MXPA06009911A - Multilayer dose - Google Patents

Abstract

The invention relates to a multilayer dose having an axis of symmetry, which is intended for the production of multilayer objects by means of compression moulding. The inventive dose comprises a first synthetic resin and a thin functional layer (3) which is trapped in the first resin, said layer (3) representing less than 20%of the volume of the dose. The multilayer dose is characterised in that the layer (3) forms the shell of a body that revolves around the axis of symmetry and in that the distance between the layer and said axis is variable.

Description

DOSAGE WITH MULTIPLE LAYERS 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.

PRIOR ART US Pat. No. 4,876,052 discloses an object with multiple layers (Figure 1), characterized in that a functional resin 3 is completely enclosed within a 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 52-392-05 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. As will be further shown below in what constitutes the invention, these quantities 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, starting from a compound dose (Figure 2), characterized in that the synthetic resin covers only the side faces of the functional resin 3. The molding by compression of this dose along its axis of symmetry, 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 of According to JP 2098415, they 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 quantity 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, 52-392-06 objects that have mechanical properties modified to a great extent, mainly in the center of the object. Another disadvantage of the patent JP 2098415 is 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 the compression of the dose. In JP 2098415, it is proposed to use a dose containing 3 layers in order to partially eliminate the disadvantages mentioned above.

(Figure 3). This dose is constituted by a first resin 4 that forms the central part of the dose, by a functional resin 3, which covers only the side faces of the first resin, and by a third resin 2 that covers only the side faces of the resin functional. 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 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 52-392-06 multiple layers, which produces objects with multiple layers without barrier property 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. The patent application CH01619 / 04 describes objects with multiple layers made from a multilayer dose compression molded (Figure 4). The objects described in this patent application have a structure with multiple layers characterized by the position of the functional layer forming a double fold in the shape of a zigzag. The functional layer is distributed correctly through the object, even in the central part. The method for making objects with multiple layers that is described in the patent application CH01619 / 04 also allows the control of the thickness of the functional layer. A layer of sive can be added between the resin that forms the surface of the object and the functional resin. However, compression of the dose requires a specific method and molding device. This method requires especially, additional movements of the tool of the matrix in relation to the basic compression process, adjusting the two parts of the mold in 52-392-05 relative movement. In the case of high speed molding, it can be detrimental to use a compression device as described in the patent application CH01619 / 04.

OBJECT OF THE INVENTION The present invention allows objects with multiple layers to be made by compression molding, eliminating the aforementioned problems. More particularly, this method allows the use of a compression device without changing 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 functional layer represents less than 20% of the volume of the dose, the dose with multiple layers is characterized in that the functional layer forms a cover of a body of revolution around the axis of symmetry and in that the distance of the layer the axis of symmetry is variable. 52-392-06 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 4 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 an annular dose with multiple layers described in the patent application CH01619 / 04. Figure 5 shows a dose with multiple layers according to the general concept of the invention. Figure 6 illustrates the flow of the material and the velocity profile during compression of the dose. Figure 7 illustrates the compression of a dose as described in patent JP 2098415, as well as the 52-392-06 object with multiple layers obtained. Figure 8 shows the limits of multi-layer objects obtained according to JP 2098415. Figures 9 to 20 present examples of multilayer dosages, their methods of embodiment and an example of a device that can be used. Figure 9 illustrates a first example of a dose corresponding to the invention. Figure 10 shows the object with multiple layers obtained after compression of the dose described in Figure 9. Figure 11 shows a dose made according to the invention and comprising 5 layers. Figures 12a and 12b illustrate an annular dose belonging to the invention. Figure 