WO2015059020A2

WO2015059020A2 - Hot runner assembly for injecting a polymeric article and method for producing such article

Info

Publication number: WO2015059020A2
Application number: PCT/EP2014/072190
Authority: WO
Inventors: Arnaud Gerbaulet; David NORDQVIST; Daniel Abegglen; Stéphane PELLEGRINI
Original assignee: Nestec S.A.
Priority date: 2013-10-22
Filing date: 2014-10-16
Publication date: 2015-04-30
Also published as: WO2015059020A3; EP3060497A2

Abstract

The present invention relates to a hot runner assembly comprising a valve member (16) having a generally annular form to be displaceable through at least an annular portion of the inner flow channel (15) the inner and nozzle gates (21, 19) also form annular openings. The invention also relates to a co-injection moulding assembly comprising the hot runner assembly and a method for producing a ring-shaped or hollow polymeric article.

Description

Hot runner assembly for injecting a polymeric article and method for producing such article

Field of the invention

The invention relates to the production of multi-layer articles by injection of polymers. The invention more particularly relates to the production of ring-shaped or hollow articles such as parts of food or beverage packaging products requiring improved gas impermeability. The invention further relates to an injection runner assembly, a co- injection moulding apparatus and a method for producing a polymeric article.

Background

It is known to produce a multi-layer polymeric container exhibiting high

impermeability to oxygen. The container is generally formed of a core layer of EVOH which has good gas barrier properties and an external shell of a different polymer(s) such as polypropylene (PP). In order to preserve the oxygen barrier properties of EVOH, it is important to protect it from external moisture. Therefore, it is preferable to encapsulate the EVOH layer from all sides by the external polymer.

For example, WO810023QA1 relates to such a multi-layer container obtained by blow moulding. Unfortunately, this method is not adapted for producing generally ring- shaped or tubular articles. This method is also complicated as it requires the production of a parison by properly controlling multiple flow steps and an additional step for inflating the parison in a blow moulding cavity to form the final article.

EP1 123241 B1 relates to a hot runner method of co-injection of a multi-layer food packaging products with a protected inner (e.g., EVOH) layer. The method is simpler since it does requires the making of a parison. However, an injection sprue is necessarily produced which so creates loss of material and an additional operation for its removal without exposing the inner layer to ambient.

EP1426160B1 also describes a hot runner assembly comprising an outer flow channel for delivering a first molten material and an inner flow channel for delivering

l a second molten material (e.g., a barrier, recycled or coloured material) and a pin valve which is selectively displaced in the inner channel and up to the nozzle gate for controlling the injection of the first and second molten materials sequentially or successively. However, the assembly, as described, is able to produce packaging products with a "closed" bottom only.

As described in US2006051548A1 , it is also possible to produce articles (such as sockets) of bi-material structure with inner soft material such as EVOH by injection- moulding. The injection moulding tool is shaped in such a way that, after injecting the soft material and opening the tool, a sprue is formed of the material. Therefore, when the sprue is removed, the inner soft material becomes exposed to the external moisture at the cut line. The gas barrier properties of the articles can so deteriorate rapidly. Furthermore, there is a great loss of material and an additional step for removing the sprue is required.

WO2012009656A1 relates to moulded containers with improved gas impermeability. However, the nozzle assembly suitable for producing the container is complex and it enables to produce only containers with a protected gas barrier inner layer with a closed bottom.

EP1504873A1 relates to an injection moulding method and apparatus from a thermoplastic material, more particularly, with a minimum of weld or fusion lines within the molded product. JP H 10-16005A relates to a valve gate for injection moulding device. The problem to be solved is for manufacturing a perforated molding in a satisfactorily finished shape. US20100007058A1 relates to an injection moulding apparatus having aligned pin and sleeve and a method of operation. The invention deals with the challenge to locate the mould gate of an injection moulding apparatus that will be used to injection mould the product.

EP2418065A1 relates to an in-mould labelled container. US20140272283 relates to a technique to mould parts with injection-formed aperture in gate. Methods and systems for co-extruding multiple polymeric material flow streams into a mould cavity to produce a moulded plastic article having an injection- formed aperture in gate region of the article are disclosed. However, there is no displaceable valve member which could have a generally annular form.

Therefore, there is a need for producing a multi-layer article of ring or hollow shape more simply and without loss of polymer material while maintaining the inner layer fully embedded and protected in the polymer external structure.

