Induction Sealing Device

Abstract

An induction sealing apparatus (15) for heat-sealing packaging material to produce a hermetically sealed package of a pourable food product, the sealing apparatus (15) being configured to induce an electric current in the packaging material and comprising: an inductor (16) having conductor elements (20, 21); a polymer insert (40) holding the conductor elements (20, 21); and a support (24) holding the polymer insert (40), the polymer insert (40) comprising a polymer matrix having graphene particles dispersed therein.

Description

[Technical Field]

[0001] The present invention relates generally to induction sealing devices. [Background technology]

[0002] Many pourable foods, such as fruit juice, UHT milk, wine, tomato sauce, etc., are sold in packages made of sterile packaging material. A typical example of this type of package is the parallelepiped package for liquids or pourable foods known as Tetra Brik Aseptic®, which is made of a laminated strip of packaging material that is folded and sealed.

[0003] The packaging material substantially has a multi-layer structure including a base layer for stiffness and strength, which may include a layer of fibrous material, e.g., paper, or mineral-filled polypropylene material, and multiple layers of heat-sealable plastic material, e.g., polyethylene film, covering both sides of the base layer.

[0004] In the case of aseptic packaging for long shelf life products such as UHT milk, the packaging material comprises a layer of gas and light barrier material such as aluminum foil or ethyl vinyl alcohol (EVOH) film, which is overlaid with a layer of heat seal plastic material and covered with another layer of heat seal plastic material to form the inner surface of the package that contacts the food.

[0005] As is well known, this type of package is produced on fully automated packaging equipment in which a continuous tube is formed from a web-fed packaging material, and the web of packaging material is sterilized on the packaging equipment by application of a chemical sterilant, such as a hydrogen peroxide solution, to the packaging material. Once sterilization is complete, the sterilant is removed from the surface of the packaging material, for example, by evaporation using heat. The thus-sterilized web of packaging material is maintained in a closed, sterile environment and is then folded lengthwise and sealed to form a vertical tube.

[0006] The tube is continuously fed in a first vertical direction, filled with sterilized or processed food, and gripped at equally spaced cross sections by two pairs of jaws that periodically and continuously act on the tube to heat seal the packaging material of the tube to form pillow packs of continuous strips connected to each other by respective transverse seal bands, i.e., extending in a second direction perpendicular to the first direction.

[0007] The pillow packs are separated by cutting the transverse sealing bands and finally sent to a folding station where they are mechanically folded into a rectangular parallelepiped shape.

[0008] The tube portion sandwiched between each jaw is heat-sealed by locally melting the two layers of heat-sealing resin material sandwiched between the jaws using a heating means attached to one of the jaws, called a sealing jaw.

[0009] Specifically, packaging materials in which the layer of barrier material comprises a sheet of conductive material, e.g., aluminum, are typically heat-sealed when the tube is gripped in its jaws by a so-called induction heat-sealing process, in which an induction sealer induces eddy currents in the aluminum sheet to locally heat the aluminum sheet, thereby locally melting the heat-sealing resin material.

[0010] More specifically, in induction sealing systems, the heating means essentially consists of an inductor driven by a high frequency current generator, where an inductor is defined herein as one or more conductor elements made of a substantially electrically conductive material that interact with the tubing material to induce eddy currents and heat it to the required sealing temperature.

[0011] Sealing devices including inductors of the above type are known, for example, from patent documents EP 1270182 and EP 2008795.

[0012] More specifically, the known sealing device may comprise a support integrally connected to the sealing jaws and defining two front seats for accommodating respective inductors, and an insert made of a composite material including a magnetic flux concentrating material, in particular a ferrite, accommodated inside the support near the conductor element.

[0013] More specifically, the support cooperates with the insert to define a peripheral portion of the sealing device surrounding the conductor element of magnetic flux concentrating material and the insert.

[0014] Although current induction sealing devices offer many advantages, there is room for improvement in terms of durability, cost effectiveness, and sealing speed. Summary of the Invention [Problem to be solved by the invention]

[0015] It is an object of the present invention to provide an induction seal device that is highly durable. It is a further object of the present invention to provide an induction seal device that is cost-effective. It is a further object of the present invention to provide an induction seal device that can achieve high sealing speeds.

[0016] These and other objects of the present invention are at least partly met by the invention as defined in the independent claims. Preferred embodiments are set out in the dependent claims.

