MXPA06009910A - Multilayer dose having a concave surface - Google Patents

Abstract

The invention relates to a dose having an axis of symmetry and used for producing multilayer objects. The inventive dose comprises a first synthetic resin and at least one thin functional resin layer entrapped at least with a large part thereof in said resin and is characterised in that the part of the surface thereof is embodied in the form of a concave.

Description

DOSE WITH MULTIPLE LAYERS THAT HAVE A CONCAVE SURFACE FIELD OF THE INVENTION The present invention relates to a method for making objects with multiple layers by compression molding a dose with multiple layers.

PREVIOUS TECHNIQUE US Patent 4 876 052 discloses a dose with multiple cylindrical layers (Figure 1), characterized in that a functional resin 3 is completely enclosed within synthetic resin 2. The functional resin and the external resin are of a different nature. For example, the functional resin has good barrier properties, while the resin forming the outer layer is chosen for its mechanical and hygienic properties. These multi-layered doses allow objects with multiple layers to be obtained by compression molding of the dose. However, the objects obtained according to the method described in US patent 4 876 052 require a large proportion of functional resin in the object, thus generating two main disadvantages: the first is a prohibitive cost and the second is a resistance decreased to mechanical stresses. The lack of adhesion between the functional resin and the external resin reduces the 52-391-06 solidity of the object and creates a risk of separation of the outer layer. Another disadvantage of the patent US 4 876 052 is based on the fact that the respective quantity of the resins 2 and 3 is only poorly adjustable, these amounts are fixed by the geometry of the object and by the flows during compression of the dose. The Japanese patent JP 2098415 proposes the realization of an object with multiple layers by compression molding, initiating a cylindrical dose (Figure 2), characterized in that the synthetic resin 2 covers only the side faces of the functional resin 3. The molding by compression of this dose along its axis of symmetry, it produces an object having a structure with multiple layers, characterized in that the synthetic resin 2 partially encloses the functional resin 3. However, the objects with multiple layers made of two Resins according to JP 2098415, have two main disadvantages: the first is that they have the functional resin 3 exposed in a central surface area of the object over at least 10% of the total surface area of the object, and the second is that it requires a amount of functional resin 3 in the object, which constitutes at least 30% of the total amount of resin. This produces, on the one hand, objects that have a prohibitive cost, and on the other hand, objects that have modified mechanical properties 52-391-06 largely, mainly in the center of the object. Another disadvantage of JP 2098415 is the fact that the respective amount of resins 2 and 3 is only slightly adjustable, these amounts are fixed by the geometry of the object and by the flows during compression of the dose. In JP 2098415, it is proposed to use a cylindrical dose containing 3 layers (Figure 3) in order to partially eliminate the disadvantages mentioned above. This dose is constituted by a first resin that forms the central part of the dose, by a functional resin 3, which covers only the lateral faces of the first resin, and by a third resin 2 that covers only the lateral faces of the functional resin . Compression of this compound dose along its axis of symmetry produces an object with multiple layers. The use of a triple layer dose has the advantage of reducing the amount of functional resin 3 used and produces objects that have slightly modified mechanical properties, in relation to the same object that contains a single resin 2. This method allows a layer to be added adhesive between the resins of different nature, thus improving the cohesion and strength of the object. However, functional resin 3 does not cover the central part of the object with multiple layers, which produces objects without property of 52-391-06 barrier near the axis of symmetry, over a surface area of at least 10% of the surface area of the object. This central region of the object not covered by the barrier resin layer 3, weakens the performance of the object barrier and makes this solution less effective.

OBJECT OF THE INVENTION The present invention allows multiple objects to be made by compression molding, eliminating the aforementioned problems. More particularly, this method allows the use of a compression device without changes of the device used to make objects with a single layer.

SUMMARY OF THE INVENTION The invention consists of a dose with multiple layers having an axis of symmetry for the realization of objects with multiple layers by compression molding, constituted by a first synthetic resin and by at least one thin functional layer enclosed in the first resin, the dose with multiple layers is characterized in that a part of its surface is concave. The concave surface can be placed on the external surface of the dose or on its internal surface, if the latter contains a hole. The orifice is possibly a passage or a 52-391-06 cavity. The invention is particularly useful for making objects with multiple layers having a hole, such as heads for tubes, or without a hole, such as plugs.

DETAILED DESCRIPTION OF THE INVENTION A better understanding of the invention will now be gained from the detailed description of the examples illustrated by the following Figures.

