A co-rotating twin screw extruder with periodically varying screw speed ratio and a processing method thereof

Abstract

The application discloses a co-rotating twin-screw extruder with periodically changed rotating speed ratio and a processing method thereof. The co-rotating twin-screw extruder with periodically changed rotating speed ratio comprises a barrel and a screw mechanism. The barrel adopts an 8-shaped structure with cylindrical holes penetrating each other in parallel with their axes. The screw mechanism is located in the barrel and comprises a first screw and a second screw. The first screw and the second screw rotate in the same direction, the average rotating speeds of the first screw and the second screw are equal, the rotating speeds of the first screw and the second screw periodically pulsate with time, the pulsation periods of the first screw and the second screw are the same, and the first screw and the second screw always rotate in meshing with each other during operation, so that the self-cleaning function is realized. The introduction of the periodic transient disturbance effect strengthens the reinforced melting, mixing and exhaust efficiency, and the co-rotating twin-screw extruder is especially suitable for low-temperature processing of a strong dispersion multi-phase material system.

Description

Technical Field

[0001] The embodiments of the present invention relate to, but are not limited to, the field of twin-screw extruder technology, and in particular to a co-rotating twin-screw extruder with a periodically changing speed ratio and its processing method. Background Technology

[0002] Currently, co-rotating twin-screw extruders are widely used in new materials, food, pharmaceuticals, and chemical industries. However, with the increasing demands for high-speed, high-efficiency, and low-temperature extrusion, the existing co-rotating twin-screw extruders are finding it increasingly difficult to meet these requirements in terms of melt plasticizing and mixing. Therefore, how to further improve the melt plasticizing and mixing effects of co-rotating twin-screw extruders has become an urgent technical problem to be solved. Summary of the Invention

[0003] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0004] This invention provides a co-rotating twin-screw extruder with periodically varying speed ratio and its processing method. By periodically varying the speed of the two screws over time, with equal average speeds and identical speed pulsation periods, the left and right screws alternate periodically during operation, alternating between left-fast and right-slow, left-slow and then fast again, introducing periodic transient disturbances to enhance melt mixing. This further improves the melt plasticizing and mixing effect of the co-rotating twin-screw extruder. Moreover, the two screws are always meshed with each other, achieving a self-cleaning function.

[0005] A first aspect of the present invention provides a co-rotating twin-screw extruder with a periodically varying speed ratio, comprising:

[0006] The barrel adopts an 8-shaped structure with interconnected cylindrical holes whose axes are parallel to each other;

[0007] A screw mechanism is located inside the barrel. The screw mechanism includes a first screw and a second screw. The first screw and the second screw rotate in the same direction. The average rotational speeds of the first screw and the second screw are equal. The rotational speeds of the first screw and the second screw change periodically with time, and the periods of the pulsations are the same. The first screw and the second screw are always meshed with each other during operation.

[0008] In some embodiments, the first screw and the second screw rotate in the same direction, and the angular velocity of the first screw is set as: 1= 0(1+ε1sin(2π 0t / α)) is the rotational speed of a single screw. 0 represents the average angular velocity, 0 < 0 < 50000; ε1 is the speed disturbance amplitude of the first screw, and 0 1; t is time; α is the screw tip angle; the rotational speed of the second screw is: 2= 0(1- sin(2π 0t / α), ε2 is the speed disturbance amplitude of the second screw, and 0 1; The speed ratio between the first screw and the second screw is (1+ sin(2π 0t / α)) / (1- sin(2π 0t / α)).

[0009] In some embodiments, the rotation center of the first screw is O, and both the top diameter and root diameter of the first screw are composed of circular arcs AB and CD, with radii R and r respectively, and corresponding central angles α; the top diameter and root diameter of the first screw are connected by a curved arc, with a corresponding central angle β. Given an integer k, k=1,2,…100, then we have…

[0010] α=

[0011] β=

[0012] The rotation center of the second screw is O1. Both the top and root diameters of the second screw are composed of arcs A1B1 and C1D1, with radii R and r respectively, and corresponding central angles of 1 / r. α The second screw's major diameter and root diameter are connected by a curved arc, with a corresponding central angle of... β Then the center distance C between the first screw and the second screw is:

