FR2865477A1 - Procedure for gluing a cap on the end of a tube e.g. for packaging, uses adhesive that expands when heated by radiation to fill any gaps - Google Patents

Abstract

Procedure for gluing a cap comprises applying an adhesive compound to at least one of the surfaces to be joined and/or the facing edge of a supple tube (4). The adhesive has expansion properties that cause an increase in volume when it is heated above a certain temperature and reaction acceleration properties that enable it to be heated quickly, evenly and without contact with the source of heat. Procedure for gluing a cap comprises applying an adhesive compound to at least one of the surfaces to be joined i.e. on a rigid cap (2) and/or the facing edge of a supple tube (4). The adhesive has expansion properties that cause an increase in volume when it is heated above a certain temperature and reaction acceleration properties that enable it to be heated quickly, evenly and without contact with the source of heat. The adhesive can be applied, for example, in a liquid or viscous phase by means of a nozzle or bath, or as a bead, and the assembly can be exposed to radiation to ensure simultaneous expansion and adhesion.

Description

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  METHOD FOR BONDING A SHUTTER AT THE END OF A TUBE FROM A COMPOSITE ADHESIVE

  FIELD OF APPLICATION OF THE INVENTION The present invention relates to the field of the assembly by gluing a shutter at the end of a tube via an adhesive material thus making it possible to produce tight joints that apply more particularly to but not exclusively, in the field of packaging.

DESCRIPTION OF THE PRIOR ART

  In general, the assembly by gluing of products and more precisely of a shutter at the end of a tube poses numerous problems, in particular of guarantee of tightness of said assembly. Indeed, it is difficult to ensure that the volume between the two surfaces to be assembled is perfectly closed after bonding especially when the surfaces are very irregular. These problems are particularly important in the field of packaging, especially for the constitution of sealed boxes or packages for the packaging of sensitive products requiring special storage conditions such as the maintenance of flavorings, or a protection against the penetration of humidity or air. The known adhesive bonding methods most often use hot-activatable adhesives. They consist in depositing the adhesive product, generally in the liquid or viscous state, on at least one of the surfaces to be joined, then putting the surfaces in contact and finally exerting pressure until the adhesive product is freezes after cooling and provides a mechanical connection.

  These solutions have several disadvantages.

  One of these disadvantages lies in the difficulty of depositing the glue evenly and continuously over the entire bonding zone: if the quantity of glue deposited is insufficient, there may be bonding defects. and, consequently, an imperfect mechanical strength and a poor seal, especially when the bonding surface has irregularities or areas in super-thickness. It is therefore necessary to deposit a sufficient amount of glue to ensure a minimum bond over the entire bonding surface. But it becomes difficult to avoid overflows of excess glue, which is generally unacceptable from an aesthetic point of view.

  Another disadvantage lies in the quality of the bonding which is difficult to ensure for rigid packaging shapes other than those having a section close to the round such as square, rectangular or more complex shapes so that we can not especially control the amount deposited in the salient angles ... in these cases, it is necessary glue removal systems and tools of complex shape, so expensive.

  Another disadvantage lies in the glue removal systems that are very restrictive to use: heating times, need frequent cleaning of the nozzles, especially after production stops, risk of burns, glue burrs ...

  Another disadvantage lies in hot-melt adhesives which, although more suitable, have an open time (maximum time after removal of the adhesive during which the two parts to be assembled can be brought into contact) rather short, which creates significant constraints. in industrial production because each machine stop requires the elimination of parts already glued and not yet assembled.

  Another disadvantage lies in the application of a pressure on the outside of the surfaces to be assembled which risks causing a degradation of the physico-chemical properties of the materials constituting these surfaces. This is particularly the case when it comes to heat-sensitive synthetic films, which are pre-printed on the outside of the package.

  There are numerous patents proposing products based on foaming polymers making it possible to give expansive properties to said product which is more particularly dedicated to solving industrial problems of tight joints or to producing structural assemblies than to implementing a bonding for assembly of two surfaces in contact.

  In this category of patents is US Pat. No. 4,555,284 (STEINWENDEL BERND ET AL.) Which proposes a sealing method using hot-melt type hot-melt glue having a melting point of the order of 100 C and in which is incorporated a product releasing nitrogen under the effect of heat. This adhesive, intended more particularly for plugging the ends of electrical or telephone cables, is softened for the purpose of removal on the surfaces to be bonded and then heated to a temperature of about 170 ° C with the aid of an open flame (of the Bunsen spout) so as to cause foaming which then ensures the closure of all the small interstices between the son on the one hand and the cable sheath on the other hand. It is thus here more than a sticky foam acting as filling joints of free spaces between various elements that an adhesive ensuring the assembly between two surfaces in contact. In addition, the thermo fusion of this adhesive foam is ensured by the application of an open flame directly on the sheath which, by conduction through the material of its wall, provides heating and swelling of said foam.

