EP1765685A1

EP1765685A1 - Lightweight flexible plastic tubes and method for making same

Info

Publication number: EP1765685A1
Application number: EP05786072A
Authority: EP
Inventors: Michel Bosshardt
Original assignee: Cebal SAS
Current assignee: Albea Tubes France SAS
Priority date: 2004-07-06
Filing date: 2005-07-04
Publication date: 2007-03-28
Anticipated expiration: 2025-07-04
Also published as: PL2022724T3; WO2006013276A1; PL1765685T3; BRPI0513140A; FR2872792B1; MX2007000233A; EP1765685B1; EP2022724A1; EP2022724B1; RU2007104344A; US20070210103A1; CN101001789A; DE602005025548D1; DE602005011293D1; US8365955B2; FR2872792A1; CN101001789B

Abstract

The invention concerns a flexible plastic or metalloplastic tube (210) having a dispensing head (230) and a cylindrical skirt (220) of diameter larger than 40 mm. Said tube is characterized in that said cylindrical skirt is less than 0.40 mm thick and comprises at least 70 wt. % of high-density polyethylene (HDPE), of specific mass ranging between 0.935 g/cm<sup

Description

LIGHTWEIGHT PLASTIC FLEXIBLE TUBES AND METHOD FOR THEIR

MANUFACTURING

TECHNICAL AREA

The invention relates to the field of flexible plastic tubes for storing and dispensing liquid to pasty products. It relates more particularly to flexible plastic tubes of large capacity, typically having a capacity greater than or equal to 150 ml.

STATE OF THE ART

Encouraged in particular by the European Directive 94.62 on reducing the weight of packaging, manufacturers seek to reduce the amount of plastic to be consumed and recycled.

To apply the provisions of this. Directive to flexible tubes, a first step is to reduce the thickness of their walls. Such a solution has been adopted without problem for the small capacity tubes, having a flexible skirt of small diameter. However, a simple reduction in the thickness of the skirt or the shoulder finds its limits in the mechanical strength of the tube, in particular for tubes with a capacity greater than 150 ml, the vast majority of which have diameters greater than 40 mm, and more particularly, the problems of mechanical strength amplifying with the diameter, for the tubes of skirt diameter greater than 45 mm. With such geometries, the rigidity of the skirt becomes insufficient and makes handling difficult both during the manufacture of the tube during its filling and use. For practical reasons, the flexible tubes have a capacity typically less than 400-500 ml, with a diameter of less than 60 mm, because beyond these dimensions, they become unmanageable and are replaced by rigid bottles. In general, a flexible tube is made by assembling two separately manufactured parts: a flexible cylindrical skirt of given length (typically 3 to 5 times the diameter) and a head comprising a neck provided with a dispensing orifice and a shoulder connecting said neck with cylindrical skirt. The plastic head can be molded separately and then welded to one end of the skirt but it is advantageously molded and welded autogenously to the skirt using either an injection molding technique (FR 1 069 414) or a technique compression molding of an extruded blank (FR 1 324 471). Depending on the use of the tube, the cylindrical skirt can be obtained industrially in two different ways. For tubes intended for storing and dispensing cosmetic products, it is generally obtained by extrusion or direct coextrusion of several plastics, in the form of a cylindrical hollow extrudate. The tube having such a skirt is in this case called "plastic tube". For tubes intended to store and distribute consumer products at low cost, a plastic strip is generally used which is shaped into a cylinder by matching (contact or superimposition) of its two longitudinal edges ( see for example US 1,007,779) and then longitudinal weld along these edges. The tube having such a skirt - which is often made of a multilayer plastic material with a barrier layer - is in this case called "rolled tube".

After assembling the skirt and the head, the tube is delivered to the conditioner, the head down and the dispensing orifice closed - for example by a cap screwed onto the neck - so that it fills the tube by the open end of the tube. To facilitate their transport to the conditioner, the tubes are placed vertically, grouped and sheaves. The sheaves are stacked on one another forming a large number of layers whose thickness corresponds to the axial length of the tube, which typically leads to stack of about fifteen layers for truck transport. Once arrived at the conditioner, the tube is filled, its open end is flattened so as to perform a weld which, by the meeting of wall portions facing each other following the flattening, seals the product thus conditioned (so-called transversal or final weld).

Another way of producing a flexible tube is for example described in US Pat. No. 5,632,951: a thin walled bottle is produced by extrusion blowing and the bottom of the bottle is cut to obtain an object very similar to the preceding flexible tubes, However, they differ from them in the presence of weld lines that extend over the entire outer surface, including the head.

For tubes of large capacity, the diameter of the skirt is typically between 40 mm and 60 mm, the thickness of the skirt of the prior art is systematically greater than 0.5 mm, that it is (co ) extruded ,. laminated, or obtained by extrusion blow molding. Indeed, whatever the embodiment of the skirt, it must undergo a large number of manipulations until the filled tube has been sealed by the final weld, These manipulations are necessary firstly to perform transfers between different manufacturing stations and secondly to ensure sufficient mechanical support during manufacturing operations or shaping (assembly of the head and the skirt, printing on the skirt, corking, ...). Upon arriving at a manufacturing or forming station, the tube is driven from a holding device mounted on a transfer chain (for example a pin, a nacelle or a mandrel) to a mandrel on which it is fitted most of time without play and even with a slight tightening. Once the operation is complete, it is extracted from the mandrel and directed to a new holding device associated with another transfer chain to drive it to another manufacturing station. - AT -

Flexible tubes that have skirts large diameter do not have sufficient rigidity if the thickness of said skirts is less than 0.5 mm. They are exposed, particularly at their open end, to a high risk of folding either during the fitting on the mandrel, or during the extraction of the mandrel. To limit this risk, it could increase the clearance between the skirt and the mandrel but this would result in less good maintenance of the skirt during the manufacturing operation or shaping and could result in insufficient quality: less accuracy the positioning of the head on the skirt which can lead to a defect of welding between the head and the skirt, bad plating of the skirt on the mandrel causing printing defects (offset printing or flexography on cylindrical wall of tubular bodies), etc.