[0013] C=2Rcos( β / 2)

[0014] The inner diameters r of the first screw and the second screw satisfy the following relationship:

[0015] r=2Rcos( β / 2)-R

[0016] The top diameter and root diameter of the first screw are connected by a curved arc BC. The rotation center O and the root diameter starting point B are connected as the polar diameter starting position Ox, with counterclockwise being positive. Given an auxiliary angle θ, the polar angle corresponding to any position of the BC arc is... 1(θ), polar radius is ,

[0017] 1(θ)=

[0018]

[0019] at this time, Among them, CD, Let CD be an arc of radius R. The corresponding central angle is α AB Let AB be an arc of radius r. The corresponding central angle is also α And the curve arc BC and ;

[0020] The first screw has a curved arc between its major diameter and root diameter. Connect the rotation center O and the root diameter starting point. As the starting position of the polar diameter O Clockwise is positive. Given an auxiliary angle θ, then The polar angle corresponding to any position of the arc is The polar radius is ,

[0021] =

[0022]

[0023] at this time, , and The rotation center O is centrally symmetric, and the corresponding central angles are all... β AB, BC, CD , , , They form a closed curved arc, which constitutes the end face of the first screw thread element.

[0024] In some embodiments, the total axial length of the threaded element of the first screw is L, mm, 0.5 ≤ L. Given a parameter t, the z-coordinate of any cross-section of the threaded element satisfies:

[0025]

[0026] here, Meanwhile, AB, BC, CD, , , , The closed curve arc formed by the threaded end face rotates clockwise or counterclockwise around the center of rotation. for:

[0027] .

[0028] In some embodiments, the top diameter and root diameter of the second screw are connected by a curved arc B1C1. The rotation center O1 and the root diameter starting point B1 are connected as the polar diameter starting position O1x1. Counterclockwise rotation is positive. Given an auxiliary angle θ, the polar angle corresponding to any position of the arc B1C1 is... 2(θ), polar radius is ,

[0029] 2(θ)=

[0030]

[0031] at this time, C1D1 Let A1B1 be an arc of radius R, with a corresponding central angle α. Let B1C1 be an arc of radius r, with a corresponding central angle of α. The rotation center O1 is centrally symmetric, and the corresponding central angle is β.

[0032] The second screw has a curved arc between its major diameter and root diameter. Connect the rotation center O1 and the root diameter starting point A1 as the starting position of the polar diameter O. Clockwise is positive. Given an auxiliary angle θ, then The polar angle corresponding to any position of the arc is The polar radius is ,

[0033] =

[0034]

[0035] at this time, , and The rotation center O1 is centrally symmetric, and the corresponding central angles are all... β ; Curve arcs A1B1, B1C1, C1D1, , , , , The closed curved arc is formed to create the end face of the second screw thread element.

[0036] In some embodiments, the total axial length of the threaded element of the second screw is L mm Given parameter t, the z-coordinate of any cross-section of the threaded element satisfies:

[0037]

[0038] in, Meanwhile, curves A1B1, B1C1, C1D1, , , , , The closed curve arc of the second screw thread end face rotates clockwise or counterclockwise around the center of rotation. for:

[0039] .

[0040] In some embodiments, the top diameters of both the first screw and the second screw are tangent to the inner wall of the barrel.

[0041] In some embodiments, the screw mechanism divides the inner cavity of the barrel into a conveying section, a melting section, a venting section, and a mixing and extrusion section in sequence; a feed inlet is provided on the barrel corresponding to the conveying section, a vent is provided on the barrel corresponding to the venting section, and a discharge outlet is provided on the barrel corresponding to the end of the mixing and extrusion section.

[0042] A second aspect of the present invention provides a processing method for a co-rotating twin-screw extruder with periodically varying speed ratios, applied to the co-rotating twin-screw extruder with periodically varying speed ratios as described in the first aspect, the method comprising:

[0043] Add materials;

[0044] The first screw and the second screw rotate in the same direction. The rotational speed of the first screw and the second screw changes periodically with time. The average rotational speed of the first screw and the second screw is the same. The pulsation period and pulsation amplitude of the rotational speed of the first screw and the second screw are the same. The material is propelled forward by the first screw and the second screw.

