Continuous treatment equipment for regeneration and modification of recycled plastic and continuous treatment method thereof

Abstract

The invention provides continuous treatment equipment for regeneration and modification of recycled plastics. The continuous treatment equipment comprises a double-screw extruder and a melt bypass connected with the double-screw extruder, wherein a filtering device is arranged on the melt bypass and is used for pressurizing and filtering a high polymer material containing a large amount of impurities to remove the impurities and then sending the high polymer material back to the double-screw extruder; the double-screw extruder sequentially and continuously comprises a melting and plasticizing section group, an extrusion section group and a control section group along the flow direction of a melt, a shunting section; a regenerated material primary mixing section group; a regeneration reaction section group; and a group of modified segments. According to the equipment provided by the invention, under the driving of an ingenious process design concept, through the design of a screw section group of a double-screw extruder, the matching design of a barrier element on a screw and the design of a bypass, a series of procedures such as melting, devolatilization, filtering, regeneration reaction and modification treatment are organically and synergistically realized; and secondary or multi-time granulation is not needed.

Description

Technical Field

[0001] This invention relates to a method and apparatus for the recycling and modification of recycled plastics. More particularly, it relates to a continuous method for the recycling and modification of recycled plastics. Background Technology

[0002] With the continuous increase in the consumption of plastic products, the amount of waste plastic is also constantly increasing. my country's annual consumption of plastics for automobiles has reached 400,000 tons, and the annual consumption of plastics for electronic appliances and home appliances has reached over 1 million tons. These products, once scrapped, become a significant source of waste plastics. It is understood that in 2004, domestic waste plastics reached approximately 11 million tons. Improper storage, transportation, processing, and subsequent application and treatment of these waste plastics will inevitably damage the environment and endanger public health.

[0003] Currently, the recycling of plastics mainly utilizes single-screw and twin-screw extruders for melting, filtration, and devolatilization. However, due to process design and the design of the accompanying equipment, many processing steps require separate processing and granulation on the extruder. Multiple extrusions and granulations not only result in high production costs but also make the plastic prone to deformation, leading to low product quality and limiting its applications. In real-world industrial production, process design is often constrained by equipment design. For example, patent EP23164886.6 (Apparatus and method for processing plastic materials) attempts to incorporate an accumulation zone in the screw extruder to complete filtration, melting, and devolatilization within a single screw. However, because the accumulation zone concentrates the molten plastic within it, it is essentially pushed back against the conveying direction. This results in a portion of the molten plastic remaining in this area for an extended period. This leads to degradation and excessive yellowing of the plastic due to prolonged exposure to the high temperatures of the extruder, ultimately failing to produce a truly ideal recycled plastic product. Meanwhile, in actual production, all or most of the plastics obtained through recycling methods require further modification. Currently, the modification of recycled plastics involves melting recycled plastic particles and then adding modifiers. If multiple modifications are required, the particles must be processed multiple times before melting. In an era of rapidly increasing waste plastics, the design of recycling and modification methods and equipment for plastics urgently needs improvement. Summary of the Invention

[0004] The purpose of this invention is to solve one or more of the aforementioned technical problems and achieve an industrial breakthrough by continuously completing the recycling and modification methods for recycled plastics on a single extruder. Therefore, this invention provides a continuous processing equipment and continuous process method for the recycling and modification of recycled plastics, enabling efficient recycling and modification of waste plastics.

[0005] This invention provides a continuous processing apparatus for the recycling and modification of recycled plastics, comprising a twin-screw extruder and a melt bypass connected to the twin-screw extruder; wherein, The melt bypass is equipped with a filter device, which is used to pressurize and filter the polymer material containing a large number of impurities in the extruder to remove impurities and then send it back to the extruder. The twin-screw extruder comprises, sequentially along the melt flow direction, the following: The melting and plasticizing section is used to heat, melt, plasticize, and remove oligomers and small molecule impurities from recycled plastics. The flow divider section is provided with a bypass outlet and a blocking element. The bypass outlet is connected to one end of the melt bypass and is used to introduce high molecular weight polymer materials containing impurities into the melt bypass. The blocking element is located downstream of the bypass outlet and is used to continue to push the pure high molecular weight polymer materials in the melt downstream in the screw extruder. The recycled material primary mixing section is connected to a recycling additive feeding device. A bypass inlet is provided downstream of the recycling additive feeding device. The bypass inlet is connected to the other end of the melt bypass and is used to mix the recycling additive with the small molecular weight pure polymer material remaining in the twin-screw extruder evenly. The recycling reaction section is used to react the mixed recycling aids with the filtered-out plastic melt; and The modified section group is connected to the filler feeding device and is used to mix and devolatilize with the filler to achieve the modification treatment of recycled plastics.