  According to the same principle, US Pat. No. 4,751,249 (WYCECH JOSEPH) proposes a similar method of manufacturing lightweight composite structures using a filling foam which, obtained from polystyrene beads coated in polymerizable epoxy polymer resins. while hot, are capable of swelling in contact with water vapor before being subjected to firing in an oven to obtain the drying and hardening of the foam thus formed. It is still not a product for bonding two surfaces to be assembled but a product filling a free space from an irreversible process using thermosetting resins to ensure the manufacture of composite structures filled with such a foam, such as the side rails of motor vehicles with the concern of lightening the structure and achieve "beam" effects.

  Still in the category of realization of seals, Japanese Patent No. 9.021.494 (SEKISUI CHEM Co Ltd.) proposes a hot melt resin for making a joint between two plastic tubes. For this purpose, the two plastic tubes are abutted in a fitting internally coated with a thermofusible resin that can swell under the effect of heat (with the aid of a heating collar or in a heated enclosure) in order to melting the swelling resin so as to fill the space between the two tubes and assemble them to said fitting while ensuring fusion between the tube materials and the resin to hold them together together at said fitting. It is also recommended in this patent to introduce into the resin a polymer with a high conductive power in order to ensure and evenly distribute in said resin the propagation of the heat transmitted by conduction through the walls of the connector and the tubes.

  There is also another method of closing a box with a bilayer lid (aluminum + PE), with activation of induction heat sealing. However, this is hot sealing, that is to say a welding using an intermediate component which is a multilayer laminated material, which requires that the geometric interface of the assemblies be located in a plane. It is therefore a layer having elastic properties, such as an expanded foam or an elastomer which is inserted inside the stopper and which provides pressure on the weld surface, between the stopper and the multilayered laminate, thanks to the tightness of the plug.

  In all the processes that have just been described above, the resin used is more particularly adapted to the production of seals for the assembly of industrial structural elements insofar as. it incorporates a foaming component producing open cells, ie with gas evolution, as an expandable agent for filling a gap between two surfaces, it uses the conductive effect of the walls of the surfaces to be filled or adhered, As a means of raising its temperature to ensure its thermo fusion, it requires very long melting times due to the transmission of heat by contact and conduction.

DESCRIPTION OF THE INVENTION

  Taking stock of this state of affairs and pre-established specifications, especially in the packaging where the products often have a food, phytosanitary or pharmaceutical purpose therefore hygiene constraints to be draconian, extremely fast bonding times of the order of the second, and walls to assemble very fragile, etc. the Applicant has devised a new bonding process which ensures the sealing assembly by bonding of two surfaces and in particular that of a shutter at the end of a tube, or even two shutters at the ends of a tubular body so as to form a hollow body 6 - tight, which can be used to package a sensitive product.

  For this purpose, the method of bonding at least one shutter at the end of a tube according to the invention consists in depositing on at least one of the two surfaces to be assembled, a composite adhesive presenting at the same time expansion properties to cause an increase in volume of the adhesive when carried beyond a defined temperature Te, so as to fill existing gaps between the two surfaces to be joined, and acceleration properties by making it capable, under the effect of radiation, to heat up without contact quickly and homogeneously, - to insert the shutter into one end of the tubular body so that the adhesive composite deposited on one of the two surfaces to be assembled facing the other of the two surfaces to be joined, and finally to expose the tube-adhesive-shutter assembly, to a radiation so as to cause the expansion of the adhesive and the collage of the obtu on the tubular body.

  The great advantage of such a method is to ensure the tight, efficient and fast assembly of a shutter at the end of a tube through the use of a composite adhesive which is able to expand and expand. ensure the bonding of the shutter at the end of the tube under the simple effect of radiation so remote and especially without any mechanical and / or thermal contact with the walls of the surfaces to be bonded. This bonding method thus makes it possible to eliminate all the above-mentioned drawbacks inherent to heating devices by mechanical and / or thermal contact of existing machines which often required tools adapted to the shapes of said tubes. Thus with the bonding method of the invention, the section of the tube and consequently the section of the shutter will have no impact on the implementation of the method since no mechanical contact is necessary.