Summary of the invention:

The invention is defined in its generality in the appended claims. In a first aspect the invention relates to a hot runner assembly for injecting a polymeric article with an outer layer formed from a first molten material and an inner layer embedded in the outer layer and formed of a second molten material;

comprising a body, a flow splitter separating an outer flow channel for delivering the first molten material and an inner flow channel for delivering the second molten material; an inner gate downstream the inner flow channel; a nozzle gate

downstream the inner gate and outer flow channel; a valve member displaceable from at least a first position of opening of the outer flow channel and closing of the inner flow channel or inner gate for enabling the first molten material to flow from the outer flow channel through the nozzle gate only and a second position of opening of both channels for enabling the first and second materials to flow from the outer and inner channels through the nozzle gate, wherein the valve member has a generally annular form to be displaceable through at least an annular portion of the inner flow channel and wherein the inner and nozzle gates also form annular openings. This arrangement of the hot runner assembly enables to controllably inject the first and second materials sequentially and/or simultaneously directly into the mould while forming an inner layer of annularly continuous arrangement in the article and which is further covered by all sides/surfaces with the outer layer, and while also preventing the formation of any significant loss of material. More particularly, the valve member is further arranged and dimensioned complementarily to the opening of the nozzle gate for closing it in a third position and preventing the flow of molten material from any of the flow channels.

The assembly preferably further comprises an inner core member in the bore formed by the annular valve member. The valve member is arranged slidably and

concentrically with respect to the inner core. The inner core member, preferably non- moving, provides guidance for the displaceable valve and participates to the tight injection engagement of the nozzle gate with the mould.

Preferably, the inner core member delimits inwardly both the annular opening of the inner gate and the annular opening of the nozzle gate. Also the body preferably delimits outwardly the annular opening of the nozzle gate. Therefore, this

arrangement reduces the number of pieces in the hot runner assembly while maintaining a high precision in the definition of the flow openings necessary to achieve the proper arrangement of embedded and layered structure.

Preferably, the valve member forms a staggered configuration with successive annular portions of progressively reduced section (e.g., diameters) which are complementary shaped to said openings for closing the latter. Such configuration enables to control with a single member the opening of the inner and nozzle gates. Furthermore, this configuration further simplifies the arrangement of the hot runner assembly (i.e., reduces the number of pieces) and participates to maintain

compression on the molten material and to control the flows and their distribution.

In a second aspect, the invention relates to a co-injection moulding apparatus for producing the polymeric article comprising a hot runner assembly as aforementioned and an injection mould assembly comprising a moulding cavity arranged in communication with the nozzle gate.

In a third aspect, the invention relates to a method for producing a polymeric article comprising an outer layer formed of a first molten material and an inner layer embedded in the outer layers and formed of a second molten material by the co- injection moulding apparatus as aforementioned, wherein it comprises the steps of:

- Injecting first molten material in the moulding cavity by placing the valve member in the first open position,

- Co-injecting first and second molten materials in the moulding cavity by displacing the valve member in second open position so that the second molten material forms an inner layer embedded in the first molten material forming the outer layer,

- Cooling the article in the moulding cavity and removing the article from the moulding apparatus when solidified.

The first molten material can be selected amongst polyolefin, thermoplastic elastomer, polyamide, thermoplastic polyester and thermoplastic polyester elastomer. More preferably, the first molten material is polyolefin such as PE or PP.

The second molten material can be a coloured, a reinforced, a recycled or functional polymer. For example, the second molten material can be selected amongst the group consisting of: polyamide (PA), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), ethylene vinyl alcohol (EVOH), polyvinylic alcohol (PVOH or PVA), polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polybutylene napthalate (PBN), polyethylene naphtalate (PEN), polyoximethylene (POM), polyphenylene sulfide (PPS) and fluorothermoplastic material.

Preferably, the second molten material is a gas barrier polymer, in particular, EVOH.

The first and second molten materials are selected to ensure compatibility during injection, in particular, on their viscosities of surfaces in the molten state. This selection of compatibility falls within the competences of the skilled person in the art.

The invention further relates to an article as obtained or obtainable by the

aforementioned method wherein it forms at least part of a body of beverage capsule intended for producing a beverage. In particular, before injection, at least an overlapping portion of a packaging or body member is inserted in or against a surface of the injection mouling cavity to enable the polymeric article to be injected over or against said portion of the packaging member. In a mode, the article forms a cup-shaped body of a beverage capsule extending at its open end by an outwardly projecting flange and comprising a bottom end with a central through-hole for forming the beverage outlet of the capsule.