[0006] In this invention, recycled plastic refers to recycled plastic materials containing waste plastics, such as plastic bottles and electronic components, which are processed through crushing or forming into granules, flakes, fibers, or certain fluid forms. Due to the influence of the sourcing method, various inorganic or organic impurities may also be present.

[0007] In this invention, the axial direction refers to the direction along the center line of the extruder screw.

[0008] The original recycling granulation process involves washing and crushing recycled plastics, then extruding and filtering them through a single extruder to remove impurities and granulate them. The recycled plastic particles are then added to a second extruder for modification and granulation. The final product's mechanical properties do not meet those of modified products made from pure resin, and its color is unstable.

[0009] One of the innovations of this invention is that it uses only one extruder to purify and re-modify recycled plastics, resulting in a final product with performance comparable to modified pure virgin resin and a stable color, while significantly reducing recycling energy consumption. Driven by ingenious process design, the equipment provided by this invention achieves a continuous series of processes—melting, devolatilization, filtration, regeneration reaction, and modification—through the design of the screw section assembly of a twin-screw extruder, the coordinated design of the barrier elements on the screws, and the bypass design, eliminating the need for secondary or multiple granulation processes. The twin-screw extruder in this invention is, as those skilled in the art typically understand it, a structural unit comprising a barrel and two screws housed within it. The extruder in this invention uses multiple extrusion sections, each with its corresponding primary function, but not limited to that function. Generally, it also has other functions such as mixing. For example, the extrusion section used for feeding primarily functions to add material to the plastic melt, but may also have functions such as mixing and heating.

[0010] Furthermore, the melt plasticizing section group includes at least a first feeding section, a conveying and heating section, a plasticizing section, and a first devolatilization section.

[0011] Furthermore, the blocking element comprises two cooperating upper and lower damping rings, and an annular first flow gap is formed between the inner wall of the barrel of the flow diversion section and the blocking element, and a second flow gap is formed between the upper and lower damping rings, the second flow gap having a zigzag structure.

[0012] Furthermore, both the upper and lower damping rings include an inner ring and an outer ring. The outer rings of the upper and lower damping rings are staggered to form an oblique flow gap. An axial flow gap is formed between the inner ring of the upper damping ring and the outer ring of the lower damping ring, and between the inner ring of the lower damping ring and the outer ring of the upper damping ring. The oblique flow gap and the two axial flow gaps together form a second flow gap.

[0013] Furthermore, the oblique flow gap of the first flow gap, the axial flow gap of the second flow gap, and the flow gap size of the second flow gap are equal or similar, and the gap size (δ) should satisfy the following formula I: (I), Where δ is the gap size in mm; ΔP is the pressure value established by the barrier element in Pa; η is the dynamic viscosity of the melt in Pa•S; Q is the average flow rate of the melt in the barrel in kg / h; R is the barrel radius in mm; and L is the thickness of the barrier element along the axial direction of the twin-screw extruder in mm.

[0014] Furthermore, the blocking element is disposed on the screw exiting the twin-screw extruder and is coaxially integrated with its upstream and downstream threads.

[0015] In this invention, the barrier element ensures that most of the melt containing impurities can stably enter the bypass melt tube and complete effective filtration. This barrier element is primarily achieved through a special design with three flow gaps. This design blocks molten material with high impurity content from flowing to the bypass, while molten material with low impurity content or even no impurities and low viscosity can flow downstream. The barrier element forms a flow gap δ1 with the inner wall of the barrel, and flow gaps δ2 and δ3 are formed between the two barrier elements. The dimensions of these three gaps are designed based on the viscosity of the polymer in its molten state (usually expressed as the dynamic viscosity η, the coefficient of internal friction characterizing liquid viscosity, in Pa·s; the dynamic viscosity of common polymer melts decreases with increasing temperature and shear rate) and the screw speed (i.e., the shear rate on the material). When the polymer melt viscosity is high at a given process temperature, the gaps can be designed to be larger; conversely, when the polymer melt viscosity is low, the gaps need to be designed to be smaller. Building upon this foundation, the barrier element incorporates the Newtonian fluid pressure-building principle in its design, satisfying Formula I. This allows for flexible design of three flow gaps based on the requirements of the processed molten material and the physical conditions of the twin-screw extruder, resulting in more precise molten material diversion. Testing in actual production applications has shown that the three flow gaps in the barrier element design are within the range of 0.1~3mm.