13 presents a multi-layered object obtained from the compression of the dose presented in Figure 12a. Figure 14 is another example of a dose belonging to the invention. Figures 15 to 19 describe methods by which doses such as those described in Figures 9, 11, 12 and 14 can be made. Figure 15 illustrates a first method for 52-392-06 perform doses, according to which the flow velocity of one of the layers varies periodically. Figure 16 shows a second method for performing doses, according to which the flow rate of two layers varies periodically and in phase opposition. Figure 17 illustrates a multi-layered rod that is used to make doses with multiple layers and that can be made with the embodiment described in Figure 16. Figure 18 illustrates a third method for making doses with multiple layers, in accordance with which the flow velocity of all layers varies periodically and with a total flow rate that fluctuates slightly. Figure 19 shows another method for performing doses with multiple layers, according to which the flow velocity of each layer varies periodically and according to which the total flow rate is periodically zero. Figure 20 illustrates a device by which doses with multiple layers according to the invention can be performed. Figures 21 to 27 illustrate another example of dose with multiple layers, one embodiment method, as well 52-392-06 as a device. Figure 21 shows another type of dose with multiple layers corresponding to the invention. Figure 22 shows the multi-layered object obtained from the compression of the dose described in Figure 21. Figures 23a to 23d illustrate the method for performing the dose described in Figure 21. Figures 24a to 24c show a method for transferring the dose in the compression mold. Figures 25a to 25c illustrate the compression of the dose in the compression device. Figure 26 shows the general concept of a device that can be used to make doses with multiple layers. Figure 27 shows a device for performing the dose shown in Figure 21.

DETAILED DESCRIPTION OF THE FIGURES The invention consists of making doses with multiple layers according to the concept represented in Figure 5. This dose is constituted by a first synthetic resin that forms the dose and by at least one second resin enclosed in the first resin and which forms a thin layer whose distance to the axis of symmetry R and whose 52-392-06 thickness E varies according to the position on the z-axis of symmetry. This type of dose allows the position of the barrier resin layer in the molded object, as well as the thickness of this layer, to be optimized together. In order to gain a better understanding of the dose previously described, it is necessary to consider the flow of the resins during compression of the dose (Figure 6). This flow is dependent mainly on the rheological properties of the resins during compression, as well as on the geometry of the object. The figure 6 shows that this flow is faster in the middle part between the walls than near the walls of the matrix tool. Next to the walls of the tool of the matrix, the speed of displacement of the particles tends to zero, but the deformation due to the shear stress is high. Conversely, in the middle between the walls, the velocity of the particles is at a maximum and the deformation due to the shear stress is at a minimum. During flow, the functional resin layer is entrained and deformed in a non-uniform manner, according to its position in the flow profile. The final position of the functional resin layer in the object is then determined by the original position of the functional layer in the dose and by the sum of the deformations 52-392-06 suffered during the flow. Figures 7a to 7c illustrate the compression of a dose as proposed in the patent JP 2098415, in order to demonstrate the limits of the objects with multiple layers obtained according to this method and to better understand the object of the present invention. Figure 7a shows a triple-layer dose carried out in accordance with patent JP 2098415. This dose contains a first resin 4 which forms the central part of the dose, a functional resin 3 covering the side faces of the first resin, and a third resin 2 covering only the side faces of the functional resin. This dose has a height referred to as Hl, an external radius Rl, and a radical position of the functional layer R. The compression of this dose results in an intermediate step illustrated in Figure 7b. Figure 7b shows the deformation of the functional layer in the partially compressed dose. It is important to note that this layer deforms towards the periphery of the object, that is, in the direction of the flows, which implies that the central part of the object can not be covered by the functional layer. It is interesting to note also, in the intermediate step, that the functional layer is still far from the front of material, which indicates that the object obtained in the intermediate step does not have barrier properties at the periphery level. Figure 7c illustrates the object obtained after 52-392-06 of the dose compression. The functional layer 3 has been dispersed towards the end of the object, while remaining encapsulated at the periphery of the