[0017] According to a first aspect of the present invention there is provided an induction sealing apparatus for heat sealing packaging material to produce a hermetically sealed package of a pourable food product, the sealing apparatus comprising: an inductor configured to induce a current in the packaging material, the inductor comprising a conductor element; a polymer insert that holds the conductor element; a support that holds a polymer insert; Equipped with The polymer insert comprises a polymer matrix in which graphene particles are dispersed.

[0018] The inventors have discovered that there are several advantages to efficient heat management in an induction sealing device.

[0019] First, efficient thermal management can result in a durable and cost-effective induction seal device. In particular, the inductor of an inductor seal device can be damaged by high temperatures, requiring maintenance and / or replacement. When the inductor breaks or reaches the end of its expected life, the entire support, including the polymer insert and inductor, must be replaced. Because an entire packaging production line or a portion of a production line may depend on the induction seal device, maintenance of the induction seal device can be costly. Therefore, effective cooling of the inductor and / or components in its vicinity can improve the durability of the induction seal device, thereby reducing costs associated with maintenance interruptions in the manufacturing process and costs associated with spare parts.

[0020] Efficient heat management then enables fast sealing speeds. During sealing, the inductor is turned on to induce eddy currents in the conductive material of the packaging material, heating it to a sealing temperature and at least partially melting the heat-sealing plastic material. The inductor is then turned off, allowing the heat-sealing plastic material to solidify, for example, while being held by the sealing jaws. In this way, effective cooling of the inductor and components in its vicinity can shorten the time it takes for the heat-sealing plastic material to solidify. The faster the heat-sealing plastic material solidifies, the faster the sealing jaws can release the packaging material. As a result, efficient heat management enables fast sealing speeds.

[0021] The inventors have recognized that dispersing graphene particles in a polymer insert can facilitate efficient thermal management of an induction seal device. The polymer insert holds the conductive element of the inductor, and the support holds the polymer insert. Dispersing graphene particles in the polymer matrix of the polymer insert can increase the thermal conductivity of the polymer insert. This allows the polymer insert to conduct heat from the inductor, e.g., to the support, so as to efficiently cool the inductor. Furthermore, the polymer insert can conduct heat from the heat seal plastic material, e.g., to the support, so as to efficiently cool the heat seal plastic material.

[0022] The increased thermal conductivity of polymer inserts is likely due to the high thermal conductivity of graphene; single-layer graphene has a thermal conductivity of approximately 1000-5000 W / (mK). The thermal conductivity of polymer inserts containing graphene may be lower. Nevertheless, the addition of graphene to a polymer matrix can sometimes result in a significant improvement in the thermal conductivity of polymer inserts.

[0023] The inventors have realized that even though graphene has high electron mobility, the conductive element may not short out because the graphene is dispersed in the polymer matrix of the polymer insert. Thus, even though high electron mobility may be problematic, tests have shown that dispersing graphene in the polymer matrix of the polymer insert may improve the performance of induction seal devices.

[0024] The inventors recognized that careful consideration must be given to selecting particles to be dispersed in a polymer matrix to reduce the defect rate during the manufacturing process. Polymer inserts are often manufactured by casting a molten polymer into a mold. For example, the molten polymer matrix is ​​cast into a recess in a support. If the molten polymer does not completely fill the mold, the manufactured polymer insert will be defective and must be discarded. Furthermore, fillers added to the polymer matrix during casting may segregate, resulting in defects in some induction sealing devices and requiring their disposal. The inventors recognized that the use of graphene may result in a lower production defect rate and potential cost savings. The reason for the low production defect rate is believed to be that the dispersion of graphene in the polymer matrix of the polymer insert does not substantially reduce the melt flow rate of the molten polymer matrix, allowing the molten polymer matrix to easily fill the mold. Another reason for the low production defect rate is believed to be that the dispersion of graphene in the polymer matrix of the polymer insert does not result in substantial segregation of the graphene. Thus, the graphene can be uniformly distributed within the polymer insert.

[0025] Furthermore, graphene can exhibit good mechanical properties. For example, graphene can have a mechanical strength of about 100 to 1100 GPa and a Young's modulus of about 1 TPa. Therefore, the mechanical properties of the polymer insert do not deteriorate due to the dispersion of graphene in the polymer matrix of the polymer insert. A durable polymer insert with good mechanical properties is important because repeated gripping and releasing of packaging materials by the packaging unit can cause significant wear. Therefore, preventing deterioration of the mechanical properties of the polymer insert is important to reduce maintenance associated with damaged polymer inserts. This leads to cost savings.

