Field of the invention

The present invention relates to a method for de-chlorinating a plastic compound comprising at least one polymer with a chloride content and to a corresponding plastic processing apparatus to execute the method.

Background of the Invention

Chlorine containing plastic materials are critical substances due to the chlorine content, when being processed further. Especially the recycling of such materials requires processes capable for removing the chlorine content in order to provide a chlorine-free or chlorine-reduced end product. The most packaging materials are contaminated with polymers with a chloride content. Packaging materials often comprise non-separable composite materials with chlorine content. Therefore, it would be desirable to use a process providing chlorine-free or chlorine-reduced end products regardless of the chlorine content of the material entering the process.

The end-products might be used for further processing, e.g. in a plastic oiling plant. JP 2007-314754 provides a plant for melt-treating waste matters, which contributes to the detoxification of various gases formed in liquefaction treatment. The plant has a melting device equipped with an inner pot which stores a molten oil for melting waste matter and has a treating space into which the waste matter can be introduced and an outer pot for heating the inner pot to maintain the temperature of the molten oil stored in the inner pot at a predetermined temperature, a de-chlorination device, a cooling device for cooling an exhaust gas from which a chlorine based gas has been removed, an oil and water recovering device for removing water and an oil content from the exhaust gas, and a gas combustion furnace for burning unrecovered gas which has not been recovered. However, thermal decomposition of plastics is performed while solid matter is contained, and there is a possibility that the quality of recovered oil is deteriorated. Further, when the plastic is not de-chlorinated desalted before the thermal decomposition of the plastic, and polyvinyl chloride is contained in the plastic to be oiled, there is a possibility that the plastic cannot be appropriately oiled.

Summary of the invention

It is an object of the present invention to provide a method and a corresponding plastic processing apparatus operated by this method providing at least a feedstock of processed plastic compound material being chlorine free or having a largely reduced chlorine content regardless of the chlorine content of the nonprocessed plastic compound at the beginning of the process.

This object is solved by a method for at least de-chlorinating a plastic compound comprising at least one polymer with a chloride content in a plastic processing apparatus comprising following steps: providing the plastic compound to the plastic processing apparatus from a feedstock; melting the plastic compound by heating the plastic compound to a predetermined melting temperature and mixing and/or homogenizing the melted plastic compound in one or more processing units for melting, mixing and/or homogenizing; chemically separating chlorine from the chlorine containing polymer in a secession unit via applying a secession temperature higher than the melting temperature and via a dwell time of the melted plastic compound in the secession unit of the plastic processing apparatus; preferably further chemical separating organic acids from the melted plastic compound in the secession unit; extracting chlorine out of the secession unit or out of a subsequent unit in process direction behind to the secession unit; and providing the melted plastic compound with at least reduced chlorine content as a petrochemical feedstock for further processes, preferably for oiling the provided petrochemical feedstock with at least reduced chlorine content via temperature increase to an oiling temperature and dwell time of the polymer mixture in an oiling unit of the plastic processing apparatus.

The claimed plastic processing apparatus may serve as a recycling device for used or misproduced packaging material for providing oiled plastics for further use in subsequent processing apparatuses. Common packaging material is commonly contaminated with polymers with a chloride content. Packaging material often comprise non-separable composite materials with chlorine content. The method according to the present invention is capable to eliminate the chlorine content from the processed plastic compound or to at least reduce the chlorine content down to 2% weight of the plastic material. As an example, the plastic compound may comprise polyethylene terephthalate and/or at least one polymer with a chloride content may comprise polyvinylchlorid.

The term “chemically separating chlorine” denotes the cracking of a chemical bond between the chlorine or a chlorine containing fraction of the polymer and the other part of the polymer resulting in a remaining polymer without chlorine content and the cracked chlorine or chlorine containing fraction as gas content of melted portion still in mixture with the plastic compound material. Within the present invention the term “chlorine” denotes a gas or a melted material consisting of chlorine or a chlorine containing fraction or material being cracked off from the former polymer, which contained chlorine before being cracked off. The term “chlorine” is not limited to a Cl-molecule. The term “chlorine” may also denotes larger organic fractions comprising one or more bonded Cl-atom.