object. As shown by Figure 7c, the functional layer has not been dispersed in the central part of the object. The object obtained according to this method, therefore, has the disadvantage of not having barrier properties at its center. Objects such as those depicted in Figure 7c have been made of doses such as those illustrated in Figure 7a. The experimental findings have been plotted in Figure 8. The surface area of the object is marked as Sp, the central surface area of the object with multiple layers not covered by the functional layer is marked S, the object thickness is marked E, the thickness of the dose is marked as Hl. The Hl / E ratio represents the compression speed. Figure 8 shows how the fraction of the surface area not covered by the functional layer S / Sp varies as a function of the compression rate H / Hl. The S / Sp ratio is greater than 10%, even for compression speeds of 20. This finding indicates that the functional layer covers, in the best of scenarios, 90% of the surface area of the object. The measurement of the barrier properties in an object having 90% of its surface area covered by the functional material, shows that this object is at least 10. 52-392-06 times more gas permeable than the same object performed according to the invention, and having 100% of its surface area covered by the functional layer. These findings were obtained using a functional resin 100 times less permeable than the base resin. Figure 9 shows a first example of a dose with multiple layers corresponding to the invention. This dose comprises a first resin layer 4 encapsulated in a functional resin layer 3, the functional resin layer 3 itself is encapsulated in a layer of resin 2 which forms the external surface 5 of the dose 1. The ends 7 and 7 ' of the functional layer are joined in 1 point, so that layer 4 is completely enclosed in functional layer 3. The position of the functional layer in the dose allows 100% of the surface area of the object, ie the periphery and the center, cover after compression. This produces a position of the functional layer in the dose according to a profile as illustrated in Figure 9, which forms a pocket class at both ends 7 and 7 'and which forms a protuberance 10 located approximately in the middle of the dose. The radial position of the protrusion is not arbitrary, it is fixed by the geometry of the object and the dose. The exact radial position of the protrusion 10 allows the layer to be dispersed outside the periphery of the object and 52-392-06 serves to ensure that the functional layer remains encapsulated in the object. Experiments have shown that the radial position of the protuberance of the functional layer in the dose was a function of the compression speed, the geometry of the object and the rheology of the resins. An example of an object with multiple layers obtained from the compression of this dose is illustrated in Figure 10. This object has the peculiarity of having a double layer of functional resin that covers the entire surface of the object. This object is obtained by compressing the dose with multiple layers in a simple compression device, which does not require a relative modification of the compression device that would be used to perform the same object in a single-layer dose. A detailed observation of the object with multiple layers at the level of the axis of symmetry, as illustrated in Figure 10, shows the ends 7 and 7 'of the functional layer forming a peak class perpendicular to the surface of the layer. Figure 11 shows that the invention is not limited to a dose with triple layer as illustrated in Figure 9. A dose comprising 5 layers, such as that illustrated in Figure 11, is particularly advantageous, since the insertion of a adhesive layer 3b and 3c in 52-392-06 any side of the barrier layer 3a allows resins of different nature to be combined, while ensuring good adhesion between the different layers, which avoids possible problems of delamination or separation in the objects with multiple layers. The adhesive and barrier layers lie in parallel and are small in quantity. The aggregate of the adhesive layers 3b and 3c and of the barrier layer 3a forming the functional layer 3 generally represents an amount of resin less than 15% of the total volume of the resin forming the dose, and preferably, a amount less than 10%. Figures 12a and 12b show that the invention is not limited to a cylindrical dose as illustrated in Figure 9, these doses can be annular for the realization of objects with multiple layers containing an orifice. The multilayer ring dose such as that shown in Figure 12a and 12b are particularly advantageous for making objects with multiple layers containing an orifice, such as, for example, tube heads. The dose presented in Figure 12a is used when the compression of the dose produces a joint flow towards the periphery and towards the center, while the dose 12b is used when the compression of the dose only gives rise to a flow towards the periphery. Figure 13 shows a tube head 52-392-06 performed by compression molding a dose with multiple layers, such as that depicted in Figure 12a. A double functional layer covering the entire surface area of the object