[0026] An inductor may comprise a conductor element that can form part of an inductor loop. The inductor loop is called a wire loop. The conductor element may be a conductive wire or a conductive bar. An inductor may comprise, for example, one or two inductor loops. Thus, an inductor may be a single-loop inductor or a double-loop inductor. Of course, an inductor may comprise three or more loops.

[0027] The inductor may be configured to be connected to an AC generator, e.g., a high frequency current generator. The inductor may be configured such that an AC current in the inductor, e.g., in the loop of the inductor, induces an AC magnetic field. The AC magnetic field may induce currents, e.g., eddy currents, in the package, e.g., in the aluminum foil of the package.

[0028] The polymer insert may be configured to retain the conductor element in various ways. The polymer insert may retain the conductor element by itself or in cooperation with another component, such as a support or other component of the induction seal device. For example, the conductor element may be partially or completely encased within the polymer insert. Alternatively, the polymer insert may press the conductor element against the support or other component of the induction seal device.

[0029] The support may be configured to hold the polymer insert in a variety of ways. The support may hold the polymer insert by itself or in cooperation with other components. For example, the polymer insert may be partially or completely encased in the support.

[0030] The graphene particles may be dispersed in the polymer matrix of the polymer insert as a filler. The polymer matrix of the polymer insert may further comprise other fillers. The graphene particles may be single-layer graphene. Alternatively, the graphene particles may be multi-layer graphene, which may comprise up to 5, up to 10, or up to 20 single graphene layers. Alternatively, the graphene particles may be a mixture of single-layer and multi-layer graphene.

[0031] The polymer insert may include magnetic particles dispersed in a polymer matrix of the polymer insert, thereby forming the polymer insert into a magnetic flux concentrating insert.

[0032] The magnetic particles may include ferromagnetic particles or ferrimagnetic particles. The magnetic particles may comprise at least one material selected from ferrite, NiZn ferrite, FeSiAl (sendust), FeSiB alloy (or derivatives thereof), and FeNi alloy (or derivatives thereof).

[0033] Flux-concentrating inserts serve to concentrate the magnetic field generated by the inductor, thereby increasing the efficiency of induction sealing devices. To function efficiently, flux-concentrating inserts are often placed in close proximity to the conductive elements of the inductor, e.g., to hold the conductive elements. Thus, a polymer insert containing both magnetic particles and boron nitride can serve the dual purpose of acting as a flux-concentrating insert and a thermal conductor to cool the inductor.

[0034] Alternatively, the polymer insert may be configured to hold the flux-concentrating insert, which includes a polymer matrix having magnetic particles dispersed therein. Thus, the graphene-containing polymer insert may be distinct from the flux-concentrating insert. However, while holding the flux-concentrating insert, the graphene-containing polymer insert may also conduct heat away from the flux-concentrating insert and / or from the inductor. Thus, the graphene-containing polymer insert can serve the dual purpose of both functioning as a holder for the flux-concentrating insert and as a thermal conductor for cooling the inductor.

[0035] The polymer insert may be configured to have a dielectric strength exceeding a threshold of 100 V / mm. Such dielectric strength can ensure that conductor elements do not short-circuit, i.e., current does not travel along unintended paths between two conductor elements. A current path from one conductor element through the polymer matrix of the polymer insert to another conductor element could degrade the functionality of the inductor. Such a current path could activate only a portion of the inductor's loops and generate a magnetic field. Therefore, the heat-seal plastic material may not heat across the intended area, resulting in a short or weak lateral seal band. It should be understood that an acceptable threshold for the dielectric strength of the polymer insert may vary depending on the embodiment. In some embodiments, the polymer insert may be configured to have a dielectric strength exceeding a threshold of, for example, 400 V / mm.

[0036] The induction seal device may be configured such that the concentration of graphene particles in the polymer insert of the induction seal device is 15% or less. Such a concentration of graphene particles can ensure that the dielectric strength of the polymer insert is high enough to prevent short-circuiting of the conductor elements. Such a concentration of graphene particles can facilitate a simple structural design of the induction seal device. For example, if the concentration of graphene particles in the polymer insert is 15% or less, it is possible to directly encapsulate an inductor in the polymer insert. If the inductor is directly encapsulated in the polymer insert, a path may exist between two conductor elements through the polymer insert, and this path passes only through the polymer insert. A concentration of graphene particles in the polymer insert of 15% or less can ensure that the path will not short-circuit. However, it should be understood that the polymer insert may contain more than 15% graphene if additional means for electrical insulation are provided. For example, if the conductor elements are provided with an electrically insulating coating, such as a polymer coating containing little or no graphene before being encapsulated in the polymer insert, the polymer insert may contain more than 15% graphene. The concentration may be measured by weight.

