METHOD FOR REDUCING VOLATILE SUBSTANCES IN A PLASTICS RECYCLING PRODUCT, RECYCLING DEVICE AND CONTROL UNIT

Description

State of the art

[0001] The invention relates to a device or a method according to the preamble of the independent claims.

[0002] For example, a plastic can be processed using an extruder with the addition of additives. Disclosure of the invention

[0003] Against this background, the approach presented here introduces a method for reducing volatile substances, particularly odors, during plastics processing, a processing device, and a control unit that utilizes this method. Advantageous further developments and improvements of the device specified in the independent claim are possible through the measures listed in the dependent claims. Generic methods and devices are described in patents EP3263302A1, JP2005271376A, DE102014016380A1, and JP2013237791A.

[0004] A method for reducing volatile substances, especially odors, during plastics processing is presented, the method comprising the following steps: Conveying a plastic into an excitation zone of a processing device; and exciting a plasma and / or applying ozone in the excitation zone to decompose the volatile substances from the plastic.

[0005] The term "plastic" can refer to a single plastic component or a mixture of different types of plastic. It can also refer to plastic components, plastic waste, and / or recycled plastics. A recycled plastic component can be understood as a plastic or plastic component that has been at least partially processed. The process can be carried out, for example, to compound the plastic. For example, the excitation zone can be located in a conveying system for transporting the plastic. The plastic can be melted, homogenized, kneaded, or pressurized during, before, or after conveying.

[0006] According to one embodiment, the method can include a step of melting the plastic. This melting step can be performed, for example, before the plastic is fed into the processing device or while the plastic is in the processing device, such as during conveying within the device. Melting the plastic can modify and improve its properties.

[0007] In particular, the molten plastic can be combined with fillers and / or reinforcing agents to achieve targeted property modifications. These property modifications can include strength, toughness, elongation, etc. Such property modifications are generally achieved through physical processes. According to the approach described here, in addition to the known property modifications, chemical reactions are used to decompose the volatile substances that escape from the plastic or its components and cause the unpleasant odor of the processed plastic.

[0008] Furthermore, this method can improve adhesion between the plastic and added additives, or intermolecular adhesion within the plastic or a plastic mixture. It also enables the in-situ generation of nanofillers such as lubricants, adhesives, or nucleating agents, as well as conductivity and optical properties. Another advantage of such a plasma-initiated, reactive compounding process is the ability to induce crosslinking or polymerization reactions through a UV component in the plasma.

[0009] According to one embodiment, the process may include a step of adding an auxiliary substance. The auxiliary substance may be, for example, a solid, liquid, or gaseous precursor, or an auxiliary gas. A precursor can be understood as a film-forming or non-film-forming starting material in chemical vapor deposition. The auxiliary substance may, for example, contain oxygen, nitrogen, argon, and / or xenon. Furthermore, the auxiliary substance may contain hexamethyldisiloxane (HMDSO).

[0010] Furthermore, a gas or gas mixture can be added as the auxiliary substance during the addition step. This can promote the outgassing of the auxiliary substance.

[0011] According to a further embodiment, the additive can be added to the plastic before and / or during conveying. This allows the plastic to be conveyed and mixed with the additive in a single step, thus accelerating the processing of the plastic.

[0012] It is advantageous to add the additive during the melting process. This ensures a uniform mixture of the additive and the plastic.

[0013] According to one embodiment, the plastic and / or the additive can be excited to plasma formation during the excitation step. This can improve the processing of the plastic. During the processing of the plastic, also called compounding, the property profile of the plastic can be changed by adding at least one additive, for example, the additive.

[0014] The additive can be excited as a degassed additive during the excitation step. Degassing the additive makes excitation very simple. Additionally or alternatively, the additive can be excited as a liquid additive. This is particularly suitable, for example, if low pressure cannot be generated to degas the additive. Additionally or alternatively, the additive can be excited as an additive mixed with the plastic. This simplifies the design of the processing equipment, as there is no need to separate the additive from the plastic.

[0015] According to a further embodiment, ozone can be generated by the plasma during the excitation step. This means that the ozone generated by the plasma acts essentially at the same location as the plasma itself, thus advantageously enhancing the plasma's effect. Through the simultaneous action of the plasma and the ozone, the volatile substances responsible for the plastic's odor change their chemical composition in such a way that they are no longer, or hardly, perceptible to humans.