can be found in the thickness of the object. The functional layer is dispersed outside the periphery of the object and as far away as the hole, while remaining fully encapsulated. In order to control the dispersion of the layer in both directions, it is necessary to adjust the geometry and position of the functional layer within the dose. Doses similar to the doses presented in Figures 9 and 12 can be made. Figure 14 shows a dose with multiple layers containing a layer of resin 4 enclosed laterally by a thin layer of functional resin 3, enclosed by itself by a layer of resin 2 which forms the external surface 5 of the dose. The functional resin layer 3 defines an axisymmetric geometry in the shape of a pear that opens at both ends, the radius Rmin defining the opening at the ends is less than or equal to 80% of the maximum radius R max that defines the protrusion of the functional layer, and Rmin is preferably less than 10% of the radius Rmax. The dose presented in Figure 14 differs singularly from the dose proposed in patent JP 2098415 (Figure 3), which is characterized in that the functional resin layer forms 52-392-06 a cylindrical geometry. The extrusion of the dose as described in JP 2098415 can produce a geometry of the functional resin layer which is not perfectly cylindrical as in Figure 3, but is slightly deformed. This slight deformation of the functional layer can be caused naturally, or by a joint effect of stress relaxation after leaving the extruder (phenomenon of increase in size) and gravitational force, which causes the dose to deform under its own weight . These deformations of the dose can produce a geometry of the functional layer which is characterized by a minimum radius Rmin greater than 80% of the maximum radius R max. As previously demonstrated, this type of dose does not produce objects with multiple layers that have good impermeability properties, due to the surface area in the center of the object that is not covered by the functional layer. The invention allows an improvement in the permeability of objects with multiple layers by significantly increasing the surface area of the object that is covered by the barrier layer. As will be explained below, the embodiment of the multilayer dose, such as that presented in Figure 14, requires a specific device and can not be performed according to the method presented in the patent JP 2098415. 52-392-06 The method for making objects with multiple layers which is discussed below is particularly advantageous for making objects such as plugs, covers, preforms, or flanges for pipe. This method can likewise be advantageously used to produce preforms in the form of a slab, these slabs are then used in thermoforming or thermoforming by blowing to form objects with multiple layers. The doses presented in Figures 9, 11, 12 and 14 can be made according to various methods. These different methods have a common element, which consists in extruding the resins to form a structure with multiple layers, and at least the resin forming the central layer 4 of the multi-layer structure is extruded with a variable flow rate. A first method for performing doses is illustrated in Figure 15. With this method, doses can be made with multiple layers corresponding to the type of dose presented in Figure 14. This method consists in coextruding a rod with multiple layers in a continuous manner, such as shown in Figure 15. The flow velocity of layer 2 forming the external surface of the dose and the flow velocity of the functional layer are constant. On the other hand, the speed of 52-392-06 Layer 4 flow that forms the inner layer of the dose fluctuates periodically between a maximum and a minimum value. The periodicity of the variations of the flow defines a wavelength that corresponds to the length of the dose and, in the same way, defines the frequency of the cut of the rod with multiple layers. This method is particularly advantageous for performing doses with multiple layers at very high speed. The embodiment illustrated in Figure 15 also allows a dose to be made, which has the layer 4 fully encapsulated in the functional resin 3. For this purpose, the resin layer 4 must have a flow rate that fluctuates between a speed of maximum flow and a flow velocity of zero. A second method for performing doses is illustrated in Figure 16. This method differs from the method illustrated in Figure 15 by the fact that the flow rate of resin layers 2 and 4 varies periodically and in phase opposition so that the total flow rate remains constant or fluctuates weakly. The flow velocity of the functional layer remains constant. The rod with multiple layers is cut after leaving the coextrusion device at the frequency set by the periodic variations in the flow velocity of layers 2 and 4. This method can be advantageous to avoid faults related to excessively abrupt variations in 52-392-06 the total flow velocity (extrusion instabilities, orange peel). The variations in the flow of layers 2 and 4 after the exit of the extrusion device are generally gradual, even if the control signal is strobe, as indicated in Figure 15. This phenomenon is related to the inertia of the resin in the device. It is also possible