[0045] The material is melted by the heat generated by the rotation of the first and second screws and external heating. Due to the periodic transient disturbance, the meshing zone can generate extrusion and stretching action to accelerate the melting process of the material and form a melt. The melt is then vented efficiently through the exhaust port under the periodic transient disturbance.

[0046] The mixture is compounded and pressurized under periodic transient disturbances through the first screw, the second screw, and the barrel, and finally extruded from the outlet to form the final product.

[0047] The co-rotating twin-screw extruder and its processing method with periodically changing speed ratio provided in the embodiments of the present invention have at least the following technical effects: (1) The two screws rotate around their respective axes, and the speed changes periodically with time. The pulsation period of the two screws is the same, which leads to the periodic change of the screw speed ratio. The left is fast and the right is slow, the left is slow and then fast again, and then the left is fast and the right is slow again. The periodic transient disturbance effect is introduced to enhance the melt mixing effect and the volatilization efficiency. (2) In order to increase the output, the present invention can appropriately increase the screw center distance, or even use a speed ratio of 1:1 to run. This can realize the periodic expansion and contraction of the meshing zone gap, thereby generating the extrusion and stretching effect of the meshing zone to enhance the melt mixing effect, enhance the dispersion and mixing of multiphase system materials and accelerate the melting effect, and is more suitable for high-speed, high-output and low-temperature extrusion processing. (3) The present invention ensures that the screws can still mesh and rotate with each other under the premise of changing speed ratio. The superimposed periodic pulsation effect can more effectively achieve the self-cleaning effect.

[0048] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0049] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0050] Figure 1 This is a schematic diagram of the structure of a co-rotating twin-screw extruder with a periodically changing speed ratio according to the present invention;

[0051] Figure 2 This is a first aspect embodiment of the present invention. The speed ratio is (1+ sin(2π 0t / α)) / (1- sin(2π 0t / α), k=1, α=π / 6 and =1 First screw end face structure diagram (excluding barrel);

[0052] Figure 3 This is a first aspect embodiment of the present invention. The speed ratio is (1+ sin(2π 0t / α)) / (1- sin(2π 0t / α), k=1, α=π / 6 and =1 Schematic diagram of the end face structure of the second screw (excluding the barrel);

[0053] Figure 4 This is a first aspect embodiment of the present invention. The speed ratio is (1+ sin(2π 0t / α)) / (1- sin(2π 0t / α), k=1, α=π / 6 and =1 Schematic diagram of the combined end face structure of the first and second screws (excluding the barrel);

[0054] Figure 5 This is a first aspect embodiment of the present invention. The speed ratio is (1+ sin(2π 0t / α)) / (1- sin(2π 0t / α), k=1, α=π / 6 and =1 Three-dimensional structural diagram of the first screw and second screw combination (excluding the barrel);

[0055] Figure 6 This is a first aspect embodiment of the present invention. The speed ratio is (1+ sin(2π 0t / α)) / (1- sin(2π 0t / α), k=1, α=π / 6 and A schematic diagram of the end face structure of the first and second screws combined with a diameter of 0.5 (excluding the barrel);

[0056] Figure 7 This is a first aspect embodiment of the present invention. The speed ratio is (1+ sin(2π 0t / α)) / (1- sin(2π Schematic diagram of the end face structure of the first screw, second screw and third screw combination (excluding the barrel) when k=1, α=π / 6 and ε=0.5.

[0057] Figure 8 This is a flowchart illustrating a processing method for a co-rotating twin-screw extruder with a periodically varying speed ratio, according to a second aspect of the present invention.

[0058] Figure label:

