermediate barrier-effect layer ; - or a second layer of HDPE which is inserted between an 5 external layer of LDPE and a second intermediate layer of LDPE which is itself disposed outside the intermediate barrier-effect layer. Such first and second layers of HDPE are conveniently employed simultaneously, with thicknesses which are respectively between 10 and 50 micrcmetres and between 60 and 140 micrometres. 10 The layer or layers of HDPE are typically 1 in a condition of continuity of fusion' with the layers between which they are inserted, their materials being compatible in terms of fusion and the production process having produced a welding effect with perfect continuity of structure of the layers between each other. A layer of HDPE which is 15 inserted in that way can then be distinguished in cross-section by micro-hardness measurements, not by virtue of the appearance of its structure. Layers which are welded in that way are obtained by co-extrusion of the skirt or by welding with overlap of the edges of a multi-layer blank which itself results frcm one or more colaminaticns 20 after assembly operations using a covering by extrusion of molten PE. Typically, the first and second intermediate layers of PE are each joined to a face of the intermediate barrier-effect layer that they enclose": by-means of a bonding layer, often of EAA (copolymer of 7 ethylene and acrylic acid) or EMA (copolymer of-ehtylene andiu • 25 methacrylic acid): The five layers in question are often?used in the ^ form of a multi-layer item^ which -is*: prepared -in advance andtiri which i'i the (barrier-effect layer, being sensitive to moisture, is relatively well protected in that regard. Among the materials for the intermediate barrier-effect layers of the skirt, which are sensitive to moisture, mention may be made of 30 E\ADH and PVCH (polyvinyl alcohol), the deterioration of which due to moisture is described in above-mentioned US-A-4 407 897, and with a degree of sensitivity smaller polyamides and modified polyamides, \ s 250882 for example polymetaxylylene adipamide (MXD6). Such an intermediate barrier-effect layer is in the skirt of a thickness which is typically between 0.01 and 0.05 mm, and there may be a plurality of barrier-effect layers which are preferably altogether of the total thickness 5 specified above. In order to make distribution of the product stored in the tube of the invention easier and more complete, the applicants developed a second means which can be used alone or in combination with the first means, requiring a mininum thickness in respect of the HDPE layers of 10 the skirt, of greater than 90 micrometres. The second means referred to above is to have a squashable annular shoulder between the skirt and the neck of the tube. It is known that the shoulder of known tubes, by virtue of the ways in which they are produced, are rigid and form a kind of wall retaining a 15 fraction of the product to be distributed, which product is typically creamy or pasty. By virtue of the production process which is the subject-matter of the present applicants' French patent specification 140 93 01065 of 27th January 1993, that preferably affords a tube in which the distribution head comprises a neck of smaller diameter than the 20 skirt and an annular shoulder connecting the neck to the skirt, the shoulder being smooth and of a thickness of between 0.9 times and 1.35 times and preferably between 0.8 times and 1.25 times the thickness of the skirt and affording continuity of structure with the skirt and comprising folds which are squashed and welded to each other, said 25 shoulder being easily squashable laterally. Said shoulder and n. typically a part at least of the neck of the tube contain the barrier layer or layers of the skirt of the tube in the form of folded and squashed prolongations contained in the foregoing squashed and welded folds which are themselves prolongations of the barrier layer or 30 layers of the skirt. The neck may be completed by an annular ring of PE which is welded to the head, the shoulder remains at least half squashable. * Available on request 250 882 i The second means therefore affords both the possibility of easier and more complete distribution of the product contained in the tube, and improved protection for its flavouring or scent, at the level of the head of the tube. The folds which are reduced in thickness at locations in a barrier layer in the shoulder usually together satisfy the preferred condition regarding a total thickness '0.01 to 0.05 mm', with increased effectiveness. The production process leading to that second means will be briefly described in the Examples. ADVANTAGE OF THE INVENTION - with an economic structure for the skirt, it provides a way of much better preserving the flavouring or the scent of the product contained in the tube; - in addition, depending on its preferred characteristics, it makes it possible to limit local squashing of the tube when pressed, the pressing effects then acting over a larger part of the tube and pressing being easier from one occasion to another; - alternatively or in combination with the effect of limiting such squashing phenomena of the skirt, the invention affords the possibility of laterally squashing the head and thus more easily and more completely expelling the product at the end of distribution thereof. EXAMPLES Figures 1 to 3 are sectional views of the skirts of three tubes, the first being outside the invention (Figure 1, reference), while the other two (Figures 2 and 3) being in accordance with the invention, Figure 4 is a view in axial section of an arrangement for measuring the elastic reaction to depression of a tube skirt, in relation to the first means involving easier and more complete distribution of the product, Figure 5 is a graph showing the gain in weight of samples of skirts in dependence on the total thickness of the layers inside the barrier layer, in a flavouring loss test. 8 Figure 6 shows in a graph the variation in the resistance to depression of the skirt in dependence on the total