[0037] It should be appreciated that the distance between conductive elements to prevent short circuits may affect the amount of graphene that the polymer insert can contain.

[0038] Therefore, in some cases, it is advantageous for the concentration of graphene particles in the polymer insert to be below a threshold of 10%. This allows, for example, for the distance between the conductor elements to be short. This allows the induction seal device to have a double loop inductor, with the conductor elements closely spaced and directly wrapped in the polymer insert. In some cases, it is advantageous for the concentration of graphene particles in the polymer insert to be below a threshold of 7.5%. In some cases, the distance between the conductor elements is long enough that the polymer insert may contain more than 15% graphene.

[0039] The polymer insert of the induction seal device may further include electrically insulating particles dispersed in the polymer matrix of the polymer insert. The inventors have recognized that the addition of electrically insulating particles may improve the dielectric strength of the polymer insert. By adding electrically insulating particles to the polymer insert, a higher percentage of graphene may be included without reducing the dielectric strength. Thus, a polymer insert including both graphene and electrically insulating particles may have high thermal conductivity and be durable and cost-effective.

[0040] The electrically insulating particles may be configured to have a thermal conductivity greater than that of the polymer matrix. Furthermore, the electrically insulating particles may be configured to have a dielectric strength greater than a threshold of 1 kV / mm. Thus, the electrically insulating particles can improve the thermal conductivity and / or dielectric strength of the polymer matrix compared to when the electrically insulating particles are not dispersed in the polymer matrix. Depending on the application, the threshold dielectric strength of the electrically insulating particles may vary. For example, the more graphene-polymer matrix the polymer insert contains, the higher the dielectric strength threshold of the electrically insulating particles may be. Thus, the electrically insulating particles may be configured to have a dielectric strength greater than or equal to a threshold of 10 kV / mm, 20 kV / mm, or 30 kV / mm.

[0041] The electrically insulating particles may include boron nitride particles. Alternatively, the electrically insulating particles are boron nitride particles. Boron nitride can have a high dielectric strength. As a result, even if the polymer insert also contains graphene, the dielectric strength of the polymer insert can be high if boron nitride is dispersed in the polymer matrix of the polymer insert. Furthermore, boron nitride can have a high thermal conductivity, and some forms of boron nitride can have a thermal conductivity of up to 2000 W / (mK). Therefore, boron nitride itself can contribute to the thermal conductivity of the polymer insert and also provide the dielectric strength that allows for a higher proportion of graphene. Furthermore, the use of boron nitride can result in a low production reject rate, potentially reducing costs. The low production reject rate is believed to be due to the fact that dispersing boron nitride in the polymer matrix of the polymer insert does not significantly reduce the melt flow rate of the molten polymer matrix.

[0042] The induction seal device may be configured to ensure that the concentration of boron nitride particles in the polymer insert is below a threshold of 20%. Such a threshold may ensure that the polymer insert has a sufficiently low reject rate. The concentration may be measured by weight.

[0043] The polymer insert of the induction seal device may be configured to have a thermal conductivity above a threshold of 0.2 W / (mK). Such a thermal conductivity can ensure effective cooling of the inductor. What is considered sufficiently effective cooling of the inductor may vary depending on the application. Some types of heat-seal plastic materials may require higher temperatures and / or higher currents in the inductor to melt, which may require a higher thermal conductivity threshold for the polymer insert. Higher heat-seal repetition frequencies may also require more effective cooling, which may require a higher thermal conductivity threshold for the polymer insert. Thus, in some embodiments, the polymer insert of the induction seal device may be configured to have a thermal conductivity above a threshold of 0.3 W / (mK). In other embodiments, the polymer insert of the induction seal device may be configured to have a thermal conductivity above a threshold of 0.4 W / (mK). In other embodiments, the polymer insert of the induction seal device may be configured to have a thermal conductivity above a threshold of 0.5 W / (mK).