[0059] Barrel 100, conveying section 110, feed inlet 111, melting section 120, venting section 130, venting port 131, mixing and extrusion section 140, discharge port 141, screw mechanism 200, first screw 210, first intermediate arc structure 211, second screw 220, second intermediate arc structure 221, flow channel 300. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0061] It should be understood that in the description of the embodiments of the present invention, "multiple" (or "amounts") means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first," "second," etc., are used in the description, they are only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0062] To address the increasingly unsatisfactory melt plasticizing and mixing effects of existing co-rotating twin-screw extruders, this invention provides a co-rotating twin-screw extruder with a periodically varying speed ratio. This extruder includes a barrel and a screw mechanism. The barrel employs an 8-shaped structure with interconnected cylindrical holes of parallel axes. The screw mechanism, located within the barrel, includes a first screw and a second screw. Both screws rotate in the same direction, with equal average speeds. The speeds of both screws pulsate periodically over time, with identical pulsation periods. The first and second screws are constantly meshed during operation. Because the first and second screws rotate in the same direction, have equal average speeds, and exhibit periodic pulsations over time, the speed ratio of the two screws changes periodically over time. This results in the material being subjected to unsteady shearing, extrusion, and stretching during conveying and processing, effectively improving the efficiency of melt plasticizing, degassing, and mixing. The two screws mesh and wipe each other, achieving a self-cleaning function in the processing. Based on this, the present invention has at least the following technical effects: (1) The two screws rotate around their respective axes, and the rotation speed changes periodically with time. The pulsation period of the two screws is the same, resulting in a periodic change in the screw speed ratio. The left is fast and the right is slow, the left is slow and then fast again, and then the left is fast and the right is slow again. This introduces a periodic transient disturbance to enhance the melting and mixing effect and the volatilization efficiency. (2) In order to increase the output, the present invention can appropriately increase the screw center distance, or even use a speed ratio of 1:1 to run. This can achieve a periodic expansion and contraction of the meshing zone gap, thereby generating a squeezing and stretching effect in the meshing zone to enhance the melting and mixing effect, strengthen the dispersion and mixing of multiphase system materials and accelerate the melting effect, and is more suitable for high-speed, high-volume and low-temperature extrusion processing. (3) The present invention ensures that the screws can still mesh and rotate with each other under the premise of variable speed ratio. The superimposed periodic pulsation effect can more effectively achieve the self-cleaning effect.

[0063] The following is for reference. Figures 1 to 5 A co-rotating twin-screw extruder with a periodically varying speed ratio is described according to an embodiment of the first aspect of the present invention.

[0064] According to a first aspect of the present invention, a self-cleaning co-rotating twin-screw extruder capable of generating a reinforcing meshing zone includes a barrel 100 and a screw mechanism 200 disposed within the barrel 100. The screw mechanism 200 includes a first screw 210 and a second screw 220; the first screw 210 and the second screw 220 are always meshed with each other; the first screw 210 and the second screw 220 rotate in the same direction with a speed ratio that changes periodically over time, and the speed pulsations of the two screws have the same period.

[0065] refer to Figures 2 to 6In some embodiments of the present invention, the top diameters of both the first screw 210 and the second screw 220 are tangent to the inner wall of the barrel 100. The root diameter and top diameter of the first screw 210 are equal to those of the second screw 220. This can result in greater agitation and mixing.

[0066] In some embodiments of the present invention, reference is made to Figure 1 The first screw 210, the second screw 220 and the barrel 100 form a flow channel 300, which is used for material passage.

[0067] In some embodiments of the present invention, reference is made to Figure 1 The screw mechanism 200 divides the inner cavity of the barrel 100 into a conveying section 110, a melting section 120, an exhaust section 130, and a mixing and extrusion section 140 in sequence. A feed inlet 111 is provided on the barrel 100 corresponding to the conveying section 110, an exhaust port 131 is provided on the barrel 100 corresponding to the exhaust section 130, and a discharge port 141 is provided at the end of the barrel 100 corresponding to the mixing and extrusion section 140.

[0068] In the conveying section 110, the first screw 210 and the second screw 220 rotate in the same direction along their respective screw axes, generating conveying force through friction and positive displacement. The material moves towards the melting section 120 under the combined action of the positive displacement conveying force and the friction between the two screws.

[0069] In the melting section 120, the barrel 100 melts the material by external heating. At the same time, periodic transient disturbances are introduced to enhance the mixing and melting efficiency. Under the action of external heating and screw mechanism 200, the material eventually becomes a melt, and then enters the exhaust section 130 under the push of the first screw 210 and the second screw 220.

[0070] In the exhaust section 130, the first screw 210 and the second screw 220 adopt a large lead structure to generate a negative pressure space. At the same time, due to the introduction of periodic transient disturbances, the exhaust efficiency is accelerated, allowing the exhaust gas to be discharged from the exhaust port 131. Simultaneously, driven by the first screw 210 and the second screw 220, the exhaust gas enters the compounding extrusion section 140.

