Co-rotating twin-screw extruder with periodically varying rotation speed ratio and machining method thereof

Abstract

Disclosed in the present invention are a co-rotating twin-screw extruder with a periodically varying rotational speed ratio and a machining method thereof. The co-rotating twin-screw extruder with a periodically varying rotation speed ratio comprises a barrel and a screw mechanism; the barrel is of a figure-eight-shaped structure with cylindrical holes which are communicated with each other and have axes parallel to each other; the screw mechanism is located in the barrel; the screw mechanism comprises a first screw and a second screw; the first screw and the second screw rotate in the same direction; the average rotation speed of the first screw is equal to the average rotation speed of the second screw; the rotation speed of the first screw and the rotation speed of the second screw undergo periodic pulsating variations along with time, and the pulsating variation cycles are the same; and during operation, the first screw and the second screw always rotate in an intermeshed fashion. A self-cleaning function is implemented, the introduction of the periodic transient disturbance effect enhances the melting, mixing and exhaust efficiency, and the present invention is particularly suitable for enhancing the dispersion of multi-phase system materials and low-temperature machining.

Description

A co-rotating twin-screw extruder with periodically changing speed ratio and processing method thereof Technical Field

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

[0002] At present, co-rotating twin-screw extruders are widely used in new materials, food, medicine, chemical industry and other fields. However, with the increasing requirements for high-speed, high-efficiency and low-temperature extrusion, the melt plasticization and mixing effects of existing co-rotating twin-screw extruders are becoming increasingly difficult to meet the above requirements. Therefore, how to further improve the melt plasticization and mixing effects of co-rotating twin-screw extruders has become a technical problem that needs to be solved urgently.

[0003] Summary of the Invention

[0004] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0005] An embodiment of the present invention provides a co-rotating twin-screw extruder with a periodically changing speed ratio and a processing method thereof. The speeds of the two screws change periodically over time, the average speeds are equal, and the speed pulsation periods are the same. During operation, the left and right screws exhibit a periodic alternation of left fast and right slow, left slow and right fast, and then left fast and right slow. The introduction of periodic transient disturbance effect strengthens melt mixing, thereby further improving the melt plasticization and mixing effects of the co-rotating twin-screw extruder, and the two screws are always engaged with each other to realize a self-cleaning function.

[0006] A first aspect of an embodiment of the present invention provides a co-rotating twin-screw extruder with a periodically changing speed ratio, comprising:

[0007] The barrel adopts an 8-shaped structure with cylindrical holes with parallel axes interpenetrating each other;

[0008] A screw mechanism is located in the barrel, and includes a first screw and a second screw. The first screw and the second screw rotate in the same direction, and the average speed of the first screw and the second screw are equal. The speeds of the first screw and the second screw both pulsate periodically over time, and the periods of the pulsation changes are the same. The first screw and the second screw are always engaged with each other during operation.

[0009] 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 to: ω1 = ω0 (1 + ε1sin (2πω0t / α)) is the rotational speed of a screw, ω0 is the average angular velocity, 0 < ω0 < 50000; ε1 is the rotational speed disturbance amplitude of the first screw, and 0 ≤ ε1 ≤ 1; t is time; α is the screw top angle, and the rotational speed of the second screw is: ω2 = ω0 (1 - ε2sin (2πω0t / α)), ε2 is the rotational speed disturbance amplitude of the second screw, and 0 ≤ ε2 ≤ 1; the speed ratio of the first screw to the second screw is (1 + ε1sin (2πω0t / α)) / (1 - ε2sin (2πω0t / α)).

