MXPA06010027A - Synthetic multilayer object - Google Patents

Abstract

The invention relates to a multilayer axisymmetric object which forms a wall having thickness E and comprises a first resin forming the object structure and constituting at least 80%of the volume thereof and a second resin forming at least two functional layers which are separately entrapped in the first type of resin. The inventive multilayer structure is characterised in that (a) the functional layers are distributed in the distinct portions of the object, (b) the functional layers form the bodies of rotation centred on the axis of symmetry of the object and (c) the two functional layers are partly superimposed in a direction perpendicular to said wall.

Description

WO 2005/084902 Al 111 lili II lilili lllll lllll ill lili européen (AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, Fl, - l'avant du délai prévu pour expiration the modification des FR , GB, GR, HU, IE, IS, IT, LT, LU, MC, NL, PL, PT, RO, revendications, will republiée if des modifications SONL Lésé, SI, SK, TR) AIPO (BF, BJ, CF, CG, Cl, CM, GA, GN, GQ, GW, ML, MR, NE, S TD, TG). In what concerns the codes? deux lettres et autres abréviations, référer aux "Notes explicatives relative aux codes el Publiée: abréviations "figurant au dé.bui de. - avec rapporl de recherche inlernationale the Gazette du PCT.

SYNTHETIC OBJECT WITH MULTIPLE LAYERS FIELD OF THE INVENTION The present invention relates to a method for making objects with multiple by compression molding a dose with multiple layers.

PRIOR ART US Patent 4,876,052 describes a multi-layered object (Figure 1), wherein a first synthetic resin 3 is completely enclosed within a second synthetic resin 2. This multi-layered object is obtained by compression molding of a compound dose, in which the first resin is completely enclosed in the second resin. The multilayer structure described in US Pat. No. 4,876,052 is particularly interesting for objects such as receptacles or covers. 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 diminished resistance to mechanical stress. The lack of adhesion between the functional resin and the external resin reduces the strength of the 52-390-06 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. This method likewise requires the intermittent extrusion of the first resin into the second resin. US Pat. No. 4,876,052 discloses a co-extrusion device having a shut-off valve mechanism for the first synthetic resin. To eliminate the disadvantages of the US 4,876,052 patent, Japanese patent JP 2098415 proposes the realization of a multi-layered object by compression molding, starting from a composite dose, characterized in that the second synthetic resin covers only the side faces of the first synthetic resin. The compression molding of this dose along its axis of symmetry, produces an object having a structure with multiple layers (Figure 2), characterized in that a first resin 2 partially encloses a second resin 3. However, the objects With multiple layers made of two resins according to the patent JP 2098415, they have two disadvantages 52-390-06 principal: the first is that they have the barrier 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 barrier resin 7 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 mechanical properties modified to a large extent, mainly at 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 dose with triple layer in order to partially eliminate the disadvantages mentioned above. This dose is constituted by a first resin 4 that forms the central part of the dose, by a second resin 3, covering only the side faces of the first resin, and by a third resin 2 covering only the side faces of the second resin. Compression of this compound dose along its axis of symmetry produces an object with multiple layers (Figure 3). The use of a triple layer dose has the advantage of reducing the amount of functional resin 3 used and produces objects that have 52-390-06 slightly modified mechanical properties, in relation to the same object that contains a single resin 2. However, the second resin 2 does not cover the central part of the object with multiple layers, which produces objects with multiple layers without property of barrier near the axis of symmetry. 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. Patent application CH01619 / 04 discloses objects with multiple layers (Figure 4) made from a multilayer dose molded by compression. 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 adhesive can be added between the resin that forms the surface of the object and the functional resin, however, the compression of the dose requires a method and a specific molding device.This method requires, in particular, additional movements of the tool. of the matrix in relation to the process of 52-390-06 basic compression, adjusting the two parts of the mold in relative motion. In the case of high speed molding, it can be detrimental to use a compression device as described in the patent application CH01619 / 04. Patent EP926078 describes obtaining a liner of a plug (Figure 5) by compression molding a dose containing a layered structure with multiple layers. The functional resin 3 forms strips dispersed in the resin 2. The method consists of extruding a laminar dose (of the thousand leaf class) with a device that generates a strip, then compressing the dose to form the coating. In the thickness of the coating (figure 5), there is a structure with multiple layers of the thousand leaf type. This method consists of the compression molding of a lamellar alloy, the number of strips in the dose is very large in number. This method has the disadvantage of requiring a high percentage of barrier resin (of the order of 20%), in order to significantly reduce the permeability of the object, since the strips do not form a continuous layer. Another disadvantage of the patent EP926078 lies in the fact that the position of the strips in the object can not be controlled. The result is that the resin that forms the surface layer of the object with multiple layers is a 52-390-06 mix of different layers that form the dose. This can limit the use of the objects described in patent EP926078, for reasons of hygiene, when the packaged product is in contact with a lamellar object with multiple layers. Another disadvantage of patent EP926078 relates to the limited choice of resins, which must exhibit viscosities and melting temperatures that allow the strips to be maintained during compression of the dose.