[0016] Furthermore, the recycled material initial mixing section group includes, in sequence along the melt flow direction, a second feeding section, a first mixing section, and a bypass inlet section.

[0017] Furthermore, the modified section group includes, in sequence along the melt flow direction, a third feeding section, a second mixing section, a shearing and dispersing section, and a devolatilization section.

[0018] Furthermore, the third feeding section is connected to a lateral feeding device.

[0019] Furthermore, a melt pump is provided on the melt bypass to draw the melt portion from the barrel into the bypass and then into the filtration device. The filtration device can be any device capable of purifying the plastic, such as a screen changer. The melt pump and filtration device divide the melt pipe into two parts: an extruder outlet pipe and a feed pipe.

[0020] Furthermore, the equipment also includes a pelletizing system. The pelletizing system of this invention is a combination of various devices for completing the underwater pelletizing process. For example, the final section at the extrusion outlet is designated as a pressure-building section. The barrel of the pressure-building section is connected to a filter, a melt tube, and a reversing valve. Additionally, a rheometer can be installed on the melt tube for testing the melt index of the product. Downstream of the reversing valve are an underwater pelletizer, a centrifugal separator, a vibrating screen, and a screw conveyor.

[0021] As a preferred embodiment, the extruder has 14 sections, zone 1-zone 14, which are: a first feeding section, a conveying section, a plasticizing section, a first devolatilization section, a bypass outlet section, a second feeding section, a first mixing section, a bypass inlet section, a regeneration reaction section, a third feeding section, a second mixing section, a shear dispersion section, a second devolatilization section, and a pressure build-up section. The extruder barrel has 14 sections, wherein... Section 1 of the barrel has a large top opening and a discharge hopper; and / or Sections 2 and 3 of the barrel are enclosed barrels used for conveying and melting / plasticizing; and / or Section 4 barrel is used for vacuum devouring; and / or Section 5 of the barrel is provided with a side opening connecting to the melt pipe of the melt bypass; and / or The sixth section of the drum belt has an opening for adding regeneration aids; and / or Section 7 is a closed barrel used for mixing regeneration aids; and / or Section 8. The side opening of the barrel connects to the melt bypass melt pipe; and / or Section 9 is a closed barrel, used to complete the regeneration reaction; and / or Section 10 of the barrel has a top opening and side openings for adding packing and venting; and / or Section 11 of the barrel is equipped with a liquid injection valve for adding liquid packing; and / or Section 12 of the barrel is a closed barrel; and / or Section 13 of the barrel has an upper opening for vacuum devouring; and / or Section 14 of the barrel is used for pressurizing and conveying the melt.

[0022] Each extrusion section in the entire system has a different function and needs to complete its own task to ultimately meet the continuous production requirements for recycling and re-modification. For example, both Zone 6 and Zone 8 are for feeding materials, but the raw materials added are different and the addition locations must be separate rather than in one place. The additives added in Zone 6 need to participate in the cross-linking reaction, causing the low-viscosity polymer in Zone 5 to undergo a cross-linking reaction to improve its performance. Zone 8 is a re-blending of most of the filtered polymer after bypassing and the added filler. Zone 9 degrades the high-viscosity polymer to appropriately reduce its molecular weight and further cross-links the low-viscosity polymer to appropriately increase its molecular weight, ultimately achieving a relatively uniform and pure polymer material with a relatively uniform molecular weight distribution.