[0044] The polymer matrix of the polymer insert in the induction seal device may be polyphenylene sulfide (PPS). PPS may be particularly compatible with fillers including graphene and / or boron nitride. Polymer inserts with a PPS polymer matrix may have a lower production reject rate. PPS may have a higher melt flow rate than alternative polymers. Therefore, more graphene and / or boron nitride may be dispersed in PPS before production reject rates become significant.

[0045] Alternatively, other polymers may be used as the polymer matrix of the polymer insert, for example, other thermoplastic polymers may be used as the polymer matrix of the polymer insert, for example, polyetheretherketone (PEEK) may be used as the polymer matrix of the polymer insert.

[0046] The polymer insert of the induction seal device may include reinforcing fibers, which may be advantageous because they can improve the mechanical properties of the polymer insert and thereby improve its durability. The reinforcing fibers may be, for example, glass fibers.

[0047] The induction seal device may include at least one groove separating two conductor elements. The groove may be a groove in a polymer insert. The groove may form a cutting groove. The groove may be disposed between two loops of the inductor. Thus, each loop forms a seal in the packaging material, and the groove may allow a cutter, e.g., a blade, to cut the packaging material between the loops. The groove may additionally or alternatively separate the two conductor elements, thereby reducing the risk of a short circuit between the conductor elements.

[0048] The support of the induction seal device may be made of metal, which may further improve cooling of the inductor. Heat may be conducted from the conductive elements of the inductor through the polymer insert that holds the conductive elements to the support that holds the polymer insert. Metal is considered herein to be a good thermal conductor, which may further remove heat.

[0049] The polymer insert of the induction seal device may be configured to have a melt flow rate above a threshold of 40 when the particle-dispersed polymer matrix is ​​in molten form. A melt flow rate above the threshold of 40 may allow the polymer insert to be manufactured by injection molding, which is a cost-effective manufacturing method. The required threshold may vary depending on the application. For example, if the polymer insert has small features, it may be advantageous to have a higher melt flow rate threshold to ensure that the polymer matrix in molten form completely fills the mold. Thus, instead of a threshold of 40, the threshold may be, for example, 50. The melt flow rate may be measured according to a standard, for example, ISO 1133. The melt flow rate may be measured at a temperature of 316°C with a 5 kg weight applied to the molten polymer matrix. [Means for solving the problem]

[0050] The above and additional objects, features and advantages of the inventive concept will be better understood through the following illustrative and non-limiting detailed description taken in conjunction with the accompanying drawings, in which like reference numerals are used for like elements unless otherwise specified. [Brief explanation of the drawings]

[0051] [Figure 1a] 1 shows a cross-sectional view of an induction sealing device. [Figure 1b] 1 shows a schematic electrical diagram of an inductor of an induction sealing device. [Figure 2a] 1 shows a cross-sectional view of an induction sealing device. [Figure 2b] 1 shows a cross-sectional view of an induction sealing device. [Figure 3a] 1 shows a cross-sectional view of an induction sealing device. [Figure 3b] 1 shows a cross-sectional view of an induction sealing device. [Figure 3c] 1 shows a cross-sectional view of an induction sealing device. [Figure 3d]1 shows a cross-sectional view of an induction sealing device. [Figure 4] The measured thermal conductivity values ​​are shown. [Figure 5] The measured values ​​of the breakdown voltage are shown. [Figure 6] The measured flow length is shown. DETAILED DESCRIPTION OF THE INVENTION

[0052] The following describes several induction sealing devices 15 for heat-sealing packaging material to produce hermetically sealed packages of pourable food products. The induction sealing device 15 may be configured to press the packaging material in direction A, and during sealing of the packaging material, the packaging material may be pressed from opposite sides by the induction sealing device 15 and anvil.

[0053] 1a shows induction seal device 15 in a cross-sectional view, with direction B perpendicular to the cross-sectional plane. In induction seal device 15, polymer insert 40 holds conductor elements 20, 21 of inductor 16, and support 24 holds polymer insert 40. Polymer insert 40 comprises a polymer matrix. In FIG. 1a, polymer insert 40 comprises magnetic particles dispersed in the polymer matrix of polymer insert 40, thereby forming magnetic flux-concentrating insert 30.

[0054] FIG. 1b shows a schematic electrical circuit diagram of the inductor 16 of FIG. 1a, viewed from direction A perpendicular to direction B. The illustrated inductor 16 comprises conductor elements 20, 21 in the form of conductive bars. The two conductor elements 20, 21 may form part of an inductor loop. FIG. 1b illustrates a double-loop inductor 16 comprising a first inductor loop 16′ and a second inductor loop 16″. The induction sealing device 15 may comprise any number of inductor loops. The inductor 16 may be connected to an alternating current generator, for example a high-frequency current generator (not shown).