The invention further relates to a composite cup-shaped container comprising said article wherein it comprises a formed body member and the article comprises an outwardly projecting flange and a binding portion which is attached to an overlapping portion of a formed body member.

Brief description of the figures: Figure 1 shows a general view of a co-injection moulding apparatus of the invention for moulding a ring shaped article;

Figure 2 shows a cross sectional view of the apparatus of figure 1 with the valve member in closure position of the nozzle gate;

Figure 3a, 3b, 3c show successive operations of the method according to the invention;

Figure 4 is a perspective view of the ring-shaped article as obtainable, respectively obtained, by the method of the invention;

Figure 5 shows a detailed cross section view of the article of figure 4;

Figure 6 shows a cross sectional view of the apparatus of the invention for moulding the body of a beverage capsule;

Figure 7 shows the body of the beverage capsule as obtainable by the method of the invention;

Figures 8 and 8A are respectively a cross section view and an enlarged view of the body of the capsule of figure 7; Figure 9 shows a cross sectional view of the apparatus in configuration for producing a composite container;

Figure 10 shows a detail of the container as obtained by the apparatus of figure 9; Figure 1 1 shows in cross section a detail of the container of figure 10. Description of the preferred modes:

Referring to Figure 1 , a co-injecting moulding apparatus 1 of the invention is represented according to a first possible mode. The apparatus comprises a hot runner assembly 2 arranged for injecting molten materials coming from two different sources of polymers in a moulding assembly 3 defining a ring-shaped moulding cavity 4. Polymer materials can be stored in reservoirs 5, 6 such as in the form granules or pellets. The polymer materials are melted and dosed in two separate dosing assemblies 7, 8, such as heated extruders, which are arranged to supply separate channels of the hot runner assembly. The dosing and melting assemblies can be otherwise such as be constituted by dosing pistons fed by melting devices. The dosing and melting assemblies are controlled by a central control unit 9 configured for properly feeding the hot runner assembly 2 with the appropriate molten materials in appropriate amounts and in a predetermined order or sequence to achieve the production of a multi-layered article. It should be noted that the

apparatus may comprise manifolds (not represented) to feed several hot runner assemblies with molten materials dosed from one dosing assembly.

In figure 2, is shown the hot runner assembly 2 in conjunction with the mould assembly 3. The hot runner assembly comprises a body 10, generally delimiting an outer surface 1 1 and inner surface or bore 12 having an hollow generally symmetrical shape. The inner surface or bore 12 is symmetrically hollow relative to a central axis O. Inside the bore of the body is arranged a flow splitter 13. A gap is provided between the flow splitter and the inner surface 12 of the body to form a first flow channel 14. On the other side of the flow splitter is provided a second flow channel 15 which is delimited by the inner surface of the flow splitter and a valve member 16. The valve member is also generally of annular form and is mounted concentrically around a core member 17. The core member 17 has a smooth annular outer surface 18 complementary designed with respect to a smooth inner surface of the valve member 16 in such a way that the valve member can move reciprocally in the axial direction of axis O for selectively opening and closing the flow channels. The body 10 and inner core member 17 further delimit a nozzle gate 19 placed at the exit of the hot runner assembly for communicating directly with the moulding cavity 4 of the mould assembly. The cavity is shaped in a closed loop fashion with a central mould portion 28 to form a central through-opening 20. The nozzle gate is also given the shape of an annulus or similar closed loop shape. Further inside of the bore is placed an inner gate 21 delimited by a distal end 22 of the flow splitter and by the inner core member. The inner gate 21 as well is given an annulus or closed loop to be able to deliver a second molten material in a closed loop flow configuration. The valve member 16 has three positions: closed, partially open and fully open (respectively represented in figures 3a, 3b and 3c). As can be seen in figure 3a, the valve member comprises successive annular portions 23, 24, 25 stepwisely arranged with reduced cross sections so forming a staggered configuration. The section of free end portion 25 is complementary to the nozzle gate 19 so that it can close it when valve member 16 is moved axially in direction A of the nozzle gate as illustrated in figure 3a. The section of the intermediate portion 24 is complementary to the inner gate 21 that is closed when the valve member is placed in the partial opening position as illustrated in figure 3b. In such position, the first flow channel 14 remains open for enabling the first molten material alone to flow in the cavity. When the valve member is sufficiently moved in the opening direction B opposite to the nozzle gate or cavity, the intermediate portion 24, is disengaged from the inner gate 21 and the two gates 19, 21 are so arranged in open configuration for enabling the two molten materials to be supplied from the first and second channels 14, 15 respectively, then combined between the two gates and pushed to the cavity as shown in figure 3c. The activation of the valve member is controlled by the central unit in the different positions (Figures 3a, 3b, 3c). The valve member can be driven pneumatically for instance or otherwise, such as hydraulically or by any other suitable means, including electrical and electromagnetic motors (e.g., solenoids).

