Method and equipment for separating different types of plastic from a material mixture

Abstract

Method for separating different types of plastic (4, 7, 10) from or in a mixture of materials (2) in the context of recycling plastic materials comprising the following steps: a) Supplying the material mixture (2), b) Melting at least part of the material mixture (2), wherein several or all types of plastic (4, 7, 10) are contained in the melted part of the material mixture (2), c) Separating one or more types of plastic (4, 7, 10) contained in the molten part of the material mixture (2) from the material mixture (2) based on the specific melt viscosity of the respective molten type of plastic (4, 7, 10), characterized in that at least the molten part of the material mixture (2) is successively passed through various filter stages (3, 6, 9), wherein each filter stage (3, 6, 9) is designed to separate molten and unmelted or higher-viscosity parts of the material mixture (2) in a specific viscosity range, wherein in each filter stage (3, 6, 9) the respective type of plastic (4, 7, 10) with the highest melt viscosity is separated from the molten part of the material mixture (2).

Description

[0001] The invention relates to a method for separating different types of plastic from or in a material mixture according to the preamble of claim 1. The invention also relates to a device for separating different types of plastic from a material mixture according to the preamble of claim 8.

[0002] In general, the invention relates to the field of recycling plastic materials. For efficient and high-quality plastic recycling, plastic materials that are as pure as possible and suitable for processing in a plastics processing plant are desired. Previous approaches often fail to economically extract such pure plastic materials from recycled plastics.

[0003] In many products, different plastics are currently inseparably combined to optimize the performance of a material or product. Examples of such products include multilayer films established in the packaging sector, which can consist of up to six or eight different plastics, or textiles, which often use mixed fabrics, possibly with an additional coating. In addition, many polymer materials are so-called plastic blends, in which different polymers are mixed together at the microstructural level to optimize processing and performance properties.

[0004] Reinforcing components, fillers, adhesives, paper, or plastic laminations pose another recycling challenge. There are currently no satisfactory recycling methods for such material mixtures. Therefore, such material mixtures are often incinerated or disposed of in landfills.

[0005] DE 10 2011 106 244 A1 discloses a method and device for processing contaminated / mixed plastics. US 2019 / 0366591 A1 discloses a recycling process for laminates and multilayer components. DE 695 07 868 T2 discloses a method for separating polymers from polymer mixtures. US 2019 / 0283278 A1 discloses systems and methods for producing continuous filaments from colored recycled PET. DE 28 37 621 A1 discloses a method and device for separating and recovering thermoplastics from plastic waste.

[0006] The invention is based on the task of improving the recycling of individual plastic types or plastic mixtures in such material mixtures. One goal is to obtain plastic recyclates that are as pure as possible from mixed waste and material composites.

[0007] This object is achieved by a method for separating different types of plastic from a material mixture according to claim 1. The method comprises the following steps: a) Feeding the material mixture, b) melting at least part of the material mixture, c) Separating one or more types of plastic contained in the molten part of the material mixture from the material mixture based on the specific melt viscosity of the respective molten plastic type.

[0008] Advantageously, the invention is based on separating plastic mixtures and polymer composites based on the different melt viscosities of the individual components, i.e., the different types of plastic. In this process, several types of plastic that are still mixed together can be separated from the molten part of the material mixture, or a single (pure) type of plastic can be separated. The material mixture can also contain composite materials, e.g., fiber-reinforced plastics such as NFRP, CFRP, GFRP, and AFRP.

[0009] The separation of one or more plastic types from the material mixture based on melt viscosity can be achieved, for example, by using one or more melt filters. Commercially available melt filters or filter cascades composed thereof, such as those used in the plastics processing industry, for example, in extrusion lines, can advantageously be used. For example, continuous screen changers or high-performance melt filters of the ERF 200, 350, or 500 types can be used. Such melt filters serve to remove solids such as paper, metal, or the like from the plastic melt so that the plastic material is not contaminated during processing. In the present invention, however, it is proposed that such a melt filter be used to separate high-viscosity and low-viscosity components of the melt.Different types of plastic differ in their specific melt viscosity when molten. This property can be used advantageously for the recycling of single-material plastics. This allows individual or multiple types of plastic that are still mixed together to be separated. Alternatively or simultaneously, non-plastic components, such as those found in composites including NFRP, CFRP, GFRP, or ARP, can be separated.