On the other hand, during their transport to the conditioner, the stacked tubes located in the lower layers must support the weight of the sheaves stacked above and they are often deteriorated at the open end of their skirt if it does not have the desired rigidity.

Finally, even if not deteriorated, the open end of the tube has a geometry which is less repetitive since the thickness is small (greater influence of the residual stresses on the shape of the free end of the skirt), which leads to difficulties when automatically filling the tube.

Since all these problems are exacerbated by the large quantities and high rates of production used for the manufacture of this type of packaging, it has been established that, in practice, such tubes must have a thickness greater than about 0.5 mm to present acceptable machinability and transportability.

Attempts to lighten the flexible tubes through a significant decrease in the thickness of the tube have not led so far to a economically profitable industrial exploitation. Other attempts at lightening have been carried out by the Applicant using a technique developed for bottles. The bottles are made in one piece by extrusion-blow molding: one extrudes a thick tube that is clamped away from the die (obtaining a parison) and then inflates the inside of the parison by sending air under low pressure through the axis of the die, the wall of the parison tapering and coming to press against the walls of a mold that gives the final shape of the bottle. For this type of packaging, US Pat. No. 6,082,563 (WELLA) describes a manufacturing process by which the constituent plastic material of the wall of the parison is partially modified by adding blowing agents. The blowing agents are introduced into an intermediate layer during coextrusion. The thickness of the expanded layer is, after extrusion and before blowing, equal to or greater than 3 mm. After blowing it is of the order of 500 microns, that is to say close to the thickness of a flexible tube skirt.

In fact, the lightening of an expanded layer with a blowing agent is only possible in this case because a thick parison of at least 3 mm is extruded. For conventional methods of manufacturing in large series and at high rates of the flexible tubes, the skirt of the tube must be obtained directly by extrusion with a thickness at least six times lower, under conditions such that it is difficult or impossible, to control the action of the swelling agent in the screw and then in the convergent zone of the extruder, so that a skirt is obtained with an expanded extruded layer with irregularities of large thickness, which does not allow to provide acceptable industrial packaging. Finally, the introduction of blowing agents entails an additional cost. PROBLEM

The Applicant has sought to obtain a flexible tube of great capacity as light as possible, which has a cylindrical skirt as strong and rigid as that of standard tubes, while offering the user a comfortable grip and resistance to stress cracking comparable to that of standard tubes.

The goal is to significantly reduce (at least 30%) the weight of the tubes while maintaining an acceptable mechanical behavior compatible with the constraints of manufacture and with its use by the consumer. In addition, insofar as these tubes are mainly intended for the cosmetics market, they must also have equivalent compatibility to these products, in particular to guarantee a low permeability to liquids (water, alcohols, oils and other fatty substances, etc.). ), and this low permeability to liquids should result in limited weight losses. It is also desirable that they have an acceptable permeability to water vapor and flavorings.

OBJECT OF THE INVENTION

A first object of the invention is a method of manufacturing a flexible tube comprising a cylindrical skirt and a dispensing head (that is to say provided with a dispensing orifice), comprising at least the following steps: a) extruding a cylindrical sleeve b) cutting the sleeve so as to produce a tube skirt to the desired length; c) molding of the flexible tube head; d) fixing the head on one end of the skirt; characterized in that the extruded sleeve has a thickness of between 0.2 and 0.4 mm, preferably between 0.25 mm and 0.35 mm and in that it comprises high density polyethylene (PE, HD), with a density of between 0.935 g / cm 3 and 0.97 g / cm 3, preferably greater than 0.945 g / cm 3, in a proportion by weight greater than 55%, preferably 70%. Advantageously, the sleeve also comprises low-density polyethylene (PE, BD) with a density of between 0.86 g / cm 3 and 0.93 g / cm 3, in a proportion by weight of less than 45%, preferably 30%, and of which more than 50%, preferably more than 90% by weight, is a PE. Linear BD (BDL),

This method incorporates the conventional steps of manufacturing a plastic tube, the skirt of which comes from the cutting of an extruded sleeve, but this sleeve is particularly thin and comprises a plastic material different from that of plastic tubes of the prior art. The sleeve is obtained by extrusion of a mixture PE, HD + PE, BD (more than half being PE, BDL) or by coextrusion of several coaxial layers, PE, HD, PE. BD (more than half being PE, BDL), or layers of PE mixtures. HD

+ PE. BD. For a given thickness, between 0.2 and 0.4 mm, the plastic tubes. thus_ realized offer _. the best characteristics (with respect to all the manufacturing and use constraints) when the sleeve has been made with more than 90% by weight of PE. HD and less than 10% by weight of PE.BDL.

