A production process for biodegradable meltblown nonwoven fabric

Abstract

This invention relates to a production process for biodegradable meltblown nonwoven fabric, comprising the following steps: S1, plasticizing and extruding PLA mixed raw materials at a temperature of 80-90℃, and plasticizing and extruding PBAT mixed raw materials at a temperature of 80-90℃; S2, selecting 75-80 parts by weight of PLA mixed raw materials, 25-30 parts by weight of PBAT mixed raw materials, 15-18 parts by weight of grafted material, and 3-5 parts by weight of electrostatic electret masterbatch; S3, uniformly dividing the grafted material into N parts, and feeding 1 / N of the grafted material, 75-80 parts by weight of PLA mixed raw materials, 25-30 parts by weight of PBAT mixed raw materials, and 3-5 parts by weight of electrostatic electret masterbatch into a third screw extruder to form intermediate raw materials; S4, extruding the melt mixture obtained in step S3 through a spinneret; S5, the meltblown fibers in step S4 are cooled by negative pressure suction molding and then enter the high-voltage electrostatic electret to carry charge. The present invention has the following advantages: it can achieve biodegradability, avoid white pollution, and at the same time ensure that the meltblown fabric produced has high filtration efficiency.

Description

Technical Field

[0001] This invention relates to the field of meltblown fabric, specifically a production process for biodegradable meltblown fabric. Background Technology

[0002] Currently, the vast majority of meltblown fabric used in the filter layer of masks is made from PP polypropylene raw materials. It takes more than 300 years to degrade such masks, thus causing a large amount of white pollution. Therefore, there is a need to propose a biodegradable meltblown fabric to replace the existing polypropylene meltblown fabric.

[0003] PLA (polylactic acid) is a polymer obtained by polymerization of lactic acid as the main raw material. The raw material is readily available and renewable, primarily from corn and cassava. However, while it has high strength, it has low elongation at break and poor plasticity, making it completely unsuitable for the manufacture of meltblown fabric. PBAT (oxalic acid-butyl terephthalate copolymer), on the other hand, is a more flexible elastomer material, belonging to thermoplastic biodegradable plastics. Although it has good ductility and elongation at break, as well as good heat resistance and impact resistance, the meltblown process accelerates its aging. Combining PLA with... PBAT blending can improve material properties while maintaining the overall eco-friendliness of the system. Meltblown fabric made by blending PLA and PBAT effectively solves the problem of biodegradation. However, it has the following technical challenges: To ensure its high-efficiency filtration, meltblown fabric requires extremely high density and filament diameter during the manufacturing process. Although PLA and PBAT blending can achieve biodegradation, the interfacial adhesion between the two systems is weak and the compatibility is poor. After blending, the matrix crystallization ability and mutual melting ability are weakened, making it impossible to achieve high-efficiency filtration of meltblown fabric and resulting in poor mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a production process for biodegradable meltblown fabric that can achieve biodegradation, avoid white pollution, and at the same time ensure that the produced meltblown fabric has high filtration efficiency.

[0005] The objective of this invention is achieved through the following technical solution: a production process for biodegradable meltblown nonwoven fabric, comprising the following steps:

[0006] S1. PLA raw material is fed into the first screw extruder with a length-to-diameter ratio of 1:33, and PLA mixed raw material is plasticized and extruded at a temperature of 80-90℃. PBAT raw material is fed into the second screw extruder with a length-to-diameter ratio of 1:33, and PBAT mixed raw material is plasticized and extruded at a temperature of 80-90℃.

[0007] S2. By weight, select 75-80 parts of PLA mixed raw material, 25-30 parts of PBAT mixed raw material, 15-18 parts of grafting material and 3-5 parts of electrostatic electret masterbatch.

[0008] S3. Divide the grafted material into N parts evenly. Add 1 / N of the grafted material, 75-80 parts of PLA mixed raw material, 25-30 parts of PBAT mixed raw material, and 3-5 parts of electrostatic electret masterbatch into the third screw extruder to form intermediate raw material. The third screw extruder has multiple equally spaced feed ports. The multiple feed ports are horizontally distributed from the inlet end to the outlet end of the third screw extruder. The N parts of grafted material are distributed in sequence at the multiple feed ports. The intermediate raw material is evenly mixed at the feed port near the inlet end of the second screw extruder and then extruded towards the outlet end. During the extrusion process, it continues to be fully mixed with the remaining grafted material and then extruded towards the outlet end to obtain a melt mixture.