[0023] This invention also provides a continuous process for the recycling and modification of recycled plastics, wherein the following process steps are completed continuously in one operation on an extruder, including: S1, Removal of oligomers and small molecule impurities: The recycled plastic is melted and plasticized, and small molecule impurities are removed by devolatilization. S2, splitting: A small portion of the pure polymer material with a small molecular weight and a large portion of the polymer material with a large amount of impurities in the melt after removing small molecule impurities are split. The small portion of the pure polymer material with a small molecular weight remains in the twin-screw extruder and moves forward, while the large portion of the polymer material with a large amount of impurities is introduced into the bypass of the twin-screw extruder. S3.1, Filtration: A polymer material containing a large number of impurities is introduced into the filtration system to complete filtration in the bypass and remove the impurities; S3.2, Preliminary mixing of regeneration aid: Add the regeneration aid to a small portion of pure polymer material with a small molecular weight, so that the regeneration aid is mixed evenly with the polymer material. S4, Regeneration reaction: The two melts obtained from S3.1 and S3.2 are combined and the regeneration reaction is completed, so that the combined melt forms a pure recycled plastic melt with controllable molecular weight and uniform distribution. S5, Modification treatment: Modified filler is added to the pure recycled plastic melt, and the recycled plastic melt is modified by mixing, dispersion and second devolatilization treatment. S6, Granulation: The product is obtained by granulating the modified recycled plastic melt.

[0024] In S2, flow diversion is achieved by setting a barrier element on the screw of the twin-screw extruder with a flow gap through which pure polymer materials with small molecular weight can pass, and by extending a melt bypass from the extruder.

[0025] In step S3.2, the regeneration aid includes a degradation aid and / or a crosslinking aid. As a preferred embodiment, the degradation aid is a peroxide or a composition containing a peroxide.

[0026] In step S3.2, functional additives that need to improve mechanical properties are mixed into the recycling additives so that the recycled plastics can form the required mechanical properties.

[0027] In step S5, the modification treatment includes adding color paste to the recycled plastic melt for color modification and / or adding mechanical property modifying fillers for mechanical property modification. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the application and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of the device according to one embodiment of the present invention (excluding the pelletizing system). Figure 2 for Figure 1 Enlarged view of the middle blocking element; Figure 3 for Figure 2 The left view; Wherein, 1: First feeding section 1, 2: Conveying section, 3: Plasticizing section, 4: First devolatilization section, 5: Bypass outlet section, 6: Second feeding section 6, 7: First mixing section, 8: Bypass inlet section, 9: Regeneration reaction section, 10: Third feeding section, 11: Second mixing section, 12: Shear dispersion section 12, 13: Second devolatilization section, 14: Pressure building section; 100: Twin-screw extruder, 101: Barrel, 102: Screw element, 30: Barrier element, 31: Upper damping ring, 311: Inner ring of upper damping ring, 312: Outer ring of upper damping ring, 32: Lower damping ring, 321: Inner ring of lower damping ring, 322: Outer ring of lower damping ring. Detailed Implementation

[0029] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0030] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or connections that allow for communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0032] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0034] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0035] like Figure 1 As shown, the first embodiment of this application illustrates a continuous processing equipment and method for the recycling and modification of recycled plastics, enabling efficient recycling and modification of waste plastics. The equipment includes a twin-screw extruder 100 and a melt bypass 20 connected to the twin-screw extruder. The melt bypass 20 has a filter device 21 for pressurizing and filtering a polymer material 30 containing a large amount of impurities to remove impurities before returning it to the twin-screw extruder 100. The twin-screw extruder includes a barrel 101 and a screw element 102 disposed within the barrel. Of course, inevitably, to achieve the operation of the twin-screw extruder, the extruder also needs at least a drive device. Furthermore, for greater intelligence, it may also include a control system and a human-machine interface device for the control system, etc. These are not shown in the figures to more clearly illustrate the inventive points of this application.

[0036] The following section uses the production and recycling of PP as an example to describe each part of the equipment in this embodiment in detail.

[0037] like Figure 1As shown, the twin-screw extruder has 14 sections, from zone 1 to zone 14, as follows: Zone 1: First feeding section 1, used for adding recycled PP and devolatilizer.