[0010] In some embodiments, the rotation center of the first screw is O, the top diameter and root diameter of the first screw are both composed of an arc AB and an arc CD, the radii of the arc AB and the arc CD are R and r respectively, and the corresponding central angles are both α; the top diameter and the root diameter of the first screw are connected by a curved arc, and the corresponding central angle is β. Given an integer k, k = 1, 2, ... 100, then,

[0011] The rotation center of the second screw is O1, and the top diameter and root diameter of the second screw are both composed of arc A1B1 and arc C1D1. The radii of arc A1B1 and arc C1D1 are R and r respectively, and the corresponding central angles are both α. The top diameter and root diameter of the second screw are connected by a curved arc, and the corresponding central angle is β. Then the center distance C between the first screw and the second screw is: C = 2Rcos(β / 2)

[0012] The inner diameters r of the first screw and the second screw satisfy the following relationship: r = 2Rcos(β / 2) - R

[0013] The top diameter and the root diameter of the first screw are connected by a curved arc BC, and the rotation center O and the root diameter starting point B are connected as the polar diameter starting position Ox. Counterclockwise is positive. Given an auxiliary angle θ, the polar angle corresponding to any position of the BC arc is The polar diameter is ρ1(θ),

[0014] at this time, Among them, CD and C'D' are arcs of radius R, and the central angles corresponding to CD and C'D' are α. AB and A'B' are arcs of radius r, and the central angles corresponding to AB and A'B' are also α. The curved arcs BC and B'C' are centrosymmetric about the rotation center O, and the central angles corresponding to BC and B'C' are both β.

[0015] The top diameter and the root diameter of the first screw are connected by a curved arc A′D, and the rotation center O and the root diameter starting point A′ are connected as the polar diameter starting position Ox′. Clockwise is positive. Given an auxiliary angle θ, the polar angle corresponding to any position of the A′D arc is The polar diameter is ρ1′(θ),

[0016] at this time, A′D and AD′ are centrally symmetrical about the rotation center O, and the corresponding central angles are both β; AB, BC, CD, A′D, A′B′, B′C′, C′D′, and AD′ form a closed curve arc, forming the end face of the first screw thread element.

[0017] In some embodiments, the total axial length of the threaded element of the first screw is L, mm, 0.5≤L, and given the parameter t, the z coordinate of any cross section of the threaded element satisfies:

[0018] Here, 0≤t≤2π. At the same time, the closed curve arc of the thread end face composed of AB, BC, CD, A′D, A′B′, B′C′, C′D′, and AD′ rotates clockwise or counterclockwise around the rotation center by an angle γ1(t):

[0019] In some embodiments, the top diameter and the root diameter of the second screw are connected by a curved arc B1C1, and the rotation center O1 and the root diameter starting point B1 are connected as the polar diameter starting position O1x1. Counterclockwise rotation is positive, and the auxiliary angle θ is given. Then, the polar angle corresponding to any position of the B1C1 arc is The polar diameter is ρ2(θ),

[0020] In this case, 0≤θ≤β / (2ω0), C1D1 and C1′D1′ are arcs with a radius of R, and the corresponding central angle is α. A1B1 and A1′B1′ are arcs with a radius of r, and the corresponding central angle is also α. The curved arcs B1C1 and B1′C1′ are centrosymmetric about the rotation center O1, and the corresponding central angles are both β.

[0021] The top diameter and root diameter of the second screw are connected by a curved arc A1D1′, and the rotation center O1 and the root diameter starting point A1 are connected as the polar diameter starting position Ox1′. Clockwise is positive. Given the auxiliary angle θ, the polar angle corresponding to any position of the A1D1′ arc is The polar diameter is ρ2′(θ),

[0022] at this time, A1′D1 and A1D1′ are centrally symmetrical about the rotation center O1, and the corresponding central angles are both β; the curved arcs A1B1, B1C1, C1D1, A1′D1, A1′B1′, B1′C1′, C1′D1′, and A1D1′ form a closed curved arc, forming the end face of the second screw thread element.

[0023] In some embodiments, the total axial length of the threaded element of the second screw is L, mm, 0.5≤L, and given the parameter t, the z coordinate of any cross section of the threaded element satisfies:

[0024] Where, 0≤t≤2π, and at the same time, the closed curve arc of the second screw thread end face composed of the curve arcs A1B1, B1C1, C1D1, A1′D1, A1′B1′, B1′C1′, C1′D1′, and A1D1′ rotates clockwise or counterclockwise around the rotation center by an angle γ2(t):

[0025] In some embodiments, the top diameters of the first screw and the second screw are tangent to the inner wall of the barrel.