[0071] In the compounding and extrusion section 140, the first screw 210 and the second screw 220 mesh in the same direction, which gives the first screw 210 and the second screw 220 better pressure building ability and extrusion characteristics. At the same time, under the enhanced compounding mechanism described in the melting section, the compounding and plasticizing effect is enhanced, so that the material that becomes melt can be stably extruded from the discharge port 141.

[0072] refer to Figure 7In some embodiments of the present invention, the screw mechanism 200 further includes a third screw with the same structure as the first screw 210, and the third screw and the second screw 220 are always meshed with each other; the third screw and the first screw 210 rotate in the same direction. The three-screw structure can bring a greater extrusion effect and significantly improve extrusion efficiency. It should be noted that since the first screw 210 and the second screw 220 are not specifically defined, the third screw can essentially be the same as either the first screw 210 or the second screw 220. However, when the third screw is the same as the first screw 210, it meshes with the second screw 220; and when the third screw is the same as the second screw 220, it meshes with the first screw 210. Figure 7 The diagram shows a three-screw mechanism 200. Typically, the first screw 210, the second screw 220, and the third screw 210 are arranged in a straight line and mesh according to their meshing conditions.

[0073] In some embodiments of the present invention, both the first screw 210 and the second screw 220 adopt a conical structure. The conical structure provides a stronger mixing effect and a greater extrusion output.

[0074] In some embodiments, the first screw and the second screw rotate in the same direction, and the angular velocity of the first screw is set as follows: 1= 0(1+ε1sin(2π 0t / α)) is the rotational speed of a single screw. 0 represents the average angular velocity, in rad / s; 0 < 0 < 50000; ε1 is the speed disturbance amplitude of the first screw, and 0 1; t is time, s; α is the screw tip angle, rad; the rotational speed of the second screw is: 2= 0(1- sin(2π 0t / α), ε2 is the speed disturbance amplitude of the second screw, and 0 1; The speed ratio of the first screw to the second screw is (1+ sin(2π 0t / α)) / (1- sin(2π 0t / α)).

[0075] In some embodiments, the rotation center of the first screw is O, and both the top diameter and root diameter of the first screw are composed of circular arcs AB and CD, with radii R and r respectively, and corresponding central angles α; the top diameter and root diameter of the first screw are connected by a curved arc, with a corresponding central angle β. Given an integer k, k=1,2,…100, then we have…

[0076] α=

[0077] β=

[0078] The rotation center of the second screw is O1. Both the top and root diameters of the second screw are composed of arcs A1B1 and C1D1, with radii R and r respectively, and corresponding central angles of r and r. α The major diameter and root diameter of the second screw are connected by a curved arc, with a corresponding central angle of . β Then the center distance C between the first screw and the second screw is:

[0079] C=2Rcos( β / 2)

[0080] The inner diameters r of the first and second screws satisfy the following relationship:

[0081] r=2Rcos( β / 2)-R

[0082] For the first screw, on the one hand, such as Figure 2 As shown, the top diameter and root diameter of the first screw are connected by a curved arc BC. The rotation center O and the root diameter starting point B are connected as the starting position Ox of the polar diameter, with counterclockwise being positive. Given an auxiliary angle θ, the polar angle corresponding to any position of the BC arc is... 1(θ), polar radius is ,

[0083] 1(θ)=

[0084]

[0085] at this time, Among them, CD, Let CD be an arc of radius R. The corresponding central angle is α AB Let AB be an arc of radius r. The corresponding central angle is also α And the curve arc BC and ;

[0086] On the other hand, the major diameter and root diameter of the first screw are connected by a curved arc. Connect the rotation center O and the root diameter starting point. As the starting position of the polar diameter O Clockwise is positive. Given an auxiliary angle θ, then The polar angle corresponding to any position of the arc is The polar radius is ,

[0087] =

[0088]

[0089] at this time, ,like Figure 2 As shown, and The rotation center O is centrally symmetric, and the corresponding central angles are all... β AB, BC, CD , , , They form a closed curved arc, which constitutes the end face of the first screw thread element.