[0010] It is therefore also advantageous to use a melt filter for separating one type of plastic which has a first melt viscosity in the molten state from another type of plastic which has a second melt viscosity in the molten state which differs from the first melt viscosity, or from other components of a plastic mixture or composite material, in particular from fibers of a composite material.

[0011] Viscosity refers to the viscosity or thickness of fluids, i.e., liquids and gases. The higher the viscosity, the thicker (less flowable) the fluid; the lower the melt viscosity, the thinner (more flowable) it is. Viscosity can, in particular, be the fluid's resistance to shear (shear viscosity).

[0012] Melt viscosity is the viscosity of a plastic grade in the molten phase at the melting point or under other conditions.

[0013] If the material mixture cannot be completely melted, ie if solid components remain, these solid components can first be separated.

[0014] According to an advantageous embodiment of the invention, several or all types of plastic contained in the molten part of the material mixture are individually separated based on the specific melt viscosity of the respective molten plastic type. The individual viscosities or viscosity differences of the components to be separated can also be specifically influenced using the other methods described below as examples. This physical, mechanical, or chemical viscosity spread enables the separation or division of plastic types. This has the advantage that the plastic types are completely separated according to their respective types. Thus, the best possible recycling quality can be achieved.

[0015] According to the invention, at least the molten portion of the material mixture is successively passed through various filter stages, each filter stage being designed to separate molten, low-viscosity and non-melted or higher-viscosity portions of the material mixture within a specific viscosity range. This has the advantage that the separation of the different plastic types is possible with manageable technical effort. In particular, the filter stages can be implemented using industrially available melt filters. Depending on the filter stage, the melt filters must then be adjusted to different viscosity limit values, which are adapted to the specific melt viscosity of the respective plastic type to be separated. At the same time, the individual viscosities or viscosity differences can be adapted to the respective filters.This means that after each separation, a change in the melt viscosity of one or more plastic types can occur through chemical, physical or mechanical influences on the materials, such as the generation of pressure or shear profiles associated with plastic types, addition of components with changed melt viscosity, variation of the temperature profile, variation of the filter stage, etc.

[0016] According to an advantageous embodiment of the invention, the filter stages are operated within an extrusion system. This allows for a simple and cost-effective implementation of a recycling plant. For example, extrusion systems based on known concepts can be used. In this case, only the melt filters need to be either supplemented or adapted to the desired specific melt viscosity of the plastic types to be separated.

[0017] According to the invention, the respective plastic grade with the highest melt viscosity is separated from the molten part of the material mixture in each filter stage. Thus, the higher-viscosity component is separated from the molten part of the material mixture at each filter stage. This ensures a high degree of purity of the recycled plastic grades.

[0018] Separation can be promoted by influencing the melt viscosities of individual or multiple plastic types, also referred to as viscosity spreading. Examples include the following: According to an advantageous embodiment of the invention, the melt viscosity of the molten part of the material mixture or the melt viscosity of at least one type of plastic contained therein is specifically influenced, e.g., by generating associated temperature profiles. In this way, the recycling quality can be further improved through additional intervention, for example, a control or regulation intervention.

[0019] According to an advantageous embodiment of the invention, the melt viscosity of the molten part of the material mixture or the melt viscosity of at least one type of plastic contained therein is specifically influenced by additional local thermal, mechanical, and / or electromagnetic energy input. In this way, the recycling quality can be further improved by the energy input. Mechanical energy input can be achieved, for example, by applying pressure to the molten part of the material mixture at a higher shear rate. Other types of energy input can include microwave, ultrasound, or electron irradiation.

[0020] According to an advantageous embodiment of the invention, the melt viscosity of the molten part of the material mixture or the melt viscosity of at least one type of plastic contained therein is specifically influenced by adding at least one additional substance. Such additional substances can specifically influence the melt viscosity of certain types of plastic, thus simplifying filtering from the material mixture. By adding at least one additional substance, for example, a chemical influence on the melt viscosity of the molten part of the material mixture or at least one type of plastic contained therein can be specifically influenced.For example, chain extenders that act selectively on individual components of the material mixture (to increase viscosity), crosslinking aids that crosslink a specific plastic in combination with electromagnetic radiation (to increase viscosity), a process-controlled thermally and / or chemically induced degradation of the molecular weight (to reduce viscosity) and / or solvents that act specifically on individual plastic components (to reduce viscosity) can be used.

