DEVICE AND METHOD FOR RECYCLING PLASTIC BEVERAGE BOTTLES

Description

[0001] The present invention relates to a system for cleaning and treating containers. Furthermore, the invention relates to a corresponding method for cleaning and treating containers.

[0002] It is known that, within the framework of deposit and return systems (reusable systems), plastic containers, especially PET containers, are brought by end consumers via appropriate collection and return systems to a facility for cleaning and refilling with a product, particularly a beverage. It is also known that industrial container cleaning machines are used for this purpose.

[0003] These machines have different treatment sections in which the containers are cleaned and treated with different process media. These process media include water for the final rinse of the containers, as well as alkali and / or acid baths. Such industrially common bottle cleaning machines are disclosed in WO 2009 / 118139 A1 and WO 2009 / 124688 A1.

[0004] Because these process media exert strong influences on the plastic material, leading to, for example, pore formation and roughening of the surface structures, plastic containers for this direct reuse must have significantly thicker walls than, for example, disposable PET containers. Therefore, plastic containers can only be directly reused in this way to a limited extent.

[0005] Devices for printing containers are known from the previously published patent application DE 10 2012 213079 A1. In preparation, the containers are first cleaned and, if necessary, coated.

[0006] From the previously published patent application US 5 849 366 A it is known to provide containers with coatings in order to improve their durability.

[0007] An object of the present invention is therefore to provide a system by means of which containers can be treated in such a way that they can be reused as primary packaging as frequently as possible.

[0008] This object is achieved according to the invention by the features of claim 1, wherein a method according to the invention is achieved by the features of claim 8. Advantageous embodiments are specified in the subclaims.

[0009] The core of this approach is that the containers intended for refilling are also coated to sufficiently increase the resistance of the container material to the cleaning steps with aggressive media required before refilling. Surprisingly, it was discovered that coating systems that serve as gas barriers for disposable plastic containers to prevent oxygen ingress (O2) or carbon egress (CO2) through the container wall are fundamentally suitable for this purpose. Furthermore, it was discovered that it is possible and advantageous to completely recoat already coated containers after cleaning.

[0010] This means that the throughput of plastic bottles in the return and deposit systems can be multiplied several times over compared to the existing systems for uncoated plastic deposit bottles.

[0011] For the purposes of this article, deposit and return systems are understood to refer only to systems in which the containers retain their shape and geometry. A deposit and return system in which the containers are destroyed or temporarily structurally altered, for example, by processing them into granules and reproducing them, is not intended.

[0012] The system according to the invention for treating plastic containers comprises at least one cleaning machine. This cleaning machine has several treatment sections in which, among other things, the interior of the container can be rinsed and / or sprayed with liquid media. At least one of the treatment sections is a lye treatment / bath, for example with sodium hydroxide solution (NaOH), whereby this treatment section has a heating device and / or is connected to such a device. The connection can also consist of the lye being heated separately and then fed to the treatment section at an elevated temperature. In addition, a further treatment step is always provided in which the containers are treated with water, in particular sprayed or rinsed. The containers themselves are usually made of PET, but can also be made of another plastic, such as PE, HDPE, PP or POC.

[0013] The system comprises a coating device as a key element downstream of the cleaning machine, and the containers can be transported from the cleaning machine to the coating device using suitable transport means. The transport means can be single- or multi-part. In particular, it can be advantageous to initially transport in bulk and subsequently hold and transport the containers individually, for example, using rotating transport star wheels.

[0014] In an improved variant, a further treatment machine is provided between the cleaning machine and the coating device, with which the containers are conditioned for coating. This can in particular be a drying device in which residual moisture in the form of drops, condensate or steam is removed from the container. For this purpose, it can be advantageous if at least one turning device for containers is provided upstream and downstream of the drying device, and the containers in the

[0015] The drying device must be held by means of guide rails and / or gripping elements in such a way that the container mouth points vertically downwards so that liquid can drain away.

[0016] According to the invention, no further container handling elements are arranged between the cleaning machine and the coating device, apart from a drying device and any associated transport or turning devices. However, one or more inspection devices with any necessary diversion elements can be provided between the cleaning machine and the coating device. These inspection devices are not considered handling elements in this case, just as they can be provided upstream of the cleaning machine.

[0017] Of course, the system can include additional machines for treating containers downstream of the coating device, in particular a filler, a sealer, a decorating machine, such as a printing device or a labeler, and / or a packaging machine. All known elements for container treatment are conceivable as needed.

[0018] In the aforementioned system, the coating device is a plasma gas separation device comprising several vacuum chambers in which the containers can be accommodated individually or in groups and coated under vacuum. For this purpose, at least one gas line leads into each vacuum chamber, which in turn is connected to at least two different process gas sources. At least one microwave generator or at least one high-frequency generator is provided for plasma generation.

