Multilayer dose having a concave surface, process for making said multilayer dose and device for manufacturing said multilayer dose

(54) Title: METHOD OF PRODUCTION OF DOSES, OF SYNTHETIC MULTI-LAYER RESIN (51) Int.CI .: B29B 11/10; B29B 11/14 (30) Unionist Priority: 01/03/2004 CH CH 00336/04, 10/04/2004 CH CH 01619/04, 12/08/2004 CH

CH 02034/04, 12/08/2004 CH CH 02033/04 (73) Owner (s): AISAPACK HOLDING SA.

(72) Inventor (s): JACQUES THOMASSET “DOSAGE PRODUCTION METHOD,

OF MULTILAYER SYNTHETIC RESIN. ”

Field of the Invention

The present invention relates to a method for making multilayer objects by molding compression of a multilayer dose.

Prior Art

United States Patent 4,876,052 describes a cylindrical multilayer dose (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 different in nature. For example, the functional resin has good gas barrier properties, so the resin that forms the outer layer is chosen for its mechanical and hygienic properties. These multilayer doses allow multilayer objects to be obtained by compression molding of that dose. However, objects obtained in accordance with the method described in United States Patent 4,876,052 require a large proportion of functional resin in the object, thereby creating two major problems: the first being a prohibitive cost and the second a lowered resistance mechanical stresses. The lack of adhesion between the functional resin and the external resin reduces the solidity of the object and creates a risk of decohesion of the external layer. Another problem with United States Patent 4,876,052 is the fact that the respective amount of resins 2 and 3 is only poorly adjustable, these amounts being fixed by the geometry of the object and by the flows during dose compression.

Japanese Patent JP 2098415 proposes the realization of a multilayer object by compression molding starting from a composite dose (Figure 2), characterized in that the synthetic resin 2 covers only the lateral faces of the functional resin 3. The compression molding of this dose to the along its geometric axis of symmetry it produces an object having a characterized multilayer structure in which the synthetic resin 2 partially encloses the functional resin 3. However, multilayered objects made from two resins, according to Japanese patent JP 2098415, have a number of major problems: the first being that of having 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 being that of requiring an amount of functional resin 3 in the object quantifying at least 30% of the total amount of resin. This produces, on the one hand, objects having a prohibitive cost and, on the other hand, objects having heavily modified mechanical properties, mainly in the center of the object. Another problem with JP 2098415 is the fact that the respective amount of resins 2 and 3 is only poorly adjustable, these amounts being fixed by the geometry of the objects and by the flows during dose compression. Japanese Patent 2098415 has a major final problem, which is the fact that both resins are located at least partially on the surface of the object, which imposes hygiene problems on the resin used.

In patent JP 2098415, it is proposed to use a cylindrical dose containing 3 layers (Figure 3) in order to partially eliminate the aforementioned problems. This dose consists of a first resin that forms the central part of the dose, a functional resin 3, which covers only the side faces of the first resin, and a third resin 2, which covers only the side faces of the functional resin. The grinding of this compound dose along its geometric axis of symmetry produces a multilayer object. The use of a triple layer dose has the advantage of reducing the amount of functional resin 3 used and produces objects having slightly modified mechanical properties in relation to the same object containing a simple resin 2. This method allows an adhesive layer to be added between the resins of a different nature, thereby improving the object's cohesion and solidity. However, functional resin 3 does not cover the central part of the multilayer object, which produces objects without a barrier property close to the geometric 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 layer of barrier resin 3 weakens the performance of the object's barrier and makes this solution less effective. Patent DP 2098415 has a major final problem which is the fact that the three resins are located at least partially on the surface of the object, which imposes hygiene problems according to the resin used.

Purpose of the Invention

The present invention allows multilayered objects to be made by compression molding, by eliminating the aforementioned problems.

Summary of the Invention

The invention consists of a multilayer dose having a geometric axis of symmetry for the realization of multilayer objects by compression molding, said dose consisting of a first synthetic resin, and at least one thin functional layer that forms the surface of a body of revolution, said functional layer being enclosed in the first resin, the multilayer dose being characterized in that no more than one end of said layer is not enclosed in the first resin.

The invention is particularly useful for making multilayer objects intended for use in the packaging field and, more particularly, in the food sector, where hygiene standards are high.