BRIEF DESCRIPTION OF THE FIGURES Figures 1 to 3 describe the multilayer doses described in the prior art for making objects with multiple layers by compression molding. Figure 1 shows a dose with double layer made according to US Pat. No. 4,876,052. Figure 2 shows a dose with double layer used in patent JP 2098415. Figure 3 illustrates a dose containing 3 layers, described in JP Patent 2098415. Figure 4 shows a dose with multiple layers according to a first embodiment of the invention. This dose comprises a concave surface that forms a 52-391-06 hole centered on the axis of symmetry. Figure 5 shows a multi-layered object having an orifice and made from the compression of the dose illustrated in Figure 4. Figure 6 shows a dose with multiple layers according to a second embodiment of the invention. This dose comprises a concave surface forming a cavity centered on the axis of symmetry. Figure 7 illustrates an object with multiple layers without orifice, obtained from the compression of the dose illustrated in Figure 6. Figure 8 shows a dose with multiple layers combining the first and second embodiments of the invention. The dose comprises a concave surface forming a cavity and a hole. Figure 9 illustrates a dose having a cavity and corresponding to the second embodiment of the invention. Figure 10 shows a tube head made according to the invention. Figure 11 shows a plug made according to the invention. Figures 12 to 17 illustrate methods for performing doses with multiple layers having a concave surface portion thereof. 52-391-05 DETAILED DESCRIPTION OF THE FIGURES The invention describes dose geometries with multiple layers that are advantageous for making objects with multiple layers. It has been found that doses having concave surfaces are particularly advantageous. The invention discloses dosages with multiple layers having at least a portion of its concave surface. According to a first embodiment of the invention, the concave surface of the dose forms an orifice, and according to a second embodiment of the invention, the concave surface of the dose forms a cavity. The invention allows a greater diversity of objects with multiple layers with or without an orifice to be realized. The invention also relates to the methods for making the doses. The invention in the same way, describes the objects with multiple layers obtained by compression molding of the doses. Figure 4 illustrates a first example of a dose with multiple layers corresponding to the invention. This dose 1 is constituted by a thin layer of the functional resin 3 enclosed in a resin 2. The geometry of the dose 1 is defined by a convex surface 4 that describes the circumference of the dose and by a concave surface 5 that forms an orifice , the hole is centered 2-391-06 generally in the axis of symmetry of the dose. A dose according to the first embodiment of the invention is particularly advantageous for making objects with multiple layers having an orifice, the diameter of the hole of the object being less than or equal to the diameter of the dose orifice. In general, it is favorable to use a dose whose orifice is substantially the same diameter as the hole of the object to be made. A dose according to the first embodiment of the invention (Figure 4), likewise allows objects with multiple layers without an orifice to be advantageously made. In JP2098415, the use of a cylindrical dose with multiple layers to form an object without a hole is described. However, the cylindrical dose such as that described in patent JP2098415 does not allow a functional layer, which is properly distributed in the central part of the object, to be obtained. In fact, the compression of the cylindrical dose described in the patent JP2098415 creates a flow towards the periphery of the object and therefore, drag the functional layer towards the periphery of the object. Therefore, it is not possible to drag the functional layer towards the center of the object. A dose according to the first embodiment of the invention, having a concave surface forming a 52-391-06 orifice, allows a flow to be created towards the periphery and towards the center of the object. The functional resin layer 3 is also dragged together towards the periphery and towards the center of the object, whereby a multilayer object having improved barrier properties can be obtained. Experiments have shown that the radial position of the thin layer of functional resin in the dose was a function of the compression rate, the geometry of the object, the rheology of the resins and the parameters related to the process. The position of the functional layer in the dose allows the surface of the object, that is, the periphery and the center, to be covered in an optimal way, after compression. The thin layer of functional resin 3 improves the impermeability of the object to gases or aromas. In general, it is advantageous to use a small amount of the functional resin for reasons of cost and properties of use. The amount of functional resin is usually less than 20% of the volume of the object and this amount is preferably less than 10%. The ends of the functional resin layer 3 may be level with the surface of the dose, but the functional resin layer 3 is generally encapsulated entirely in the resin 2. 52-391-06 Figure 5 illustrates an object made of a dose corresponding to the first embodiment of the invention. This object contains a hole 7. The functional resin layer 3 is encased in the resin 2 and forms a fold near the periphery of the object. The ends 6 and 6 'of the layer 3 are located close to the hole 7 and are generally absent from the surface of the object, so that the layer 3 is completely enclosed in the resin 2. The dose according to the first embodiment of the invention allows the realization of objects comprising an orifice and having a functional layer 3 distributed in at least 90% of the object. Figure 6 presents a dose with multiple layers according to the second embodiment of the invention. This dose 1 is constituted by a thin layer of functional resin 3 enclosed in a resin 2. The geometry of the dose 1 is defined by a convex surface 4 that describes the circumference of the dose and by a concave surface 5 that forms a cavity, the cavity is generally centered on the axis of symmetry of the dose. As illustrated in Figure 6, the functional resin layer 3 has only one free end 6, whose end may be level with the surface of the dose or may be enclosed in the resin 2. A dose according to the second embodiment of the invention is particularly advantageous for performing 52-391-06 objects without a hole. Figure 6 shows the functional layer 3 enclosed in the resin 2, the resin layers 2 located on either side of the functional