to control flow variations progressively by using appropriate devices. Figure 17 illustrates a rod with multiple layers that can be obtained according to the method described in Figure 16. Periodic cutting of the multi-layer rod after the exit of the co-extrusion device allows a multi-layer dose to be obtained. The multi-layer rod is obtained by extruding the functional layer with a constant flow rate and extruding the resin layers 2 and 4 with a flow rate that varies periodically and in phase opposition. The flow rate of the resin layer 4 fluctuates periodically between a maximum flow velocity and a flow velocity of zero, leading to a total encapsulation of the resin layer 4 within the functional resin layer. Figure 18 illustrates the method for performing doses with multiple layers identical to those presented in 52-392-06 Figure 9. This method consists of coextruding a rod with multiple layers comprising a resin layer 4, a functional layer 3 and a resin layer 2 that forms the outer surface of the rod. The flow velocity of resin layers 2 and 4 varies periodically and in phase opposition. The flow rate of the resin 2 forming the external layer of the rod fluctuates periodically between a "minimum and a maximum value" The flow velocity of the functional layer 3 varies periodically and has a value of zero during a period ti. flow rate of layer 4 also varies periodically and has a value of zero during a period t2.The variation of the flow of the layers is effected at a frequency corresponding to the frequency of production of the dose. External layer 2 is extruded, during the period (t2-tl) only layers 2 and 3 are extruded Another method for making doses with multiple layers such as those illustrated in Figure 14 consists of a discontinuous coextrusion process, characterized in that The total flow rate of the co-extruded resin ranges from a maximum value to a value of zero, the quantity of the material dosed during a period corresponding to a dose. is illustrated in Figure 19. During a ti period, the total speed of the 52-392-06 coextruded flow is zero, and during the period t2-tl only layers 2 and 3 are extruded, which allows layer 4 to be encapsulated within the functional resin layer 3. The method for performing doses with Multiple layers according to the method 19 has the advantage of allowing a volumetric dosage of the dose with multiple layers, therefore, a greater regularity of the dose. The invention is not limited to a method for making doses with 3 layers with multiple layers. For example, for the performance of a 5 layer dose, as illustrated in Figure 11, a control method similar to the method illustrated in Figure 18 can be used. Similarly, the invention is not limited to methods for performing cylindrical doses, ring doses, for example, which are capable of being performed. Various devices can be used to perform doses with multiple layers according to the methods illustrated in Figures 15 to 18, these methods consist in coextruding a rod or tube with multiple layers and in varying the flow rate of one or more layers periodically, the The rod or tube with multiple layers is then cut periodically to form the doses. The device comprises at least one coextrusion head connected to a plurality of extruders for feeding the molten resins in the coextrusion head, and means 52-392-06 to vary the flow rate of one or more layers periodically. Figure 20 illustrates an example of a device for making a dose with multiple layers. This device comprises the conduits 11, 12 and 13 for the respective feed of the resins 2, 3 and 4, the resin 3 forms the functional layer and the resins 2 and 4 respectively form the external and internal layers of the dose. The conduits 11, 12 and 13 are connected to the extruders by known suitable means. The device also comprises a distributor 14, by which each layer can be distributed appropriately on the circumference. Various types of distributors can be used, such as, for example, helical distributors or distributors with cardioid geometry or portmanteau distributors. The device comprises a connector 15, which allows the geometry of the rod or the extruded tube to be modified by changing the geometry of the connector. The device will preferably have a common joint 16 of the layer of resins 2, 3 and 4. This common joint 16 allows an easy variation of the position of the functional layer 3, varying the respective flow rates of the layers 2 and 4. The device is characterized by means 17 and 18, by means of which the flow rate of the resin layers 2 and 4 can 52-392-06 vary periodically. The alternating movement of the rams 17 and 18 allows a rapid and periodic variation of the flow velocity of layers 2 and 4. A falling movement of the ram creates a rise in pressure and consequently, an increase in the flow velocity of the layer. Conversely, a ram lift creates a drop in pressure and reduces the flow velocity of the layer. For greater effectiveness, the ram may be linked with one or more shut-off valves, the first being located upstream and the second downstream of the ram. The ram can be operated mechanically or by means of a cylinder. The invention is not limited to the device previously described. The rams