[0009] S4. The molten mixture obtained in step S3 is sprayed out through a spinneret. The die head temperature of the spinneret is 220-240℃. Under the traction of hot air flow at a spinneret temperature of 240-260℃, it is spun into a Teflon mesh belt to obtain meltblown fibers.

[0010] S5. The meltblown fibers in step S4 are cooled by negative pressure suction molding, then enter the high-voltage electrostatic electret to carry charges, and are wound up to obtain biodegradable meltblown fabric.

[0011] A further improvement of the present invention is that the grafting material is nano-HA raw material.

[0012] A further improvement of the present invention is that: the third screw extruder includes a barrel and an extrusion screw placed inside the barrel, a plurality of equally spaced feed ports are provided on the barrel, and the barrel is also provided with a discharge port. The feed ports have a mixing overflow component, the upper end of the feed port is a closed surface, the feed port includes an upper conical part and a lower straight cylindrical part, the upper conical part and the lower straight cylindrical part are connected to the barrel, and the mixing overflow component stirs and mixes the raw material in the feed port and flows vertically into the barrel, while preventing the intermediate raw material in the barrel from overflowing to the feed port.

[0013] A further improvement of the present invention is that: the mixing overflow assembly includes a rotating shaft that extends vertically through the closed surface, the lower end of the rotating shaft is placed inside the lower straight cylinder of the feed inlet, the upper end of the rotating shaft is placed above the closed surface and connected to a drive motor, a plurality of stirring rods are connected to the outer circumference of the rotating shaft placed in the upper conical part, a spiral extrusion part is provided on the outer circumference of the rotating shaft placed inside the lower straight cylinder, the extension direction of the spiral extrusion part is perpendicular to the extension direction of the extrusion screw, and an inclined nozzle is embedded in the inner wall of the lower end of the lower straight cylinder, the spray direction of the nozzle is downward.

[0014] A further improvement of the present invention is that the stirring rod includes a crossbar portion fixedly connected to the rotating shaft and a stirring portion located at the outer end of the crossbar portion. The extending direction of the crossbar portion is perpendicular to the extending direction of the rotating shaft, and the extending direction of the stirring portion is consistent with the extending direction of the inner wall of the upper conical portion. Adjacent stirring portions are staggered vertically.

[0015] A further improvement of the present invention is that a pressure sensor is provided at the leading edge of the inner wall of the barrel near the feed port. The raw material in the barrel moves to the next feed port as it is extruded by the extrusion screw. When it passes the pressure sensor of the corresponding feed port, the pressure sensor detects that the pressure value inside the barrel is greater than a predetermined value. The drive motor of the feed port near the pressure sensor is started, which drives the rotating shaft to rotate so that the nano HA raw material in the feed port is uniformly stirred and then uniformly mixed with the raw material in the barrel. Thus, it continues to move as a whole to the next feed port as it is driven by the extrusion screw, and mixes with the nano HA raw material in the next feed port.

[0016] A further improvement of the present invention is that the time t1 required for the raw material in the barrel to move from the position of the pressure sensor to the corresponding feed port is consistent with the time t2 required for the nano HA raw material in the feed port to be squeezed into the barrel.

[0017] A further improvement of the present invention is that the grafted material is evenly divided into 3 parts, the number of feed inlets is 3, the number of pressure sensors is 2, and the two pressure sensors are placed at the leading edge of the two feed inlets near the outlet end of the material cylinder.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. This invention adds nano-HA raw material to PLA and PBAT. The addition of nano-HA raw material enhances the compatibility of PLA and PBAT, changes the glass transition temperature, crystallization and melting behavior of PLA and PBAT matrices, significantly improves the heterogeneous nucleation effect, and increases the crystallinity of the matrix. The higher the crystallinity, the higher the impact strength and toughness of the material, and the mechanical properties of meltblown fabric are also relatively improved. At the same time, it can achieve biodegradability and avoid white pollution.