[0019] In one embodiment, one of the process gas sources is at least a gas tank for hexamethyldisilazane (HMDSN), hexamethyldisiloxane (HMDSO), or acetylene (ethyne), or these process media are stored in liquid form, so that a liquid tank with an evaporator unit is included. Such systems for processing a precursor liquid are generally known from the prior art. Furthermore, at least one supply line is provided for one of the following gases: oxygen (O2), nitrogen (N2), or a noble gas, such as argon (Ar), but also helium (He) or xenon (Xe). Supply lines for O2, N2, and a noble gas are primarily provided.

[0020] The invention also encompasses a method for treating containers made of plastic, in particular containers made of PET, PE, PP or POC, in which, in a first step, the containers, in particular the respective container interior, are cleaned by means of liquid treatment media, wherein at least one of the treatment media is a lye, such as NaOH lye, and at least one treatment medium is water.

[0021] Further known cleaning steps can be carried out using acid baths or multiple treatments, with improved cleaning processes.

[0022] In a subsequent step, the containers, in particular the inner container walls, are coated using a PCVD process with at least two layers, in particular layers on the inner surface of the containers. In particular, the plasma is induced using a microwave generator or high-frequency generator. Coating is understood to mean an application of multiple layers, which also includes the application of multiple layers with different functions and / or compositions. These functions can be, for example, adhesion promoter (adhesion promoter layer, base coat), barrier (barrier layer), and security (top coating, security layer), although these can also be performed multiple times, depending on the final high-quality coating of the reusable container.

[0023] Ideally, the containers have gone through a deposit and return system prior to the first cleaning step and are transported to the first step as complete containers.

[0024] In an improved process, the containers have at least a partial coating of the inner surface before the first cleaning step, which can also be designed as a multi-layer system.

[0025] The advantage of this is that the inner container wall is protected from the aggressive cleaning agents. Surprisingly, it has been shown that multiple coatings are possible at any time, even if an existing coating is incomplete or damaged. Furthermore, coating even new bottles ensures the long-term quality of the plastic surface, making them easier to recoat after an initial cleaning cycle and subsequent coating.

[0026] In the aforementioned method or its embodiments, the containers are coated with at least two layers using a gas deposition process, namely a PCVD process, which are deposited in particular on the inner surface of the containers. Plasma ignition or induction is advantageously carried out using at least one microwave generator (MW) or a radio-frequency generator (RF).

[0027] In an advantageous variant of the process, in which the generator for plasma induction is a microwave generator, I have surprisingly shown that the resistance to alkali influences is improved when the average energy input during coating is low, namely when the average energy input from active pulse time to total pulse time multiplied by the generator power is in the range of 10 to 120 watts, ideally in the range of 20 to 100 watts.

[0028] It has also been shown that it is advantageous if, at low energy input, the active pulse time is in the range of 0.1 ms to 1 ms and the ratio of active pulse time to total pulse time is in the range of 0.01 to 0.05.

[0029] For example, in a test with very good resistance values ​​against NaOH, the pulse time is 0.5 ms, the pulse-pause time is 20 ms and the microwave power is 1.8 kW, so that the average energy input E m is calculated as follows: E m = 0,5 ms / 20,5 ms * 1,8 kW = 24,39 W .

[0030] In the alternative method, in which the generator for plasma induction is a high-frequency generator, a comparable, advantageous range for the average energy input of 10 to 120 watts was observed, which ideally lies in the range of 20 to 100 watts.

[0031] This observation is very surprising because the average energy input for the previously known process and device for generating a good gas barrier is in the range of 210 to 450 watts.

[0032] A particularly advantageous process variant involves applying a multi-layer coating to the newly produced containers in a preliminary step before the first filling and ideally immediately after production. This multi-layer coating consists of at least three layers: a base coating, a barrier coating, and a protective top coat.

[0033] After use, for example by end users and return of the containers via a deposit and return system, the containers are cleaned as described above using a cleaning machine and then only partially recoated or supplemented, namely only with the barrier layer (barrier coating) and the protective layer (top coat) or ideally only the outermost layer, especially the protective layer (top coat), is reapplied.

[0034] Surprisingly, it has been shown that the wet cleaning treatment of the containers can partially damage the coating, but has no adverse effect on such a supplementary coating.

[0035] The advantage of only partial or supplementary coating is that known coating devices can be operated at significantly increased performance by eliminating the first coating steps.

[0036] The difference in the formulation of a barrier layer and a protective layer is basically known in the prior art and, on the process side, consists in the fact that, for example, the HDMSO or HDMSN flow when applying the protective layer is at least 1.5 times to 4 times higher than the gas flow when applying the barrier layer.

