Device for coating fiber-based hollow body

Abstract

The invention relates to a device (11) for coating a hollow fiber-based body (17) with a barrier layer, comprising an electrically conductive mould (13) having a first port for receiving the body (17) and comprising a spray gun (15) having a second port, the spray gun (15) being insertable into the body (17) and a polymer powder being insertable into the body (17) by means of the spray gun. A power source may be connected to the first port and the second port so that a voltage may be effected between the mold (13) and the lance (15). An electrically conductive and compressible compensation element (19) is arranged on the inner side of the mold.

Description

Technical Field

[0001] The invention relates to a device for coating a fiber-based hollow body according to the preamble of claim 1 and to a fiber-based closure element according to the preamble of claim 15 . Prior art

[0002] In recent years, fiber materials have gained new attention as packaging materials because they are particularly sustainable. Advances in wet forming technology for parts with undercuts (such as containers and bottles) are opening up new areas of application. Other new technologies (such as dry forming of fiber mats) enable new fiber-based bodies, such as closures. These products compete with previously known products that are mainly made of plastic materials. The disadvantage of fiber-based materials is that, as known from plastic materials, they are essentially unable to be protected from external media such as water or water vapor. Therefore, for many applications, it is necessary to protect the formed fibers in further process steps and provide products with barrier properties. There are several technical solutions for applying such barriers, and it is necessary to distinguish which medium the barrier is intended to protect the fiber-based body from, and in this case whether the shape of the filler material or the fiber-based body is to be protected. External protection can be achieved by introducing chemical additives, for example, AKD (alkyl ketene dimer), which is well known in the fiber industry and makes the fiber surface hydrophobic. However, such additives cannot provide a barrier for water vapor or other gases and allow them to penetrate unimpeded, and therefore cannot fully protect the contents.

[0003] Coatings for fiber-based containers are known in the prior art, which have a powder coating on the inside of their shell. The powder coating is applied to the shell using an electrostatic high-voltage method. This allows the shell to be equipped with a barrier layer. However, fiber-based bodies have the following characteristics: they have relatively large manufacturing tolerances compared to plastic bodies. Therefore, fiber-based bodies with electrostatic coatings have the following disadvantages: the charge areas are not uniform, and therefore the coating can have different thicknesses and uniform gaps.

[0004] Purpose of the invention

[0005] The disadvantages of the prior art described gave rise to the object of providing an apparatus which improves the above-mentioned coating method.

[0006] describe

[0007] The proposed object is achieved by a device for coating a fiber-based hollow body with a barrier layer by means of the features listed in the characterizing part of claim 1. The dependent claims relate to developments and / or advantageous alternative embodiments.

[0008] A preferred feature of the invention is that the electrically conductive and compressible compensating element is arranged on the inner side of the mould. Since the manufacturing tolerances of these fibre-based hollow bodies are relatively high due to the manufacturing method of the fibre-based hollow bodies, the inner side of the mould may not completely and precisely abut against the outer side of the hollow body. This may cause an interruption of the charge, resulting in a mottled and uneven coating. The electrically conductive and compressible compensating element ensures, due to its flexibility, that the outer surface of the body, whose corresponding inner surface is to be coated, is in full-surface contact with the compensating element. Defects and irregularities in the coating are thus reliably prevented.

[0009] In a particularly preferred embodiment of the invention, the compensating element is a conductive foam and / or a 3D printed conductive filament body. The foam is usually used with an additional carrier element, while the filament body is both the carrier element and the electrical conductor. The foam is preferably a polyurethane foam coated with copper and nickel.

[0010] 3D printing enables very precise surfaces that are also highly flexible. This filament body can only be produced exclusively using 3D printing, as it must be built up in layers to create the wound filaments. The wound filaments ensure compressibility and flexibility of the filament body. This filament body is intended for parts where the contours of the mold do not allow the conductive foam to be bonded to it.

[0011] In a further particularly preferred embodiment, the mould consists of a plurality of electrically conductive segments, so that the body to be coated can be surrounded by these segments. This means that the charge can be present on all surfaces of the hollow body, which should be coated evenly and without gaps. The segments are preferably made of aluminium, as this metal has a high electrical conductivity. The segments may also be free of foam or filamentary bodies. This is preferred for the interface of the hollow body which needs to transmit forces and be screwed together.

[0012] The combination of compensating elements and segments enables the hollow body to be surrounded by the mould over the entire surface area and at the same time the voltage is present on all surfaces to be coated. For the device to function reliably, these features must cooperate.