[0016] According to a further embodiment, in the ozone application step, the ozone can be supplied by an external unit, in particular an ozone generator. This allows the amount of ozone that decomposes the volatile substances to be precisely controlled. This is particularly suitable for plastics with a high recycled content, which have a high concentration of volatile substances.

[0017] According to one embodiment, the excitation zone is shaped to allow at least one additive to outgas from the plastic. Outgassing can be understood as the spontaneous escape of gases from the plastic. It can also refer to the controlled removal of gases from the plastic, which can also be called degassing. In this case, the excitation zone can be designed as a low-pressure zone. A low-pressure zone can be understood as a region of the processing device that has a lower pressure compared to the ambient pressure of the processing device. Alternatively, the ambient pressure, also called atmospheric pressure, can prevail in the excitation zone. According to one embodiment, the excitation zone is a conventional opening in the cylinder of the processing device, also called a compounder.

[0018] Thus, according to different embodiments, the plastic and / or the additive can be exposed to low pressure or atmospheric pressure in the excitation zone. Alternatively, the plastic and / or the additive can be exposed to overpressure. For example, the pressure within the excitation zone can be adjusted to optimally excite the additive.

[0019] It is further advantageous if, during the plasma excitation and / or ozone application step, the plasma and / or ozone act on a surface of the plastic to decompose the volatile substances emanating from the plastic. The plastic can be in solid, liquid, or molten form. This ensures that the volatile substances are exposed to the plasma and / or ozone immediately after escaping the plastic or the molten plastic, thus decomposing them effectively and efficiently.

[0020] According to one embodiment, the plasma and / or ozone can be excited and / or applied over a large area and / or locally at various points on the surface of the plastic. This can be achieved, for example, via a plurality of nozzles through which the plasma and / or ozone is directed onto the surface of the plastic. The nozzles can be arranged at openings along the processing device. The nozzles can be operated under both negative pressure and ambient pressure. This results in particularly efficient decomposition of the volatile substances.

[0021] It is also advantageous if at least one additional additive is added to the plastic during the addition step. During the conveying step, the plastic can be conveyed into the excitation zone. According to one embodiment, outgassing of the additional additive from the plastic can be enabled. During the excitation step, the additional additive can be excited in the excitation zone to form the plasma and, additionally or alternatively, a further plasma for processing the plastic. The additional additive can be a substance with properties different from those of the additive. Accordingly, the further plasma can have properties different from those of the additive. This embodiment enables comprehensive manipulation and optimization of the plastic using various additives.

[0022] The process can optionally include an addition step in which at least one additive is added to the plastic. This additive can be added before the mixing process and / or during the excitation phase. An additive, similar to an auxiliary substance, can be understood as a substance used to influence the properties of the plastic. The additive can have different properties than the auxiliary substance, thereby further improving the properties of the plastic.

[0023] According to a further embodiment, the method can include a step for removing exhaust gases generated during excitation. This embodiment prevents contamination of the plastic during excitation.

[0024] This process can be implemented, for example, in software or hardware, or in a hybrid form of software and hardware, such as in a control unit.

[0025] The approach described here also creates a processing device for reducing volatile substances, especially odors, during plastics processing, wherein the processing device has the following features: an excitation zone; a conveying device configured to convey a mixture of an auxiliary substance and the plastic into the excitation zone; and an excitation device configured to excite a plasma (112) and / or apply ozone in the excitation zone (108) to decompose the volatile substances from the plastic (104).

[0026] The processing device could, for example, be an extruder with a screw conveyor as the conveying unit. The excitation zone could be located within the conveying unit. The excitation unit could, for example, be a radiation source for irradiating the surface of the plastic with electromagnetic radiation, such as a laser beam. The excitation unit could be located, at least partially, within the excitation zone.

[0027] According to one embodiment, the conveying device can be designed as a screw conveyor. Additionally or alternatively, the conveying device can be designed as a component of an extruder. For example, the conveying device can be configured to convey the plastic to an exit opening of the extruder. This embodiment enables efficient conveying and processing of the plastic.

[0028] According to a further embodiment, the excitation device can include an ozone application unit connected to an ozone source, in particular an ozone generator. This allows the amount of ozone that decomposes the volatile substances to be precisely controlled and supplied to the plastic. This is particularly suitable for plastics with a high recycled content, which have a high concentration of volatile substances.