  According to this method of the invention, the composite adhesive may be deposited on the lateral periphery of the shutter so that the expansion of the adhesive causes a radial pressure which equilibrates on the inner surface of the tubular body . Thus, during the bonding of the shutter at the end of the tube, the expansion of the adhesive generates a peripheral tension which, applied to the inner wall of the tube, is balanced by a contact pressure between the two surfaces to be assembled. and spread over the entire bonding area so that it is no longer necessary to use tools of appropriate mechanical shape to exert a bonding pressure.

  The method of the invention is characterized in that the adhesive is deposited on at least one of the surfaces to be assembled prior to the activation of its expansion. In this case, it will be necessary, according to a preferred feature of the invention, that the expansion temperature is greater than the temperature at which the adhesive is sufficiently viscous to be deposited or injected. Indeed, this is necessary so that the adhesive can be deposited prior to assembly and activate the expansion later, at the time of assembly, by heating to the expansion temperature. The fact of depositing the glue on one of the surfaces to be assembled in a first step, which may be prior to the assembly step (especially at the time of the manufacture of a component) thus offers a major industrial advantage. The operation of pre-removal of the glue makes it possible to overcome during the assembly operation on the production site all the disadvantages mentioned in the description of the prior art mentioned at the beginning of this document and relating to the removal of glue. It is very important to remember here that the reversible adhesive pre-dispensing method is only possible because of the reactivability of the composite adhesive of the invention under the effect of heat. This means that the composite adhesive can be carried in the first phase at a temperature lower than Te to make the deposit, then allow it to cool to room temperature, store the pre-sized component, transport it to the site of assembling and reheating the adhesive at the time of assembly, after the components to be bonded have been brought into contact, up to the temperature Te to obtain the final bond after cooling.

  The pre-removal of adhesive can be done in different ways, namely. By depositing adhesive rendered in the viscous state by a system with melter and controlled gun, by direct molding of the adhesive on the component by bi-material injection, by prior molding and separated from the adhesive under a form close to the shape of the interface (for example a toric-shaped bead) and mechanically deposited on the component of this piece of solid or flexible adhesive.

  In fact, this process by pre-removal of the reactivatable adhesive under heat fundamentally distinguishes it from other methods for obtaining foaming glues and which have the particular objective of reducing the amount of adhesive deposited and filling the interstices, in particular depositing an already expanded adhesive on the surface to be bonded, the foaming being obtained by means of a diazo powder mixed continuously with the molten glue at the outlet of the dispensing nozzle.

  Since the basic concepts of the invention have been set forth above in their most basic form, other details and features will emerge more clearly on reading the description which follows and with reference to the appended drawings, giving by way of nonlimiting example, an embodiment illustrating the method of bonding a shutter at the end of a tube, in accordance with the provisions of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

On these drawings.

  Figures la and lb are perspective views of a shutter assembled on the end of a tubular body according to the bonding method of the invention.

  Figures 2a and 2b are sectional views of a shutter assembled on the end of a tubular body according to the bonding method of the invention.

  Figures 3a and 3b are sectional views of a shutter assembled on the end of a tubular body both having an irregular contact surface.

  Figure 4 is a vertical sectional view showing the pressure forces exerted between the obturator and the tubular body during expansion of the adhesive.

  Figures 5a and 5b are views of a tubular body seen from the front as a sheet before winding and in perspective in the form of tube after the winding of the sheet on itself.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS

  The drawing of FIG. 1b shows a hollow body or cylindrical box 1 obtained by assembling two shutters 2 and 3 on a tubular body 4, made according to the bonding method of the invention, that is to say starting from a composite adhesive 5 which, when exposed to radiation, causes its expansion and the bonding of the shutters 2 and 3 to the tubular body 4.

  The three steps of this bonding process are as follows.

  The first step is to deposit either on the surface of the shutter 2 to be assembled (see Figures la and lb) or on the inner surface of the tubular body 4 (see Figures 5a and 5b), the composite adhesive 5 having both expansion properties and reaction acceleration properties making it capable, under the effect of radiation, to heat up without mechanical and / or thermal contact, quickly and homogeneously.

  According to the first embodiment of the first step of the bonding method of the invention as illustrated in the drawings of Figures 1a and 1b, this composite adhesive 5 may be deposited on the shutter 2 - in the unexpanded liquid phase or in the unexpanded viscous phase, and just before the assembly operation, - at the time of assembly by a controlled system with a nozzle gun or a bath system, - in the form of a cord, having a substantially toroidal shape close to that of the interface between the tubular body 4 and the shutter 2, so as to be mechanically deposited on the periphery of the shutter 2 prior to the assembly operation, it being understood that this cord will be flexible or solid and previously manufactured by injection or extrusion, - when the shutter 2 is plastic, at the time of manufacture by bi-material injection of the plastic component of the shutter 2 and the adhesive 5 in the viscous phase unexpanded, the shutter then being delivered with a bead of pre-deposited adhesive in solid phase, in liquid form flat on a film in the bonding zone at the time of manufacture of the shutter by thermoforming, it being understood that the composite adhesive may be deposited only on the bonding zones, or incorporated in a film previously laminated onto the plastic film constituting the shutter when the shutter is subsequently manufactured by thermoforming, it being understood that the adhesive will be present on the entire surface of the shutter and the radiation will, in this case, be limited to the bonding area at the time of assembly.