[0055] In FIG. 1a, polymer insert 40 is flux-concentrating insert 30. Alternatively, as shown in FIGS. 2a and 2b, polymer insert 40 may hold flux-concentrating insert 30. Thus, as shown in FIGS. 2a and 2b, one polymer matrix containing magnetic particles may form flux-concentrating insert 30, while another polymer matrix and another polymer insert 40 containing, for example, graphene and / or boron nitride, may conduct heat away from inductor 16. Alternatively, as shown in FIG. 1a, the polymer matrix may contain both magnetic particles and thermally conductive particles, such as, for example, graphene and / or boron nitride.

[0056] In FIG. 1a, the polymer insert 40 holds the conductor elements 20, 21 by partially encasing them, here encasing them on three sides. Alternatively, the polymer insert 40 may hold the conductor elements 20, 21 by holding another portion of the induction seal device 15 that holds the conductor elements 20, 21. FIG. 2a shows the polymer insert 40 holding another part of the induction seal device 15, in this case the magnetic flux concentrating insert 30, which holds the conductor elements 20, 21. As a further alternative, the polymer insert 40 can hold the conductor elements 20, 21 by pressing the conductor elements 20, 21 against the support 24 or another portion of the induction seal device 15. FIG. 2b shows the polymer insert 40 holding the conductor elements 20, 21 by pressing the conductor elements 20, 21 against another portion of the induction seal device 15, in this case the magnetic flux concentrating insert 30.

[0057] Many design options are possible for induction sealing device 15. In addition to those shown in Figures 1a and 2a-b, several design options are shown in Figures 3a-d. Induction sealing device 15 may be configured to bring inductor 16 and / or magnetic flux concentrating insert 30 into close proximity with the packaging material. For example, induction sealing device 15 may be configured to be pressed against the packaging material in direction A as shown.

[0058] The surface of the induction sealing device 15 configured to press against the packaging material may be provided with one or more ridges 51 configured to apply localized pressure to the packaging material. The ridges 51 may be formed, for example, by a flux-concentrating insert 30, as shown in FIG. 1a, by a polymer insert 40, as shown in FIG. 2b, or by conductor elements 20, 21, as shown in FIG. 3b. The ridges 51 may be disposed on the conductor elements 20, 21, as shown in FIG. 1a or FIG. 3b, or between two conductor elements 20, 21, as shown in FIG. 2a. Alternatively, the induction sealing device 15 may lack the ridges 51, as shown in FIGS. 3a, 3c, and 3d.

[0059] The surface of the induction sealing device 15 that is configured to press against the packaging material may be angled, as shown in Figure 3a. Thus, the induction sealing device 15 may be configured to press the pourable food product away from a central region of the induction sealing device 15. This may reduce the risk of the pourable food product degrading the seal.

[0060] The inductor 16 of the induction sealing device 15 may include, for example, a first inductor loop 16' and a second inductor loop 16'', as shown in Figures 1a and 3c. Alternatively, the inductor 16 of the induction sealing device 15 may include only a first inductive loop 16', as shown in Figure 3d.

[0061] The induction sealing device 15 may include a groove 33. The groove 33 may form a cutting groove. The groove may be disposed, for example, between two inductor loops 16′ and 16″, as shown in FIG. 1a. Each inductor loop may form a seal in the packaging material, and the groove 33 may allow a cutter, e.g., a blade, to cut the packaging material between the loops. The groove 33 may additionally or alternatively separate the two conductor elements 20, 21, thereby reducing the risk of a short circuit between the conductor elements 20, 21.

[0062] The support 24 may be made of metal, for example, in any of the devices shown in Figures 1-3. Alternatively, the support 24 may be made of ceramic. Alternatively, the support 24 may be made of a polymer with a thermally conductive filler, such as graphene.

[0063] The induction sealing device 15 may include a cooling system, for example a cooling system that circulates a cooling liquid. The cooling system may be connected to a support for the induction sealing device 15.

[0064] The polymer matrix of polymer insert 40 may be, for example, polyphenylene sulfide (PPS) in any of the devices shown in Figures 1-3. The polymer matrix of magnetic flux concentrating insert 30 may be, for example, PPS in any of the devices shown in Figures 1-3. Alternatively, other polymer matrices may be used for either polymer insert 40 or magnetic flux concentrating insert 30. For example, other thermoplastic polymers may be used as the polymer matrix. For example, polyetheretherketone (PEEK) may be used as the polymer matrix.