[0029] According to a further embodiment, the excitation device can have a plurality of nozzles with which the plasma can be excited on a surface of the plastic and / or the ozone can be applied to a surface of the plastic, wherein the plurality of nozzles are arranged on the excitation device such that the plasma and / or the ozone acts over a large area and / or locally at different points on the surface of the plastic in order to decompose the volatile substances emanating from the plastic. This results in particularly efficient decomposition of the volatile substances.

[0030] According to another embodiment, the excitation zone can be designed to subject the plastic to a maximum pressure of 1 bar. This enables efficient outgassing of the additive.

[0031] The approach presented here further creates a control unit that is configured to perform, control, or implement the steps of a variant of the method presented here in appropriate devices. This embodiment of the invention in the form of a control unit also allows the problem underlying the invention to be solved quickly and efficiently.

[0032] For this purpose, the control unit can have at least one processing unit for processing signals or data, at least one storage unit for storing signals or data, at least one interface to a sensor or actuator for reading sensor signals from the sensor or for outputting control signals to the actuator, and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The processing unit can be, for example, a signal processor, a microcontroller, or the like, while the storage unit can be flash memory, an EPROM, or a magnetic storage device.The communication interface can be configured to read or output data wirelessly and / or via wired connections, whereby a communication interface that can read or output wired data can, for example, read this data electrically or optically from or output it into a corresponding data transmission line.

[0033] In this context, a control unit can be understood as an electrical device that processes sensor signals and outputs control and / or data signals accordingly. The control unit can have an interface, which can be implemented in hardware and / or software. In the case of a hardware-based interface, the interfaces can, for example, be part of a so-called system ASIC, which incorporates various functions of the control unit. However, it is also possible that the interfaces are separate integrated circuits or at least partially comprised of discrete components. In the case of a software-based interface, the interfaces can be software modules, which, for example, are located on a microcontroller alongside other software modules.

[0034] Exemplary embodiments of the invention are shown in the drawings and explained in more detail in the following description. It shows: Fig. 1 a schematic representation of a processing device according to an exemplary embodiment; Fig. 2 a schematic representation of a control unit according to an exemplary embodiment; and Fig. 3 a flowchart of a process according to an exemplary embodiment.

[0035] In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and acting similarly, without repeating these elements.

[0036] Fig. 1 Figure 1 shows a schematic representation of a processing device 100 according to an exemplary embodiment. The processing device 100 comprises a conveying device 102, here a screw conveyor, for conveying a plastic 104. The conveying device 102 is designed to convey the plastic 104 into an excitation zone 108 of the processing device 100.

[0037] One or more plasma sources 111 and / or ozone sources 113 arranged on the excitation device 110, particularly in an excitation zone 108, are designed to decompose the volatile substances emanating from the plastic 104. According to this embodiment, three plasma sources 111 and / or ozone sources 113, each with an excitation zone 108, are provided. The plasma sources 111 can be supplied by an external gas supply, for example with oxygen, nitrogen, argon, xenon, and / or hexamethyldisiloxane (HMDSO), to generate a plasma 112. The ozone sources 113 can be supplied by an ozone generator, particularly an external one. Furthermore, the plasma sources 111 can be designed to also generate ozone during plasma formation.The plasma 112, the ozone formed by the plasma sources 111 and / or the ozone from the ozone sources 113 decompose volatile substances emanating from the plastic 104, which are responsible for the odor of the products made from the plastic 104.

[0038] According to a further embodiment, the excitation device 110 can have a plurality of nozzles 115 with which the plasma 112 can be excited on a surface of the plastic 104 and / or the ozone 113 can be applied to a surface of the plastic 104, wherein the plurality of nozzles 115 are arranged on the excitation device 110 such that the plasma 112 and / or the ozone 113 acts over a large area and / or locally at different points on the surface of the plastic 104.

[0039] In another embodiment, the plastic 104 can be mixed with an additive 106 containing, for example, oxygen, nitrogen, argon, and / or xenon. The additive 106 can also contain hexamethyldisiloxane (HMDSO). When the plastic 104 is subjected to a specific pressure, the additive 106 can outgas from the plastic. The conveying device 102 is designed to convey the mixture of the plastic 104 and the additive 106 into three excitation zones of the processing device 100, which, according to this embodiment, are configured as low-pressure zones 108. The pressure in these zones is lower than the ambient pressure of the processing device 100, specifically the conveying device 102. The negative pressure prevailing in the low-pressure zones 108 causes the additive 106 to outgas from the plastic 104.An excitation device 110, arranged adjacent to the low-pressure zones 108 and comprising a plasma source 111 and / or an ozone source 113, is designed to excite the auxiliary substance 106 outgassing from the plastic 104 to a plasma 112 in an active plasma zone and / or to apply ozone to the plastic 104. The volatile substances from the plastic 104 are selectively decomposed by the plasma 112 and / or the ozone. Furthermore, the properties of the plastic 104 can be selectively modified and improved by the plasma 112.