[0038] Zone 2: Conveying section 2, which enables heating and conveying of recycled PP materials; Zone 3: Plasticizing section 3, completes the melting and plasticizing of recycled PP material; Zone 4: First devolatilization stage 4, using negative pressure vacuum to remove small molecules and / or oligomers; Zone 5: Bypass outlet section 5, where the screw is equipped with a blocking element 30, so that most of the melt containing impurities enters the melt pipeline of the melt bypass 20 for pressurization and melt filtration to remove impurities. In addition, a small portion of the melt without impurities overflows through the blocking element 30 and flows to Zone 6 and Zone 7. Zone 6: Second feeding section 6, used for adding regeneration aids; Zone 7: First mixing section 7, where a small amount of impurity-free melt passing through the barrier element 30 is premixed with the regeneration aid; Zone 8: Bypass inlet section 8, where most of the melt, after impurities have been removed, flows back into the extruder barrel; Zone 9: Regeneration reaction section 9, where the regeneration aid is mixed with the melt returning from Zone 8 and the corresponding chemical reaction is completed; Zone 10: Third feeding section 10, where modified filler is added via a side feeder; Zones 11 & 12, the second mixing section 11 and the shear dispersion section 12, complete the filling, dispersion and mixing of the modified filler; Zone 13: Second devolatilization section 13, where small molecules and / or oligomers are removed again under negative pressure vacuum. Zone 14: Pressure building section 14, pressure building and compression of the melt.

[0039] The above 14 segments are closely linked in sequence to form 5 functional segment groups.

[0040] The melt plasticizing section (Zone 1-Zone 4) is used to heat, melt, plasticize, and remove oligomers and small molecule impurities from recycled plastics. The flow divider (Zone 5) is equipped with a bypass outlet and a blocking element. The bypass outlet is connected to one end of the melt bypass and is used to introduce high molecular weight polymers containing impurities into the melt bypass. The blocking element is located downstream of the bypass outlet and is used to continue to push the pure high molecular weight polymers in the melt downstream along the screw extruder. The primary mixing section group of recycled materials (Zone6-Zone8) is connected to a recycling aid feeding device. A bypass inlet is provided downstream of the recycling aid feeding device. The bypass inlet is connected to the other end of the melt bypass and is used to mix the recycling aid with the pure polymer material with small molecular weight remaining in the twin-screw extruder evenly. The recycling reaction zone (Zone 9) is used to react the mixed recycling aids with the filtered-out plastic melt; and The modified section group (Zone10-Zone13) is connected to the filler feeding device and is used to mix and devolatilize with the filler to achieve the modification treatment of recycled plastics.

[0041] Each extrusion section in the entire system has a different function and needs to complete its own task to ultimately meet the continuous production requirements for recycling and re-modification. For example, both Zone 6 and Zone 8 are for feeding materials, but the raw materials added are different and the addition locations must be separate rather than in one place. The additives added in Zone 6 need to participate in the cross-linking reaction, causing the low-viscosity polymer in Zone 5 to undergo a cross-linking reaction to improve its performance. Zone 8 is a re-blending of most of the filtered polymer after bypassing and the added filler. Zone 9 degrades the high-viscosity polymer to appropriately reduce its molecular weight and further cross-links the low-viscosity polymer to appropriately increase its molecular weight, ultimately achieving a relatively uniform and pure polymer material with a relatively uniform molecular weight distribution.

[0042] Accordingly, the extruder barrel has 14 sections. Section 1 of the barrel has a large top opening and a discharge hopper; and / or Sections 2 and 3 of the barrel are enclosed barrels used for conveying and melting / plasticizing; and / or Section 4 barrel is used for vacuum devouring; and / or Section 5 of the barrel is provided with a side opening connecting to the melt pipe of the melt bypass; and / or The sixth section of the drum belt has an opening for adding regeneration aids; and / or Section 7 is a closed barrel used for mixing regeneration aids; and / or Section 8. The side opening of the barrel connects to the melt bypass melt pipe; and / or Section 9 is a closed barrel, used to complete the regeneration reaction; and / or Section 10 of the barrel has a top opening and side openings for adding packing and venting; and / or Section 11 of the barrel is equipped with a liquid injection valve for adding liquid packing; and / or Section 12 of the barrel is a closed barrel; and / or Section 13 of the barrel has an upper opening for vacuum devouring; and / or Section 14 of the barrel is used for pressurizing and conveying the melt.