thickness of the layers of HDPE which are present therein. Figures 7 to 10 relate to the second means involving improved 5 distribution, namely a squashable shoulder; Figure 7 is an iscmetric projection of a comparison tube produced by shaping at ambient temperature, Figure 8 is a half view in axial section of a tube according to the invention having a squashable shoulder, 10 Figure 9 is a half view in axial section of another tube with a squashable shoulder, provided with an annular ring of PE constituting the exterior of its neck, and Figure 10 is a view in axial section of a micrographic aspect of the top of the shoulder of the tube and the connection of the shoulder 15 to the annular ring. 1) Structure of the skirts of the tubes of Figures 1 to 3 These three structures all have an intermediate barrier-effect layer 20 of EVOH of a thickness of 0.02 mm, joined by two adhesive layers 21 and 22 of EMA copolymer (copolymer of ethylene and 20 methacrylic acid) each of a thickness of 0.01 nm to layers of PE comprising in contact with said bonding layers 21 and 22 LDPE with a 3 specific mass of 0.92 g/cm in layer 1 or in intermediate sub-layer 11 or 12. The limits of layers of different natures are marked in solid lines while the invisible limits between LDPE and HDPE sub-layers, 25 resulting from assembly thereof in a molten state at least at the ^ surface, are shown by broken lines. The term 'sub-layer' is used here in respect of such layers in which at least one limit surface is invisible, these are however layers entirely involved in regard to the technical functions studied 30 in the present invention. They may be identified by measurements in respect of micro-hardness. 25088 It can also be seen, frcm Figures 1 to 3, that the sub-layers 13 and 14 of HDPE, with a specific mass of 0.95 g/crn^, are each disposed between an intermediate sub-layer 11 or 12 of LDPE and an internal linear low density PE sub-layer 100 or an external LDPE sub-layer 10. 5 Going frcm the interior of the tube outwardly, the successions of thicknesses are as follows, the details of sub-layers being shown in parentheses: - Tube A (Figure 1): layer '1' LDPE 0.035 rrm; layers EMA '21' of 0.01 mm, EMDH '20' of 0.02 mm, EMA '22' of 0.01 mm; layer of PE 10 '12+14+10* of 0.215 mm (LDPE '12' of 0.082 rrm - HDPE '14' of 0.0105 mm - external LDPE '10' of 0.023 mm); - Tube B (Figure 2): internal layer of PE '100+13+11' of 0.09 mm (internal linear low density PE ' 1001 of 0.01 nm - HDPE 113' of 0.02 mm - LDPE '11' of 0.06 mm); succession of EMA, EWH and EMA as for A; 15 layer of PE '12+14+10' of 0.215 mm, of the same composition as for A; and - Tube C (Figure 3): internal layer '1' of LDPE of 0.125 mm; succession of EMA, EVOH and EMA as for A and B; layers of PE '12+14+10' of 0.175 mm (LDPE *12' of 0.073 mm - HDPE '14' of 0.084 mm 20 - external LDPE '10' of 0.018 mm). The skirts of the tubes A, B and C were rolled-welded frcm blank-forming films of the structures and thicknesses indicated above, then the heads of the tubes were moulded on to the skirts. 2) Flavouring loss tests 25 Circular portions of a diameter of 50 mm of the three qualities ft. indicated above, as shown in Figures 1 to 3, were subjected to impregnation of their face which is the internal face in the skirt, being that of the layer 1 or 100, with a standard toothpaste containing 25% of water and menthol, for a period of 4 weeks, being 30 maintained in an enclosure at 38°C. At the end of the test toothpaste remaining at the surface of the sample is cleaned off. The gain in weight of the sample is ascertained, and it takes account of the loss of water and flavouring. 250 10 The wish is to have a quality which, in this test, gives a gain 2 in weight per unit of surface area of less than 1.2 mg/cm and 2 preferably less than 0.66 mg/cm . A is satisfactory in accordance with the first criterion but not the second. The results of the tests are set out in Table 1 and shown in Figure 5. Interpretation is as follows: there are no samples in which the barrier layer of EVOH is bare on the inward side of the skirt as such a layer of EVOH would then be completely degraded by moisture during manufacture of the corresponding multi-layer item. For such a sample which in fact is theoretical, the result that would be observed in Figure 5 would be a high gain in weight, due to the fact that moisture passes easily through the EVOH and that such moisture is absorbed by the layers outside the EVOH. When one has 0.02 mm of layers which are internal to the EVOH, a considerable gain in 2 weight is still observed, more than 2.5 mg/cm . The gain in weight decreases considerably when the thickness of the layers which are internal to the EVOH exceeds 0.03 rrm and the steep linear curve portion in which A is located corresponds to absorption with degradation of the EVOH due to the moisture, and then the passage through that EVOH of water and flavouring, the water and flavouring then being absorbed both by the layers which are external to the EVOH, at 21, 12, 14 and 10, and by the internal layers such as 21 and 1. The decrease from A to B corresponds to a preponderant protection effect in relation to the layer 20 of EVDH, by virtue of the increasing thickness of the internal layers, and the subsequent rise frcm B to C corresponds to the influence, which has become preponderant, of the absorption of water and flavouring by the internal layers, their thickness and therefore their absorption capacity increasing as the EVOH is sufficiently protected. 3) Pressing test or test in respect of resistance to depression of the skirt A sample 15 of skirt is held in such a way as to form a 250$8? 