The invention describes multilayered doses that allow packaging or packaging components to be obtained, which have a functional layer totally absent from that packaging wall surface that is in contact with the packaging product.

According to a first embodiment of the invention, the thin functional layer 3 is completely enclosed in the dose-forming resin 2. The obtained multilayer object is characterized in that the functional layer 3 is totally enclosed in the wall of said object, such that only resin 2 is present on the surface of said object.

According to a second embodiment of the invention, the thin functional layer 3 is completely enclosed away from one of its ends, said end being visible on the surface of said dose. The obtained multilayer object, containing an inner face and an outer face, is characterized in that the functional layer 3 is at least absent from one of the faces of the object.

The method for obtaining multilayered objects is described in the present invention.

Detailed Description of the Invention

A better understanding of the invention will be shown below from a detailed description of the examples illustrated by the figures that follow.

Brief Description of the Figures

Figures 1 to 3 describe the multilayer doses described in the prior art for making multilayer objects by compression molding.

Figure 1 shows a double layer dose carried out in accordance with US patent 4 876 052.

Figure 2 shows a double layer dose used in JP 2098415.

Figure 3 illustrates a dose containing 3 layers, described in patent JP 2098415.

Figure 4 shows a first example of a multilayer dose corresponding to the first embodiment of the invention. This cylindrical dose comprises a first functional layer 3 of resin, completely enclosed within the resin 2 that forms the dose.

Figure 5 illustrates a multilayer object realized from the compression in a mold of the dose illustrated in Figure 4. The functional layer 3 forms a fold, and is completely absent from the surface of the object.

Figure 6 illustrates a multilayer dose corresponding to the second embodiment of the invention. This cylindrical dose comprises a thin functional layer of resin 3, an end 5 of which is not enclosed within the resin 2 that forms said dose.

Figure 7 illustrates a multilayered object obtained from the compression in a mold of the dose illustrated in Figure 6. The layer of functional resin 3 is enclosed in resin 2, away from its end 5 which rests embedded with the external surface 11 of said object .

Figure 8 illustrates another example of a multilayer dose according to the first embodiment of the invention. This tubular dose is formed by a thin functional layer 3 totally enclosed within the resin 2 that forms said dose.

Figure 9 shows a tube shoulder obtained by compression in a mold of the dose shown in Figure 8. Functional layer 3 is totally absent from the surface of said tube shoulder.

Figure 10 illustrates another example of a multilayer dose performed in accordance with the second embodiment of the invention. This tubular dose is formed by a thin functional layer 3 partially enclosed within the resin 2 that forms said dose. The end 5 of the functional layer 3 is present on the surface of the dose.

Figure 11 shows a tube shoulder obtained by compression in a mold of the dose shown in Figure 10. Functional layer 3 is totally absent from the inner surface 10 of said tube shoulder, said inner face being in contact with the packaged product . The functional layer 3 is partially absent on the outer surface of the pipe shoulder.

Figures 12, 13, 14 and 15 show other examples of a multilayer dose corresponding to the invention.

Figure 16 shows a first method for performing doses according to the first embodiment of the invention.

Figure 17 illustrates another method for performing doses according to the first embodiment of the invention.

Figure 18 shows a method for making doses corresponding to the second embodiment of the invention.

Figure 19 illustrates another method for performing doses according to the second embodiment of the invention.

Detailed Description of the Figures

The invention describes multilayered doses that are advantageous for making multilayered objects and, in particular, packaging or packaging components. For reasons of hygiene, it is often desirable for the packaged product not to be in direct contact with functional resins. Functional resins can be barrier resins that are used to provide properties that offer impermeability to gases or scents, or adhesive resins that can be used to combine a plurality of resins.

The invention describes multilayered doses that allow packaging or packaging components to be obtained, which can be used in the food sector, the functional layer 3 being totally absent from the packaging surface that is in contact with the packaging product.

According to a first embodiment of the invention, it has been found that a dose having a thin functional layer 3 completely enclosed in a first resin 2 has been particularly advantageous for making multilayered objects having good hygienic properties. The obtained multilayer object is characterized in that the functional layer 3 is completely enclosed in the wall of said object, such that only resin 2 is present on the surface of said object.