[0043] The working process of the equipment in this embodiment is as follows: Cleaned and crushed recycled plastic and some additives are continuously and quantitatively fed into the first barrel section of the twin-screw extruder using a loss-in-weight feeder. The plastic is melted and plasticized in the second and third barrel sections, and oligomers and small molecules are removed under vacuum in the fourth barrel section. When the melt reaches the fifth barrel section, it is drawn into the bypass by the melt pump 21 of the melt bypass 20 and filtered by the connected filter device 22 to remove impurities before re-entering the eighth barrel section of the twin-screw extruder. The melt is then conveyed forward by the twin screws to the eighth barrel section, where it undergoes a cross-linking and degradation reaction with the recycled additives previously fed in the sixth barrel section. This results in a relatively uniform molecular weight distribution of the plastic melt, yielding a pure plastic melt. The tenth barrel section has top and side openings for adding filler and venting. Mixing takes place in barrels 10-12, while the eleventh barrel section uses online color testing to inject liquid color paste for dynamic color adjustment to ensure uniform color of the recycled material. The modified melt is tested online to obtain qualified molten material, which is then fed into an underwater pelletizer. After granulation and cooling, the pelletizing process water is carried to a centrifugal separator for dewatering. The dewatered particles are then screened by a vibrating screen to remove particles and fine powder that are not up to size. Finally, the particles are conveyed and dried by a screw conveyor.

[0044] like Figure 2-3 As shown, this embodiment employs a key blocking element 30. The blocking element 30 includes two cooperating upper damping rings 31 and lower damping rings 32. The upper damping ring includes an inner ring 311 and an outer ring 312, and the lower damping ring includes an inner ring 321 and an outer ring 322. A first annular flow gap δ1 is formed between the inner wall of the barrel in the bypass outlet section (Zone 5) and the blocking element. An oblique flow gap δ3 is formed by the staggered fit between the outer ring 312 of the upper damping ring and the outer ring 322 of the lower damping ring. An axial flow gap δ2 is formed between the inner ring 311 of the upper damping ring and the outer ring 322 of the lower damping ring, and between the inner ring 321 of the lower damping ring and the inner ring 312 of the upper damping ring. The oblique flow gap δ3 and the two axial flow gaps δ2 together form a second flow gap (δ2+δ3+δ2) with a broken line structure.

[0045] The dimensions of the first flow gap δ1, the oblique flow gap δ3 of the second flow gap, and the axial flow gap δ2 of the second flow gap are equal or similar, and the gap dimensions (δ) should satisfy the following formula I: (I), Where δ is the gap size in mm; ΔP is the pressure value established by the barrier element in Pa; η is the dynamic viscosity of the melt in Pa•S; Q is the average flow rate of the melt in the barrel in kg / h; R is the barrel radius in mm; and L is the thickness of the barrier element along the axial direction of the twin-screw extruder in mm.

[0046] The blocking element 30 is disposed on the screw element 12 at the outlet of the twin-screw extruder and is formed integrally with its upstream and downstream threads on the same axis.

[0047] In this invention, the barrier element 30 ensures that most of the melt containing impurities can stably enter the bypass melt tube and complete effective filtration. This barrier element is primarily designed with three flow gaps to block molten material with high impurity content from flowing to the bypass, while molten material with low impurity content or even no impurities and low viscosity can flow downstream. The barrier element forms a flow gap δ1 with the inner wall of the barrel, and flow gaps δ2 and δ3 are formed between the two barrier elements. The dimensions of these three gaps are designed based on the viscosity of the polymer in its molten state (usually expressed as the dynamic viscosity η, the coefficient of internal friction characterizing liquid viscosity, in Pa·s; the dynamic viscosity of common polymer melts decreases with increasing temperature and with increasing shear rate) and the screw speed (i.e., the shear rate on the material). When the polymer melt viscosity is high at a certain process temperature, the gaps can be designed to be larger; conversely, when the polymer melt viscosity is low, the gaps need to be designed to be smaller. Building upon this foundation, the barrier element incorporates the Newtonian fluid pressure-building principle in its design, satisfying Formula I. This allows for flexible design of three flow gaps based on the requirements of the processed molten material and the physical conditions of the twin-screw extruder, resulting in more precise molten material diversion. Testing in actual production applications has shown that the three flow gaps in the barrier element design are within the range of 0.1~3mm.