[0021] Furthermore, the viscosity of a plastic melt depends on the deformation rate or shear rate. As the deformation rate increases, the viscosity decreases, also known as the structural viscosity of plastics.

[0022] In addition, viscosity can also be reduced by physically acting mechanisms (e.g. gases or gas-forming components) or increased by fillers.

[0023] This also allows the viscosity differences of the material components to be separated to be adjusted and, if necessary, increased, i.e. a viscosity spread can be achieved.

[0024] The aforementioned object is also achieved with a device according to claim 8 for separating different types of plastic from a material mixture. The device comprises several filter stages arranged one behind the other, each filter stage being designed to separate molten, low-viscosity and unmelted or higher-viscosity parts of the material mixture within a specific viscosity range. This also allows the previously explained advantages to be realized.

[0025] According to an advantageous embodiment of the invention, the facility comprises an extrusion system on which the various filter stages are arranged as a filter cascade. This allows for a simple and cost-effective implementation of a recycling plant.

[0026] The viscosity ranges of the various filter stages can differ from one another. In particular, each filter stage can have its own viscosity limit, which differs from other filter stages and represents a limit for the melt viscosity of the melt components to be filtered out.

[0027] With this invention, previously non-economically separable plastic mixtures can be economically and efficiently separated into their individual material components / plastic types and subjected to higher-quality recycling through a combination of melt filter cascades with appropriately designed and continuously operating filter stages, gradual temperature profiles, and, if necessary, additional local energy input, different pressures, and the additional addition of viscosity-modifying substances. Furthermore, the separation of non-plastic components in composite materials is possible, e.g., the separation of short-fiber materials including glass, carbon, cellulose, and natural fibers.

[0028] Compared to previous recycling approaches, the present invention represents a robust industrial process for the economical separation and recycling of material mixtures and composite materials with a high plastic content. The present invention also enables the separation of non-meltable components, such as fillers, reinforcing fibers, or cotton in a blended fabric, and the recycling of the individual components. Furthermore, the invention also allows for the economical separation and further use of minor material components of a plastic mixture or composite material for which economical separation was previously not possible.

[0029] The invention will be explained below using an embodiment using the Fig. 1 is explained in more detail.

[0030] The Fig.Figure 1 shows a device for separating different types of plastic from or in a material mixture 2. First, the material mixture 2 is fed, for example, into a storage container 1. The material mixture 2 is melted, for example, by heating the storage container 1 or an upstream extruder section. The melted portion of the material mixture 2 is fed to a filter or a filter cascade comprising a first filter stage 3, a second filter stage 6, and a third filter stage 9.

[0031] The first filter stage 3 is designed as a melt filter with a first viscosity limit. The first viscosity limit is a relatively high-viscosity limit, meaning that the highly viscous components are separated from the melt in the first filter stage 3. For example, a first plastic type 4 is separated and fed to a collecting container 5.

[0032] The second filter stage 6 is designed as a melt filter with a second viscosity limit, which can, for example, be lower than the first viscosity limit. A second plastic type 7 is separated in the second filter stage 6 and fed to a collecting container 8.

[0033] The third filter stage 9 is designed as a melt filter with a third viscosity limit value, which can, for example, be smaller than the second viscosity limit value.

[0034] In the third filter stage 9, a third type of plastic 10 is separated and fed into a collecting container 11.

[0035] The parts of the melted part of the material mixture remaining in the third filter stage 9 are fed to a collecting container 13 as residual material stream 12.

[0036] The described device can be controlled by a control unit 14. For example, the control unit 14 can control and / or regulate the local pressure and temperature conditions in each filter stage 3, 6, 9 based on pressure signals p and temperature signals T.