[0020] 2. In this invention, the nano-HA raw material is divided into N equal parts and mixed with PLA and PBAT raw materials through multiple intervals of uniform feeding. After the nano-HA raw material is added to the PLA and PBAT matrix once, a large number of modified nano-HA particles are attached to the surface of the mixed matrix. The large number of modified nano-HA particles will hinder the movement of PLA chain segments to a certain extent, resulting in a decrease in crystallinity and a certain degree of agglomeration and uneven dispersion. The multiple uniform feeding method allows the nano-HA particles to fully integrate with the mixed matrix, improve the heterogeneous nucleation effect, increase crystallinity, thereby improving the mechanical properties of meltblown fabric, meeting the density and filament diameter requirements of meltblown fabric, and achieving the high-efficiency filtration performance of meltblown fabric.

[0021] 3. The third screw extruder used in this invention has multiple feed ports. The feed port near the inlet of the third screw extruder contains a mixture of PLA, PBAT, 1 / N grafted material (nano HA raw material), and electrostatic electret masterbatch, while the other feed ports contain 1 / N grafted material (nano HA raw material). This allows for segmented and intermittent feeding of the grafted material. The feed port contains a stirring rod and a spiral extrusion section. After being fully stirred by the stirring rod, the raw material in the feed port moves vertically towards the spiral extrusion section and finally falls into the barrel to continue mixing with the raw material in the barrel until it reaches the next feed port. In this application, the spiral extrusion section in the feed port not only extrudes the raw material from the feed port, but also provides a certain resistance to the movement of the mixed raw material in the barrel into the feed port under the lateral extrusion force of the extrusion screw, thereby ensuring the normal extrusion efficiency of the mixed raw material in the barrel.

[0022] 4. The pressure sensor at the feed inlet ensures that the time it takes for the intermediate raw material in the barrel to reach the lower end of the corresponding feed inlet is the same as the time it takes for the nano HA raw material in the feed inlet to reach the barrel. This allows for seamless mixing of the two at the feed inlet, thus ensuring the uniformity of the mixing of the raw materials in the barrel. Secondly, the nozzle at the lower end of the feed inlet blows air into the barrel, further preventing the intermediate raw material in the barrel from moving upwards towards the feed inlet under the lateral extrusion force of the extrusion screw. At the same time, it ensures a certain degree of dispersion when feeding the nano HA raw material, thereby ensuring uniform mixing with the raw materials in the barrel. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the third screw extruder in this invention.

[0024] Numbering on the map:

[0025] 1-Inlet, 2-Barrel, 3-Extrusion screw, 4-Outlet, 5-Mixing overflow assembly, 6-Sealed surface;

[0026] 11-Upper conical part, 12-Lower straight cylindrical part;

[0027] 51-Rotating shaft, 52-Drive motor, 53-Stirring rod, 54-Spiral extrusion section, 55-Nozzle, 56-Pressure sensor; 531-Crossbar section, 532-Stirring section. Detailed Implementation

[0028] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0029] This invention discloses a specific embodiment of a production process for biodegradable meltblown nonwoven fabric, comprising the following steps:

[0030] S1. PLA raw material is fed into the first screw extruder with a length-to-diameter ratio of 1:33, and PLA mixed raw material is plasticized and extruded at a temperature of 80-90℃. PBAT raw material is fed into the second screw extruder with a length-to-diameter ratio of 1:33, and PBAT mixed raw material is plasticized and extruded at a temperature of 80-90℃.

[0031] S2. By weight, select 75-80 parts of PLA mixed raw material, 25-30 parts of PBAT mixed raw material, 15-18 parts of grafting material and 3-5 parts of electrostatic electret masterbatch.

[0032] S3. Divide the grafted material into N parts evenly. Add 1 / N of the grafted material, 75-80 parts of PLA mixed raw material, 25-30 parts of PBAT mixed raw material, and 3-5 parts of electrostatic electret masterbatch into the third screw extruder to form intermediate raw material. The third screw extruder has multiple equally spaced feed ports 1. The multiple feed ports 1 are horizontally distributed from the inlet end to the outlet end of the third screw extruder. The N parts of grafted material are distributed in sequence at the multiple feed ports. The intermediate raw material is evenly mixed at the feed port near the inlet end of the second screw extruder and then extruded towards the outlet end. During the extrusion process, it is further fully mixed with the remaining grafted material and then extruded towards the outlet end to obtain a melt mixture.