The hot runner assembly 2 is arranged to engage with the mould assembly 3 during the injection operations. The mould assembly may comprise a first mould part 26 and a second mould part 27 joining together to delimit the moulding cavity 4 having a closed loop shape with a through-opening or bore 20 formed by a central (preferably, cylindrical) portion 28 of mould. The central portion 28 of the first mould part 26 also engages the outer surface of the inner core 17 in a tight manner to prevent molten material from flowing inwardly between the two assemblies. The second mould part 27 comprises a peripheral portion 29 engaging the outer surface of the body to prevent molten material from flowing outwardly. The method of the invention for producing the article 30 of figures 4 and 5 can be described as follows in relation to figures 3a-3b.

In a first step, first molten material is injected in the cavity by placing the valve member in the first open (intermediate) position (figure 3b). In this position, the second inner flow channel 15 is closed and the first outer flow channel 14 is open. The control unit controls the position of the valve and controls the first dosing device to dose and dispense first material through the hot runner assembly into the moulding cavity.

In a second step (figure 3c), first and second molten materials are co-injected in the cavity 4. In this position, the valve member is placed in a second (fully) open position. In this step, the second molten material is supplied in the cavity as an inner layer positioned between an outer layer of the first molten material. In this step, the control unit controls the position of the valve and the activation of the two dosing members. Optionally, the injection step may be ended by returning the valve member into the first open (intermediate) position of figure 3b to inject a small amount of the first molten material. This step will ensures that the inner layer of second molten material is fully encased in the layers of the first molten material. The control unit then moves the valve member in the closing direction A to close the nozzle gate 19 (figure 3a). After injection, the article is allowed to cool down in the moulding cavity until it solidies. Then, the cavity is open for removing the article by moving the moulding parts 26, 27 and hot runner assembly 2 apart. In general, depending on the complexity of the article to be produced, the injection time can last of from about 500 milliseconds to 5 seconds and the total cycle time can last between 5 and 30 seconds.

Figure 4 and 5 illustrate a ring-shaped moulded article 30 comprising a central through-opening 20 as obtained in the co-injection moulding apparatus. As apparent in figure 5, the resulting article comprises an outer layer 31 fully embedding an inner layer 32. The inner layer is, therefore, protected by the outer layer such as against moisture coming from the surroundings.

Figure 6 illustrates a co-injection moulding assembly similar to the one of the previous embodiment but for injection of a more complex hollow article. For sake of simplicity, the same reference numbers have been used to indicate the same parts. The description of the apparatus will not be repeated here. The only significant difference comes from the narrower hot runner assembly forming a narrow annular nozzle gate 19 enabling to mould a hollow cup-shaped body 33 at an opened bottom 34. Figure 8 shows a cross-section of the cup-shaped body with a through-opening 35 at the bottom on one side, a sidewall 36 and a flange 37 at the opposite side. The structure of polymer is such that the inner layer 32 is fully embedded by the outer layer 33. Similarly, at the flange end, the outer layer covers the inner layer. For instance, the inner layer is a gas barrier layer such as EVOH and the outer layer is polyolefin(s) such as polypropylene or polyethylene.

The article 33 can form the cup-shaped body of a beverage capsule extending wherein the central through-hole 35 forms the beverage outlet of the capsule. At this bottom end 38, in particular, at the edge of the through-hole, the outer layer further covers the inner layer. In the next embodiment of figures 9 to 1 1 , a composite container 39 can be produced by co-injecting a loop-shaped, preferably annular-shaped, article 30 in a mould cavity 4 (in the manner described earlier) which receives an overlap portion of a pre-formed packaging or body member 40. Therefore, the article can be directly attached by over-moulding to the body member 40 after the co-injection operations. A composite container 39 in the form of a cup with a closed (or possibly open) bottom can be obtained. In particular, the moulding assembly comprises a first mould part 41 having a cup-shaped cavity 42 for receiving the complementarily formed body member 40. The body member can be pre-formed in a separate forming device such as from a flat piece (not represented) and be placed in the cup-shaped cavity 42 after such forming. The forming of the body member can be obtained by deep-drawing, thermoforming or injection-moulding. The moulding assembly further comprises a central mould part 43 which tightly engages against the inner core member 17 when the hot runner assembly is assembled to the moulding assembly.