[0037] Furthermore, an additional substance can be added to the molten portion of the material mixture. This is illustrated by way of example in the second filter stage 6. An additional substance Z is fed from a container 15 to the melt stream in the second filter stage 6. The addition, i.e., the time and amount of the additional substance Z, can be controlled or regulated by the control unit 14.

[0038] In addition, the melt viscosity of the melted part of the material mixture or at least of a plastic type contained therein can be specifically influenced by additional energy input E. The energy input can be provided by an energy source 16, which can be controlled or regulated by the control unit 14.

[0039] By generating appropriate temperature profiles in combination with such a melt filter cascade, which consists of various continuously operating filter stages connected in series, such material mixtures can be separated into their individual components, i.e., the respective pure plastic types. Through adjustable temperature control and additional local thermal, mechanical, or electromagnetic energy coupling, the melt viscosities of the individual material components to be separated can be precisely adjusted. During extrusion, the pressures upstream of the respective filters can also be adjusted, and additional substances can be added to specifically and selectively influence the melt viscosity of the various plastic types to support such a separation and filtration process based on viscosity differences.

[0040] With such an approach, even complex material composites, such as composite films, textile blends or composite materials, can be separated into the individual plastic types and / or fibers of the composite material can be removed.

Claims

[1] Method for separating different types of plastic (4, 7, 10) from or in a material mixture (2) in the context of the recycling of plastic materials, comprising the following steps: a) feeding the material mixture (2), b) melting at least part of the material mixture (2), wherein several or all types of plastic (4, 7, 10) are contained in the melted part of the material mixture (2), c) separating one or more types of plastic (4, 7, 10) contained in the molten part of the material mixture (2) from the material mixture (2) based on the specific melt viscosity of the respective molten type of plastic (4, 7, 10), characterized bythat at least the melted part of the material mixture (2) is passed successively through various filter stages (3, 6, 9), wherein each filter stage (3, 6, 9) is designed to separate melted and non-melted or higher-viscosity parts of the material mixture (2) in a specific viscosity range, wherein in each filter stage (3, 6, 9) the respective plastic type (4, 7, 10) with the highest melt viscosity is separated from the melted part of the material mixture (2). [2] Method according to claim 1, characterized by that several or all types of plastic (4, 7, 10) contained in the molten part of the material mixture (2) are each individually separated based on the specific melt viscosity of the respective molten type of plastic (4, 7, 10). [3] Method according to claim 1 or 2, characterized by that the filter stages (3, 6, 9) are operated within an extrusion plant. [4] Method according to one of the preceding claims, characterized by that the melt viscosity of the melted part of the material mixture (2) or the melt viscosity of at least one type of plastic (4, 7, 10) contained therein is specifically influenced by generating associated temperature profiles. [5] Method according to one of the preceding claims, characterized by that the melt viscosity of the melted part of the material mixture (2) or the melt viscosity of at least one type of plastic (4, 7, 10) contained therein is specifically influenced by generating associated pressure or shear profiles. [6] Method according to one of the preceding claims, characterized bythat the melt viscosity of the melted part of the material mixture (2) or the melt viscosity of at least one type of plastic (4, 7, 10) contained therein is specifically influenced by additional local thermal, mechanical and / or electromagnetic energy coupling. [7] Method according to one of the preceding claims, characterized by that the melt viscosity of the melted part of the material mixture (2) or the melt viscosity of at least one type of plastic (4, 7, 10) contained therein is chemically or physically influenced in a targeted manner by adding at least one further substance. [8] Device for separating different types of plastic (4, 7, 10) from a material mixture (2) in the context of recycling plastic materials, wherein several or all types of plastic (4, 7, 10) are contained in a melted part of the material mixture (2), comprising one or more filter stages (3, 6, 9) arranged one behind the other, characterized by that at least the molten part of the material mixture (2) is passed successively through various filter stages (3, 6, 9), each filter stage (3, 6, 9) being designed to separate molten and non-melted or higher-viscosity parts of the material mixture (2) in a specific viscosity range, the respective plastic type (4, 7, 10) with the highest melt viscosity being separated from the molten part of the material mixture (2) in each filter stage (3, 6, 9). [9] Device according to claim 8, characterized bythat the device comprises an extrusion system on which the various filter stages (3, 6, 9) are arranged as a filter cascade.

Images