The interest of such a process is observed especially for large diameter plastic tubes, from 34mm and especially above 44 mm, because these, much lighter than standard tubes of the same capacity, have a large diameter. Rigid cylindrical skirt which offers a good compromise between the constraints of manufacturing in large series and the constraints of use by the consumer, The good resistance to stress cracking is ensured by the high proportion of PE. HD and PE.BDL. Rolled tubes with a diameter greater than 44 mm also exhibit these advantageous properties. Another object of the invention is a flexible tube having a dispensing head and a cylindrical skirt of plastic or metalloplastic material, of diameter greater than 44 mm, more particularly greater than 49 mm, characterized in that said cylindrical skirt has a thickness between 0.2 mm and 0.4 mm, preferably between 0.25 mm and 0.35 mm, in that it comprises high-density polyethylene (PE HD) with a density of between 0.935 g / cm 3 and 0.97 g / cm 3, preferably greater than 0.945 g / cm 3, in a weight proportion greater than 55%, preferably 70%. Advantageously, the cylindrical skirt also comprises low density polyethylene (PE, BD) with a density of between 0.86 g / cm3 and 0.93 g / cm3, in a proportion by weight of less than 45%, preferably 30%, and of which more than 50%, preferably more than 90% by weight, is a PE. Linear DB (BDL).

The tube according to the invention is a plastic tube or a rolled tube having a head provided with a dispensing orifice and a cylindrical skirt of large diameter, typically greater than 44 mm. The head generally comprises a neck which encloses the dispensing orifice and a shoulder which connects the neck to the skirt. The skirt is cylindrical but its section is not necessarily circular. In fact, the tube is here described in its filling configuration, before completion of the final transversal weld which seals the packaged product. The skirt may have a circular or elliptical orthogonal section or any other shape

(This is imposed by the periphery of the shoulder which is fixed on the end of the skirt) but, during the manufacture of the tube, it is generally fitted on a cylindrical sleeve with circular section and it is why we are referring here to a diameter. It goes without saying that for a skirt of non-circular section, it is its perimeter which must be greater than π * 44 is about 138 mm. For an elliptical skirt, if a is the half major axis and b is the half minor axis, ψ \ a ^ b) is greater than 44 mm.

Traditionally, flexible tubes have skirts composed mainly or entirely of PE. BD. A tube according to the invention having the same diameter as a traditional tube has a thinner skirt but composed predominantly - or in full - of PE.HD. If the PE.HD is not alone, the skirt may be made of a single material, for example a blend resulting from a mixture according to the invention of PE.HD and PE.BD, the major part of which is a Linear PE.BD. The presence of PE.BDL and the percentage of PE.HD within such a blend can be determined for example using two complementary techniques: Fourier transform infrared spectroscopy (FTIR), for example using a spectrometer FTIR Nicolet 510P and Differential Scanning Calorimetry, for example using a complete Perkin Elmer DSC 7 analysis system, this method can itself be implemented in a conventional manner (up-down cycle - temperature rise), that is, when necessary, according to the method SIST (Stepwise Isothermal Technical Segregation.

The skirt, laminated or coextruded, may also be made of a multilayer material comprising PE.HD layers, PE.BD layers, the major part of which is a PE.Bpjinéaire, and / or layers of PE mixtures. HD + PE.BD.

The Applicant has found that, made of a more rigid material, the skirt may have, due to its lower thickness, a resistance to radial penetration identical or lower than that of a skirt of the prior art while by presenting, despite this lower thickness, a similar or better resistance to buckling and bending under the effect of the same compressive axial force. In other words, by combining the thickness and nature of the constituent material, the contradictory requirements of machinability, flexibility and user comfort can be met, which until now the PE.BD was supposed to be the only material capable of satisfy, provided however that it is in the form of a sufficiently thick layer. Contrary to appearances, the use of a material more rigid than the PE. BD to compensate for loss of rigidity due to thinning is not obvious. Indeed, it is known from experience that the use of more rigid materials leads to a loss of ergonomics of use. The grip of the tube is indeed less easy, the tube is not flexible enough (it is less easy to extract the product by simply applying pressure on the wall of the skirt) or too elastic behavior: the product just out of the orifice, is reabsorbed inside the tube as soon as the pressure on the skirt decreases. In addition, it is desirable to avoid that the tube easily returns to its original shape, because in such a case, the user is not aware of the amount of product that still contains. Such a property is illustrated by the magnitude of the elastic recovery of the material after plastic deformation by folding: the greater this return, the greater the "shape memory" is important and degrades the ergonomics of use. This shape memory is often characterized by the angle obtained after folding and elastic return of a band of constant thickness: the larger the angle, the higher the shape memory is important; conversely, the weaker the angle, the better is its ability to keep the new form, translated by the Anglo-Saxon term of "dead fold". The metal tubes have a very good ability to wrinkle while the plastic tubes have a wrinkle ability generally poor or poor. In this case, the Applicant has found that, thanks to the significant decrease in the thickness of its wall, the tube has a better property at "dead fold", that is to say a better ergonomics of use despite the use of a material (PE.HD) more rigid than PE. BD.

In the case where the skirt is a multilayer material, the outer layers are preferably PE. HD: this results in slightly better axial buckling resistance. In addition, the PE.HD outer layers are less sensitive to stress cracking. On the other hand, the EP. HD has a much lower liquid permeability than PE. BD, in a ratio such that the decrease in thickness does not cause a degradation of the liquid barrier properties (water, alcohols, oils and other fatty substances that may be contained in the cosmetic product to be packaged), which maintains the performance in terms of acceptable weight losses. On the other hand, there is a slight improvement in the barrier properties to its diffusion of gases and aromas.

According to the invention, PE.BD, if it exists in the skirt, is a minor constituent material, limited to 30% by weight, preferably 10%. It consists for the most part of linear PE.BD (or PE.BDL), that is to say a polyethylene copolymer comprising non-polar alphaolefins (such as butene or hexene) whose molecules have only side chains short and regular. The addition of linear PE.BD is recommended to improve on the one hand the weldability of the skirt and on the other hand the resistance to stress cracking.