The chemical separation process is mainly determined by secession temperature and dwell time, where a higher secession temperature increases the secession rate of chlorine. The secession rate denotes the amount of chlorine that is separated from the original chlorine-containing polymer by bond breaking per time unit. At a certain secession temperature, the secession amount will increase with increase dwell time. In this case, the secession rate keeps constant, but the longer process time (dwell time) results in more chemically separated chlorine. Therefore, a longer dwell time at a lower secession temperature might lead to the same amount of chemically separated chlorine as processing the plastic compound with shorter dwell time at higher secession temperature. In case of applying vacuum during the chemical separation step, the secession might be further improved due to high chlorine partial pressure effects. Suitable dwell times are between Imin and 15min depending on the applied secession temperature.

The extracting step might be executed by release of chlorine gas from the secession unit or a subsequent unit along the process way. Preferably the chlorine gas is released at a process position as early as possible after having chemically separated the chlorine to avoid contamination or corrosion of processing units downstream the process flow. After chemical separation of chlorine, the chlorine gas may have a large partial pressure suitable to stream out the particular unit without further measures. Nevertheless, the extraction of chlorine gas might be improved by applying a vacuum (under-pressure) to the secession unit or a subsequent unit, where the chlorine gas shall be extracted. Suitable vacuum pressures (or under-pressure) to be applied are less than lOOmbar, preferably less than lOmbar, more preferably less than Imbar. People skilled in the art can select suitable pumping units to provide such vacuum (under-pressure), e.g. suitable dry running pumps. In case of fluid chlorine contents within the melted plastic compound, the fluid chlorine content might be extracted by suitable melt filter units downstream to the secession unit. The above specified process is capable to reduce the remaining content of the feedstock at the end of the de-chlorination below at least 2% weight, under specific circumstances below at least 1.5% weight or even less than 1% at the most.

The plastic processing apparatus is adapted suitably to guarantee transport capability of the plastic compound along the process way ion process direction from the process entry to the process end. This capability might be provided by a continuous material flow from the process entry, e.g. by an extruder device as part of the plastic processing apparatus, which conveys the material in the process direction (direction of material flow) also serving for material convey in the units following to the extruder device. In an embodiment an additional first minimum pressure is applied to the melted plastic compound before entering the secession unit for executing at least the chemical separation step. In another embodiment alternatively or in combination with to the previous embodiment a second minimum pressure might be applied to the melted plastic compound with at least reduced chlorine content before entering the oiling unit for executing the oiling step. The build-up first and/or second pressure further improves the material convey along the process flow. The pressure build-up might be provided by the pipes connecting each particular unit to another along the process flow. The chlorine-binding material with bonded chlorine might be extracted from the melted plastic compound with a melt filter unit arranged in the process flow direction behind the secession unit. In case of further processing the provided petrochemical feedstock, e.g. oiling the petrochemical feedstock, the term “petrochemical feedstock” does not imply any intermediate storage of the petrochemical feedstock waiting for further processing. In one embodiment the petrochemical feedstock might leave the secession unit or any further unit directly to another unit, where further processing is executed. The other unit might be directly connected to the secession unit or any following unit along the process flow. In other embodiment, the petrochemical feedstock might be stored and transported to another further processing location.

The method according to the present invention provides at least a feedstock of processed plastic compound material being chlorine free or having a largely reduced chlorine content regardless of the chlorine content of the non-processed plastic compound at the beginning of the process.

In an embodiment the predetermined melting temperature is adjusted to a temperature, where the plastic compound is melted while chemical separation of chlorine is negligible compared to the amount of chlorine chemically separated in the secession unit. The term “negligible” denotes a secession rate of 10% or less compared to the secession rate within the secession unit. The avoidance or the at least reduction of chemical separation of chlorine within the processing unit for melting, mixing and/or homogenizing avoids corrosion of process equipment at stages, where corrosion resistance is not foreseen. Furthermore, the melting compound does not comprise a significant gas content lowering or avoiding a gas pressure within the processing unit for melting, mixing and/or homogenizing to not disturb the melting, mixing and/or homogenizing process as well as avoiding negative impacts on the unit construction and material. Typical melting temperatures are below 200°C. However, the required melting temperature depends on the specific composition of the plastic material to be processed. For example, composite materials and/or polyamide materials require higher melting temperatures. In case of applying melting temperatures above 200°C it is advantageous, if the processing unit for melting, mixing and/or homogenizing is made of a material with higher resistance against chemical separated chlorine or chlorine-based materials.