  According to the second embodiment of the first step of the bonding method of the invention as illustrated in the drawings of FIGS. 5a and 5b, this composite adhesive 5 may also be deposited on the internal face of the tubular body 4. The body tubular of such a tube may be obtained: - by winding on itself a rectangle 6 cut in a serai-rigid film with the composite adhesive deposited on the inner face of the rectangle before winding on one or more zones of bonding 8, the rectangle of the film 6 being welded or glued on itself along a generatrix 7 so as to constitute the tubular body 4; by winding on itself a rectangle cut in a semi-rigid film with the composite adhesive deposited on all or part of the surface of the film constituting the tubular body by an impregnation process in the form of a coating, of an impression, or of a screen printing, - by winding on itself a rectangle cut in a semi-rigid film with the composite adhesive deposited on the entire surface of the film constituting the tubular body by laminating against a film incorporating said adhesive, by spirally winding several layers of flexible materials in coils with the material of the first layer which incorporates the composite adhesive, - by incorporation in a film previously laminated on the plastic film constituting said tubular body of the tube - or by winding on itself a flexible film 35, plastic or cardboard.

  The second step of the bonding process consists in inserting the shutter 2 into one of the ends of the tubular body 4 so that the composite adhesive 5 deposited on the shutter 2 is facing the inner face. tube 4 and vice versa when the adhesive 5 is deposited on the inner face of the tube 4. The contact is not required since precisely the glue will swell. It is sufficient for the two components to be placed opposite each other in the relative position that they must occupy after bonding (for example, it is possible to have a round shutter with a diameter smaller than the inside diameter of the tube, this facilitates the automatic insertion operation and decreases the geometric tolerance constraints of manufacturing components).

  And finally the third step consists in exposing the assembly 4-adhesive 5-shutter 2, to a radiation so as to cause the expansion of the composite adhesive 5 on the tubular body 4. Since a judicious control of temperatures allows to control the evolution of the adhesive both in its phases of deposition on the surfaces to be glued, as in those of expansion, gluing and decomposition (of the adhesive agent), it will be possible to cause either simultaneously one after the other, the expansion of the adhesive and the bonding of the shutter 2 on the tubular body 1.

  As illustrated in the drawing of Figure 4, since the body 4 is tubular forming a closed chamber, the expansion of the adhesive creates a peripheral voltage T in the wall of the tube which equilibrates with a contact pressure P between the two surfaces to be assembled (of the body 4 and shutters 2 and 3) distributed over the entire bonding area. this avoids the use of mechanical tools of shape to exert pressure on the bonding surfaces.

  It will be understood that the method just described above has been for disclosure rather than limitation. Of course, various arrangements, modifications and improvements may be made to the example above, without departing from the scope of the invention as defined in the claims.

  For example, the shutter 2 can be made in any rigid or semi-rigid material that can be glued such as preformed cardboard or injected plastic or thermoformed, that from a flexible film to base of plastic and / or paper. The upper shutter 2 may also have a structure enabling it to provide service functionalities, such as a lid, a pourer, a dispenser, a lid, a sprinkler, a tamper evidence or means allowing multiple successive openings and closures of the container. It may also comprise a fixed outer part intended to be assembled on the tubular body and a movable inner part intended to ensure the closure of the container thus produced, which can be connected to the fixed part by means of a connection of hinge type.

  The tubular body 4 can also be made of any type of material that can be glued, such as cardboard, plastic, metal, glass, wood, earth ... by extrusion, molding, machining, spiral winding several layers of flexible materials in coils, folding sheets .... The section of the tube may be of any shape (round, oval, rectangle, ...).