and closing valves can also be linked to the functional layer 3. A device similar to that described in Figure 20 can be used to make a dose with 5 layers. Figure 21 illustrates another dose with multiple layers particularly advantageous for making objects with multiple layers by compression molding. This dose comprises a first layer of resin 4 that forms the internal part of the dose, a thin layer of functional resin that encapsulates the resin layer 4, and a layer of resin 2 that forms the outer layer of the dose and that encapsulates the functional resin layer 3. Functional layer 3 defines a 52-392-06 three-dimensional geometry, axisymmetric in the shape of a pear and has an end 7 located near the axis of symmetry, which forms a small, slightly conical opening. Layer 3 intersects the axis of symmetry at a point opposite to the end 7. These doses with multiple layers are particularly advantageous for forming objects with multiple layers by compression molding the dose in a mold. Figure 22 shows an object with multiple layers made of doses shown in Figure 21. This object contains a double functional layer 3a and 3b enclosed in the wall of the object, the functional layer has a discontinuity at the level of the axis of symmetry of the object. This discontinuity takes the form of a hole of small diameter in the functional layer 3b of the object. This hole corresponds to the end 7 of the functional layer 3. The diameter of the hole in the functional layer 3b is less than 10 mm in value and is generally less than 3 mm. The multi-layered object 22 obtained from the dose shown in Figure 21 has a first layer 3a completely absent from the surface of the object, as well as a second layer 3b having an opening and possibly present on the surface of the object. For reasons of hygiene and reasons pertaining to the performance of the object with multiple layers 22, it is preferable that layer 3b is not placed on that side of 52-392-06 the surface of the object that is in contact with the packaged product. The invention is not limited to a dose having 3 layers, as in Figure 21. It may be advantageous to have a greater number of layers, especially to improve adhesion between the layers. In this sense, the functional layer 3 presented in Figure 21 can be considered as an aggregate of a plurality of thin parallel layers. For example, the functional layer can itself contain 3 layers, of which a layer of barrier resin is sandwiched between two layers of adhesive resin. The method for performing doses with multiple layers depicted in Figure 21 is illustrated in Figure 23a to 23d. This method consists in shaping the dose with multiple layers and is characterized in that the resins are fed sequentially into a variable cavity of a transfer mold 19, the volume of the cavity varies with the amount of resin fed into the cavity. These doses have then been transferred into the molten state in the compression mold to realize the object with multiple layers. Figure 23a shows the transfer mold 19 before filling with the resins. The casing 20a, the ram 20b and the cover 21 constitute the transfer mold 19 and define a cavity that 52-392-06 has an opening created by the orifice 22. Before the resins are fed, the volume of the cavity is reduced. The method consists in feeding, first of all, the resin 2 that forms the external layer of the dose. Figure 23b shows the resin 2 fed through the orifice 22, causing displacement of the ram 20 and together inducing an increase in the volume of the cavity of the transfer mold 19, to provide the volume of the resin fed. The method consists in then feeding the functional resin 3 into the transfer mold 19. Figure 3c shows the feeding of the resin 3 and its dispersion inside the resin 2 already in the mold. The method is finally to feed the resin 4 that forms the internal layer of the dose. Figure 3d illustrates the feeding of the resin 4 and its dispersion within the functional layer 3, together with the displacement of the ram 20. The doses with multiple layers in the molten state are then transferred from the transfer mold to the mold. compression. The transfer method is briefly illustrated from Figures 24a to 24c. The first step of this method, illustrated in Figure 24a, is to separate or open the cover 21 on the contact surface with the lower surface of the dose with multiple layers. The dose is expelled to 52-392-06 continuation of the transfer mold 19 by means of the ram 20b, as illustrated in Figure 24b. Figure 24c shows the dose with multiple layers deposited in the cavity of the compression mold 23. The dose with multiple layers must be in the molten state during its transfer in the compression mold 23, to allow compression molding and avoid imperfections. For this, the control of the temperature of the transfer mold 19 and the residence time of the dose in the transfer mold is very important. The temperature of the parts constituting the transfer mold 19 must be adjusted to allow, jointly, the unmolding of the dose and the formation of a skin on the surface of the dose, which is sufficiently thin to be remelted before of compression. The temperature of the transfer mold should be as high as possible to approximate