[0026] In some embodiments, the screw mechanism divides the inner cavity of the barrel into a conveying section, a melting section, an exhaust section and a mixing and extrusion section in sequence; a feed port is provided on the barrel corresponding to the conveying section, an exhaust port is provided on the barrel corresponding to the exhaust section, and a discharge port is provided on the end of the barrel corresponding to the mixing and extrusion section.

[0027] A second aspect of an embodiment of the present invention provides a processing method for a co-rotating twin-screw extruder with a periodically changing speed ratio, which is applied to the co-rotating twin-screw extruder with a periodically changing speed ratio as described in the first aspect, and the method comprises:

[0028] Add materials;

[0029] The first screw and the second screw rotate in the same direction, the rotational speeds of the first screw and the second screw vary periodically over time, the average rotational speeds of the first screw and the second screw are the same, the pulsation period and the pulsation amplitude of the rotational speeds of the first screw and the second screw are the same, and the material is propelled forward by the first screw and the second screw;

[0030] 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, this process can produce an extrusion and stretching effect in the meshing area to accelerate the melting process of the material and form a melt. The melt is efficiently exhausted through the exhaust port under the periodic transient disturbance.

[0031] The first screw, the second screw and the barrel are used to mix and build up pressure under periodic transient disturbance, and finally extruded from the outlet to form the product.

[0032] The embodiment of the present invention provides a co-rotating twin-screw extruder with a periodic speed ratio change and a processing method thereof, which has at least the following technical effects: (1) The two screws rotate around their respective axes, and the speed changes periodically with time, and the pulsation period of the two screws is the same, resulting in a periodic change in the screw speed ratio, with a periodic alternation of left fast to right slow, left slow to right fast, and then left fast to right slow. The introduction of a periodic transient disturbance effect enhances the melt mixing effect and the devolatilization efficiency. (2) In order to increase the output, the present invention can appropriately increase the screw center distance, and even operate with a speed ratio of 1:1, which can achieve the periodic expansion and contraction of the meshing zone gap, thereby generating an extrusion and stretching effect in the meshing zone to enhance the melt mixing effect, enhance the dispersion mixing and accelerated melting of the multiphase system material, and be more suitable for high-speed, large-volume and low-temperature extrusion processing. (3) The present invention ensures that the screws can still mesh with each other and rotate under the premise of a variable speed ratio. The superposition of the periodic pulsation effect can more effectively achieve a self-cleaning effect.

[0033] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation to the technical solution of the present invention.

[0035] FIG1 is a schematic structural diagram of a co-rotating twin-screw extruder with a periodically changing speed ratio according to the present invention;

[0036] 2 is a schematic diagram of the end face structure of the first screw (excluding the barrel) in an embodiment of the first aspect of the present invention, wherein ω0=1, the speed ratio is (1+ε1sin(2πω0t / α)) / (1-ε2sin(2πω0t / α)), k=1, α=π / 6, and ε1=ε2=1;

[0037] 3 is a schematic diagram of the end face structure of the second screw (excluding the barrel) in an embodiment of the first aspect of the present invention, wherein ω0=1, the speed ratio is (1+ε1sin(2πω0t / α)) / (1-ε2sin(2πω0t / α)), k=1, α=π / 6, and ε1=ε2=1;

[0038] 4 is a schematic diagram of the end structure of the first screw and the second screw assembly (excluding the barrel) in an embodiment of the first aspect of the present invention, wherein ω0=1, the speed ratio is (1+ε1sin(2πω0t / α)) / (1-ε2sin(2πω0t / α)), k=1, α=π / 6, and ε1=ε2=1;

[0039] 5 is a schematic diagram of the three-dimensional structure of the first screw and the second screw assembly (excluding the barrel) in an embodiment of the first aspect of the present invention, wherein ω0=1, the speed ratio is (1+ε1sin(2πω0t / α)) / (1-ε2sin(2πω0t / α)), k=1, α=π / 6, and ε1=ε2=1;