layer 3 generally have a substantially constant thickness. The second embodiment of the invention is not limited to the geometry of the dose illustrated in Figure 6. Depending on the device used to make the dose with multiple layers, it is found that the respective thickness of the layers is not necessarily constant, resulting in therefore, in a wide variety of doses. All the doses obtained according to the second embodiment of the invention have a concave surface 5 that forms a cavity. The position of the functional layer in the dose is defined so that the layer is dispersed outside the periphery of the object in the course of compression. When the functional layer 3 is brought closer to the convex surface 4 of the dose, the functional layer approaches the periphery of the object. Figure 7 illustrates a multi-layered object obtained by compressing a dose made in accordance with the second embodiment of the invention. This multilayer object has improved barrier properties, since the functional layer 3 is present through the object, both in the central part and in the periphery. The functional layer 3 forms a fold close to 52-391-06 the periphery of the object. The functional layer 3 is preferably completely enclosed in the resin 2, even at its free end 6. Figure 8 illustrates a dose resulting from the combination of the first and second embodiments of the invention. This dose 1 is constituted by a thin layer of functional resin 3 enclosed in a resin 2. The geometry of the dose 1 is defined by a convex surface 4 that describes the circumference of the dose and by a concave surface 5 that forms a cavity and a hole, the cavity and the hole are generally centered on the axis of symmetry of the dose. As illustrated in Figure 8, the functional resin layer 3 has two ends 6 and 6 ', which ends may be level with the surface of the dose or be enclosed in the resin 2. The dose presented in Figure 8 it is particularly advantageous to realize objects with multiple layers with or without a hole. The position of the functional layer in the dose is defined so that the layer disperses out towards the periphery of the object during compression. When the functional layer 3 is brought closer to the convex surface 4 of the dose, the functional layer approaches the periphery of the object. The diameter of the hole and the volume of the cavity are optimized so that the functional layer is dispersed jointly towards 52-391-06 the center and towards the periphery of the object. Figure 9 illustrates a dose having a cavity and corresponding to the second embodiment of the invention. This dose 1 is constituted by a thin layer of functional resin 3 enclosed in a resin 2. The geometry of the dose 1 is defined by a convex surface 4 that describes the circumference of the dose and by a concave surface 5 that forms a cavity, the cavity and the orifice are generally centered on the axis of symmetry of the dose. As illustrated in Figure 8, the functional resin layer 3 has two ends 6 and 6 ', ends which may be level with the surface of the dose or may be enclosed in the resin 2. The dose presented in the Figure 8 is particularly advantageous for making objects with multiple layers without a hole. The 6 'end of the functional layer 3 forms a possible discontinuity that forms a hole in the layer. In order to obtain the best barrier properties, it is advantageous to eliminate or reduce this discontinuity. Figure 10 shows a tube head made of a dose with multiple layers having a part of its concave surface and forming a hole. Figure 11 shows a plug made of a dose with multiple layers having a part of its concave surface and forming a cavity. These objects have the peculiarity of having 52-391-06 a thin layer of functional resin that covers the entire surface of the object and forms a fold at its periphery. These objects are obtained by compressing the dose with multiple layers in a simple compression device that does not require modification in relation to the compression device that would be used to make the same object from a dose with a single layer. More complex compression devices, fixed parts of the moving die tool, can be used to promote the flow of resins in one direction. These devices can be useful for geometries of complex objects and to optimize the dispersion of the barrier layer through the object. Objects 10 and 11 have been made with a thin layer of barrier resin (EVOH) enclosed in a polyethylene (PE) resin. These objects have a great impermeability to oxygen or aromas. In order to simplify what constitutes the invention, the Figures are deliberately represented with only a functional layer 3 enclosed in a second resin 2. It is known that the combination of only two resins generally does not allow sufficient adhesion to be obtained in the interface between the two resins. It is also customary to use intermediate layers of adhesive, which allow resins of different nature to be combined, 52-391-06 while ensuring a good level of adhesion between the layers. Thus, the insertion of an adhesive layer on either side of the barrier layer avoids possible problems of delamination or separation in objects with multiple layers. The adhesive and barrier layers are parallel and in a small amount. The aggregate of the adhesive layers forming the functional layer 3 generally represents an amount of resin of less than 15% of the total volume of the resin that forms the dose, and preferably less than 10%. The present invention is therefore not limited to doses of 3 layers such as those depicted in Figures 4, 6, 8 and 9, but more generally contain 5 or more layers. The resins used in the scope of the invention correspond to the thermoplastic resins currently used, and more particularly to those used in the packaging industry. Among the barrier resins that can be used to form functional layer 3, mention may be made of ethylene vinyl alcohol copolymers (EVOH), polyamides such as Nylon-MXD6, acrylonitrile-methyl acrylate copolymers (BA EX), fluorinated polymers such as PVDF. In relation to this, a few resins can also be cited that can be used to form the structure 2 of the object: polyethylene (PE), polypropylene (PP), polystyrene (PS), 52-391-06 polyamide (PA), polyester (PET). This list is not exhaustive. In the choice of resins, it is important to select products that have close viscosities. In general, it is preferable to use resins that at the working temperature, have a viscosity ratio of less than 10, and preferably, a viscosity ratio of less than 3 will be chosen. The compression molding method consists of feeding a dose with multiple layers of synthetic resins in the molten state in the cavity of a mold, forming the object by compression molding the doses in the mold cavity, cooling the object and then removing it from the mold. The invention allows the realization of objects having a very thin functional layer, which functional layer can represent less than 5% of the volume of the object. Methods for making objects with multiple layers according to the invention require that doses be made with multiple layers having a part of their concave surface. A first method is illustrated in Figures 12 and 13. This method consists in making a tubular coextrusion with multiple layers tai as illustrated in Figure 12. The flow with multiple layers flows in a matrix tool comprising at least one matrix 8 and a mandrel 9. 