[0065] Thermally conductive particles may be dispersed in the polymer matrix of the polymer insert 40, such as in the polymer insert 40 of any of the devices shown in Figures 1-3. The thermally conductive particles may be graphene and / or boron nitride. For example, the polymer insert 40 may comprise a PPS polymer matrix with graphene and / or boron nitride dispersed therein.

[0066] The graphene particles may have a thickness of one monolayer. The graphene particles may have a thickness greater than one monolayer. The thickness of the graphene particles may be expressed, for example, by a thickness distribution of 10 to 100% of the particles having a thickness of a monolayer. The lateral size of the graphene particles may be, for example, 0.1 to 10 μm or 0.0001 to 2 mm. The graphene particles may be produced, for example, by liquid-phase exfoliation of graphite, oxidation of graphite followed by exfoliation and / or reduction, or chemical vapor deposition.

[0067] The boron nitride particles may have a hexagonal, cubic, or wurtzite morphology. The boron nitride particles may have a platelet shape. Other shapes of boron nitride particles may alternatively be used, such as granules, platelet-shaped granules, aggregates, or platelet-shaped aggregates. The size of the boron nitride particles may be, for example, 0.1 to 10 μm or 0.0001 to 2 mm.

[0068] When fillers are dispersed in the polymer matrix of the polymer insert 40, the properties of the polymer matrix may change. Examples of properties that may change include thermal conductivity, dielectric strength, and melt flow index. Below, the above properties of PPS are described as a function of filler concentration for two fillers, graphene and boron nitride. Filler concentrations of 0%, 5%, 7.5%, and 10% were measured. Concentrations were measured by weight.

[0069] Figure 4 shows the measured thermal conductivity of PPS as a function of the filler concentration of graphene and boron nitride. As can be seen, for both graphene and boron nitride, the thermal conductivity increases with filler concentration. The thermal conductivity of pure PPS is 0.326 W / (mK). The thermal conductivity of PPS with 10% graphene is 1.019 W / (mK), an increase of approximately 210%. The thermal conductivity of PPS with 10% boron nitride is 0.502 W / (mK), an increase of approximately 50%. Further improvements in thermal conductivity are expected with higher filler concentrations. Further measured thermal conductivities are shown in Table 1.

[0070] [Table 1]

[0071] Figure 5 shows the measured maximum breakdown voltage of PPS as a function of graphene and boron nitride filler concentration, measured on 0.5 mm thick samples. The dielectric strength can be calculated by dividing the breakdown voltage by the sample thickness. It should be noted that some samples exhibited lower breakdown voltages than those presented. However, achieving the highest possible breakdown voltage for a particular filler concentration may require optimization of the manufacturing process. Therefore, it is the maximum measured breakdown voltage that is of interest. As can be seen from the figure, the breakdown voltage can increase with increasing boron nitride concentration. Furthermore, the breakdown voltage can decrease with increasing graphene concentration. Pure PPS exhibited a breakdown voltage of 2088 V, which corresponds to a dielectric strength of 4176 V / mm. The breakdown voltage of PPS containing 10% graphene exhibited a maximum breakdown voltage of 102 V, which corresponds to a dielectric strength of 204 V / mm. PPS containing 10% boron nitride exhibits a maximum breakdown voltage of 2339 V, which corresponds to a dielectric strength of 4678 V / mm. However, it should be noted that the dielectric strength of pure PPS can range from 11 to 24 kV / mm, depending on the material specifications. Therefore, measurements may underestimate the actual dielectric strength by a factor of 3 to 6.

[0072] Figure 6 shows the flow length measured in a snake flow test for PPS as a function of the filler concentration of graphene and boron nitride. The flow length was measured by injection molding a molten polymer matrix containing dispersed fillers into a snake-shaped mold. The injection molding was performed at a melt temperature of approximately 335°C, an injection pressure of 150 MPa, and an injection rate of 40 ccm / s. As can be seen from the figure, a decrease in the flow length was observed as a function of the filler concentration for both graphene and boron nitride. All measured flow lengths correspond to melt flow rates above 40.

[0073] Based on the studies shown in Figures 4-6, it is estimated that the polymer insert 40 may have one of the following configurations:

[0074] The polymer insert 40 of at least some of the devices of Figures 1-3, for example the device of Figure 2a or Figure 2b, may be made of 15% graphene dispersed PPS.