[0040] According to these embodiments, the processing device 100 is designed as an extruder with an outlet opening 114. The conveying device 102 is rotatably arranged in a housing 116 of the extruder and is designed to convey the plastic 104 from a feed device 118 via the low-pressure zone 108 to the outlet opening 114. The additive 106, plastic waste, and / or recyclates can be added to the plastic 104 via the feed device 118.

[0041] According to Fig. 1 The housing 116 has a cross-section that tapers towards the outlet opening 114, resulting in a concentric shape of the housing 116 in the conveying direction. The conveying device 102 has a tip 120 at one end facing the outlet opening 114, the contour of which essentially corresponds to the contour of the tapered cross-section of the housing 116. The feeding device 118 is designed as a material container, for example as a pressure pot, with an outlet opening 122. The housing 116 has a housing opening 124, which is arranged opposite the outlet opening 122. The auxiliary material 106, the plastic waste and / or the recyclates can thus enter the conveying device 102 through the outlet opening 122 and the housing opening 124. The low-pressure zone 108 is arranged between the outlet opening 114 and the housing opening 124.

[0042] The conveying device 102 can optionally be implemented with a first threaded section 126 and a second threaded section 128 adjacent to the first threaded section 126, wherein the pitch of the first threaded section 126 differs from the pitch of the second threaded section 128. According to this embodiment, the conveying device 102 is positioned in the housing 116 such that the first threaded section 126 lies at least partially within the low-pressure zones 108 and the second threaded section 128 extends from the first threaded section 126 at least to the housing opening 124. According to this embodiment, the first threaded section 126 has a lower pitch than the second threaded section 128.

[0043] Optionally, the addition device 118 can be used to add additives, polymers or precursors that differ from the auxiliary substance.

[0044] During excitation, additives, precursors, or auxiliary gases can optionally be added. This is indicated by arrow 117. Exhaust gases generated during excitation can optionally be removed, for example, by extraction. This is indicated by another arrow 118.

[0045] To adjust the property profile of the plastic 104, the plastic 104 can be mixed with additives, fillers, aggregates, or reinforcing agents, depending on the embodiment. This can be done in a compounding process using an extruder or compounder, such as a single- or twin-screw extruder, or using a kneader as a conveying device 102. During compounding, the mechanical properties of a base polymer of the plastic 104 can be modified by adding reinforcing agents and fillers or by modifying the impact strength to adjust mechanical parameters such as tensile strength, elongation at break, and impact toughness. Furthermore, color settings can be changed during compounding, and stabilizers and stabilizer systems can be added to prevent temperature-induced chain degradation during processing or application and to improve weather resistance, or processing aids can be added.During compounding, the plastic 104 can also be provided with a flame retardant.

[0046] By selecting a screw geometry for the conveying device 102, the low-pressure zone 108, which can be used for degassing a melt of the plastic 104, can be created in the compounding process.

[0047] According to a further embodiment, the processing device 100 has an excitation zone 108 in which atmospheric pressure prevails.

[0048] Regardless of the pressure prevailing in the excitation zone 108 during operation of the processing device 100, the auxiliary substance 106 can be at least partially dissolved from the plastic 104 for excitation in the excitation zone 108. The auxiliary substance 106 can be present in outgassed or liquid form and be excited. According to one embodiment, the auxiliary substance 106 is excited in the excitation zone 108 while it is still mixed with the plastic 104. According to another embodiment, not only the plastic 104 but also the auxiliary substance 106 is excited in the excitation zone 108.

[0049] Fig. 2 Figure 1 shows a schematic representation of a control unit 200 according to an exemplary embodiment. The control unit 200 can be configured to perform a previously defined function based on Fig. 1 The control unit 200 comprises a feed control unit 202 configured to generate a feed control signal 204 for controlling the feeder of the processing device, the feeder being configured to convey the plastic into the excitation zone using the feed control signal 204. Furthermore, the control unit 200 comprises an excitation control unit 206 configured to generate an excitation control signal 208, using the feed control signal 204, for controlling the excitation device of the processing device, such as a plasma source and / or an ozone source of the control device.The excitation device is designed to generate a plasma in the excitation zone using the excitation control signal 208 and to direct it onto the plastic, as well as to apply ozone generated by the plasma and / or supplied by an external ozone source to the plastic.