11 reproducible semicircular cylindrical dome 16 of a diameter of 25 rrm and a length of 100 mm, and it is pressed with a rigid rod 17 of a diameter of 3 mm along the linear generatrix 18 of the top of the dome. The broken line 19 indicates the shape assumed by the dome 16 5 when depression of the rod 17 at a constant speed has progressed. A system (not shown) measures the reaction exerted by the dome 16 or 19 against the rod 17 and determines the maximum thereof. When that reaction is strong, the corresponding tube skirt resists better to pressing forces and depression thereof remains in part at least in 10 the elastic range, which makes it possible to avoid local constrictions, which is opposite to the teaching of EP-A-0 084 922. The results of the tests are shown in Table 2 and Figure 6. The representative points A, B and C are aligned in Figure 6. As the reaction in the absence of HDPE in the skirt, then entirely of LDPE 15 except for the EVOH and the thin adhesive layers 21 and 22 which surround it, is necessarily slightly positive (representative point Z), it can be seen that the effect of an increasing thickness of HDPE on reaction of the skirt to depression involves an increase which accelerates between 40 and 70 micrcmetres (broken-line curve portion 20 ZX). At the level of the thickness of 90 micrometres which has been taken as a minimum, the effect is confirmed. The tube B according to the invention has a skirt which has good resistance to depression, but the tube C is inadequate in that respect. The tube A which is 25 inadequate in relation to losses of flavouring and which therefore falls outside the scope of the invention claimed in the present application is satisfactory in terms of resistance to depression. 4) Second means of easier and more complete distribution of the product contained in the tube: tube with squashable shoulder (Figures 30 7 to 10). The process for producing this tube involves starting frcm a tubular blank which is longer than the skirt and constricting a 250882 12 portion thereof by shaping just that portion which is heated above the fusion temperature of its surface layers, preferably at between 140 and 220°C in the case of surface layers of polyethylene, then crushing that portion between tools, so that the portion crumples in the form 5 of folds, the folds perfectly welding to each other at each face thereof and the faces of the shoulder being typically obtained in a perfectly smooth condition. Figure 7 shows a tube having a shoulder formed at ambient temperature, showing that the double folds as at 31 and 32 correspond 10 to inward undulations 31 or outward undulations 32, which have been squashed. In the hot-shaping operation indicated above, the folds are greatly squashed, including those of the barrier layer 20 which ate included therein. It is possible to produce a shoulder 38 which is 15 thinner than the skirt. Figure 8 shows a tube 34 with a screwthreaded neck, in accordance with the invention, which is produced directly by that hot-shaping operation, the internal tool means and annular sliders of the external tool means forming between them the screwthread35 on the neck at the end of the clamping operation. Figure 20 9 shows a tube 36 of the same nature which is produced by hot-shaping and then capped by an external annular ring 37 of PE, to complete the neck of the tube. The ring 37 is perfectly welded to the outside and to the upper end of the hot-shaped tube 36, it was set in position by shaping with compression of an annular blank of PE heated to 160°C, 25 this thus involving moulding in a pasty state which is above the ^ melting point. An annular ring can also be set in position by injection moulding or by ultrasonic welding. The tubes 34 and 36 each have a skirt of type B,: 0.345 mm in thickness, which is not modified by the operation of hot-shaping of the head, and their annular 30 shoulder 38 is of a thickness which is adjusted as desired at between 0.3 and 0.4 mm. In the case of the tube 36 (Figure 9), the annular 250 13 ring 37 occupies less than half of the width of the annular shoulder 38, the latter can still be laterally squashed sufficiently to improve expulsion of the product. The section of the tube 36 containing the junction of its 5 shoulder 38 to the annular ring 37 (see Figure 10) shows the effectiveness of squashing and welding of the folds in the constricted head, as well as perfect welding of the annular ring 37: - a double fold 39 of barrier layer 20 has an end 40 which has escaped from the superposed relationship of and the squashing effect 10 on the folds, followed by two folds 41 which are greatly reduced in thickness; - a second portion 42 of barrier layer 20 belongs to a fold welded to the double fold which contains the double fold 39 of barrier layer 20; 15 - disposed on the right of the end 40 and the double fold 39 is the ring 37, being of PE, like the surface layers of the tube 36; - continuity of welding as between the folds, and as between those folds forming the shoulder and the annular ring, is perfect. The section shows in places the adhesive layers such as 21, but there is 20 no other discontinuity in the PE which encloses the elements described; - the reduction in thickness achieved is astonishing, it can be adjusted as desired by means of the choice of the hot-shaping temperature used and by the clamping effect of the tools. 25 INDUSTRIAL APPLICATION Tubes with a flexible skirt of plastics material affording improved preservation of the flavour or scent of the product contained therein, for example liquid, creamy or pasty. Tubes thus permitting easier and more complete distribution of the product. In particular in 30 the industries of cosmetic, pharmaceutical, hygiene and foodstuff products and maintenance products. 250882 14 TABLE 1 Gains in weight of samples of skirts after impregnation for 4 weeks with a flavoured toothpaste Tube Thickness of the on the internal layer of EVOH layers disposed face of the Gain in weight (mg/cm2) A (reference) 45 *jm 0.83 B (invention) 100 juim 0.12 C (invention) 135 ,um 0.59 TABLE 2 Maximum reaction of the tube skirts to depression in the pressing test (Figure 4) Tube Thickness of Total thickness Total thickness Max. the skirt (jjm) of HDPE (jjm) of HDPE + reaction 2 x thickness (N) of EVOH (um) A (reference) 290 105 145 6.6 B (invention) 345 125 165 8.7 C (invention) 340 84 124 4.2 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 250 882 15 WHAT f/WE CLAIM IS :