[0013] It has proven useful if the mould has a plurality of side segments, a bottom segment and a shoulder segment. This means that the hollow body can be easily inserted into the mould and is in full contact with the segments after the mould is closed.

[0014] Conveniently, the mold has a neck section and a separation section, which is adjacent to the neck section. The neck section and the separation section form a boundary edge between the coated area and the uncoated area on the outer surface of the neck thread. The neck section is a contact part and is therefore responsible for potential equalization. The separation section does not contact the outer surface of the bottle. This section produces a "clearer" boundary edge of the coating. The fiber-based hollow body can also be optionally coated on the outside of the front surface or sealing surface and on the filaments. Usually, the coating ends directly after the end of the thread.

[0015] It is advantageous if the separator and neck sections are free of compensating elements. Likewise, for the hollow body, an aluminum section without compensating elements is preferred, since it is more conductive than the foam and filament body and enables the coating to withstand higher loads due to its improved adhesion. This prevents the coating from falling off at interfaces where forces are transmitted and where screwing together is required.

[0016] As already explained above, it is advantageous if the coated area on the body can be limited by separating sections. This gives a precise demarcation of the coating from the uncoated parts of the hollow body.

[0017] A preferred feature of the invention is also that the segments can be transferred in a mold-like manner from an open position, in which the body can be inserted into the mold, to a closed position, in which the body can be completely surrounded by the segments. This makes the device ideal for mass production of fiber-based hollow bodies. Increased manufacturing tolerances of the production series of hollow bodies are compensated by the compensating element.

[0018] In a further preferred embodiment of the invention, the surface of the segment covered with the compensating element or the surface without the compensating element defines the coating zone in the closed position of the mold. This allows the entire interior to be coated particularly uniformly, thinly and without gaps.

[0019] It is preferred if the side sections are covered with foam material, since the foam can be glued to the contour of the side section with a conductive adhesive and thus attached to the section. The foam has good electrical conductivity and good compensation properties.

[0020] It is preferred if the bottom section is covered with a filament body, since the foam does not stick to the bottom section. This is because the bottom section as well as the shoulder section usually always have contours that cannot be reproduced using foam alone. In particular, radii, edges and other 3D shapes can only be reproduced with very thin elastic materials. However, the foam usually has to be about 5 mm thick, since, on the one hand, it has a compensating function and, on the other hand, the copper-nickel coating is not elastic. Therefore, on contours to which the foam does not stick, the filament body is a suitable alternative to the foam.

[0021] The lance can conveniently be inserted into the mould through the shoulder section, as this is also where the filling or pouring opening of the fibre-based hollow body is located.

[0022] In a further preferred embodiment of the invention, the spray gun is designed so that the polymer powder is charged as it flows through the spray gun, and the segments can be charged oppositely to the polymer powder. This causes the powder particles to be attracted to the inside of the hollow body, where potential equalization occurs. The spray gun can be designed like a "corona gun".

[0023] Due to the above advantages, the device is particularly suitable for fiber-based bottles and closures, as the compensating element can compensate for manufacturing tolerances and complex geometries.

[0024] A further aspect of the invention relates to a fiber-based closure comprising a cover plate and a cylindrical housing with an internal thread adjoining the cover plate. The inner side of the cover plate and the housing can be coated with a polymer powder particularly advantageously using the present device. On the one hand, the barrier layer is applied uniformly over the entire surface area. On the other hand, the polymer coating increases the rigidity of this area. This can increase the maximum tightening torque of the closure. In addition, the friction surface (e.g. the thread) prevents the fibers from detaching from the surface when the surfaces are moved relative to each other, which would impair the function of the closure if the closure is used multiple times.

[0025] Further advantages and features will become apparent from the following description of embodiments of the invention with reference to the schematic drawings, in which:

[0026] Figure 1 A cross-sectional view of an apparatus for coating a fiber-based hollow body with a mold is shown, the mold being open;

[0027] Figure 2 showing a cross-sectional view of the device in a partially closed position of the mold;

[0028] Figure 3 A cross-sectional view showing the device in the closed position of the mold;

[0029] Figure 4 Shows Figure 3 A detailed drawing of the mould; and

[0030] Figure 5 A perspective view of the apparatus with the mold and the spray gun is shown.