Stress cracking ("stress cracking") is a property related to long-term behavior: by immersing the material under stress in a surfactant liquid, cracking appears after a certain time. This phenomenon, very important in the case of polyethylene, strongly depends on the surface tension exerted by the medium, the molecular weight and the morphology of the polymer. It is known that cracking occurs all the more quickly as the stress is high and that the material (polyethylene in this case) has a significant melt index ("melt index").

The linear PE.BDL (PE.BDL) is in a proportion by weight greater than 50%.

This proportion is preferably higher as the proportion of PE.BD is important in the material of the skirt. This makes it possible to improve the weldability and resistance to stress cracking of the skirt. So, for a melange 70% PE. HD + 30% PE. BD, the latter should preferably be greater than 90% by weight of PE.BDL.

For a given thickness, between 0.2 and 0.4 mm, the plastic and laminated tubes offer the best characteristics relating to all the constraints of manufacture and use when the skirt comprises more than 90% by weight of PE . HD and less than 10% by weight of PE.BDL.

Preferably, the flexible tube also has a lightened dispensing head to which must be attached a plug or a dispensing tip, such as a service capsule. In general, the tube head comprises a neck surrounding the dispensing orifice and a shoulder connecting said neck to the skirt and it is on said neck that is fixed that plug or this capsule-service. In the context of the invention, a neck provided with a securing means such as a snap-fitting bead is preferred to a neck provided with a screw thread, which is more sensitive to stress cracking. the thickness of the goulpt and. of _. the shoulder, at a value typically less than 1 _. mm. Said head is preferably made of a material which comprises high density polyethylene (HDPE), with a density of between 0.935 g / cm 3 and 0.97 g / cm 3, preferably greater than 0.945 g / cm 3, in a proportion by weight greater than 55%, preferably 70%. Advantageously, the head also comprises low density polyethylene (PE, BD) with a specific gravity of between 0.86 g / cm 3 and 0.93 g / cm 3, in a proportion by weight of less than 45%, preferably 30%, and more than 50%, preferably more than 90% by weight, is a linear PE.BD (PE.BDL)

According to this embodiment of the invention, the tube has a head composed predominantly - or totally - of PE. HD. If the EP. HD is not alone, the head may be made of a single material, for example a blend resulting from a mixture according to the invention of PE. HD and PE.BD, most of which is a linear PE.BD. The head can also have a multi-layer wall with PE layers. HD and / or PE. BD, most of which is an EP. BD linear, and / or mixtures PE.HD + PE.BD. The head can be molded separately and then welded to one end of the skirt, but it can also be molded and welded autogenously to the skirt. This multilayer head can be obtained either by co-injection according to a process such as that described in EP 1 123 241, or by compression molding of a coextruded blank.

The best results (weldability, comfort of use, weight loss, etc.) are obtained when the head has been made with more than 90% by weight of PE. HD and less than 10% by weight PE. BDL,

In this way, the head may have a neck and a shoulder less than 1 mm thick. A te! tube has a substantial saving in weight: while a standard tube typically weighs between 0.80 and 1.10 g per centilitre of useful volume, a tube according to the invention of the same capacity weighs between 0.55 and 0.80 g by cl of useful volume. Thus, only with the flexible tube, a weight gain of 30% is obtained. _.. _This gain can. to be, still increased if one continues the effort of lightening on the cork.

Another object of the invention is a tube such as the flexible tube described above, also provided with a stopper, This stopper can be a lighter service capsule so that the tube + capsule-service assembly has a mass between 0.80 and 1.10 g / cl of useful volume of product to be dispensed against a value of between 1.20 and 1.80 g / cl for the prior art dispensing tubes. Thus, thanks to the invention, the new tube provided with its new service capsule has a weight approximately identical to that of the tube alone of the prior art: the gain is reflected in a weight reduction equivalent to the weight of the capsule. service!

To achieve such a gain in weight, the capsule-service itself has been designed in a particular way, with a thickness and height as low as possible. The capsule-service has an overall structure identical to that of the service capsules of the prior art, which comprise a base intended to be fixed irreversibly on the head of the tube and a cap pivoting around a hinge located at the periphery of the base and the cap, the cap from closing a hole formed on the base and in communication with the dispensing orifice of the tube head. The base comprises a tray, provided with said orifice, a fixing skirt and an outer lateral skirt, generally cylindrical and configured so that it is approximately in the extension of the skirt of the tube, when the service capsule is fixed. on said tube. In such a configuration, the open end of this outer side skirt approximates the peripheral contour of the shoulder. The fixing skirt is an internal cylindrical skirt, provided for example with a snap-fitting bead. It is intended to be fitted around the neck of the tube. The service capsule according to the prior art has a thick and rigid base, in particular to have a clear opening, the cap pivoting about a fixed axis connected to the tube. The rigidity of the base also made it possible to rapidly unmold the capsule-service using the conventional positioning of the extractor assisting the demolding of the capsule-service: the latter comes into abutment on the open end of the outer side skirt. The rigidity was ensured on the one hand by the thickness of the walls of the base and on the other hand by the presence of radial ribs, at least 6, typically 8, attached to the inner surface of the outer side skirt and to the surface internal plateau. These notably prevented the outer side skirt from deforming, or even turning around like a sock, when the extractor was activated to demold the entire capsule-service.