OBJECT OF THE INVENTION The invention relates to the realization of objects with multiple layers, made by compression molding a dose with multiple layers, while allowing the elimination of the aforementioned disadvantages.

SUMMARY OF THE INVENTION The invention consists of an axisymmetric object with multiple layers forming a wall of thickness E, the object is composed of a first resin that forms the structure of the object and that represents at least 80% of the volume of the object, and of a second resin forming at least two thin functional layers, the functional layers are separately enclosed in the first resin, the multi-layer structure is characterized in that 52-390-06 a. the functional layers are distributed in separate parts of object b. the functional layers form bodies of revolution centered on the axis of symmetry of the object c. the two functional layers are partially placed one on top of the other in a direction perpendicular to the wall.

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

BRIEF DESCRIPTION OF THE FIGURES Figures 1 to 5 illustrate objects with multiple layers of the prior art. Figure 1 shows an object with multiple layers described in the patent US4876052. This object 1, made by compression molding, comprises a functional resin layer 3 completely encapsulated in a resin 2 that forms the visible surface of the object. Figure 2 illustrates an object with multiple layers described in patent JP2098415. This object 1 comprises a functional resin layer 3 partially encapsulated in a resin layer 2 which forms the visible surface of the 52-390-06 obj eto. Figure 3 shows another object with multiple layers described in patent JP2098415. This object comprises a thin layer of functional resin 3 enclosed between two layers of resins 2 and 4 which form the object. Figure 4 shows an object with multiple layers described in the application CH01619 / 04. This object is characterized by the double zigzag-shaped fold of the functional layer 3. Figure 5 shows an object comprising a layered structure with multiple layers described in patent EP926078. Figures 6 to 11 show objects with multiple layers corresponding to the invention. Figure 6 illustrates a first object with multiple layers that make up the inventive concept. The structure with multiple layers is observed in a sectional plane that passes through the axis of symmetry of the object.

The functional layers 3, 5 and 7 form a superposition. Figure 7 shows a second example of an object with multiple layers having a central surface area S not covered by the functional layers. Figures 8 and 9 illustrate objects made in accordance with the invention and having an orifice 15. Figure 10 shows a plug with multiple 52-390-06 layers, made according to the invention. Figure 11 shows a preform with multiple layers made according to the invention. Figure 12 illustrates the flow profile during compression of the dose. Figure 13 shows the method for obtaining objects with multiple layers and, in particular, the relationship between the dose and the object. Figure 14 shows how the S / Sp ratio of the surface area not covered by the functional layer over the surface area of the object varies as a function of the compression speed H / E. Figure 15 illustrates the embodiment of an object according to the patent JP 20418415. Figure 16 shows how the ratio S / Sp varies as a function of H / E for an object realized according to the patent JP 20418415. Figure 17 shows another example of the embodiment of an object according to the invention.