[0040] 6 is a schematic diagram of the end structure of the first screw and the second screw assembly (excluding the barrel) in an embodiment of the first aspect of the present invention, wherein ω0=1, the speed ratio is (1+ε1sin(2πω0t / α)) / (1-ε2sin(2πω0t / α)), k=1, α=π / 6, and ε1=ε2=0.5;

[0041] 7 is a schematic diagram of the end structure of the first screw, the second screw, and the third screw assembly (excluding the barrel) when ω0=1, the speed ratio is (1+ε1sin(2πω0t / α)) / (1-ε2sin(2πω0t / α)), k=1, α=π / 6, and ε=0.5 in an embodiment of the first aspect of the present invention;

[0042] FIG8 is a flow chart of a processing method of a co-rotating twin-screw extruder with a periodically changing speed ratio according to an embodiment of the second aspect of the present invention.

[0043] Reference numerals:

[0044] Barrel 100, conveying section 110, feed port 111, melting section 120, exhaust section 130, exhaust 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 DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present 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 only used to explain the present invention and are not intended to limit the present invention.

[0046] It should be understood that in the description of the embodiments of the present invention, "multiple" (or multiple) means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, and "above," "below," and "within" are understood to include the number itself. The terms "first," "second," and so on are used solely to distinguish technical features and are not to be construed as indicating or implying relative importance, or implicitly indicating the number of the indicated technical features, or implicitly indicating the order of the indicated technical features.

[0047] In order to solve the technical problem that the melt plasticization and mixing effects of the co-rotating twin-screw extruder in the prior art are increasingly difficult to meet the requirements, an embodiment of the present invention provides a co-rotating twin-screw extruder with a periodic change in speed ratio, the co-rotating twin-screw extruder with a periodic change in speed ratio includes a barrel and a screw mechanism, the barrel adopts an 8-shaped structure in which cylindrical holes with axes parallel to each other are connected; the screw mechanism is located in 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 speed of the first screw and the second screw are equal, the speeds of the first screw and the second screw are both periodically pulsating over time, and the period of the pulsating change is the same, and the first screw and the second screw are always engaged with each other during operation. Since the first screw and the second screw rotate in the same direction, the average speed of the two screws is equal, and the speed changes periodically over time, the period of the speed pulsation is the same, resulting in the speed ratio of the two screws changing periodically over time, so that the material is always subjected to non-steady-state shearing, extrusion and stretching during the conveying process, which can effectively improve the melt plasticization, exhaust and mixing efficiency of the material. The two screws mesh and run and wipe each other, realizing the self-cleaning function of the processing process. Based on this, the present invention has at least the following technical effects: (1) The two screws rotate around their respective axes, and the speed changes periodically with time, and the pulsation period of the two screws is the same, resulting in a periodic change in the screw speed ratio, with a periodic alternation of left fast, right slow, left slow, right fast, and then left fast, right slow. The introduction of a periodic transient disturbance effect enhances the melt mixing effect and devolatilization efficiency. (2) In order to increase production, the present invention can appropriately increase the screw center distance, and even use a speed ratio of 1:1 to operate, which can achieve the periodic expansion and contraction of the meshing zone gap, thereby generating an extrusion and stretching effect in the meshing zone to enhance the melt mixing effect, enhance the dispersion mixing and accelerated melting of the multiphase system material, and be more suitable for high-speed, large-volume and low-temperature extrusion processing. (3) The present invention ensures that the screws can still mesh with each other and rotate under the premise of a variable speed ratio. The superposition of the periodic pulsation effect can more effectively achieve a self-cleaning effect.

[0048] A co-rotating twin-screw extruder with a periodically changing rotational speed ratio according to an embodiment of the first aspect of the present invention will be described below with reference to FIG. 1 to FIG. 5 .

[0049] According to an embodiment of the first aspect of the present invention, a self-cleaning co-rotating twin-screw extruder capable of producing a meshing zone strengthening effect includes a barrel 100 and a screw mechanism 200 arranged in the barrel 100, and is characterized in that 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 at a speed ratio that changes periodically with time, and the speed pulsation periods of the two screws are the same.