In the spirit of the invention, the service capsule has been designed in order to reduce the weight, reduce the cooling times after molding and facilitate demolding. This is why the thickness of the wall of the plate, that of the outer lateral skirt and that of the cap has been decreased, especially at the level of the upper part of the finger grip. We deleted also the set of radial ribs, but defining a particular demolding protocol, different from that practiced in the prior art: the extractor is placed differently and bears on the open end of the fixing skirt which has not not thinned. The capsule-service according to the invention thus has at least one, and preferably all, of the following geometrical features:

• the inner surface of the base is free from any stiffening radial rib; it contains at most one longitudinal rib which serves for the angular orientation of the service capsule relative to the decoration of the skirt of the flexible tube (indexing);

The fixing skirt is relatively thicker than the rest of the service capsule: by applying to the mold the extractor on the open end of the said fixing skirt, the entire capsule can be demolded easily despite its thinned portions; and although it is not supported by radial ribs; thus, the fixing skirt is thicker, typically a few tenths of a millimeter, than the rest of the capsule service, including the tray and the outer side skirt.

• the cap has on its inner face an undercut wall at the upper part of the fingertip; in the prior art, there was defined at this location a vertical wall, which had the advantage of facilitating demolding and disadvantage of greatly increase the thickness and thus weigh down the cap. Indeed, at the right of the upper part of the finger grip, the wall is in cant and if one seeks to maintain a constant thickness, this part in cant results in an undercut difficult to unmold if one uses a standard tool, that is to say in the absence of slide-type sliding tool or upward shim. The Applicant has found that it is still possible to achieve an undercut with a slope less than 35 ° without having any particular difficulty in demolding with a standard mold, but using an extractor acting in the center of the cap. Thus molded, the cap has, facing the upper part of the finger grip, a wall inclined at an angle less than 35 ° - with respect to the axis of the capsule - towards the inside of the base of the capsule.

On the other hand, the geometry of the outer side skirt is preferably defined, in particular its height, so that when the service capsule is fastened to the tube head, the open end of said outer side skirt is a distance d as small as possible from the shoulder of the tube, typically a mean distance of between 0.1 and 0.7 mm, preferably between 0.2 and 0.5 mm. For this, the dimensional manufacturing tolerances imposed on the tube head and the service capsule are suitably defined. Thus, if the fixing means of the service capsule on the tube head are snap-fitting beads arranged on the one hand on a fixing skirt attached to the capsule plate and on the other hand on the neck of the head. of the tube, the minimum distance LI between the end of the outer side skirt and the point of contact on the bead of the fixing skirt is made to be greater than L2-d, L2 being the maximum distance between the contact on the bead of the neck and the point of the shoulder being in line with the axial extension of the outer side skirt of the capsule-service. In this way, the end of the outer side skirt of the base of the capsule-service is immediately in local support on the shoulder as soon as the user manipulates the tube and this gives the entire capsule-service an unexpected and sufficient rigidity despite the absence of ribs and the thinness of the plate. To further improve the rigidity of the assembly, the shoulder of the tube is advantageously provided with a sidewalk around which the open end of the outer side skirt engages with a radial clearance as low as possible, typically an average radial clearance less than 0.5 mm, preferably 0.3 mm.

Moreover, the capsule-service must be generally indexed, namely placed in a precise angular position relative to a decoration of the skirt of the tube. The very reliable but rather heavy indexing means described in EP-B-0 633 197 may, where possible, be replaced by a single longitudinal rib attached to the inner surface of the outer side skirt which is trapped between two studs of low extent and low height, located on the shoulder. The attachment of the service capsule on the tube is effected by a driving movement and rotation. During the driving, the capsule is immobilized in axial displacement, for example by means of complementary snap-fastening means of the fixing skirt and the neck described above. Then, during the rotation, the base of the longitudinal rib comes into contact with the top wall of the first stud which slopes gently in the circumferential direction. In this way, thanks to the overall elasticity of the capsule and the tube head, the longitudinal rib follows the top wall which, like a cam surface, imposes a certain axial translation to the outside of the tube. Arriving at the end of the cam path, the end of the longitudinal rib is no longer supported, elastically releases and is trapped in the interval between the two pads. The relief of the second stud is less progressive so that the latter acts as a stop and prevents the longitudinal rib from continuing to move angularly.

Here too, again for the sake of lightening, the upper part of the mandrel which serves as a mold part at the tube head advantageously has two protuberances which serve as "cores" for the formation of these pads, so that these are made with a constant thickness and have a hollow towards the inside of the tube.

Finally, the longitudinal rib attached to the inner surface of the outer side skirt and used for indexing is advantageously located in the median plane of the hinge: this facilitates the feeding of the narrow channels defining the different parts of the hinge (tensioning elements and chαrnière proper) and this improves the mechanical strength of the capsule when the cap is requested at the opening.

Figure 1 illustrates, in diametral section, a 150 ml tube of the prior art, provided with a service capsule, for the storage and distribution of shampόing.

Figure 2 illustrates, in diametral section, a tube according to the invention of the same capacity as that of Figure 1, and for the same application.

FIG. 3 illustrates, in diametral section, a detail of the tube of FIG. 2.

FIG. 4 illustrates, in diametral section, a detail of the molding tool of a lighter service capsule according to the invention, situated at the level of the cap.

EXAMPLE

The flexible tubes presented in this example offer a useful volume of 150 ml for the shower gel that they are intended to contain. A tube of the prior art is illustrated in FIG. 1. A particular tube according to the invention is illustrated in FIG. 2. This tube may be equipped with a service capsule such as that illustrated in FIG. 3 and molded in a tooling of which a detail is illustrated in Figure 4.