[0048] Regarding the addition of recycling aids, functional fillers, etc., this embodiment takes the production of recycled PP as an example. The cleaned and crushed rPP fragments and the devolatilizer (BYK-P4200) are continuously and quantitatively fed into the first barrel of the twin-screw extruder using a loss-in-weight feeder. The devolatilizer, whose main component is a surfactant, helps the rPP to melt and plasticize through the second and third barrels of the extruder, and makes it easier to remove oligomers and small molecules under vacuum in the fourth barrel. When the melt reaches the 5th barrel, it is drawn into the bypass by the melt pump and filtered to remove impurities in the screen changer connected to it before re-entering the 8th barrel of the twin-screw extruder. The melt is conveyed forward by the twin screw to the 9th barrel, where it is fed in metered amounts of peroxide (such as peroxydi-tert-butyl DTBP), rubber POE (a thermoplastic elastomer copolymerized with ethylene and octene / butene), and coupling agent (such as polysulfonyl azide compound) in the 6th barrel. The peroxide can partially degrade PP and crosslink POE, thereby improving the toughness of rPP. The coupling agent fed in metered amounts in this barrel is mixed with the filler fed in metered amounts in the 8th barrel in the 10th-12th barrels to improve the mechanical strength of rPP. At the same time, the 11th barrel injects liquid color paste through online color testing to dynamically adjust the color to achieve the goal of uniform color of the recycled material.

[0049] The chemical reaction mechanism by which peroxides can partially degrade PP and cross-linked POE, thereby improving the toughness of rPP, is as follows: 1) DTBP partially degrades PP:

[0050] 2) Crosslinking reaction of DTBP (PoE)

[0051] Similarly, other thermoplastic recyclable plastics such as rPET and rPA can be recycled and modified using the corresponding process schemes described in this patent, which involve partial chemical reactions to conform to their respective chemical properties.

Claims

1. A continuous processing apparatus for the regeneration and modification of recycled plastics, characterized by, The device comprises a twin-screw extruder and a melt bypass connected with the twin-screw extruder, wherein, The melt bypass is provided with a filtering device for pressurizing and filtering the polymer material containing a large amount of impurities in the extruder to remove the impurities and then returning the material to the extruder. The twin-screw extruder successively comprises, along the melt flow direction: a melting plasticizing section group for heating, melting, plasticizing, devolatilizing and removing oligomers and small molecular impurities from the recycled plastic; a shunt section provided with a bypass outlet and a blocking element, the bypass outlet being connected with one end of the melt bypass, and the blocking element being located downstream of the bypass outlet; a regenerated material initial mixing section group connected with a regenerated auxiliary agent feeding device, provided with a bypass inlet downstream of the regenerated auxiliary agent feeding device, and connected with the other end of the melt bypass; a regenerated reaction section group for completing the reaction of the mixed regenerated auxiliary agent and the plastic melt from which the impurities are filtered; and a modification section group connected with a filler feeding device for mixing with the filler, devolatilizing and realizing the modification treatment of the regenerated plastic.

2. The apparatus of claim 1, wherein, The melting plasticizing section group at least comprises a first feeding section, a conveying and heating section, a plasticizing section and a first devolatilizing section.

3. The apparatus of claim 1, wherein The blocking element comprises two mutually cooperating upper and lower damping rings, a first flow gap in the form of a ring is formed between the inner wall of the shunt section and the blocking element, and a second flow gap is formed between the upper and lower damping rings, the second flow gap being in the form of a broken line.

4. The apparatus of claim 3 wherein, The upper and lower damping rings each comprise an inner ring and an outer ring, wherein the outer rings of the upper and lower damping rings are staggered to form an oblique flow gap, and the inner ring of the upper damping ring and the outer ring of the lower damping ring, and the inner ring of the lower damping ring and the outer ring of the upper damping ring each form an axial flow gap, and the oblique flow gap and the two axial flow gaps together form the second flow gap.

5. The apparatus of claim 1 wherein, The gap size of the first flow gap, the oblique flow gap of the second flow gap and the axial flow gap of the second flow gap is equal or similar, and the gap size (δ) should satisfy the following formula I: （Ⅰ）， wherein δ is the gap size, in mm; ΔP is the pressure value established by the blocking element, in Pa; η is the melt dynamic viscosity, in Pa•S; Q is the average flow of the melt in the cylinder, in kg / h; R is the cylinder radius, in mm; and L is the thickness of the blocking element along the axial direction of the twin-screw extruder, in mm.

6. The apparatus of any one of claims 1-5, wherein, The blocking element is arranged on the screw of the twin-screw extruder and is coaxial with the threads upstream and downstream thereof to form an integral whole.