[0033] S4. The molten mixture obtained in step S3 is sprayed out through a spinneret. The die head temperature of the spinneret is 220-240℃. Under the traction of hot air flow at a spinneret temperature of 240-260℃, it is spun into a Teflon mesh belt to obtain meltblown fibers.

[0034] S5. The meltblown fibers in step S4 are cooled by negative pressure suction molding, then enter the high-voltage electrostatic electret to carry charges, and are wound up to obtain biodegradable meltblown fabric.

[0035] Furthermore, the grafting material is nano-HA raw material.

[0036] This invention incorporates nano-HA raw materials into PLA and PBAT. The addition of nano-HA raw materials enhances the compatibility of PLA and PBAT, alters the glass transition temperature, crystallization, and melting behavior of the PLA and PBAT matrices, significantly improves the heterogeneous nucleation effect, and increases the crystallinity of the matrix. Higher crystallinity results in higher impact strength and toughness of the material, which also relatively improves the mechanical properties of meltblown fabric. At the same time, it can achieve biodegradability and avoid white pollution.

[0037] Secondly, this invention divides the nano-HA raw material into N equal parts and mixes it with PLA and PBAT raw materials through multiple intervals of uniform feeding. After the nano-HA raw material is added to the PLA and PBAT matrix once, a large number of modified nano-HA particles are attached to the surface of the mixed matrix. The large number of modified nano-HA particles will hinder the movement of PLA chain segments to a certain extent, causing a decrease in crystallinity and a certain degree of agglomeration and uneven dispersion. The multiple uniform feeding method allows the nano-HA particles to fully integrate with the mixed matrix, improves the heterogeneous nucleation effect, increases crystallinity, thereby improving the mechanical properties of meltblown fabric, meeting the density and filament diameter requirements of meltblown fabric, and achieving the high-efficiency filtration performance of meltblown fabric.

[0038] The first screw extruder, the second screw extruder, and the spinneret in this invention are all conventional equipment for preparing meltblown fabric, which are common knowledge known to those skilled in the art. Therefore, their specific structures and working principles will not be described in detail.

[0039] Furthermore, such as Figure 1 As shown, the third screw extruder includes a barrel 2 and an extrusion screw 3 placed inside the barrel 2. Multiple equally spaced feed ports 1 are provided on the barrel 2. The barrel 2 is also provided with a discharge port 4. The feed port 1 has a mixing overflow component 5. The upper end of the feed port 1 is a closed surface 6. The feed port 1 includes an upper conical part 11 and a lower straight cylindrical part 12. The upper conical part 11 and the lower straight cylindrical part 12 are connected to the barrel 2. The mixing overflow component 5 stirs and mixes the raw material in the feed port 1 and then flows vertically into the barrel 2, while preventing the intermediate raw material in the barrel 2 from overflowing into the feed port 1.

[0040] Furthermore, the mixing overflow assembly 5 includes a rotating shaft 51 that extends vertically through the closed surface 6. The lower end of the rotating shaft 51 is placed inside the lower straight cylinder 12 of the feed inlet 1, and the upper end of the rotating shaft 51 is placed above the closed surface 6 and connected to a drive motor 52. Multiple stirring rods 53 are connected to the outer circumference of the upper conical part 11. The outer circumference of the rotating shaft 51 inside the lower straight cylinder 12 has a spiral extrusion part 54. The extension direction of the spiral extrusion part 54 is perpendicular to the extension direction of the extrusion screw 3. An inclined nozzle 55 is embedded in the inner wall of the lower end of the lower straight cylinder 12. The spray direction of the nozzle 55 is downward.

[0041] Furthermore, the stirring rod 53 includes a crossbar portion 531 fixedly connected to the rotating shaft 51 and a stirring portion 532 located at the outer end of the crossbar portion 531. The extension direction of the crossbar portion 531 is perpendicular to the extension direction of the rotating shaft 51, and the extension direction of the stirring portion 532 is consistent with the extension direction of the inner wall of the upper conical portion 11. Adjacent stirring portions 532 are staggered vertically.