In another embodiment the secession temperature applied in the chemical separation step is at least 250°C, preferably higher than 300°C, more preferably between 300°C and 400°C. The secession temperature leads to a chemical separation of chlorine from the chlorine containing polymer. The chemically separated chlorine might be present as gas or melted portion within the melted plastic compound at this process stage. In order to achieve a desired reduction of the chlorine content within the plastic compound, the applied temperature might be increased or decreased within the above specified temperature ranges in dependence of the chemical bonding properties of the chlorine in the processed plastic material. With the above specified secession temperatures, the still remaining content of chlorine containing polymers after the secession step is below 2% weight. Generally, the hotter the secession temperature the lower is the content of still chlorine containing polymers within the melted plastic compound.

In another embodiment, in the extracting step the chlorine is extracted as chlorine gas, preferably by applying a vacuum, or as fluid material consisting of chlorine or chlorine containing material. The extracting step removes the separated chlorine from the melted plastic compound to be able to provide a safe and nonpoisoning and non-aggressive feedstock for further processing in the plastic process apparatus. After extraction, the chlorine gas might be rained off in a separator or stored as solid material originating from fluidly extracted chlorine.

In another embodiment the method further comprises the step of pre-treating a feedstock of the plastic compound to be provided to the plastic processing apparatus, preferably followed by a step of preconditioning the plastic compound, before providing it to the plastic processing apparatus. Pre-treating and/or preconditioning is used to filter the feedstock in order to remove metallic, inorganic or other solid materials like wood or sand not being plastic compounds out of the material to be fed into the plastic processing apparatus not to disturb or contaminate the subsequent plastic processing. In case of using a feedstock of a sufficient purity, the pre-treating and preconditioning steps are not necessary.

In another embodiment a chlorine-binding compound is added to the feedstock of plastic compound before providing it to the plastic processing apparatus and/or at one or more later process steps executed by the plastic processing apparatus, preferably the chlorine-binding compound is a calcium compound such as calcium oxide or calcium carbonate. The added chlorine-binding compound shall bind chlorine being chemically separated from the former chlorine containing polymer. In this case the cracked off chlorine is not present as gas but as bonded material in a fluid phase. This method to bind the cracked off (chemically separated) chlorine can avoid or at least largely reduce generation of chlorine gas to avoid or at least reduce corrosion effects in the secession unit or in subsequent units until the chlorine is extracted from the melted plastic compound. The chlorine-binding compound might be added at an early position within the process flow, e.g. in the feedstock prior to the plastic processing or at the beginning of the melting process to enable a good and homogeneous distribution of the chlorine-binding compound within the plastic compound for the later occurring secession process in the secession unit. Additionally, when adding the chlorine-binding compound in an early stage it would enable to also bind chemically separated chlorine, which cracks off from the chlorine-containing polymer prior to the secession unit due to temperature effect also present at lower temperatures. Such early chlorine separation occurs at significant lower secession rates. However, such early separated chlorine can be bonded to the chlorine- binding compound before causing any trouble. The chlorine-binding compound might also be added at any later stage of the plastic processing as an alternative or cumulative measure to bind chlorine to the chlorine-binding compound. There might be one or more positions along the process flow, where chlorine-binding compound is added to the to be melted or already melted plastic compound. In case of adding the chlorine-binding compound at a later stage of the process, the chlorine-binding compound will have its full binding capacity for chemically separated chlorine.

In another embodiment volatiles, preferably water or humidity, are extracted from the melted plastic compound before entering the chemical separation step. Volatiles might be extracted in order to improve the purity of the processed plastic compound. In case of extracting water or humidity, the building of chlorine acid from reaction of chlorine with water or humidity can be avoided or at least largely reduced. This helps to reduce corrosion effects or other critical effects due to the present of separated chlorine. Especially polyethylene terephthalate introduces a higher water content to the process and additionally requires higher melting temperatures releasing chlorine and/or organic acids to a certain extend. For the resulting amount of chemically separated chlorine during melting, the reduction of water or humidity is beneficial in the process steps before the plastic compound enters the secession unit.