[0090] Given that the total axial (z-direction) dimension of the threaded element of the first screw is L (mm), and 0.5 ≤ L, and given the parameter t, the z-coordinate of any cross-section of the threaded element satisfies:

[0091]

[0092] here, Meanwhile, AB, BC, CD, , , , The closed curve arc formed by the threaded end face rotates clockwise or counterclockwise around the center of rotation. for:

[0093] .

[0094] Corresponding to the second screw, such as Figure 3 As shown, on one hand, the top diameter and root diameter of the second screw are connected by a curved arc B1C1. The rotation center O1 and the root diameter starting point B1 are connected as the starting position O1x1 of the polar diameter. Counterclockwise rotation is positive. Given an auxiliary angle θ, the polar angle corresponding to any position of the arc B1C1 is... 2(θ), polar radius is ,

[0095] 2(θ)=

[0096]

[0097] at this time, Thus, as Figure 2 As shown, C1D1, Let A1B1 be an arc of radius R, with a corresponding central angle α. Let B1C1 be an arc of radius r, with a corresponding central angle of α. The rotation center O1 is centrally symmetric, and the corresponding central angle is β.

[0098] On the other hand, such as Figure 3 As shown, the critical diameter and root diameter of the second screw are connected by a curved arc. Connect the rotation center O1 and the root diameter starting point A1 as the starting position of the polar diameter O. Clockwise is positive. Given an auxiliary angle θ, then The polar angle corresponding to any position of the arc is The polar radius is ,

[0099] =

[0100]

[0101] at this time, ,like Figure 2 As shown, and The rotation center O1 is centrally symmetric, and the corresponding central angles are all... β ; Curve arcs A1B1, B1C1, C1D1, , , , , The closed curved arc is formed to create the end face of the second screw thread element.

[0102] Similarly, the total axial (z-direction) dimension of the threaded element of the second screw is... L mm Given parameter t, the z-coordinate of any cross-section of the threaded element satisfies:

[0103]

[0104] in, Meanwhile, curves A1B1, B1C1, C1D1, , , , , The closed curve arc of the second screw thread end face rotates clockwise or counterclockwise around the center of rotation. for:

[0105] .

[0106] Furthermore, in embodiments of the present invention, the center distance C between the two screws can be appropriately increased to increase the flow rate of material passing through the gap between the two screws and to improve the randomness of movement in the meshing zone, thereby further enhancing the melting and plasticizing effect.

[0107] In some embodiments, the top diameters of both the first screw and the second screw are tangent to the inner wall of the barrel.

[0108] In some embodiments, the screw mechanism divides the inner cavity of the barrel into a conveying section, a melting section, a venting section, and a mixing and extrusion section in sequence; a feed inlet is provided on the barrel corresponding to the conveying section, a vent is provided on the barrel corresponding to the venting section, and a discharge outlet is provided on the barrel corresponding to the end of the mixing and extrusion section.

[0109] In some embodiments, the screw mechanism further includes a third screw with the same structure as the first screw, the third screw being always meshed with the second screw; the third screw and the first screw rotate in the same direction.

[0110] like Figure 8 As shown, this embodiment of the invention also provides a processing method for a co-rotating twin-screw extruder with a periodically varying speed ratio, applied to the aforementioned co-rotating twin-screw extruder with a periodically varying speed ratio. The method includes at least the following steps:

[0111] Step S101: Add materials;

[0112] Step S102: The first screw and the second screw rotate in the same direction. The rotational speed of the first screw and the second screw changes periodically with time. The average rotational speed of the first screw and the second screw is the same. The pulsation period and pulsation amplitude of the rotational speed of the first screw and the second screw are the same. The material is propelled forward by the first screw and the second screw.

[0113] Step S103: The material is melted by the heat generated by the rotation of the first and second screws and external heating. During this process, due to the periodic transient disturbance, a squeezing and stretching effect can be generated in the meshing zone to accelerate the melting process of the material and form a melt. The melt is vented efficiently through the exhaust port under the periodic transient disturbance.

[0114] Step S104: The mixture is pressed and compounded under periodic transient disturbances through the first screw, the second screw, and the barrel, and finally extruded from the outlet.