According to a second embodiment of the invention, the thin functional layer 3 is completely enclosed, spaced apart at the level of one of its ends, said end being visible on the surface of said dose. The multilayer object obtained by compressing the dose in a mold contains an inner face and an outer face, and is characterized in that the functional layer 3 is at least absent from one of the faces of the object.

A wide variety of multilayer doses can be made according to the invention. Said doses can be of the cylindrical or tubular type, or of more complex geometry.

The invention also relates to methods for carrying out said doses.

The invention likewise describes multilayered objects obtained by compression molding of said doses.

Figure 4 illustrates a multilayer dose corresponding to the first embodiment of the invention. This dose 1 consists of a thin layer of functional resin 3 encased in a resin 2. The thin layer of functional resin 3 contains two free ends 4 and 5 located within the resin 2, said ends being separated from the surface of said dose for a distance 6, 7 sufficient for these ends to likewise be absent from the surface of the shaped object. The functional layer 3 is arranged in such a dose that said layer 3 is distributed throughout the molded object without said layer 3 being visible on the surface of said object. Figure 4 illustrates a dose in which the functional layer describes a cylinder housing centered on the dose-symmetry geometric axis. This dose has the advantage of being easily produced.

Functional layer 3 ideally represents a small part of the volume of the dose or object, the volume of layer 3 being generally less than 20% of the total volume, and preferably less than 10%.

Figure 5 shows the multilayer object obtained from compression in a mold of the dose shown in Figure 4. This object contains the thin functional layer 3 totally enclosed in the wall of said object, said layer 3 forming a fold close to the periphery of said object , said fold and said ends 4 and 5 being totally enclosed in said object.

The relationship between the position of the thin layer 3 in the dose and in the object is defined by the multilayer flow during the compression of that dose in the mold.

It was found that the fold position of the functional layer 3 on the object depends on the radial position of the layer 3 at the said dose; when layer 3 approaches the periphery of the dose, the fold of layer 3 approaches the periphery of the object. If layer 3 is very close to the dose periphery, part of layer 3 is found on the object's surface. There is, therefore, an optimal position of layer 3 in said dose, which leads to the spreading of layer 3 and the formation of a fold close to the periphery of the object, said layer 3 remaining enclosed in the object.

It has also been found that the position of the ends 4 and 5 of the functional layer 3 on the object is little dependent on flows during compression. It has also been observed that it is difficult to enclose the ends of functional layer 3 in the object when this layer is not closed in the dose. Conversely, it has been found that when ends 4 and 5 of functional layer 3 are absent from the surface of the dose, they are likewise absent from the surface of the object. It was likewise observed that a very small distance between the edges of layer 3 and the surface of the dose was sufficient for these edges to be absent from the surface of the object. The distances 6 and 7 of less than 50 microns between the edges of layer 3 and the surface of the dose are sufficient to prevent the edges of layer 3 from being located on the surface of the object.

Figure 6 illustrates a multilayer dose corresponding to the second embodiment of the invention. This dose 1 consists of a thin layer of functional resin 3 encased in a resin 2. The thin layer of functional resin 3 contains two free ends 4 and 5, the first end 4 being completely encased in resin 2 such that the end 4 is totally absent from the surface of said dose, the second end 5 being present on the surface of said dose. The first end 4 is separated from the surface of said dose by a distance 6 sufficient for this end to likewise be absent from the surface of the molded object. The functional layer 3 is arranged in such a dose that said layer 3 is distributed throughout the molded object without said layer 3 being visible on the surface of said object's wall in places where hygiene restrictions are important.

Figure 7 shows a multilayer packaging obtained from the compression in a mold of the dose represented in Figure 6. This packaging has the thin functional layer 3 totally absent from the surface 10 of the said packaging wall that is in contact with the packed product. The functional layer 3 forms a fold close to the periphery of said packaging, said fold and said end 4 being completely enclosed in the packaging wall. The end 5 of the functional layer 3 is present at the level of the outer surface 11 of the packaging, said outer surface 1 not being in contact with the packaging product. Layer 3 is only present on a very small part of the packaging surface, this surface generally representing less than 1% of the total surface area, and preferably less than 0.1% of the total surface area, keeping in mind the small thickness of said layer 3.

A number of multilayer doses corresponding to the first or second embodiments of the invention are described by way of example.