In another embodiment foreign materials are removed from the melted plastic compound via melt filtration prior to the chemical separation step of chloride and/or prior to further following process steps for the de-chlorinated plastic compound. The term “foreign material” denotes any material not wanted to be present in the de-chlorinated plastic compound as petrochemical feedstock for further following processes. Foreign materials usually denote impurities of the feedstock. The removal might be executed with melt filtration. In case of arranging the melt filtration behind the secession unit, the removal may incorporate removal (extraction) of the chlorine-binding material with bonded chlorine. The melt filtration might be executed in a melt filtration unit. In another embodiment, where the resulting petrochemical feedstock for further processes is used for oiling the petrochemical feedstock material, the applied oiling temperature is higher than the secession temperature to obtain a hydrocarbon oil gas by thermal decomposition. Applied oiling temperatures can be larger than 350°C, preferably larger than 400°C. The oils resulting from oiling the petrochemical feedstock material might be oil of monomers or oligomers as start material for other processes or might by combustible oils for energy supply.

In another embodiment the method further comprises a recovery step of cooling the hydrocarbon oil gas and recovering the hydrocarbon oil gas as a hydrocarbon oil.

The present invention further relates to a plastic processing apparatus for at least de-chlorinating a plastic compound comprising at least one polymer with a chloride content adapted to execute the method according to the present invention comprising: one or more processing units for melting the plastic compound provided from a feedstock by heating the plastic compound to a predetermined melting temperature and mixing and/or homogenizing the melted plastic compound; a secession unit for chemically separating chlorine from the chlorine containing polymer via applying a secession temperature higher than the melting temperature and via a dwell time of the melted plastic compound, preferably also for further chemical separating organic acids from the melted plastic compound; wherein the secession unit or a subsequent unit of the plastic processing apparatus arranged in process direction behind to the secession unit are adapted for extracting chlorine; and where the plastic processing apparatus is adapted for providing the melted plastic compound with at least reduced chlorine content as a petrochemical feedstock for further processes, preferably for oiling the melted plastic compound with at least reduced chlorine content via temperature increase to an oiling temperature and dwell time of the polymer mixture in an oiling unit of the plastic processing apparatus.

The plastic processing apparatus according to the present invention provides at least a feedstock of processed plastic compound material being chlorine free or having a largely reduced chlorine content regardless of the chlorine content of the non-processed plastic compound at the beginning of the process.

In an embodiment the one or more processing units, the secession unit, a unit to extract the chlorine and possible additional units are suitably connected to continuously process the plastic compound until the petrochemical feedstock for further processes is obtained, where the process direction extends from the unit for melting the plastic compound along the other units to the petrochemical feedstock, preferably further comprising additional units for further process steps arranged along the process direction in between two units or as first or last unit in process direction. The optional oiling unit is one of the possible additional units. The suitable connection between the units might be flanges of connection pipes or other suitable connection. The arrangement of the units might be a linear arrangement resulting in a linear process of the plastic compound.

In another embodiment the plastic processing apparatus comprises at least one of an internal mixer, a single-screw extruder, a twin-screw corotating extruder, a twin-screw counter rotating extruder, a continuous mixer, a co-kneader or any other machine suitable to melt, mix and/or homogenizing the plastic compound, preferably plastic processing apparatus comprises a planetary roller extruder, as one or more units. The above listed components of the plastic processing apparatus are known to skilled people. A planetary roller extruder is beneficial, because the planetary roller extruder provides a good melting, mixing and homogenizing properties combined with the possibility to provide dedicated process properties such as temperature profiles within certain process parts and the possibility to add and/or extract materials along the process flow.

In another embodiment the plastic processing apparatus further comprises one or more pre-treating units for pre-treading a feedstock of plastic compound to be provided to the plastic processing apparatus, preferably additionally a preconditioning unit for preconditioning the plastic compound before providing it to the plastic processing apparatus.

In another embodiment the plastic processing apparatus further comprising one or more feeder units for adding a chlorine-binding compound to the feedstock of plastic compound before providing it to the plastic processing apparatus and/or at one or more later process steps executed by the plastic processing apparatus.

At this point it should also be mentioned that in the context of the present patent application the expression "in particular" is always to be understood in such a way that an optional, preferred feature is introduced with this expression. Accordingly, the expression is not to be understood as "and indeed" and not as namely".