[0037] Furthermore, it has proven advantageous if the temperature of at least one of the treatment media for the containers, which is a caustic solution, is in the range of 30°C to 70°C, ideally in the range of 40°C to 60°C. The aforementioned layers are sufficiently resistant to these caustic temperatures and thus provide the necessary protection for the container wall material. At the same time, the required cleaning performance can be achieved.

[0038] In general, the features of the system and method mentioned can be used as required and, in particular, the method is carried out using the system described above.

Claims

1. A system for the treatment of containers made of plastic, in particular, made of PET, PE, PP or POC, comprising a cleaning machine, wherein it has a plurality of treatment stages, in which the container interior can be rinsed with liquid media and wherein at least one of the treatment stages - is a lye treatment that comprises a heating device and / or is connected to such a device and - a treatment step is a water treatment, wherein a coating device is provided downstream of the cleaning machine, wherein the cleaning machine is connected to the coating device by transport means for the containers, characterized in that the coating device is a gas separation device by means of plasma, which comprises a plurality of vacuum chambers in which the containers can be coated under a vacuum, and wherein the vacuum chamber for gas pipelines is connected to at least two different process-gas sources, and wherein at least one microwave generator or at least one high-frequency generator is provided for forming plasma.

2. The system according to Claim 1, characterized in that a further treatment machine is provided between the cleaning machine and the coating device, such as a drying device.

3. The system according to Claim 2, characterized in that a turning device for containers is provided upstream and downstream of the drying device, and the containers are held in the drying device by means of gripping elements in such a way that the container aperture points vertically downwards.

4. The system according to any one of the preceding Claims 1 to 3, characterized in that no other treatment elements for the containers are arranged between the cleaning machine and the coating device other than a drying device.

5. The system according to any one of the preceding claims, characterized in that further machines are provided downstream of the coating device for the treatment of containers, in particular, a filler, a capper, a decorating machine and / or a packaging machine.

6. The system according to any one of the preceding claims, characterized in that one of the process-gas sources comprises at least one gas tank or one liquid tank with an evaporator unit for hexamethyldisilazane (HMDSN), hexamethyldisiloxane (HMDSO) or acetylene (ethine).

7. The system according to any one of the preceding claims, characterized in that at least one supply line is still provided for one of the following gases, oxygen (O2), nitrogen (N2) or a noble gas, in particular Argon (Ar), wherein priority is given to all of the aforementioned supply lines.

8. A method for the treatment of containers made of plastic, in particular, containers made of PET, PE, PP or POC, wherein, at a first step, the containers, in particular, the respective container interior(s), are cleaned by means of liquid treatment media, wherein at least one of the treatment media is a lye, such as NaOH, and at least one treatment medium is water, characterized in that, at a subsequent step the containers, in particular, the inner walls of the vessel are coated by a gas separation process, namely by means of a PCVD process with at least two layers, in particular, layers on the inner surface of the containers, and, in particular, wherein the plasma is induced by means of a microwave generator or high-frequency generator.

9. The method according to Claim 8, characterized in that the containers pass through a deposit and return system prior to the first step of cleaning and are transported as complete containers to the first step of cleaning.

10. The method according to Method Claim 8 or 9, characterized in that the generator for plasma induction is a microwave generator, in particular, a high-frequency generator, and the mean energy input from active pulse time to the total pulse time multiplied by the generator power is within the range of 10 to 120 watts, ideally within the range of 20 to 100 watts.

11. The method according to Method Claim 10, characterized in that the active pulse time is within the range of 0.1 ms to 1 ms and the ratio of active pulse time to total pulse time is within the range of 0.01 to 0.05.

12. The method according to any one of the preceding method claims, characterized in that a single or multiple coating is already applied to the inner surface of newly produced containers before the first step of cleaning.

13. The method according to any one of the preceding method claims, characterized in that at least one three-layer system consisting of an adhesive (base coating), a barrier layer (barrier coating) and a protective layer (top coat) is applied to newly produced containers and before the first filling and ideally immediately after production, and wherein, after the container has been used and the containers are returned by means of the deposit and return system, these are cleaned and then coated only partially or additionally by applying - at least one additional barrier layer (barrier coating) and at least one additional protective layer (top coat) or - only another (new) protective layer (top coat) as the outermost layer.

14. The method according to any one of the preceding method claims, characterized in that the temperature of at least one of the treatment media for the containers, which is a lye, is within the range of 30 °C to 70 °C, ideally within the range of 40 °C to 60 °C.

15. The method according to any one of the preceding method claims, characterized in that it is carried out using a system according to any one of the Claims 1 to 7.