An example of a dose corresponding to the first embodiment of the invention is illustrated in Figure 8. This dose comprises a thin functional layer 3 encased in a resin 2 that forms the dose. The functional layer is closed both laterally and in terms of its ends 4 and 5, such that the functional layer 3 is totally absent from the dose surface. The dose contains an orifice 8 centered on the geometric axis of symmetry.

Figure 9 shows a shoulder of everything obtained by compression in a mold of the dose illustrated in Figure 8. The thin layer 3 is found totally absent from the inner surface 10 and outer 11 of said shoulder, the layer 3 forming a fold at the periphery of the shoulder , and the ends 4 and 5 of said layer being close to the orifice 9 of said object.

Figure 10 illustrates a dose containing an orifice, and performed according to the second embodiment of the invention. This dose 1 consists of a thin layer of functional resin 3 encased in a resin 2. The thin layer of functional resin 3 contains two free ends 4 and 5, the first end 4 being completely encased in resin 2, the second end 5 being present on the surface of that dose.

Figure 11 shows a shoulder of everything obtained by compression in a mold of the dose shown in Figure 10. The thin layer 3 is found totally absent from the shoulder surface 10, said surface being located inside the tube, and in contact with the product. put up. Layer 3 forms a fold at the periphery of the shoulder, and is completely enclosed within the wall of the tube. The end 5 of the layer is present on the outer surface 11, the surface 11 being outside the packaging.

Figure 12 shows another example of a dose that is particularly advantageous for making multilayer objects. The closure of the ends 4 and 5 of the thin functional layer 3 within the resin 2 allows an object to be obtained that is totally devoid of said layer 3 on the surface. These doses are particularly advantageous for making multilayered objects with or without orifice.

Figure 13 illustrates a dose geometry having a cavity at its center. This multilayer dose comprises a thin functional layer 3 staged in a first resin 2 that forms at least 80% of said dose. The end 4 of layer 3 is located at a distance 6 from the surface of the dose, such that, during the compression of said dose, the end 4 of said layer 3 is absent from the surface of the object.

Figure 14 shows a multilayer dose 1 comprising a thin functional layer 3 at least partially enclosed in a first resin 2, said resin 2 representing at least 80% of the dose volume. Layer 3 forms the casing of a body of revolution centered on the geometric axis of symmetry of said dose. According to the first embodiment of the invention, the ends 4 and 5 of the layer are likewise enclosed in the first resin 2, such that layer 3 is completely enclosed in resin 2. According to the second embodiment of the invention, only the end 5 of layer 3 is not encased in resin 2, such that, following the compression of the dose in a mold, only the end 5 of layer 3 is located on the surface of the molded object.

Figure 15 illustrates another example of a dose comprising two thin functional layers 3 'and 3 ”centered on the geometric axis of symmetry of said dose, and at least partially enclosed in a first resin 2. According to the first embodiment of the invention, the layer 3 is completely encased in resin 2, even at the level of its ends 4 ', 5' and 4 ”, 5”. According to the second embodiment of the invention, only the 5 'and 5 ”ends of layers 3' and 3” are not encased in resin 2.

The objects represented in Figures 9 and 11 were made with a thin layer of barrier resin (EVOH) enclosed in a polyethylene (PE) resin. These objects have great impermeability to oxygen and aromas.

In order to simplify the account of the invention, the Figures were deliberately represented with only a functional layer 3 enclosed in a second resin 2. It is known that the combination of only two resins does not generally allow sufficient adhesion to be obtained at the interface between the two resins . It is also customary to use intermediate layers of adhesive, which allow resins of a different nature to be combined, while ensuring a good level of adhesion between the layers. In this way, the insertion of an adhesive layer on either side of the barrier layer prevents possible problems of delamination or decohesion in multilayer objects. The adhesive and barrier layers are parallel and in small quantities. The aggregate of adhesive layers forming the functional layer 3 generally represents an amount of resin less than 15% of the volume of total resin that forms the dose, and preferably less than 10%. The present invention is therefore not limited to doses of 3 layers, as shown in Figures 4, 6, 8, 10, 12, 13 and 14, but generally contains 5 layers or more.