[0042] The third screw extruder used in this invention has multiple feed ports 1. The feed port 1 near the inlet end of the third screw extruder contains a mixture of PLA, PBAT, 1 / N grafted material (nano HA raw material), and electrostatic electret masterbatch, while the other feed ports 1 contain 1 / N grafted material (nano HA raw material), thereby achieving segmented and intermittent feeding of the grafted material. The feed port 1 has a stirring rod 53 and a spiral extrusion section 54. After being fully stirred by the stirring rod 53, the raw material in the feed port 1 moves vertically towards the spiral extrusion section 54 and finally falls into the barrel 2 to continue mixing with the raw material in the barrel 2 before entering the next feed port 1. In this application, the spiral extrusion section 54 in the feed port not only has the function of extruding and feeding the raw material in the feed port 1, but also provides a certain resistance to the movement of the mixed raw material in the barrel 2 into the feed port 1 under the lateral extrusion force of the extrusion screw 3, thereby ensuring the normal extrusion efficiency of the mixed raw material in the barrel 2.

[0043] Furthermore, a pressure sensor 56 is located on the inner wall of the barrel 2 near the leading edge of the feed inlet 1. As the raw material in the barrel 2 is extruded by the extrusion screw 3, it moves to the next feed inlet 1. When it passes the pressure sensor 56 of the corresponding feed inlet 1, the pressure sensor 56 detects that the pressure value inside the barrel 2 is greater than a predetermined value. Then, the drive motor 52 of the feed inlet near the pressure sensor 56 is started, which drives the rotating shaft 51 to rotate so that the nano HA raw material in the feed inlet 1 is uniformly stirred and then uniformly mixed with the raw material in the barrel 2. Thus, as the extrusion screw 3 drives, it continues to move as a whole to the next feed inlet 1 and mixes with the nano HA raw material in the next feed inlet 1.

[0044] Furthermore, the time t1 required for the raw material in the barrel 2 to move from the position of the pressure sensor 56 to the corresponding feed port 1 is consistent with the time t2 required for the nano HA raw material in the feed port 1 to be squeezed into the barrel 2.

[0045] Furthermore, the grafted material is evenly divided into 3 parts, with 3 feed inlets 1 and 2 pressure sensors 56. The two pressure sensors 56 are placed at the leading edge of the two feed inlets 1 near the outlet end of the material cylinder 2.

[0046] The pressure sensor 56 at the feed inlet 1 ensures that the time it takes for the intermediate raw material in the barrel 2 to reach the lower end of the corresponding feed inlet 1 is the same as the time it takes for the nano HA raw material in the feed inlet 1 to reach the barrel 2, so that the two can be seamlessly connected and mixed at the feed inlet 1, thereby ensuring the uniformity of the mixing of the raw materials in the barrel 2. Secondly, the nozzle 55 at the lower end of the feed inlet 1 blows air into the barrel 2, further preventing the intermediate raw material in the barrel 2 from moving upwards towards the feed inlet 1 under the lateral extrusion force of the extrusion screw 3. At the same time, it ensures a certain degree of dispersion when feeding the nano HA raw material, thereby ensuring uniform mixing with the raw materials in the barrel 2.