DETAILED DESCRIPTION OF THE FIGURES The invention relates to an object with multiple layers that has at least two independent layers of a functional resin distributed in a thin layer in a second resin that forms the structure of the object, the 52-390-06 layers are distributed in separate parts of the object and form a partial overlap. The term "functional resin" designates a resin chosen for its barrier properties with respect to gases or aromas. Figure 6 illustrates an object with multiple layers corresponding to the invention. The thickness of the object is observed along a section made perpendicular to the surface of the object and passing through the axis of symmetry. This figure shows the distribution of the functional layers in the thickness of the part. The functional resin forms the thin layers 3, 5 and 7 distributed in the base resin forming the structural layers 2, 4 and 6 of the object. The amount of functional resin generally represents less than 10% of the total volume of the resin. In order to obtain advantageous barrier properties, it was observed that the functional layers had to be placed partially on top of each other, to form the superposition L. In a preferred embodiment (not illustrated), a value of the superposition L varying between 1 and 3 times the thickness E, allows that a permeability is obtained, which is close to that obtained with a single continuous layer of identical thickness. In Figure 6, the central part of the object is formed by the layer 7 of the functional resin. The amount of the functional resin that forms the central layer 7 of the object represents less than the 52-390-06 5% of the total volume of the resin and generally less than 3%. The central layer 7 of the functional resin is present on a surface area S that represents less than 3% of the total surface area of the object, and preferably less than 1%. The ends 9, 10 and 11 of the resin functional layers 3, 5 and 7 are located close to the upper and lower surfaces of the object, the ends of the layers mentioned above can be flush with the surface of the object or be completely encapsulated . The functional layers 3, 5 and 7 respectively form the folds 12, 13 and 14. The fold 12 of the layer 3 is generally located close to the side wall of the object, to have impermeability properties over the entire surface of the object. In certain cases, it is not necessary to make the entire surface of the object impermeable, in which case the invention allows the layer 3 to be dispersed only in the part in which the object must be impermeable. The folds 13 and 14 of the resin functional layers 5 and 7 are placed one on top of the other at the ends 9 and 10 of the functional layers 3 and 5 and form an overlap. The superposition of the functional layers allows a good level of impermeability to be ensured, despite the discontinuity created by the different layers. Figure 7 shows a second example of a 52-390-06 object with multiple layers made according to the invention, this object is distinguished from the object presented in figure 6 by its central part. The object presented in figure 7 shows the arrangement of the independent functional layers 3, 5 and 7 in the resin layers 2, 4, 6 and 8 which form the structure of the object. The resin functional layers 3, 5 and 7 form the respective folds 12, 13 and 14. The folds 13 and 14 are placed one on top of the other at the ends 9 and 10 of the resin functional layers 3 and 5 and form an overlay by which a good level of impermeability can be ensured. The ends 11 of the functional resin layer 7 do not cover the central part of the object, leaving a permeable surface area S. It was found that the leak created by the surface area S is very small, considering the S / Sp ratio of the surface area not covered by the functional layers over the total surface area exposed. The invention allows an S / Sp ratio of less than 2% to be obtained, which produces negligible leaks. Figure 8 illustrates a third object with multiple layers made according to the inventive method. This object 1 contains a central hole 15, as well as two thin layers 3 and 5 of functional resin distributed between the layers 2, 4 and 6 of the resin forming the structure of the object. Functional layers 3 and 52-390-06 5 form the folds 12 and 13, the fold 13 is superimposed with the ends 9 of the functional layer 3. Figure 9 shows another example of an object with multiple layers, having a hole. This object differs from the object presented in Figure 8 by the orientation of the folds 12 and 13 of the resin functional layers 3 and 5. The method for making objects with multiple layers which is set forth below is particularly advantageous for realizing objects such as plugs, covers, preforms or actually flanges for tube. This method can likewise be advantageously used to make preforms in the form of a plate, which plates are then used in thermoforming or thermoforming by blowing to form objects with multiple layers. Figure 10 illustrates a structure with multiple layers that can be obtained in a geometry of a plug-type object and Figure 11 shows a multilayer preform made in accordance with the invention. These objects have a partial overlap of the resin functional layers, by means of which the objec- tiveness of the object can be ensured. Figure 10 shows that functional layer 3 is generally the combination of three parallel thin layers 52-390-06 3a, 3b, 3c, the layers 3b and 3c are adhesive layers located on either side of the barrier layer 3a. This combination 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 objects with multiple layers. The adhesive and barrier layers lie 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%. The method for making objects with multiple layers according to the invention is particularly advantageous, since it requires very little modification of existing devices. As will be shown further below, this method allows objects with multiple layers to be produced at a high production speed. The method consists in coextruding a tubular or cylindrical dose with multiple layers, feeding this dose with multiple layers in the molten state in a compression device, then compressing the dose in a mold to form the object, this method is characterized by the geometry of the dose with multiple layers (height, 52-390-06 diameter) and the position of the functional layers in the dose. In order to gain a better understanding of the spirit of the invention, it is necessary to hold the link connecting the dose with multiple layers with the object with multiple layers. Figure 12 shows the flow of the resins during compression of the dose. This flow is mainly dependent on the rheological properties of the resins during compression, as well as the geometry of the object. Figure 12 shows that this flow is faster halfway between the walls than near the walls of the die tool. Next to the walls of the tool of the matrix, the speed of displacement of the particles tends towards zero, but the deformation by the shear stress is high. Conversely, halfway 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 suffered during the flow. Figure 13 shows the dose with multiple layers 52-390-06 16 used to make an object with multiple layers 1. A cylindrical dose 16 corresponding to a portion of the coextruded multi-layer rod, comprises two thin layers 3 and 5 of the functional resin enclosed between the layers 2, 4 and 6 of the base resin. The dose 16 corresponds to a radial stacking of the tubular layers, the central layer 6 is cylindrical. The proportion of the functional resin does not generally exceed 20% of the volume of the dose, and this amount is generally less than 10%. The compression of this dose generates a flow of resin towards the periphery, which drags and deforms the functional layers 3 and 5 in this direction. The object obtained with multiple layers 1 is illustrated in figure 13. In this object can be found the resin functional layers 3 and 5 which form a fold in the direction of flow, the fold 13 of the functional layer 5 which forms a superposition L with the end 9 of the functional layer 3. The value of the superposition L and the dispersion of the fold 12 outside the end of the object are related to the original geometry of the dose and to the position of the functional layers in the dose. To obtain an object with multiple layers as illustrated in Figure 13, it is necessary to