1. A tube —G-,—34-;—36* for the storage and distribution of a product which is for example flavoured or scented and which contains water, comprising a distribution head (30 ond 35) which is fixed on a flexible multi-layer skirt, said skirt essentially comprising an intermediate polymeric layer (20■> with a barrier effect relative to oxygen and flavouring or scents, said layer being sensitive to moisture, and on each face of said intermediate layer one or more polymeric layers (1, 100, 13, 11 ond 12, 14, 10) based on polyolefins, all said layers being continuously joined together, characterised in that the assembly of the layers which are disposed on the internal face of said intermediate barrier-effect layer f-t;——100,—i3-;—ii, is of a total thickness of between 40 and 150 micrcmetres, so as better to preserve the flavouring or the scent of a product which is or may be contained therein.

2. A tube according to clainl wherein said total thickness of the layers 4-t;——100,——±4—34r) which are disposed on said internal face of the intermediate layer is between 55 and 140 micrometres, preferably between 65 and 130 micrometres.

3. A tube according to either one of claims 1 and 2 wherein said polymeric layers based on polyolefins consist on the one hand of an internal surface layer of low density (1) ■ or very low density or linear low density (100)- polyethylene, of a specific mass of between 3 0.86 and 0.93 g/cm , and on the other hand other layers which are respectively either of low density polyethylene (LDPE) of a specific 3 mass of between 0.90 and 0.93 g/cm or high density polyethylene 3 (HDPE) of a specific mass of between 0.935 and 0.97 g/cm '(13,—14 )■.