52-391-06 The mandrel 9 is equipped at its end with a shut-off valve, which allows the tube to be periodically cut and the doses to be formed. The flow with multiple layers is created upstream of the tool of the matrix represented in Figure 12 according to known methods. The tests on which the patent application is based were carried out with three extruders connected to the extrusion head. Figure 12 shows the position of the mandrel, which extends beyond the matrix by a height H and which allows the creation of the dose cavity. After the exit of the tool from the matrix, the flow is wound around the mandrel and allows the geometry of the dose to be modified. It has been found experimentally that the winding of the material flow around the end of the mandrel 12 is dependent on the height H, the geometry of the shut-off valve, the extruded resins, as well as the movements of the mandrel 9. By optimizing these parameters, it is possible to produce doses with an orifice (Figures 4 and 8) or without an orifice (Figure 6). Figure 13 illustrates closing the shut-off valve and cutting the dose. By modifying the process parameters such as the opening and closing speed of the shut-off valve, the extrusion speed, the temperatures, or by modifying the geometry of the tool 52-391-06 of the matrix, it is possible to optimize the concavity of the dose. Figures 14 and 15 illustrate another process for the realization of concave doses. This process consists in creating a tubular coextrusion in the tool of the matrix represented in Figure 14. This tool of the matrix comprises at least one matrix 8 and a mandrel 9, the mandrel 9 extends beyond the matrix 8 by a height H. Depending on the geometry of the dose to be performed, the mandrel 9 is fixed, or is activated by a reciprocating, periodic, periodic movement in phase with the dose cut-off. In order to simplify what constitutes the invention, Figure 15 represents a mandrel and a matrix of a cylindrical geometry. The invention also covers other geometries of the tool that are based on the same principle and allow a dose having a part on its concave surface to be produced. The method illustrated in Figure 14 and 15 consists of extruding the materials through the tool of the matrix 8 and 9 at a constant speed, and periodically cutting the material ejected from the tool of the matrix by means of a cutter shown in FIG. Figure 15. The distance H corresponds to the maximum distance between the ends of the mandrel and the matrix, generally varying between 1 mm and 5 cm. 52-391-06 Cutting of the dose can be done according to other known methods, including, for example, rotary cutters to cut the rod as it leaves the extruder. This type of cutter can be used simultaneously to transfer the doses in the mold. The transfer of the dose can be effected by known methods, such as by gravity or by means of a transfer device. The placement of the dose in the compression mold must be precise, and in particular, the axis of symmetry of the dose must be aligned precisely with the axis of symmetry of the mold cavity. The doses are compressed along the axis of symmetry of the dose. Figure 17 illustrates another method for performing doses where a part of its surface is concave. This method consists of making a tubular dose, then modifying its concavity during the cutting or in the course of transferring the dose into the compression mold. Figure 16 shows the extrusion with multiple tubular layers through the matrix 8 and the mandrel 9. This extrusion is preferably carried out at a constant speed. Figure 17 illustrates the cutting of the extrudate with multiple layers with the cutter 10. The movement of the cutter 10 has the effect of periodically cutting the extrudate and closing in a manner 52-391-06 joint the end of the dose 1. Similar methods can be considered to cut and close the end of the dose simultaneously or sequentially. The doses with multiple layers are extruded in the molten state at temperatures suitable for the resins used. Doses with multiple layers remain in the molten state during the step of being transferred into the compression mold. The doses are compression molded and the object obtained is at least partially cooled in the mold before ejection. In the examples presented here, the dose and the objects are of simple geometry, but the invention obviously relates to any geometry of the dose and the object. The objects obtained according to the invention contain a functional layer 3 that forms at least one fold at the periphery of the object. Objects can be obtained that also contain a second fold near the axis of symmetry of the object. A zigzag arrangement of the functional layer in the object is obtained. Numerous arrays of functional layer 3 are possible in the dose. It may be advantageous to place the functional layer 3 in the dose, so that the functional layer 3 forms the cover of a body of revolution centered on the axis of symmetry. When the distance from the 52-391-06 functional layer 3 the axis of symmetry is variable, objects with multiple advantageous layers can be obtained. The invention has been described with a single functional layer 3 distributed in the dose. The doses comprising a plurality of functional layers 3 can also be used, the functional layers are all centered on the axis of symmetry of the doses. The objects with multiple layers obtained are characterized in that the functional layers are placed at least partially on top of each other and are distributed through the object. The realization of packaging or packaging components for food applications requires good hygiene properties. Therefore, it is often desirable that the functional layer 3 not be in direct contact with the packaged product. It may be advantageous to enclose the functional layer 3 completely in the dose, so that the functional layer is completely enclosed in the object, so that the functional layer is absent from that part of the object that requires high hygiene properties. Alternatively, it is possible that only one end of the barrier layer is not enclosed. 2-391-06