place the resin layers 3 and 5 correctly in the dose. The geometry of the dose and the position of the functional layers in the dose can be defined by calculation or experimentally. It is noted 52-390-06 experimentally that the ratio of the radial positions Ri and Rj of the two adjacent functional layers i and j is constant and less than or equal to 0.5, layer i is located closer to the axis of symmetry than layer j. Object 1 illustrated in Figure 13 has a central surface area S not covered by the functional layer. The S / Sp ratio, which corresponds to the ratio of the uncovered surface area to the surface area of the object, is presented in Figure 14. It has been found that this relationship depends on the rate of compression of the dose, i.e. of the Hl / E ratio, Hl corresponds to the height of the dose and E to the thickness of the object. Figure 14 shows how the ratio S / Sp varies as a function of Hl / E. It was observed experimentally that for compression speeds of 5, the S / Sp ratio of object 1 was less than 10%, and for a compression speed of 10, this ratio was less than 2%. This result indicates that for a compression velocity of 10, the surface area S that generates a leak represents less than 2% of the surface area of the object. In order to show the advantage of the objects made according to our invention, these have been compared with objects obtained according to the method described in patent JP 2098415. Figure 15 illustrates the compression of a dose 52-390-06 such as the proposal in patent JP 2098415 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 15 shows a triple layer dose 16 made in accordance with patent JP 2098415. This dose contains a first resin 4 forming the central part of the dose, a functional resin 3 covering only the side faces of the first resin, and a third resin 2 covering only the side faces of the functional resin. Figure 15 illustrates the object 1 obtained after compression of the dose 16. The functional layer 3 has been dispersed outside the end of the object, while remaining encapsulated at the periphery of the object. As shown in Figure 15, the functional layer has not been dispersed in the central part of the object 1. The experimental findings corresponding to the realization of objects with multiple layers according to the patent JP 2098415 have been plotted in figure 16. Figure shows how the fraction of the surface area not covered by the functional layer S / Sp varies as a function of the compression speed H / Hl. it is observed experimentally that for compression speeds of 5, the S / Sp ratio of object 1 is greater than 25%, and for a compression speed of 10, this ratio is close to 20%. This finding indicates that for a speed of 52-390-06 i compression of 10, the surface area S that generates a leak represents approximately 20% of the surface area of the object. The barrier properties of the objects realized in accordance with patent JP 2098415 (figure 15) and according to the invention (figure 13) have been compared. Discs 1 mm thick and 40 mm in diameter were made, starting with a dose with multiple cylindrical layers of height Hl close to 10 mm and of a diameter substantially equal to 12.7 mm. The base resin used is an HDPE (high density polyethylene), the functional resin used is an EVOH (ethylene vinyl alcohol). The measurement of oxygen permeability shows that objects made according to the invention are approximately 5 to 10 times more barrier formers than objects made according to patent JP 2098415. In both cases, 8% of the resin was used functional. The superposition L of the functional layers is approximately 1 mm. Figure 17 illustrates a second example of making objects with multiple layers. A dose 16 comprises resin functional layers 3, 5 and 7 encapsulated laterally in the resin layers 2, 4 and 6. The functional resin layer 7 forms the central part of the dose. This dose is made from a rod that has been coextruded and 52-390-06 cut periodically as you leave the coextrusion head. This dose is then transferred into a compression mold, then compressed. The vertical compression of the dose 16 along its axis of symmetry produces the object 1 shown in FIG. 17. The functional resin layer 7 makes the central part of the object impermeable. The method for making objects with multiple layers according to the invention requires the realization of doses with multiple layers. A first method consists of coextruding a rod or tube with multiple layers at a constant flow rate and periodically cutting the rod or tube, as the tool leaves the matrix, in order to form the doses. This first method can be advantageous for making objects with multiple layers at high speed. A second method consists of forming the doses by virtue of a discontinuous periodic flow, the amount of material coextruded during a period forms a dose. This second method can be advantageous for obtaining doses with multiple layers that have a great regularity in terms of weight. The dose can be cut according to known methods. In this regard, for example, rotary cutters can be cited to cut the rod as it leaves the extruder. This type of cutter can 52-390-06 used simultaneously to transfer the dose to the mold. A method for cutting the dose by closing the extrusion duct is used in discontinuous extrusion devices. The transfer of the dose can be carried out by known methods, such as 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 precisely aligned with the axis of symmetry of the mold cavity. The doses are compressed along the axis of symmetry of the dose. 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 cooled at least partially in the mold before ejection. 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 layers 3, 5 and 7, mention may be made of copolymers of 52-390-06 ethylene vinyl alcohol (EVOH), polyamides such as Nylon-MXD6, acrylonitrile-methyl acrylate copolymers (BAREX), fluorinated polymers such as PVDF. In relation to this, there are also a few resins that can be used for layers 2 and 4, 6 and 8 that form the structure of the object: 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 devices used in the realization of the objects in accordance with the invention are known. The device comprises at least means for coextruding doses with multiple layers, means for transferring the dose with multiple layers in a compression mold, and means for compressing the dose to form the object. The invention has the advantage of allowing the production of objects with multiple layers at a high production speed, without substantial modifications in relation to a device used in the realization of objects with a single layer. The invention requires replacement, in 52-390-06, of the extrusion device with a single layer by means of an extrusion device with multiple layers. In the examples presented herein, the doses and objects are of a simple geometry, but the invention obviously relates to any geometry of the dose and the object. The objects obtained according to the invention contain at least two functional layers, each one forming a fold and being. partially placed one on top of the other. The invention also allows objects to be obtained that contain a plurality of functional layers placed one on top of the other, each of which is capable of forming more than one fold. Functional layers are obtained in zigzag form. Numerous arrays of functional layers in the dose are possible. It can be advantageous to couple the invention to a particular arrangement of the functional layers, the arrangement is characterized in that the functional layer has a variable distance to the axis of symmetry. According to this variant, at least one functional layer forms a cover of a body of revolution centered on the axis of symmetry, and the distance of the layer to the axis of symmetry is variable. Other geometries of the dose can be used. It has been observed that doses that have a part of their 52-390-06 concave surface are particularly advantageous. Such geometries of the doses facilitate the good distribution of the barrier 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 layers are not in direct contact with the packaged product. It may be advantageous to enclose the functional layers completely in the dose, so that the functional layers are totally enclosed in the object. Alternatively, it is possible that only one end of the barrier layer is not enclosed. 2-390-06