the temperature of the molten resin and the residence time in the transfer mold should be as short as possible. The ejection of the dose with multiple layers in the compression mold can be effected by a method different from that illustrated in Figure 24. For example, a lateral opening in the envelope 20a perpendicular to the axis of symmetry allows for easier removal of the dose. Figures 25a to 25c illustrate the compression of 52-392-06 the dose with multiple layers. Figure 25a shows the placement of the dose in the mold cavity 23. Figure 25b shows the plunger 24 falling which compresses the dose and forms the object with multiple layers. Figure 25c illustrates the object with multiple layers that is obtained. A . device for making objects with multiple layers of a molded dose is presented schematically in Figure 26. This device is constituted by u first carousel 25 comprising molds, means for compressing the dose and means for ejecting the molded objects. This device is also constituted by a second carousel comprising the molds 19, means for feeding the resins sequentially in the transfer molds, means for increasing the volume of the cavity of the transfer molds as the resins are fed into the molds. the mol3.es, and also means to transfer the dose in the compression molds. The transfer of the • dose takes place at the meeting point 27 of the trajectory of the transfer molds and the compression molds. The device further comprises means for adjusting the carousels in routing and means for adjusting and controlling the parameters. -'- The description of the transfer carousel 26 is - illustrated in the Figure. 27. This rotating carrousel carries ... r, .. E2-392-Ü6 the transfer molds 19. During the. rotation of the carousel 26, the molds 19 pass sequentially above a first feed channel 28, a second feed channel 29 and a third feed channel 30. The feed channels 28, 29 and 30 are fixed and connected to the .extruders. When the transfer mold 19 passes in line with a channel, the resin that is fed under pressure into the channel fills the mold cavity. Figure 27 indicates that a mold passing sequentially above the channels 28, 29 and 30 sequentially filled with resins fed into the respective channels. Thus, by feeding the resins 2, 3 and 4 respectively into the channels 28, 29 and 30, a dose identical to that presented in Figure 21 is obtained. The respective amounts of resins fed into the cavity of the transfer mold 19 can be adjusted with the respective lengths Ll, L2 and L3 of channels 28, 29 and 30, as well as with the pressure fed from each resin. The objects made according to the invention have particularly advantageous barrier properties. This can be explained, in part, by recognizing that most objects made according to the invention have a functional layer that sufficiently covers the surface area of the object and in particular, the surface area near the axis of symmetry of the object. 52-392-06 The resins used within 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 (BAREX), fluorinated polymers such as PVDF. . In relation to this can also be cited a few resins that can be used for layers 2 and 4 of the dose: polyethylene (PE), polypropylene (PP), polystyrene (PS), 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 which, 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 invention also relates to multilayer doses comprising a plurality of functional layers, the functional layers are individually encased in a resin that forms at least 80% of the volume of the dose. According to the invention, at least one functional layer has a variable distance to the axis of 52-392-06 symmetry. The use of a dose comprising a plurality of functional layers can be advantageous at a very high production rate. Actually, at very high speeds, it is difficult to obtain strong variations in the flow velocity. The second functional layer can be of tubular geometry centered on the axis of symmetry of the dose, the radial position of this layer in the dose is such that the compression of the layer produces an object with multiple layers having two independent functional layers that are they partially place one on top of the other and produce properties similar to those of a continuous layer. The second functional layer can likewise have a variable distance to the axis of symmetry. A particularly interesting dose has its two functional layers in parallel. The invention is of particular interest for the realization of objects with multiple layers such as preforms or caps. In the examples presented herein, the doses and the objects are of simple geometry, but the invention obviously relates to any geometry of the doses and the object. The objects obtained according to the invention contain a functional layer 3 which forms at least one fold at the level of the periphery of the object. May 52-392-06 obtain objects that also contain a second fold near the axis of symmetry of the object. A zigzag arrangement of the functional layer is obtainable in the object. The invention has been described as 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 dose. 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. Other geometries of the doses can be used.