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Claims (23)

  1. A method of bonding at least one shutter at the end of a tube, CHARACTERIZED IN THAT IT consists in: - depositing on at least one of the two surfaces to be assembled, a composite adhesive having both expansion properties to cause an increase in volume of the adhesive when carried beyond a defined temperature Te, so as to fill existing gaps between the two surfaces to be joined, and acceleration properties by making it capable, under the effect of radiation, to heat up without contact quickly and homogeneously, - to insert the shutter into one end of the tubular body so that the adhesive composite deposited on one of the two surfaces to be assembled facing the other of the two surfaces to be assembled, and finally to expose the tube-adhesiveobturator assembly, to a radiation so as to cause the expansion of the composite adhesive and the collage of the obt urator on the tubular body.   2. A method of bonding according to claim 1, CHARACTERIZED IN THAT it consists in exposing the tube-adhesive-shutter assembly, to a radiation so as to cause the expansion of the glue then the bonding of the shutter on the tubular body.   3. A method of bonding according to claim 1, CHARACTERIZED IN THAT it consists in exposing the tube-adhesive-shutter assembly, to a radiation so as to simultaneously cause the expansion of the adhesive and the bonding of the shutter on the tubular body.   4. A method of bonding according to claim 1, CHARACTERIZED IN that it consists in depositing the above composite adhesive on at least one of the two surfaces to be assembled, prior to the assembly operation.   5. A method of bonding according to claim 1, CHARACTERIZED IN THAT the composite adhesive is deposited on the lateral periphery of the shutter so that the expansion of the adhesive causes a radial pressure which balance on the inner surface of the tubular body.   6. A method of bonding according to claim 1, CHARACTERIZED IN THAT the composite adhesive is deposited in liquid phase unexpanded just before the assembly operation.   7. A method of bonding according to claim 1, CHARACTERIZED IN THAT the composite adhesive is deposited in unexpanded viscous phase just before the assembly operation.   8. A method of bonding according to claim 6 or 7, CHARACTERIZED IN THAT the composite adhesive is deposited by a controlled system with nozzle gun.   9. Bonding method according to claim 6 or 7, CHARACTERIZED IN THAT the composite adhesive is deposited by a bath system.   10. A method of bonding according to claim 1, CHARACTERIZED IN THAT the composite adhesive is in the form of a bead, having a substantially toric shape close to that of the interface between the tubular body and the shutter, of way to be mechanically deposited on the periphery of the shutter prior to the assembly operation.   11. A method of bonding according to claim 1 wherein the shutter is plastic, CHARACTERIZED IN THAT the composite adhesive is deposited on the shutter at the time of its manufacture by bi-material injection of the constituent plastic of the shutter and of the non-expanded viscous adhesive, the shutter then being delivered with a pre-deposited bead of adhesive in the solid phase.   12. A method of bonding according to claim 1, CHARACTERIZED IN THAT the composite adhesive is deposited in liquid form flat on a film in the bonding zone at the time of manufacture of the shutter by thermoforming.   13. A method of bonding according to claim 1 and wherein the shutter is manufactured by thermoforming, CHARACTERIZED IN THAT the composite adhesive incorporated in a film is pre-laminated to the plastic film constituting said shutter after thermoforming.   14. A method of bonding according to claim 1, CHARACTERIZED IN THAT the composite adhesive is deposited on the inner face of the tubular body.   15. A method of bonding according to claim 1, CHARACTERIZED IN THAT the tubular body of the tube is obtained by winding on itself a rectangle cut in a semi-rigid film and that the composite adhesive is deposited on the inner face of the rectangle before its winding on one or more bonding areas.   16. A method of bonding according to claim 1, CHARACTERIZED IN THAT the tubular body of the tube is obtained by winding on itself a rectangle cut in a semi-rigid film and that the composite adhesive is deposited on all or part of the surface of the constituent film of the tubular body by an impregnation process.   17. A method of bonding according to claim 1, CHARACTERIZED IN THAT the tubular body of the tube is obtained by winding on itself a rectangle cut in a semi-rigid film and that the composite adhesive is deposited on any surface of the constituent film of the tubular body by laminating a film incorporating said adhesive.   18. A method of bonding according to claim 1, CHARACTERIZED IN THAT the tubular body of the tube is obtained by spiral winding of several layers of flexible materials in coils and that the first layer is a material incorporating the composite adhesive.   19. A method of bonding according to claim 1, a film is previously laminated on the plastic film constituting said tubular body of the tube.   20. A method of bonding according to claim 1, CHARACTERIZED IN THAT the composite adhesive is deposited on the inner face of the tubular body by an extrusion process.   21. A method of bonding according to claim 1, CHARACTERIZED IN THAT the tubular body of the tube is obtained by winding on itself a flexible film.   22. A method of bonding according to any one of claims 1 to 21, CHARACTERIZED IN THAT said shutter is made of any rigid material capable of being bonded.   23. A method of bonding according to any one of claims 1 to 21, CHARACTERIZED IN THAT said shutter is made from a flexible film based on plastics material and / or paper. BY PROXY Cabinet DELHAYE