Claims (2)

1. CLAIMS; 1. An axisymmetric object with multiple layers that form a wall of thickness E, the object is composed of a first resin that forms the structure of the object and that represents at least 80% of the volume of the object, and a second resin that forms at least two thin functional layers, the functional layers are enclosed separately in the first resin, the structure with multiple layers is characterized in that d. the functional layers are distributed in separate parts of the object e. the functional layers form bodies of revolution centered on the axis of symmetry of the object f. the two functional layers are placed partially on top of each other in a direction perpendicular to the wall. 2. The object according to claim 1, wherein the distance of the overlap is at least equal to the thickness E of the object. 3. The multi-layer object according to claim 1 or 2, wherein the functional layers themselves form a multilayer structure comprising a layer of barrier resin enclosed between two layers of adhesive resin. 4. The object according to any of the 52-390-06 previous claims, wherein the first resin represents at least 85% of the volume of the object. 5. A multilayer object obtained by compression molding a dose with multiple layers, the dose with multiple layers in a radial stack of a plurality of layers, contains at least 2 thin functional layers enclosed between the layers composed of a first resin , the layers constituted by the first resin represent at least 80% of the volume of the dose, the distance of the first layer to the axis of symmetry is less than or equal to half the distance of the second layer to the axis of symmetry. 6. A dose with multiple layers with an axis of symmetry for the realization of objects with multiple layers by compression molding, the structure with multiple layers consists of a radial stack of a plurality of layers, the structure with multiple layers contains at least 2 layers. fine functional layers enclosed between the layers composed of a first resin, the structure with multiple layers is characterized in that a. the layers constituted by the first resin represent at least 80% of the volume of the dose b. the distance of the first layer to the axis of symmetry is less than or equal to half the distance of the second layer to the axis of symmetry. 52-390-06 7. The multilayer dose according to claim 6, wherein the functional layers themselves form a multilayer structure comprising a layer of barrier resin enclosed between two layers of adhesive resin. The dose with multiple layers according to any of claims 6 and 7, comprising at least three functional layers, wherein the ratio of the radial distances between two neighboring layers is less than or equal to 0.5.
2. 2-390-06