Geometries and positive weight gains 1, 2 and 3)

The tube 110 of the prior art has a diameter D of 50 mm and an overall height (greater than H + h) close to 175 mm. It has a skirt 120 and a dispensing head 130 provided with a neck 131 and a shoulder 132 for connecting said neck to said skirt. The skirt 120 is PE.BD. It has a thickness ei of 0.6 mm, which gives the tube dispenser shower gel a certain rigidity. The head 130 is also in PE.BD. The shoulder 132 has a thickness e2 of 1.1 mm.

The weight of the tube according to the prior art is 16.4 g.

This tube is provided with a service capsule 140 made of polypropylene, of height h = 25.2 mm. The service capsule 140 comprises a base 141 intended to be fixed irreversibly on the neck 131 of the tube and a cap 142 pivoting about a hinge 143 located at the periphery of the base and the cap, the cap sealing a orifice 150 formed on the base 141. The base 141 comprises a plate 1411, provided with the dispensing orifice and an outer lateral skirt 1410 cylindrical and configured so that it is approximately in the extension of the skirt 120 of the tube . The service cap 140 according to the prior art has a thick and rigid base. The rigidity is supported by the presence of 8 radial ribs 144, attached to the inner surface of the outer side skirt 1410 and to the inner surface of the plate 1411. The lip 142 has, at the top portion 147 of the fingertip , a vertical wall 148.

The tube + capsule-service set weighs 26 g.

The tube 210 according to the invention has a diameter D ¹ of 50 mm neighbor and an overall height (H + h ') close to 173 mm. It has a skirt 220 and a dispensing head 230 provided with a neck 231 of diameter approximately 20 mm and a shoulder 232 intended to connect said neck to said skirt. The skirt 220 is PE.HD. It has a thickness é1 of 0.35 mm, which gives the shower gel dispenser tube a greater flexibility, acceptable by all users.

The head 230 is also PE.HD. The shoulder 232 has a thickness e2 of 1 mm. The weight of this tube is 1 1 g. We could still define locally lower thicknesses, of the order of 0.5 mm. The centering studs 235 are made with a constant thickness, that is to say having a hollow towards the inside of the tube.

This tube is provided with a service capsule 240 made of polypropylene, with a height h equal to 22.7 mm. The service capsule 240 comprises a base 241 intended to be fixed irreversibly on the neck 231 of the tube and a cap 242 pivoting about a hinge 243 located at the periphery of the base and the cap, the cap closing off a orifice 250 formed on the base 241. The cap 242 pivots around the hinge 243 when the user exerts a force in the upper part 247 of the finger grip located on the cap. The base 241 comprises a plate 2411 surrounded by an outer cylindrical lateral skirt 2410, configured so that it is approximately in line with the skirt 220 of the tube. The service capsule 240 does not have 8 radial ribs to improve its rigidity, but only one longitudinal rib 245, thin and of low radial height, attached to the inner surface of the outer lateral skirt 2410. This longitudinal rib 245 allows indexing the capsule-service relative to the tube skirt, by trapping between two small and low-height studs located on the shoulder 230. One of these pads is illustrated in Figure 2 with the reference 235. The capping 242 has, at the level of the upper portion 247 of the finger grip, a wall 248 in a slope, inclined at about 25 ° with respect to the axis of the capsule and oriented towards the inside of the base 241 of the capsule 240. The axis of the capsule is the axis of the mounting skirt 246. It coincides with the axis of the tube when the service capsule is fixed on said tube.

The attachment means of the service capsule on the tube head are snap beads disposed on the one hand on a fastening skirt 246 attached to the plate 2411 and on the other hand on the neck 231 of the tube head. The geometry of the outer side skirt 241 has been defined, in particular its height h ¹ , so that when the service capsule 240 is fixed on the tube head, the open end of the outer side skirt 2410 is close of the shoulder 230 of the tube, typically at a distance of less than 0.5 mm from the

2320 point of the shoulder located at the right of the axial extension of the outer side skirt 2410. For this, the manufacturing dimensional tolerances imposed on the tube head and the capsule service are defined so that the distance minimum LI between the end of the outer side skirt 2410 and the point of contact on the bead 2460 of the skirt of

fixation 246 is greater than L2-d, where L2 is the maximum distance between the point of contact on the bead 2310 of the neck 231 and the point of the shoulder 2320. In this way, the end of the outer side skirt of the base of the capsule-service is immediately in local support on the shoulder as soon as the user manipulates the tube and this confers on the whole capsule-service

/ 5 an unexpected and sufficient rigidity despite the absence of ribs and the small thickness of the plate The tube + capsule-service assembly weighs 16.7 g.

On the other hand, the fixing skirt 246 on the neck 231 has a thickness of 0 1, 2 mm, greater than that of the rest of the service capsule, in particular the outer side wall 2410 (0.9 mm). By applying to demolding an extractor exclusively on the open end thereof, it is easy to demold the entire capsule despite its thinned portions and although it is not supported by radial ribs. The fastening skirt 246 also has a discontinuous snap-in bead (in the form of regularly distributed grains of rice) cooperating with the snap-fitting bead 2310 of the neck 231.

It is thus found that, thanks to the invention, the weight of the dispensing tube has been increased from 26 g to 16.7 g, a gain of nearly 36%. Other tubes were made with skirts 0.35 mm thick and made of the following materials:

• entirely in PE. HD

• biend PE.HD 70% + PE.BDL 30% • coextruded structure skirt: PE.HD (120 μm) / PE.BDL (1 10 μm) / PE.HD (120 μm)

• Coextruded structure skirt: PE.BDL (50 μm) / PE.HD (240 μm) / PE.BDL (60 μm)

• coextruded structure skirt: blend PE.HD 70% + PE.BDL 30% (170 μm) / adhesive layer EMA (10 μm) / EVOH (15 μm) / adhesive layer EMA

(10 μm) / blend PE.HD 70% + PE.BDL 30% (170 μm) with EMA = methyl acrylate polymer and EVOH = copolymer (ethylene, vinyl alcohol)

The gains in weight are equivalent. The comfort of use is equivalent. But we see that the higher the PE content. BD increases, less machinability is good.