7. The apparatus of claim 1 wherein, The regenerated material initial mixing section group successively comprises, along the melt flow direction, a second feeding section, a first mixing section and a bypass inlet section.

8. The apparatus of claim 1 wherein, The modification section group successively comprises, along the melt flow direction, a third feeding section, a second mixing section, a shearing and dispersing section and a devolatilizing section.

9. The apparatus of claim 1 wherein, The third feeding section is connected with a lateral feeding device.

10. The apparatus of claim 1, wherein, The melt bypass is further provided with a melt pump for pumping part of the melt in the cylinder into the bypass and then into the filtering device.

11. The apparatus of claim 1, wherein, The device further comprises a pelletizing system.

12. The apparatus of claim 1, wherein, The extruder is provided with 14 sections, namely zone 1-zone 14, in sequence: a first feeding section, a conveying section, a plasticizing section, a devolatilization section, a bypass outlet section, a second feeding section, a first mixing section, a bypass inlet section, a regeneration reaction section, a third feeding section, a second mixing section, a shearing dispersion section, a devolatilization section and a pressure building section.

13. The apparatus of claim 12, wherein, The barrel of the extruder is provided with 14 barrel sections, wherein, the first barrel section has a large upper opening and a hopper; and / or the second and third barrel sections are closed barrel sections for conveying and melting plasticizing; and / or the fourth barrel section is used for vacuum devolatilization; and / or the fifth barrel section is provided with a lateral opening and a melt pipe of a melt bypass; and / or the sixth barrel section has an upper opening for adding a regeneration aid; and / or the seventh barrel section is a closed barrel section for mixing the regeneration aid; and / or the eighth barrel section has a lateral opening to connect a melt pipe of a melt bypass; and / or the ninth barrel section is a closed barrel section for completing the regeneration reaction; and / or the tenth barrel section has an upper opening and a lateral opening for adding a filler and venting; and / or the eleventh barrel section is provided with a liquid injection valve for adding a liquid filler; and / or the twelfth barrel section is a closed barrel section; and / or the thirteenth barrel section has an upper opening for vacuum devolatilization; and / or the fourteenth barrel section is used for melt pressure building and conveying.

14. A continuous process for the regeneration and modification of recycled plastics, characterized in that, The following process steps are completed on the extruder in one time and continuously, including: S1, removal of oligomers and small molecular impurities: the recycled plastic is melted and plasticized, and small molecular impurities are removed through devolatilization treatment; S2, splitting: a small part of small molecular weight pure high molecular material and a large part of high molecular material containing a large amount of impurities in the melt after removal of small molecular impurities are split, wherein the small part of small molecular weight pure high molecular material is still pushed forward in the twin-screw extruder, and the large part of high molecular material containing a large amount of impurities is introduced into the bypass of the twin-screw extruder; S3.1, filtration: the high molecular material containing a large amount of impurities is introduced into the filtration system in the bypass to complete the filtration and remove the impurities; S3.2, preliminary mixing of the regeneration aid: the regeneration aid is added to the small part of small molecular weight pure high molecular material to mix the regeneration aid with the part of high molecular material uniformly; S4, regeneration reaction: the two parts of melt obtained in S3.1 and S3.2 are combined, and the regeneration reaction is completed, so that the combined melt has a controllable molecular weight and a uniform distribution, i.e. a pure regenerated plastic melt is obtained; S5, modification treatment: the modified filler is added to the pure regenerated plastic melt, and the modified regenerated plastic melt is obtained after mixing, dispersion and second devolatilization treatment; S6, granulation: the modified regenerated plastic melt is granulated to obtain the product.

15. The method of claim 14, wherein, In S2, the splitting is realized by providing a barrier element with a flow gap through which the small molecular weight pure high molecular material can pass on the screw of the twin-screw extruder and extending a melt bypass from the extruder.

16. The method of claim 15, wherein, In S3.2, the regeneration aid includes a degradation aid and / or a crosslinking aid.

17. The method of claim 15, wherein, The degradation aid is a peroxide or a composition containing a peroxide.

18. The method of claim 14, wherein, In the S3.2, functional additives needed to improve mechanical properties are mixed into the recycling aids, so that the recycled plastics form the required mechanical properties.

19. The method of claim 14, wherein, In the S5, the modification treatment includes adding color paste to the recycled plastic melt for color modification and / or adding mechanical property modification fillers for mechanical property modification.

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