[0050] Fig. 3 Figure 300 shows a flowchart of a process 300 according to an exemplary embodiment. The process 300 for reducing volatile substances, especially odors, during plastics processing can, for example, be used in conjunction with a previously described process based on… Fig. 2 The described control unit is used. In step 310, the plastic is conveyed into the low-pressure zone of the processing device. In step 320, a plasma is excited and / or ozone is applied to decompose the volatile substances from the plastic.

[0051] Steps 310 and 320 can be performed simultaneously. Furthermore, steps 310 and 320 can be performed consecutively.

[0052] According to one embodiment, in an optional step of the process, 300 film-forming or non-film-forming precursors in solid, liquid, or gaseous form, or auxiliary gases, are added to the plastic in a compounding process or an upstream process step, such as in a pressure chamber. In step 310, the introduced precursors or auxiliary gases are then degassed in the low-pressure zone of the compounder. For example, in step 310, the precursors or auxiliary gases are excited to the plasma by means of electromagnetic waves, lasers, electrical discharges, or similar methods.

[0053] Used process gases can be easily removed by extraction in an optional process step.

[0054] Optionally, additional additives can be added in the low-pressure zone. This addition can take place, for example, in step 310, step 320, or both steps.

[0055] Auxiliary materials in the form of precursors or auxiliary gases can be dosed more easily compared to minute quantities of powders or fine-grained solids.

[0056] An additional improvement in the properties of the compounded plastic achieved by means of process 300 enables the use of economical raw materials with originally inferior material properties, such as plastic waste.

Claims

1. Method (300) for reducing volatile substances, in particular odours, in the processing of a plastic, wherein the method (300) comprises the following steps: conveying (310) a plastic (104) into an excitation zone (108) of a processing device (100); and exciting (320) a plasma (112) and applying (320) ozone (113) in the excitation zone (108) in order to decompose the volatile substances from the plastic (104), wherein a step of melting the plastic (104) is additionally provided before or during the step of exciting (320) or applying (320), and wherein, in the step of exciting (320) the plasma (112), ozone (113) is formed by the plasma (112), wherein in the step of exciting (320) the plasma (112) and of applying (320) the ozone (113), the plasma (112) and the ozone (113) act on a surface of the plastic (104) in order to decompose the volatile substances leaving the plastic (104).

2. Method (300) according to Claim 1, in which a gas or gas mixture is added as an auxiliary (106) to the plastic (104) before and / or during the conveying (310) and / or during the melting.

3. Method (300) according to Claim 1 or 2, in which, in the step of exciting (320), the plastic (104) and / or the auxiliary (106) is excited to form plasma.

4. Method (300) according to one of Claims 1 to 3, in which, in the step of applying (320) ozone (113), the ozone (113) is supplied by an external unit, in particular by an ozone generator.

5. Method (300) according to Claim 1, in which the plasma (112) is excited and the ozone (113) is applied over a large area and / or locally at various places on the surface of the plastic (104).

6. Processing apparatus (100) for reducing volatile substances, in particular odours, in the processing of a plastic, wherein the processing apparatus (100) has the following features: an excitation zone (108); a conveying device (102), which is designed to convey a plastic (104) into the excitation zone (108); and an excitation device (110), which is designed to excite a plasma (112) in the excitation zone (108) and to apply ozone (113), wherein the plasma (112) and the ozone (113) act on a surface of the plastic (104) in order to decompose the volatile substances from the plastic (104), wherein the excitation zone (108) has a means for melting the plastic (104) before or during the exciting of the plastic (104) and in which the excitation device (110) has an ozone application unit, which is connected to an ozone source, in particular to an ozone generator.

7. Processing apparatus (100) according to Claim 6, in which the excitation device (110) has a plurality of nozzles (115), with which the plasma (112) can be excited on a surface of the plastic (104) and the ozone (113) can be applied on a surface of the plastic (104), wherein the plurality of nozzles (115) are arranged on the excitation device (110) in such a way that the plasma (112) and the ozone (113) act over a large area and / or locally at various places on the surface of the plastic (104) in order to decompose the volatile substances leaving the plastic (104).

8. Controller (200) with units (202, 206) which are designed to perform and / or to activate the method (300) according to one of Claims 1 to 5 on a processing apparatus according to one of Claims 6 to 7.