Characterization of the mechanical behavior of skirts

Tests to estimate flexibility and comfort of use (Radial driving forces)

The flexibility of the tube skirt is characterized by the value of a force necessary to obtain a certain radial depression after a certain time. The lower this value, the more flexible the tube. Moreover, by comparing the values corresponding to two different radial depressions, one can evaluate the comfort of use (of "grip") by noting the difference to the proportionality: if the value corresponding to a double radial depression is greater at double the corresponding effort, the tube opposes increasing resistance to the action of the user. The more the difference between these values is importαnt, the more the tube is difficult to empty. Conversely, if the value corresponding to a double radial depression is less than twice the corresponding effort, the tube empties easily. The greater the difference between these values, the more the tube tends to collapse abruptly, which may surprise the user with a larger output stream than expected.

The flexibility can be measured with standardized bending tests using the method of the support blade: a skirt half is cut in a diametral plane and then recessed at its ends on a support. The top of the arch thus formed is driven by an axial device bearing on the generatrix of the top of the arch. The value of the driving force corresponding to two given deflections is measured: for example 5 mm and 10 mm.

The following table shows the value of the forces (in N) relative to these two depressions for skirts of diameter 50 having the structures described previously:

On the one hand, it can be seen that the skirts of the tubes B to D according to the invention are more flexible than the skirts of the prior art (Tube A), on the other hand that the gap to the proportionality is of the same order of magnitude (ratios between forces of between 2.6 and 2.8 for a double depression): the tubes according to the invention are more flexible than that of the prior art while presenting a comfort of use identical.

Test to evaluate machinability

The machinability of the tube is characterized by the ability of the skirt to withstand an axial compressive force.

The skirt is cut to a given length (80 mm in this case), one of the free ends of the sleeve thus obtained is fitted and a force distributed over the circumference is applied to the other free end, with the aid of a plateau that sinks at a constant speed in the axial direction of the sleeve. The value of the compression peak is measured just before folding or buckling of the sleeve.

The following table shows the value of the maximum forces (in N) obtained with the previous types of skirt (diameter 50 mm).

These results show that the tube B, whose skirt is entirely PE.HD has, despite its small thickness, better machinability than the tube of the prior art. The tubes having skirts with mixture PE.BD and PE.HD also have a good aptitude, the mixture 70% PE.HD, 30% PE.BDL having a behavior comparable to that of the tube of the prior art.

Tests to estimate the ability to "fold dead"

It can be seen that a PE.BD tube of thickness 0.5 has a lot of memory (it comes back to 128 ° (for a complete memory, the angle after elastic return would be 180 °), whereas for the tube in PE.HD 0.35 thickness, the angle after elastic return is equal to only 61. It is close to the behavior of the flexible metal tube.

Illustration of weight gain for truck loads

A standard (non-lowered) truck can carry 66 pallets of 50 mm diameter tubes (150 ml capacity), or about 140,000 tubes.

With a gain of 9.3 g per tube we gain about 1, 3 ton. In addition to the gain associated with better handling of the tubes of the lower pallets, the truck carries a significantly lower load and thus saves energy, which, moreover, makes it possible to reduce the emission of carbon dioxide into the vehicle. atmosphere. Demoulαqe of a lightweight capsule-service with an undercut at the fingertips f Figure 4).

FIG. 4 illustrates, in diametral section, a detail of the molding tool 300 of a lighter service capsule according to the invention such as the capsule 240. The tooling is in several parts: an upper part 310, a part lower part 320 provided with an extractor 330. The pivoting cap of the service capsule is made by molding in the cavity 342. The lower part 320 of the mold comprises a wall 321 which delimits the upper part 2421 (external) of the fingertip and a wall 322 located on the other side of the wall 321 and facing the inside of the cap. In the prior art, the wall 322 was vertical, which had the advantage of facilitating demolding and the disadvantage of greatly increasing the thickness and thus weigh down the cap. The Applicant has found that one could still achieve a wall 322 with an undercut of less than 35 ° slope without having difficulty in demolding with a standard mold, that is to say without drawer or shim, but using an extractor 330 acting in the center of the cap. Thus molded, the cap has, facing the upper part 247 of the finger grip, an inclined wall - an angle less than 35 ° with respect to the axis of the capsule-service - to the inside of the base of the capsule. The axis of the service capsule is the axis 250 of the fixing skirt whose cavity is indicated by the reference 346. It coincides with the axis of the tube when the service capsule is fixed on said tube.

ADVANTAGES

• reduced energy spent on tube shaping, soldering and recycling

• good resistance to stress cracking

• Improved liquid and perfume barrier.

Claims

1. A method of manufacturing a flexible tube comprising a cylindrical skirt and a dispensing head, comprising at least the following steps: a) extrusion of a cylindrical sleeve b) cutting of the sleeve so as to produce a skirt to the length desired; c) molding of the flexible tube head; d) fixing the head on one end of the skirt; characterized in that the extruded sleeve has a thickness of between 0,

2 m and 0.4 mm, preferably between 0.25 mm and 0.35 mm and in that it comprises high density polyethylene (PE.HD) of specific gravity between

0.935 g / cm 3 and 0.97 g / cm 3, preferably greater than 0.945 g / cm 3, in a proportion by weight greater than 55%, preferably 70%.