The body member is positioned with at least one annular end portion 44 overlapping in the injection cavity 4 of the mould assembly as represented in figure 1 1 . When the article is co-injected, the first molten material flows against the surface of the end portion 44 causing the binding of the annular article with the body member. Preferably, the cavity is given the cross-section of an inverted "L" so as to form a portion of sidewall 45 forming a binding portion with end portion 44 and an outwardly projecting flange 37 for the container.

Claims

Claims:

1 . A hot runner assembly (2) for injecting a polymeric article with an outer layer (31 ) formed from a first molten material and an inner layer (32) embedded in the outer layer and formed of a second molten material; comprising a body (10), a flow splitter (13) inside the body separating an outer flow channel (14) for delivering the first molten material and an inner flow channel (15) for delivering the second molten material; an inner gate (21 ) downstream the inner flow channel (15); a nozzle gate (19) downstream the inner gate and outer flow channel; a valve member (16) displaceable from at least a first position of opening of the outer flow channel (14) and closing of the inner flow channel (15) or inner gate (21 ) for enabling the first molten material to flow from the outer flow channel (14) through the nozzle gate (19) only and a second position of opening of both channels (14, 15) for enabling the first and second materials to flow from the outer and inner channels (14, 15) through the nozzle gate, characterized in that:

the valve member (16) has a generally annular form to be displaceable through at least an annular portion of the inner flow channel (15) and in that the inner and nozzle gates (21 , 19) also form annular openings.

2. Hot runner according to claim 1 , wherein the valve member (16) is

arranged and dimensioned complementarily to the opening of the nozzle gate (21 ) for closing it in a third position and preventing the flow of molten material from any of the flow channels (14, 15).

3. Hot runner according to claims 1 or 2, wherein it comprises an inner core member (17) in the bore formed by the annular valve member; the valve member (16) being so slidably and concentrically arranged with respect to the inner core (17).

4. Hot runner according to claim 3, wherein the inner core member (17) delimits the annular opening of the inner gate (21 ) and the annular opening of the nozzle gate (19) inwardly.

5. Hot runner according to claim 4, wherein the body (10) delimits outwardly the annular opening of the nozzle gate (19).

6. Hot runner according to any of the preceding claims, wherein the valve member (16) forms a staggered configuration with successive annular portions (23, 24, 25) of progressively reduced section (e.g., diameters) which are complementary shaped to said openings for closing the latter.

7. A co-injection moulding apparatus (1 ) for producing the polymeric article comprising a hot runner assembly (2) as claimed in the preceding claims and an injection mould assembly (3) comprising a moulding cavity (4) arranged in communication with the nozzle gate (19).

8. A method for producing a polymeric article comprising an outer layer (31 ) formed of a first molten material and an inner layer (32) embedded in the outer layers and formed of a second molten material by the co-injection moulding apparatus (1 ) according to claim 7, wherein it comprises the steps of:

- Injecting first molten material in the moulding cavity (4) by placing the valve member (16) in the first open position,

- Co-injecting first and second molten materials in the moulding cavity (4) by displacing the valve member (16) in second open position so that the second molten material forms an inner layer (32) embedded in the first molten material forming the outer layer (31 ),

- Cooling the article in the moulding cavity (4) and removing the article from the moulding apparatus when solidified.

9. Method according to claim 8, wherein the second molten material is a gas barrier polymer, in particular, EVOH.

10. Method according to claims 8 or 9, wherein the first molten material is polyolefin, in particular, PE or PP.

1 1 . Method according to any one of claims 8 to 10, wherein before injection, at least an overlapping portion (44) of a packaging or body member (40) is inserted in or against a surface of the injection moulding cavity (4) to enable the polymeric article (30) to be injected over or against said portion of the packaging member (40).

12. An article as obtained or obtainable by the method according to any of claims 8 to 1 1 , wherein it forms at least part of a body (33, 39) of a beverage capsule intended for producing a beverage.

13. Article according to claim 12, wherein it forms a cup-shaped body of a beverage capsule extending at its open end by an outwardly projecting flange (37) and comprising a bottom end (34) with a central through-hole (35) for forming the beverage outlet of the capsule.

14. Cup-shaped container (39) comprising an article as obtained or obtainable by the method according to any of claims 8 to 1 1 , wherein it comprises a formed body member (40) and the article comprises an outwardly projecting flange (30) and a binding portion (45) which is attached to an overlapping portion (44) of a formed body member (40).