[0075] The polymer insert 40 in at least some of the devices of Figures 1-3, for example the device of Figure 2a or Figure 2b, may be made from PPS with 30% boron nitride dispersed therein.

[0076] The polymer insert 40 in at least some of the devices of Figures 1-3, for example, the device of Figure 1a or Figure 3a, may be made of PPS dispersed with 15% graphene and 60% ferrite, such that the polymer insert 40 forms the magnetic flux concentrating insert 30.

[0077] The polymer insert 40 in at least some of the devices of Figures 1-3, for example, the device of Figure 1a or Figure 3a, may be made of PPS dispersed with 20% boron nitride and 60% ferrite, such that the polymer insert 40 forms the flux-concentrating insert 30.

[0078] The polymer insert 40 in at least some of the devices of Figures 1-3, for example, the device of Figure 1a or Figure 3a, may be made of PPS dispersed with 10% graphene, 10% boron nitride, and 60% ferrite, such that the polymer insert 40 forms the magnetic flux concentrating insert 30.

[0079] The polymer insert 40 in at least some of the devices of Figures 1-3, for example, the device of Figure 1a or Figure 3a, may be made of PPS dispersed with 20% graphene, 20% boron nitride, and 50% ferrite, such that the polymer insert 40 forms the magnetic flux concentrating insert 30.

[0080] The polymer insert 40 in at least some of the devices of Figures 1-3, for example, the device of Figure 1a or Figure 3a, may be made of PPS dispersed with 5% graphene, 5% boron nitride, and 80% ferrite, such that the polymer insert 40 forms the magnetic flux concentrating insert 30.

[0081] While the inventive concept has been described above primarily with reference to a limited number of embodiments, those skilled in the art will readily appreciate that other embodiments besides those disclosed above are equally possible within the scope of the inventive concept as defined by the appended claims.

Claims

1. 1. An induction sealing apparatus (15) for heat sealing packaging material to produce hermetically sealed packages of pourable food products, said induction sealing apparatus (15) comprising: an inductor (16) configured to induce a current in the packaging material and comprising conductor elements (20, 21); a polymer insert (40) that holds the conductor elements (20, 21); a support (24) for holding said polymer insert (40); Equipped with 1. An induction sealing device (15), wherein the polymer insert (40) comprises a polymer matrix having graphene particles dispersed therein, the concentration of the graphene particles in the polymer insert (40) being equal to or less than a threshold value of 15%.

2. 10. The induction seal device (15) of claim 1, wherein the polymer insert (40) comprises magnetic particles dispersed in a polymer matrix of the polymer insert (40), the polymer insert (40) forming a magnetic flux concentrating insert (30).

3. 10. The induction seal device of claim 1, wherein the polymer insert is configured to retain a magnetic flux concentrating insert, the magnetic flux concentrating insert comprising a polymer matrix having magnetic particles dispersed therein.

4. The induction sealing device (15) of any one of claims 1 to 3, wherein the concentration of the graphene particles in the polymer insert (40) is below a threshold of 10%.

5. The induction seal device (15) of any one of claims 1 to 4, wherein the polymer insert (40) further comprises electrically insulating particles dispersed in a polymer matrix of the polymer insert (40).

6. 6. The induction sealing device (15) of claim 5, wherein the electrically insulating particles are boron nitride particles.

7. 7. The induction seal device (15) of claim 6, wherein the concentration of the boron nitride particles in the polymer insert (40) is 20% or less.

8. The induction sealing device (15) of any one of claims 1 to 7, wherein the polymer insert (40) is configured to have a thermal conductivity above a threshold of 0.2 W / (mK).

9. The induction seal device (15) of any one of claims 1 to 8, wherein the polymer matrix of the polymer insert (40) is polyphenylene sulfide (PPS).

10. The induction seal device (15) of any one of claims 1 to 9, wherein the polymer insert (40) comprises reinforcing fibers.

11. The induction seal device (15) of any one of claims 1 to 10, further comprising at least one groove (33) separating the two conductor elements (20, 21).

12. The induction sealing device (15) according to any one of claims 1 to 11, wherein the support (24) is made of metal.

13. The induction seal device (15) of any one of claims 1 to 12, wherein the polymer insert (40) is configured to have a melt flow rate above a threshold value of 40 when the polymer matrix having the particles dispersed therein is in a molten form.

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