[0115] In some embodiments, the processing method includes adding material, rotating a first screw and a second screw in the same direction, with the rotational speed of the two screws varying periodically over time, having the same average rotational speed, and having the same pulsation period and amplitude. The material is propelled forward by the first and second screws. The material is melted by the heat generated by the rotation of the first and second screws and external heating. Due to the periodic transient disturbance and the different geometry of the screws and grooves, extrusion and stretching effects can be generated in the meshing zone, which can effectively enhance the melting and dispersion mixing effect of the multiphase system material, accelerate the melting process, and form a melt. The melt is vented efficiently through the vent under the periodic transient disturbance. Finally, the material is mixed and pressurized under the periodic transient disturbance of the first screw, the second screw, and the barrel, and finally extruded from the outlet to form a mold.

[0116] Based on this, the present invention has at least the following technical effects: (1) The two screws rotate around their respective axes, and the rotation speed changes periodically with time. The pulsation period of the two screws is the same, which leads to the periodic change of the screw speed ratio. The left is fast and the right is slow, the left is slow and then fast again, and then the left is fast and the right is slow again. The periodic transient disturbance effect is introduced to enhance the melting and mixing effect and the volatilization efficiency. (2) In order to increase the output, the present invention can appropriately increase the screw center distance, or even use a speed ratio of 1:1 to run. This can realize the periodic expansion and contraction of the meshing zone gap, thereby generating the squeezing and stretching effect of the meshing zone to enhance the melting and mixing effect, enhance the dispersion and mixing of multiphase system materials and accelerate the melting effect, and is more suitable for high-speed, high-volume and low-temperature extrusion processing. (3) The present invention ensures that the screws can still mesh and rotate with each other under the premise of variable speed ratio. The superimposed periodic pulsation effect can more effectively achieve the self-cleaning effect.

[0117] The above provides a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

Claims

1. A co-rotating twin-screw extruder with a periodically varying speed ratio, characterized in that, include: The barrel adopts an 8-shaped structure with interconnected cylindrical holes whose axes are parallel to each other; A screw mechanism is located inside the barrel. The screw mechanism includes a first screw and a second screw, which rotate in the same direction. The average rotational speeds of the first and second screws are equal. The rotational speeds of both the first and second screws periodically pulsate over time, and the periods of these pulsations are identical. The first and second screws are always meshed during operation. The angular velocity of the screws is defined as their rotational speed. The rotational speed of the first screw is: 1= 0(1+ sin(2π 0t / α)), 0 represents the average angular velocity, 0 < 0 < 50000; Let be the rotational speed disturbance amplitude of the first screw, and 0. 1; t is time; the screw apex angle of the first screw and the second screw is α, and the rotational speed of the second screw is: 2= 0(1- sin(2π 0t / α)), Let be the speed disturbance amplitude of the second screw, and 0. 1; The speed ratio between the first screw and the second screw is (1+ sin(2π 0t / α)) / (1- sin(2π 0t / α)).

2. The co-rotating twin-screw extruder with periodically varying speed ratio according to claim 1, characterized in that, The rotation center of the first screw is O. Both the top and root diameters of the first screw are composed of circular arcs AB and CD, with radii R and r respectively, and corresponding central angles α. The top and root diameters of the first screw are connected by a curved arc, with a corresponding central angle β. Given an integer k, k = 1, 2, ..., 100, then... α= β= The rotation center of the second screw is O1. Both the top and root diameters of the second screw are composed of arcs A1B1 and C1D1, with radii R and r respectively, and corresponding central angles of 1 / r. α The second screw's major diameter and root diameter are connected by a curved arc, with a corresponding central angle of... β Then the center distance C between the first screw and the second screw is: C=2Rcos( β / 2) The radii r of the first screw and the second screw satisfy the following relationship: r=2Rcos( β / 2)-R The top diameter and root diameter of the first screw are connected by a curved arc BC. The rotation center O and the root diameter starting point B are connected as the polar diameter starting position Ox, with counterclockwise being positive. Given an auxiliary angle θ, the polar angle corresponding to any position of the BC arc is... The polar radius is , = in, CD Let CD be an arc of radius R. The corresponding central angle is α AB Let AB be an arc of radius r. The corresponding central angle is also α And the curve arc BC and ; The first screw has a curved arc between its major diameter and root diameter. Connect the rotation center O and the root diameter starting point. As the starting position of the polar diameter O Clockwise is positive. Given an auxiliary angle θ, then The polar angle corresponding to any position of the arc is The polar radius is , = in, , and The rotation center O is centrally symmetric, and the corresponding central angles are all... β AB, BC, CD , , , They form a closed curved arc, which constitutes the end face of the first screw thread element.