[0031] Figure 5 An apparatus for coating a fiber-based hollow body is shown, comprising an electrically conductive mold 13 and a spray gun 15, and is indicated as a whole by reference numeral 11. The mold 13 functions similarly to a casting mold, with the mold sections being able to be in an open position ( Figure 1 ) and closed position ( Figure 3) between. In the open position, a hollow body (e.g., a fiber-based bottle 17) can be inserted into the mold 13. In the context of the present application, a fiber-based hollow body is understood to mean a hollow body formed from compressed pulp, which forms a dimensionally stable shell and encloses an inner space. Pulp is generally understood to be a mixture of water, fibers (especially paper fibers) and a binder.

[0032] The mold 13 and the spray gun 15 have a first electrical port and a second electrical port, respectively, to which a voltage can be applied. Because the mold 13 is made of a conductive material (e.g., aluminum), an electric charge can act on the hollow body or bottle 17 even if the fiber is not conductive. The more precisely the mold 13 fits the bottle, the more uniform the coating inside will be. In order to coat the inside of the bottle 17, a voltage is applied to the first port and the second port. For example, the polymer powder blown by the spray gun 15 is positively charged. Because the mold 13 is negatively charged, the powder particles adhere to the inside of the bottle 17. Subsequently, the bottle 17 is removed from the mold 13, and the powder is melted by heat energy in a subsequent step. In this case, the heat energy can be introduced in the form of convection energy or radiation energy. The powder forms a uniform layer in the melt and solidifies in a subsequent cooling process.

[0033] Typically, fiber-based hollow bodies have relatively large manufacturing tolerances compared to plastic bodies. On the other hand, the mold 13 must fit as precisely and completely as possible against the hollow body in order to generate a charge field that reproduces the interior of the hollow body as precisely as possible.

[0034] In order to achieve this exact fit of the mold 13 on the bottles 17, which differ from one another in size due to the material, an electrically conductive and compressible compensating element 19 is arranged on the inside of the mold 13. This compensating element 19 rests over its entire surface on the outer contour of the bottle 17, since it can be more or less compressed. The coating is thus particularly uniform and thin and adapts internally to the geometry of the hollow body. Even complex shapes, such as the threads of a fiber-based nut, can be precisely coated.

[0035] The mold 13 consists of a plurality of conductive segments, so that the body to be coated can be surrounded by these segments. Preferably, the mold 13 has a plurality of side segments 21, a bottom segment 23 and a shoulder segment 25. The segments can be lined with conductive foam 19a or with a 3D-printed conductive filament body 19b. Filaments are wound plastic fibers that are compressible or flexible and conductive. For parts whose contours do not allow conductive foam to be glued thereon, it is advantageous to use a filament body 19b. The filament body 19b can be produced with the highest manufacturing tolerances and complex shapes using 3D printing methods.

[0036] Segments, such as side segments 21, may be lined with conductive foam 19a. The conductivity and compensation properties of the conductive foam are higher than those of the filament body. The foam is used for all segments where the foam can be glued to the profile.

[0037] The fiber-based bottle 17 is inserted into the shoulder section 25 with its shoulder 27 ( Figure 1 ). Figure 2 The fixing of the bottle 17 between the shoulder section 25 and the bottom section 23 is shown. The bottle 17 is fixed by moving the bottom section 23 vertically onto the base 29. After closing the bottom section 23, the side sections 21 are closed, so that the bottle is completely surrounded by these sections. Preferably, four side sections 21 are provided, which are first moved in the vertical direction and then in the radial direction in order to cover the shell of the bottle 31. The inner surface of the side sections 21 is covered with conductive foam 19a. After closing the sections, the surfaces of these sections covered with the compensation element 19 define the coating area ( Figure 3 ). That is, all surfaces of the bottle 17 connected to the compensation element 19 (foam 19a or filament body 19b) can be coated with the charged polymer powder uniformly and without gaps over the entire surface.

[0038] Following the shoulder section 25, the mold 13 has a neck section 33. The neck section 33 and the adjoining separating section 35 are closed by two pneumatic clamps. The neck section is a contact part responsible for potential equalization.

[0039] The separation section 35 is arranged next to the neck section 33. The neck section 33 ensures that there is a coating at the transition between the shoulder 27 and the neck 33. The separation section 35 enables a clean separation or "sharper boundary edge" between the coated area and the uncoated outer mouth area on the neck of the bottle 37. To establish the interface, neither the neck section 33 nor the separation section 35 has compensating elements. Both sections are made of aluminum and therefore have good electrical conductivity.