It has been observed that doses having a part of their concave surface are particularly advantageous. Such geometries of the doses facilitate the good distribution of the functional layer in the object with multiple layers. 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 properties of 52-392-06 hygiene. Alternatively, it is possible that only one end of the barrier layer is not enclosed. 2-392-06

Claims (2)

1. CLAIMS; A dose with multiple layers (1) having an axis of symmetry for the realization of objects with multiple layers by compression molding, constituted by a first synthetic resin (2) and by a thin functional layer (3) enclosed in the first resin (2), the functional layer (3) represents at least 20% of the volume of the dose (1), wherein the functional layer (3) forms the cover of a body of revolution centered around the axis of symmetry and in that the distance from the functional layer (3) to the axis of symmetry is variable. The dose (1) according to claim 1, wherein the ratio (Rmin-RO) / (Rmax-RO) is less than 0.8, Rmax and Rmin are respectively the maximum and minimum distances from the functional layer (3) to the axis of symmetry and RO is the radius of an orifice centered around the axis of symmetry, the value of RO complies with the following relationship: 0 < RO < Rmin. 3. The dose (1) according to any of the previous claims, wherein the functional layer (3) itself forms a structure with multiple layers (3a, 3b, 3c) comprising a layer of barrier resin (3c) enclosed between two layers of adhesive resin (3a, 3b). 4. The dose (1) according to one of the preceding claims, comprising a plurality 52-392-06 of functional layers. 5. A multilayer object obtained by compression molding a dose with multiple layers (1) having an axis of symmetry, the dose (1) is constituted by a first synthetic resin (2) and by a thin functional layer ( 3) enclosed in the first resin (2), the functional layer (3) represents less than 20% of the volume of the dose (1), the functional layer (3) forms the cover of a body of revolution around the axis of symmetry of the dose (1) and the distance of the functional layer (3) to the axis of symmetry is variable. 6. A process for the production of an axisymmetric dose with multiple layers according to any of claims 1 to 4, comprising the step of in which the distance from the functional layer (3) to the axis of symmetry of the dose (1) is varied, the process consists of coextruding a rod or tube with multiple layers of resins in a molten state, then periodically cutting the rod or tube in the molten state, the flow velocity of at least one layer varies periodically, the periodicity of the flow velocity is equal to the periodicity of the cut. The process according to claim 6, wherein the flow velocity of the two layers varies periodically and in phase opposition. 8. A process for the production of a dose 52-392-06 with multiple layers according to any of claims 1 to 4, comprising a step in which the distance from the functional layer (3) to the axis of symmetry of the dose (1) is varied, the process consists of injecting, in the cavity of a mold, a plurality of resins (2, 3) in the molten state, at least one of which is a functional resin (3), the injection of the functional layer (3) is preceded and followed by the injection of at least one resin (2), then in expelling the dose (1) in the molten state of the mold cavity, and in varying the volume of the cavity proportionally to the volume of the injected resin.
2. 2-392-06