Claims (14)

1. CLAIMS: 1. A dose with multiple layers in the molten state (1) having an axis of symmetry for the realization of objects with multiple layers by compression molding, comprising a first synthetic resin (2) and at least one thin layer of functional resin (3) enclosed at least to a large extent in the resin (2), wherein a part of its surface (5) is concave.
2. 2. The dose according to claim 1, comprising an orifice, the concave surface (5) is constituted by at least part of the internal surface formed by the orifice.
3. 3. The dose according to claim 2, wherein the orifice forms a passage through the dose.
4. 4. The dose according to claim 3, wherein the orifice forms a cavity that is open on one side of the dose (1).
5. The dose (1) according to any of the preceding claims, wherein the thin functional layer (3) itself forms a multilayer structure comprising a layer of barrier resin enclosed between two layers of adhesive resin.
6. 6. An object with multiple layers obtained from a dose with multiple layers in the molten state (1) according to any of claims 1 to 5, which 52-391-06 contains at least a portion in which the thin functional layer (3) forms a fold.
7. The object with multiple layers according to the preceding claim, having an axis of symmetry, wherein the thin functional layer (3) forms a body of revolution centered around the axis of symmetry.
8. The object with multiple layers according to claim 7, wherein the body of revolution is open.
9. The object with multiple layers according to the preceding claim, wherein the body of revolution contains an opening centered on the axis of symmetry.
10. The object with multiple layers according to any of claims 6 to 9, which contains a hole that forms a passage through the dose.
11. 11. The object with multiple layers according to any of claims 6 to 9, which does not contain an orifice.
12. 12. The object with multiple layers according to claim 7, wherein the body of revolution is closed.
13. 13. A production process for a dose with multiple layers in the molten state (1), according to any of claims 1 to 5, wherein the resins constituting the dose (1) are extruded simultaneously 52-391-06 and coaxially, initially in a rectilinear direction, and wherein the direction of the extrusion is then modified in such a way as to form the concave surface (5). A device for producing a dose with multiple layers in the molten state (1), according to any of claims 1 to 5 and using the process according to claim 13, wherein it comprises a passage (8) for the linear, simultaneous flow and coaxial of the resins constituting the dose (1) and means (9) to modify the extrusion direction in such a way as to form the concave surface (5), the means (9) are mounted to slide within the passage (8) .