2. The manufacturing method as claimed in claim 1, in which said sleeve also comprises low density polyethylene (PE, BD) with a specific gravity of between 0.86 g / cm 3 and 0.93 g / cm 3, in a proportion by weight. less than 45%, preferably 30%, and more than 50%, preferably more than 90% by weight, is a linear PE.BDL (PE.BDL).

20

3. The manufacturing method according to claim 1 or 2 wherein a sleeve comprising at least 90% by weight of PE.HD and at most 10% of PE.BDL is extruded.

4. Manufacturing process according to any one of claims 1 to 3 wherein is extruded a sleeve thicker than 34 mm.

5. Flexible tube (210) having a dispensing head (230) and a cylindrical skirt

(220) made of plastic or metalloplastic material, with a diameter greater than

44 mm, characterized in that said cylindrical skirt has a thickness of between 0.2 mm and 0.4 mm, preferably between 0.25 and 0.35 mm, it comprises high density polyethylene (HDPE) with a density of between 0.935 g / cm 3 and 0.97 g / cm 3, preferably greater than 0.945 g / cm 3, in a proportion by weight greater than 55%, of preferably 70%.

6. Tube according to claim 5, characterized in that said skirt also comprises low-density polyethylene (PE, BD) with a specific gravity of between 0.86 g / cm3 and 0.93 g / cm3, in a proportion by weight of less than 45%, preferably 30%, and of which more than 50%, preferably more than 90% by weight, is a linear PE.BDL (PE.BDL).

7. Flexible tube according to claim 5 or 6 wherein the diameter of the skirt is greater than 45 mm.

8. Flexible tube according to any one of claims 5 to 7 wherein the skirt comprises at least 90% by weight of high density polyethylene (HDPE).

9. Flexible tube according to any one of claims 5 to 8 wherein the skirt comprises at most 10% low density polyethylene (PE.BD).

10. Flexible tube according to any one of claims 5 to 9 characterized in that Iq dispensing head is provided with a snap-fitting bead for fixing a plug or a dispensing tip, such as a capsule-service.

1. Flexible tube according to any one of claims 5 to 10 characterized in that the dispensing head comprises high density polyethylene (PE.HD), specific gravity of between 0.935 g / cm3 and 0.97 g / cm3 preferably greater than 0.945 g / cm 3, in a proportion by weight greater than 55%, preferably 70%.

12. Flexible tube according to any one of claims 5 to 10 characterized in that the dispensing head also comprises low density polyethylene (PE BD), specific gravity of between 0.86 g / cm3 and 0.93 g / cm3, in a weight ratio of less than 45%, preferably 30%, and of which more than 50%, preferably more than 90% by weight, is a linear PE.BD (PE.BDL).

The flexible tube of claim 11 or 12 wherein the dispensing head comprises at least 90% by weight of high density polyethylene (HDPE) and at most 10% by weight of linear low density polyethylene (PE.BDL). .

14. Flexible tube according to any one of claims 5 to 13 wherein the head comprises a shoulder whose thickness is less than 1 millimeter.

Flexible tube according to any one of claims 5 to 14 characterized in that it has a diameter greater than or equal to 50 mm and that it weighs less than 0.80 g per centilitre of useful volume offered to the product it is meant to contain.

16. A set of flexible tube (210) provided with a plug (240) characterized in that it comprises a flexible tube according to claims 5 to 15.

17. A service capsule (240) provided with a cap (242) and a base (241) comprising a tray (241 1), a skirt (246) for attachment and an outer side skirt (2410) characterized in that that the fixing skirt (246) is thicker, typically a few tenths of a millimeter, than the plate (241 1) and the outer side skirt (2410).

18. Service capsule (240) according to claim 19 characterized in that the inner surface of the base (241) is free of any radial rib attached to the plate (241 1) and the outer side skirt (2410).

19. Capsule-service (240) according to claim 17 or 18, characterized in that the inner wall of the cap (242) facing the upper portion (247) of the finger grip is inclined at an angle less than 35 ° with respect to the axis of the service capsule and oriented towards the inside of the base (241) of said service capsule.

20. Service capsule (240) according to any one of claims 17 to 19, characterized in that its base is provided with a longitudinal rib (245) attached to the inner surface of the outer side skirt (2410).

The service capsule (240) of claim 20 wherein said longitudinal rib (245) is located in the medial plane of the hinge (243).

22. The assembly of claim 16 characterized in that said cap is a service capsule according to any one of claims 19 to 21.

23. The assembly of claim 16 or 22 wherein the service capsule and the shoulder of the tube are provided with indexing means, the service capsule having a longitudinal rib (245) attached to the inner surface of the outer side skirt. (2410), the shoulder (230) having two studs (235) of small extent, low height and angularly spaced, the longitudinal rib being trapped in the space between said two pads.

24. The assembly of claim 23 wherein the shoulder of the tube has studs (235) of constant thickness, that is to say oriented towards the outside of the tube and having a hollow towards the inside of the tube.

25. The assembly of claim 22 or 23 wherein the open end of the outer side skirt (2410) is at an average distance from the shoulder of the tube of between 0.1 mm and 0.7 mm, preferably between

0.2 mm and 0.5 mm,

26. The assembly of claim 25 wherein the shoulder (230) of the tube is provided with a sidewalk around which the open end of the outer side skirt (2410) s'emmanche with an average radial clearance less than 0.5 mm

preferably less than 0.3 mm.

27. An assembly according to any one of claims 22 to 26 characterized in that the diameter of the tube is greater than 50 mm and in that it weighs less than 1.1 g per centilitre of useful volume offered to the product it is destined to

/ 5 store and distribute.