The resins used within the scope of the invention correspond to the thermoplastic resins currently being used, and, more particularly, those used in the packaging industry. Among the barrier resins that can be used to form functional layer 3 there may be cited ethylene vinyl alcohol copolymers (EVOH), polyamides such as Nylon-MXD6, acrylonitrile-methylacrylate copolymers (BAREX), fluorinated polymers such as PVDF. In this set, a few resins can also be mentioned that can be used to form the structure 2 of the object: polyethylene (PE), polypropylene (PP), polystyrene (PS), polyamide (PA), polyester (PT). This list is not exhaustive. When choosing resins, it is important to select products that have approximate viscosities. In general, it is preferable to use resins that, at operating 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 multilayer dose of synthetic resins in the molten state into a mold cavity, forming the object by compression molding the said dose into the cavity of said mold, cooling the object and then , removing it from the mold.

The invention also allows the realization of objects having a very thin functional layer, whose functional layer can represent less than 5% of the object's volume.

The method for making multilayer objects that is placed below is particularly advantageous for making objects such as plugs, caps, preforms, or indeed, pipe bosses. This method can likewise advantageously be used to make preforms in the form of a plate, these plates then being used in thermoforming or blow thermoforming to form multilayered objects.

The doses previously presented can be performed according to a number of methods.

A first method consists of coextruding the resins to form a multilayer structure, and at least the functional layer 3 being extruded intermittently.

An example of this method is illustrated in Figure 16. A multilayer rod is coextruded continuously, the flow of functional layer 3 being periodic and intermittent, the periodicity of layer 3 of the cut of said rod being identical. This method is particularly advantageous for carrying out high-speed multilayer doses. This method is advantageously used to carry out doses with the functional layer 3 totally enclosed in the resin 2.

A second example of carrying out multilayer doses according to this first method is illustrated in Figure 17. A multilayer rod is coextruded discontinuously, such that the total flow of coextruded resin fluctuates between a maximum value and a zero value, the amount of material dosed for a period corresponding to a dose. Functional layer 3 is fed for a shorter time than resin 2, such that the ends of layer 3 are enclosed in resin 2.

A second method for producing a multilayer dose according to the invention consists of closing at least one end of layer 3 in resin 2, said closing being carried out outside the extrusion die.

An example of this second method is illustrated in Figure 18. A cutter 9 periodically cuts the multilayer flow as it leaves the extrusion die 9, thereby forming doses 1. Dose 1 contains a functional layer 3 enclosed in resin 2, spaced at the level of the end 5 of said layer 3. The end 4 of said layer 3 is enclosed in resin 2, the closure being carried out during the cutting of the multilayer rod by the cutter 9. The geometry of the cutter 9, combined with the cutting movement of said cutter, restricts some resin 2, which proceeds to close the end 4 of layer 3.

Another example of carrying out multilayer doses according to the second method is illustrated in Figure 19. The doses are formed from a tubular multilayer flow. After leaving the extrusion die 8, the cutter 9 periodically cuts the dose 1, and together ends the end 4 of the functional layer 3 in the resin 2.

Similar methods can be used to enclose one or both ends of layer 3 in resin 2. These methods can be applied during dose cutting, during transfer in the mold cavity, or within the molding device. These methods have a common element, which consists of modifying the original geometry of the dose in order to restrict resin 2 and enclose the end of layer 3.

In the examples that are presented here, doses and objects are of simple geometry, but the invention obviously refers to any dose and object geometry.

The objects obtained according to the invention contain a functional layer 3 forming at least one fold 10 at the level of the periphery of the object. Objects also containing a second fold near the object's symmetry geometric axis can be obtained. A zigzag arrangement of the functional layer is obtainable on the object.

Numerous functional layer 3 arrangements in the 15 dose are possible. It may be advantageous to arrange the functional layer 3 in the dose such that said functional layer 3 forms the casing of a body of revolution centered on the geometric axis of symmetry. When the distance from functional layer 3 to the geometric axis of symmetry is variable, advantageous multilayer objects 20 can be obtained.

Doses comprising a plurality of functional layers 3 can also be used, said functional layers all being centered on the geometric axis of symmetry of said dose. The obtained multilayer objects are characterized in that two functional layers are placed at least partially on top of each other, and each forms at least one fold.

Other dose geometries can be used. It has been found that doses that have a part of their concave surface are particularly advantageous. Such dose geometries facilitate good distribution of the functional layer in the multilayer object.

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