It is understood that features of the solutions described above or in the claims may also be combined, if necessary, in order to be able to implement the advantages and effects achievable herein in a correspondingly cumulative manner. The above-mentioned embodiments of the present invention can also be combined with each other in deviation from the claim references given in the claims.

Brief Description of the Drawings

In addition, further features, effects and advantages of the present invention are explained with reference to the accompanying figures and the following description. Components which in the individual figures at least essentially correspond with respect to their function are marked here with the same reference signs, whereby the components do not have to be numbered and explained in all figures.

The figures show:

Fig. 1 : is a schematic illustration of a plastic processing apparatus for at least de-chlorinating a plastic compound comprising at least one polymer with a chloride content as an embodiment of the present invention, and Fig. 2: is a flowchart of an embodiment of the method for at least dechlorinating a plastic compound according to the present invention. Description of detailed embodiments

Fig. 1 shows a schematic illustration of a plastic processing apparatus 1 for oiling a plastic compound PC comprising at least one polymer with a chloride content as an embodiment of the present invention comprising the following components of one or more processing units 2 for melting the plastic compound PC provided from a feedstock F by heating the plastic compound PC to a predetermined melting temperature and mixing and/or homogenizing the melted plastic compound PC; a secession unit 3 for chemically separating chlorine from the chlorine containing polymer via applying a secession temperature higher than the melting temperature and via a dwell time of the melted plastic compound PC, preferably also for further chemical separating organic acids from the melted plastic compound PC; wherein the secession unit 3 or a subsequent unit 4 of the plastic processing apparatus 1 arranged in process direction PD behind to the secession unit 3 are adapted for extracting chlorine; and where the plastic processing apparatus 1 is adapted for providing the melted plastic compound PC with at least reduced chlorine content as a petrochemical feedstock PF for further processes, preferably for oiling the melted plastic compound PC with at least reduced chlorine content via temperature increase to an oiling temperature and dwell time of the polymer mixture in an oiling unit of the plastic processing apparatus 1. The one or more processing units 2, the secession unit 3, a unit to extract the chlorine 4 and possible additional units 6 are suitably connected (not shown here) to continuously process the plastic compound PC until the petrochemical feedstock PF for further processes is obtained, where the process direction PD extends from the unit 2 for melting the plastic compound PC along the other units to the petrochemical feedstock PF, preferably further comprising additional units 6 for further process steps along the process direction PD. Additional unit 6 might be a melt filtration unit 6, e,g, arranged in process direction PD behind the processing unit 2, e.g. a planetary roller extruder, or in process direction PD behind the secession unit 3 or behind the subsequent unit 4. In an embodiment the subsequent unit 4 might be the melt filtration unit 6. In order to process the plastic compound, the plastic processing apparatus 1 comprises at least one of an internal mixer, a single-screw extruder, a twin-screw corotating extruder, a twin-screw counter rotating extruder, a continuous mixer, a co-kneader or any other machine suitable to melt, mix and/or homogenizing the plastic compound, preferably plastic processing apparatus comprises a planetary roller extruder, as one or more units. The plastic processing apparatus 1 further comprises a pre-treating unit 7 for pre-treating a feedstock of plastic compound PC to be provided to the plastic processing apparatus 1, preferably additionally a preconditioning unit 8 for preconditioning the plastic compound PC before providing it to the plastic processing apparatus 1. The plastic processing apparatus 1 may further comprise one or more feeder units 9 for adding a chlorine-binding compound to the feedstock F of plastic compound PC before providing it to the plastic processing apparatus 1 and/or at one or more later process steps executed by the plastic processing apparatus 1 as indicated by the dashed lines to each of 2, 3, 4 and 6. In an embodiment, a separate feeder unit 9 is connected to each of the indicated units 2, 3, 4, 6. In other embodiments, there might by only one feeder unit 9 connected to one of the units 2, 3, 4, 6. In another embodiment, one single feeder unit 9 may supply chlorine-binding compounds to two or more of the units 2, 3, 4, 6.