[0040] Figure 5 The spray gun 15 is shown before being inserted into the bottle 17 through the shoulder section 25. The spray gun can be designed as a "corona gun". When leaving the spray gun 15, the polymer powder is charged with the reverse charge of the conductive compensation element 19. This allows the powder to adhere to the inner surface of the bottle to be coated.

[0041] The 3D printed filament body 19b and in particular the foam 19a enable geometrically complex shapes to be coated with a thin polymer layer with a uniform layer thickness. In addition, the polymer layer is completely closed so as to create a reliable barrier layer. Therefore, the device 11 is also suitable for coating the inside of fiber-based nuts. In this case, the internal threads of the closure are also completely coated. By using a polymer powder that adheres extensively to the geometric shapes, the rigidity of this area is also increased. This can increase the maximum tightening torque of the closure. In addition, the friction surface (e.g., the thread) prevents the fibers from detaching from the surface when the surfaces move relative to each other, which would impair the function of the closure if it is used multiple times.

[0042] Reference numerals list :

[0043] 11. Installation

[0044] 13. Mould

[0045] 15. Spray gun

[0046] 17Fiber-based bottles, fiber-based hollow bodies

[0047] 19 Compensation components

[0048] 19a Conductive foam

[0049] 19b 3D printed conductive filament body

[0050] 21 Side section

[0051] 23 Bottom section

[0052] 25 Shoulder Section

[0053] 27 Bottle Shoulder

[0054] 29 Bottom of bottle

[0055] 31 Bottle shell

[0056] 33 Neck section

[0057] 35 Separation section

[0058] 37 Bottle neck

Claims

1. A device (11) for coating a fiber-based hollow body (17) with a barrier layer, the device comprising: - a conductive mold (13) having a first port for receiving the body (17), a spray gun (15) for dispensing polymer powder using a second port, said spray gun (15) being positionable at a distance from said body (17), - a power source, which can be connected to the first port and the second port, so that A voltage can be realized between the mold (13) and the spray gun (15), characterized in that An electrically conductive and compressible compensating element (19) is arranged on the inner side of the mold.

2. The device according to claim 1, characterized in that The compensating element is a conductive foam (19a) and / or a 3D printed conductive filament body (19b).

3. The device according to any one of claims 1 or 2, characterized in that: The mold (13) consists of a plurality of conductive segments (21, 23, 25, 33, 35), so that the body (17) to be coated can be surrounded by the segments (21, 23, 25, 33, 35).

4. The device according to claim 3, characterized in that The mold has a plurality of side sections (21), a bottom section (23) and a shoulder section (25).

5. The device according to any one of claims 3 or 4, characterized in that: The mold has a neck section (33) and a separation section (35) which adjoins the neck section (33).

6. The device according to claim 5, characterized in that The dividing section (35) and the neck section (33) are free of the compensating element (19).

7. The device according to any one of claims 5 or 6, characterized in that The coating area on the body (17) can be limited by the separation section (35).

8. The device according to any one of claims 3 to 7, characterized in that The segments (21, 23, 25, 33, 35) can be transferred in a casting-like manner from an open position, in which the body (17) can be inserted into the mold, to a closed position, in which the body (17) can be completely surrounded by the segments (21, 23, 25, 33, 35).

9. The device according to any one of claims 3 to 8, characterized in that The surface of the segments (21, 23, 25, 33, 35) covered with the compensating element or the surface without the compensating element defines a coating zone in the closed position of the mold (13).

10. The device according to any one of claims 4 to 9, characterized in that The side sections (21) are covered with foam (19a).

11. The device according to any one of claims 4 to 10, characterized in that The bottom section (23) is covered with the filament body (19b).

12. A device according to any one of the preceding claims, characterised in that The lance (15) can be inserted into the mold (13) via the shoulder section (25).

13. A device according to any one of the preceding claims, characterised in that The spray gun (15) is designed so that the polymer powder is charged when flowing through the spray gun (15), and the segments (21, 23, 25, 33, 35) are capable of being charged opposite to the polymer powder.

14. Use of a device (11) according to any of the preceding claims for coating fiber-based containers, in particular fiber-based bottles (17) and fiber-based closures.

15. A fiber-based closure component, comprising: - cover plate, and - a cylindrical housing connected to the cover plate and having an internal thread, characterized in that At least the cover plate and the inner side of the housing are coated with a device (11) according to claims 1 to 13.

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