4. A tube —34-;—36) ■ according to claim 3 wherein said layers of polyethylene contain one or more layers of HDPE •(■13; 14)- of a total thickness which is at least equal to 90 micrcmetres. ^ 5 0 8 8 2 16

5. A tube according to claim 4 wherein said sum of the thicknesses of the layers of HDPE (13;—±4-) is between 100 and 140 micrcmetres, the thickness of said skirt being between 260 and 380 micrometres.

6. A tube according to claim 4 wherein the sun of twice the thickness of said barrier layer (20 j and said thicknesses of the layers of HDPE (13,—±4-} is between 130 and 180 micrcmetres, the thickness of said skirt being between 260 and 380 micrcmetres.

7. A tube according to any one of claims 3 to 6 wherein said layers of polyethylene comprise a first layer i 13) of HDPE which is inserted between said internal surface layer (100 )■ and a first intermediate layer <11)- of LDPE which is itself disposed cn the interior of the intermediate barrier-effect layer (20).

8. A tube according to any one of claims 3 to 7 wherein said layers of polyethylene comprise a second layer ■( 14-) of HDPE which is inserted between an external layer {■ 10) of LDPE and a second intermediate layer <12) of LDPE which is itself disposed on the exterior of the intermediate barrier-effect layer (20).

9. A tube according to either one of claims 7 and 8 wherein said first layer (13 > of HDPE and/or said second layer ■( 14) of HDPE is or ace in a condition of continuity of fusion with said layers of LDPE (100, 11| 12,1 10) between which it or they is or are inserted.

10. A tube (B; 34, 36) according to claim 8 when appended to claim 7 wherein the thicknesses of said first and second layers (13, 14) of HDPE are respectively between 10 and 50 micrometres and between 60 and 140 micrometres. 17

11. A tube according to claim 10 wherein said first and second intermediate layers of LDPE are each joined to a face of said intermediate barrier-effect layer by a bonding layer of copolymer of ethylene and acrylic acid (EAA) or copolymer of ethylene and methacrylic acid (EMA).

12. A tube according to any one of claims 1 to 11 wherein said intermediate barrier-effect layer of the skirt is of one of the materials of the group formed by: copolymer of ethylene and vinyl alcohol (EVOH), polyvinyl alcohol (PVOH), polyamide (PA), and modified polyamide, and is of a thickness of between 0.01 and 0.05 mm.

13. A tube (34, 3G )■ according to any one of the preceding claims wherein said distribution head (38 and 35| comprises a neck f3§-) of smaller diameter than the skirt and an annular shoulder (38;) connecting the neck (35^ to the skirt, said shoulder being of a thickness of between 0.9 times and 1.35 tires the thickness of the skirt and affording continuity of structure with said skirt and comprising folds which are squashed and welded to each other, said shoulder being squashable laterally.

14. A tube -(36) according to claim 13 wherein the folds of said shoulder which are squashed and welded together contain folded and squashed prolongations (39, 41)- of said intermediate barrier-effect layer (20)- of the skirt.

15. A tube according to claim 1 and substantially as herein described with reference to any embodiment shown in the accompanying drawings. CEftflL Sfl By the authorised agents A J PARK & SON </div>