Fig. 2 shows a flowchart of an embodiment of the method 100 de-chlorinating a plastic compound PC according to the present invention, where the plastic compound PC comprises at least one polymer with a chloride content in a plastic processing apparatus 1 comprising following steps of providing 110 the plastic compound PC to the plastic processing apparatus 1 from a feedstock F; melting 120 the plastic compound PC by heating the plastic compound PC to a predetermined melting temperature and mixing and/or homogenizing the melted plastic compound PC in one or more processing units 2 for melting, mixing and/or homogenizing; chemically separating chlorine 130 from the chlorine containing polymer via applying a secession temperature higher than the melting temperature and via a dwell time of the melted plastic compound PC in a secession unit 3 of the plastic processing apparatus 1, where volatiles, preferably water or humidity, are extracted from the melted plastic compound PC before entering the chemical separation step 130; preferably further chemical separating organic acids 140 from the melted plastic compound PC in the secession unit 3 indicated by dashed lines; extracting chlorine 150 out of the secession unit 3 or out of a subsequent unit 4 in process direction PD behind to the secession unit 3, where the chlorine is extracted as chlorine gas CG, preferably by applying a vacuum, or as fluid material FM consisting of chlorine or chlorine containing material; and providing 160 the melted plastic compound PC with at least reduced chlorine content as a petrochemical feedstock PF for further processes. A further process might be oiling 170 the provided petrochemical feedstock PF with at least reduced chlorine content via temperature increase to an oiling temperature and dwell time of the polymer mixture in an oiling unit 5 of the plastic processing apparatus 1. The applied oiling temperature is higher than the secession temperature to obtain a hydrocarbon oil gas by thermal decomposition. The oiling step 170 might be followed by a recovery step 200 of cooling the hydrocarbon oil gas and recovering the hydrocarbon oil gas as a hydrocarbon oil. The predetermined melting temperature is adjusted to a temperature, where the plastic compound PC is melted while chemical separation of chlorine is negligible compared to the amount of chlorine chemically separated in the secession unit 3. The secession temperature applied in the chemical separation step 130 is at least 250°C, preferably higher than 300°C, more preferably between 300°C and 400°C. Foreign materials might be removed from the melted plastic compound PC via melt filtration prior to the chemical separation step 130 of chloride and/or prior to further following process steps for the de-chlorinated plastic compound PC.

Before starting melting of the plastic compound PC the step of pre-treating 180 is executed to the feedstock of plastic compound to be provided to the plastic processing apparatus, preferably followed by a step of preconditioning 190 the plastic compound, before providing it to the plastic processing apparatus 1.

To enhance the chemical extraction of chlorine from the melted plastic compound a chlorine-binding compound is added to the feedstock of plastic compound PC before providing it to the plastic processing apparatus 1 and/or at one or more later process steps executed by the plastic processing apparatus 1, preferably the chlorine-binding compound is a calcium compound such as calcium oxide or calcium carbonate.

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. It should also be noted that not all combinations of the features described in the embodiments are necessarily essential to means for solving the problem of the invention.

List of Reference numerals

1 plastic processing apparatus

2 one or more processing units for melting, mixing and/or homogenizing

3 secession unit for chemically separating chlorine from the chlorine containing polymer

4 subsequent unit in process direction behind to the secession unit

5 oiling unit

6 melt filtration unit

7 pre-treating unit for pre-treading a feedstock of plastic compound

8 a preconditioning unit for preconditioning the plastic compound

9 feeder unit(s) for adding a chlorine-binding compound

100 method for de-chlorinating a plastic compound

110 providing the plastic compound

120 melting the plastic compound by heating the plastic compound to a predetermined melting temperature and mixing and/or homogenizing the melted plastic compound

130 chemically separating chlorine from the chlorine containing polymer

140 chemical separating organic acids from the melted plastic

150 extracting chlorine out of the secession unit or out of a subsequent unit in process direction behind to the secession unit

160 providing the melted plastic compound with at least reduced chlorine content as a petrochemical feedstock

170 oiling the provided petrochemical feedstock

180 pre-treating a feedstock of plastic compound 190 preconditioning the plastic compound

200 recovery step of cooling the hydrocarbon oil gas and recovering the hydrocarbon oil gas as a hydrocarbon oil

CG chlorine gas

FM fluid material consisting of chlorine or chlorine containing material

F feedstock of material to be processed in the plastic processing apparatus

PC plastic compound comprising at least one polymer with a chloride content

PD process direction

PF petrochemical feedstock