3. The co-rotating twin-screw extruder with periodically varying speed ratio according to claim 1, characterized in that, The total axial length of the threaded element of the first screw is L (mm), 0.5 ≤ L. Given parameter t, the z-coordinate of any cross-section of the threaded element satisfies: in, Meanwhile, AB, BC, CD, , , , The closed curve arc formed by the threaded end face rotates clockwise or counterclockwise around the center of rotation. for: 。 4. The co-rotating twin-screw extruder with periodically varying speed ratio according to claim 3, characterized in that, The major diameter and root diameter of the second screw are connected by a curved arc B1C1. The rotation center O1 and the root diameter starting point B1 are connected as the starting position O1x1 of the polar diameter. Counterclockwise rotation is positive. Given an auxiliary angle θ, the polar angle corresponding to any position of the arc B1C1 is... The polar radius is , = in, C1D1 Let A1B1 be an arc of radius R, with a corresponding central angle α. Let B1C1 be an arc of radius r, with a corresponding central angle of α. The rotation center O1 is centrally symmetric, and the corresponding central angle is β. The second screw has a curved arc between its major diameter and root diameter. Connect the rotation center O1 and the root diameter starting point A1 as the starting position of the polar diameter O. Clockwise is positive. Given an auxiliary angle θ, then The polar angle corresponding to any position of the arc is The polar radius is , = in, , and The rotation center O1 is centrally symmetric, and the corresponding central angles are all... β A1B1, B1C1, C1D1 , , , , The closed curved arc is formed to create the end face of the second screw thread element.

5. The co-rotating twin-screw extruder with periodically varying speed ratio according to claim 4, characterized in that, The total axial length of the threaded element of the second screw is L mm Given parameter t, the z-coordinate of any cross-section of the threaded element satisfies: in, A1B1, B1C1, C1D1 , , , , The closed curve arc formed by the second screw thread end face rotates clockwise or counterclockwise around the center of rotation. for: 。 6. The co-rotating twin-screw extruder with periodically varying speed ratio according to claim 1, characterized in that, The top diameters of both the first screw and the second screw are tangent to the inner wall of the barrel.

7. The co-rotating twin-screw extruder with periodically varying speed ratio according to claim 1, characterized in that, The screw mechanism divides the inner cavity of the barrel into a conveying section, a melting section, a venting section, and a mixing and extrusion section in sequence; the barrel is provided with a feed inlet corresponding to the conveying section, a venting outlet corresponding to the venting section, and a discharge outlet corresponding to the end of the mixing and extrusion section.

8. The co-rotating twin-screw extruder with periodically varying speed ratio according to claim 1, characterized in that, The screw mechanism also includes a third screw with the same structure as the first screw, and the third screw is always meshed with the second screw; the third screw and the first screw rotate in the same direction.

9. A processing method for a co-rotating twin-screw extruder with a periodically varying speed ratio, characterized in that, The method, applied to a co-rotating twin-screw extruder with a periodically varying speed ratio as described in any one of claims 1 to 8, comprises: Add materials; The first screw and the second screw rotate in the same direction. The rotational speed of the first screw and the second screw changes periodically with time. The average rotational speed of the first screw and the second screw is the same. The pulsation period and pulsation amplitude of the rotational speed of the first screw and the second screw are the same. The material is propelled forward by the first screw and the second screw. The material is melted by the heat generated by the rotation of the first and second screws and external heating. Due to the periodic transient disturbance, the meshing zone can generate extrusion and stretching action to accelerate the melting process of the material and form a melt. The melt is then vented efficiently through the exhaust port under the periodic transient disturbance. The mixture is compounded and pressurized under periodic transient disturbances through the first screw, the second screw, and the barrel, and finally extruded from the outlet to form the final product.

Images