[0047] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A production process for biodegradable meltblown nonwoven fabric, characterized in that, Includes the following steps: S1. PLA raw material is fed into the first screw extruder with a length-to-diameter ratio of 1:33, and PLA mixed raw material is plasticized and extruded at a temperature of 80-90℃. PBAT raw material is fed into the second screw extruder with a length-to-diameter ratio of 1:33, and PBAT mixed raw material is plasticized and extruded at a temperature of 80-90℃. S2. By weight, select 75-80 parts of PLA mixed raw material, 25-30 parts of PBAT mixed raw material, 15-18 parts of grafting material and 3-5 parts of electrostatic electret masterbatch. S3. Divide the grafted material evenly into N parts. Add 1 / N of the grafted material, 75-80 parts of PLA mixed raw material, 25-30 parts of PBAT mixed raw material, and 3-5 parts of electrostatic electret masterbatch into the third screw extruder to form an intermediate raw material. The third screw extruder has multiple equally spaced feed ports. The multiple feed ports are horizontally distributed from the inlet end to the outlet end of the third screw extruder. The N parts of grafted material are sequentially distributed at the multiple feed ports. The intermediate raw material is evenly mixed at the feed port near the inlet end of the second screw extruder and then extruded towards the outlet end. During the extrusion process, it continues to be fully mixed with the remaining grafted material and then extruded towards the outlet end to obtain a melt mixture. S4. The molten mixture obtained in step S3 is sprayed out through a spinneret. The die head temperature of the spinneret is 220-240℃. Under the traction of hot air flow at a spinneret temperature of 240-260℃, it is spun into a Teflon mesh belt to obtain meltblown fibers. S5. The meltblown fibers in step S4 are cooled by negative pressure suction molding, then enter the high-voltage electrostatic electret to carry charges, and are wound up to obtain biodegradable meltblown fabric.

2. The production process of biodegradable meltblown nonwoven fabric according to claim 1, characterized in that, The grafting material is nano-HA raw material.

3. The production process of a biodegradable meltblown nonwoven fabric according to claim 2, characterized in that, The third screw extruder includes a barrel and an extrusion screw placed inside the barrel. Multiple equally spaced feed ports are provided on the barrel, and the barrel is also provided with a discharge port. The feed ports have a mixing overflow component. The upper end of the feed port is a closed surface. The feed port includes an upper conical part and a lower straight cylindrical part. The upper conical part and the lower straight cylindrical part are connected to the barrel. The mixing overflow component stirs and mixes the raw material in the feed port and then flows vertically into the barrel, while preventing the intermediate raw material in the barrel from overflowing into the feed port.

4. The production process of biodegradable meltblown nonwoven fabric according to claim 3, characterized in that, The mixing overflow assembly includes a vertically penetrating rotating shaft through the closed surface. The lower end of the rotating shaft is placed inside the lower straight cylinder of the feed inlet, and the upper end of the rotating shaft is placed above the closed surface and connected to a drive motor. Multiple stirring rods are connected to the outer circumference of the upper conical part of the rotating shaft. The outer circumference of the rotating shaft inside the lower straight cylinder has a spiral extrusion part. The extension direction of the spiral extrusion part is perpendicular to the extension direction of the extrusion screw. An inclined nozzle is embedded in the inner wall of the lower end of the lower straight cylinder, and the spray direction of the nozzle is downward.

5. The production process of a biodegradable meltblown nonwoven fabric according to claim 4, characterized in that, The stirring rod includes a crossbar fixedly connected to the rotating shaft and a stirring part located at the outer end of the crossbar. The extension direction of the crossbar is perpendicular to the extension direction of the rotating shaft, and the extension direction of the stirring part is consistent with the extension direction of the inner wall of the upper conical part. The two adjacent stirring parts are staggered vertically.

6. The production process of a biodegradable meltblown nonwoven fabric according to claim 5, characterized in that, A pressure sensor is located on the inner wall of the barrel near the feed inlet. As the extrusion screw pushes the raw material in the barrel towards the next feed inlet, when the pressure sensor detects that the pressure inside the barrel is greater than a predetermined value, the drive motor of the feed inlet near the pressure sensor is activated, driving the shaft to rotate and uniformly stir the nano-HA raw material in the feed inlet and then mix it with the raw material in the barrel. As the extrusion screw continues to drive, the raw material continues to move towards the next feed inlet as a whole and mixes with the nano-HA raw material in the next feed inlet.

7. The production process of a biodegradable meltblown nonwoven fabric according to claim 6, characterized in that, The time t1 required for the raw material in the barrel to move from the position of the pressure sensor to the corresponding feed port is the same as the time t2 required for the nano HA raw material in the feed port to be squeezed into the barrel.

8. The production process of a biodegradable meltblown nonwoven fabric according to claim 6 or 7, characterized in that, The grafted material is evenly divided into 3 parts, there are 3 feed inlets, and there are 2 pressure sensors. The two pressure sensors are placed at the leading edge of the two feed inlets near the outlet end of the material cylinder.

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