[0050] 2 to 6 , in some embodiments of the present invention, the top diameters of the first screw 210 and the second screw 220 are both tangential to the inner wall of the barrel 100. The root diameter and top diameter of the first screw 210 are equal to the root diameter and top diameter of the second screw 220. This provides greater agitation and mixing.

[0051] In some embodiments of the present invention, referring to FIG. 1 , the first screw 210 , the second screw 220 and the barrel 100 form a flow channel 300 , and the flow channel 300 is used for the passage of materials.

[0052] In some embodiments of the present invention, referring 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 port 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.

[0053] 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 a conveying force through friction and positive displacement; the material moves toward the melting section 120 under the combined action of the positive displacement conveying force and the friction between the two screws.

[0054] In the melting section 120 , the barrel 100 melts the material through external heating and, at the same time, introduces periodic transient disturbances to enhance mixing and melting efficiency. The material eventually becomes a melt under the action of external heating and the screw mechanism 200 , and then enters the exhaust section 130 under the push of the first screw 210 and the second screw 220 .

[0055] 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 disturbance, the exhaust efficiency is accelerated, and the exhaust gas is discharged from the exhaust port 131. At the same time, the first screw 210 and the second screw 220 push the exhaust gas into the mixing and extrusion section 140.

[0056] In the mixing and extrusion section 140 , the first screw 210 and the second screw 220 mesh and operate in the same direction, so that the first screw 210 and the second screw 220 have better pressure-building capabilities and extrusion characteristics. At the same time, under the action of the enhanced mixing mechanism described in the melting section, the mixing and plasticizing effect is enhanced, so that the molten material can be stably extruded from the discharge port 141 .

[0057] Referring to FIG. 7 , in some embodiments of the present invention, the screw mechanism 200 further includes a third screw having the same structure as the first screw 210 . The third screw is constantly meshed with the second screw 220 ; the third screw and the first screw 210 rotate in the same direction. The use of a three-screw structure can achieve a greater extrusion effect and significantly improve extrusion efficiency. It should be noted that since the first screw 210 and the second screw 220 themselves are not specifically defined, the third screw can be essentially the same as either the first screw 210 or the second screw 220 . The third screw meshes with the second screw 220 when it is identical to the first screw 210 , and meshes with the first screw 210 when it is identical to the second screw 220 . FIG. 7 shows a schematic diagram of the 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 meshed according to the meshing conditions.

[0058] In some embodiments of the present invention, both the first screw 210 and the second screw 220 have a conical structure, which can provide a stronger mixing effect and a larger extrusion output.

[0059] 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 to: ω1 = ω0 (1 + ε1sin (2πω0t / α)) is the rotational speed of a screw, ω0 is the average angular velocity, rad / s, 0 < ω0 < 50000; ε1 is the rotational speed disturbance amplitude of the first screw, and 0 ≤ ε1 ≤ 1; t is time, s; α is the screw top angle, rad, the rotational speed of the second screw is: ω2 = ω0 (1 - ε2sin (2πω0t / α)), ε2 is the rotational speed disturbance amplitude of the second screw, and 0 ≤ ε2 ≤ 1; the speed ratio of the first screw to the second screw is (1 + ε1sin (2πω0t / α)) / (1 - ε2sin (2πω0t / α)).

[0060] In some embodiments, the rotation center of the first screw is O, and the top diameter and root diameter of the first screw are both composed of an arc AB and an arc CD. The radii of the arc AB and the arc CD are R and r, respectively, and the corresponding central angles are both α. The top diameter and the root diameter of the first screw are connected by a curved arc, and the corresponding central angle is β. Given an integer k, k = 1, 2, ... 100, then,

[0061] The rotation center of the second screw is O1. The top diameter and root diameter of the second screw are composed of arcs A1B1 and C1D1. The radii of arcs A1B1 and C1D1 are R and r respectively, and the corresponding central angles are both α. The top diameter and root diameter of the second screw are connected by a curved arc, and the corresponding central angle is β. Then the center distance C between the first screw and the second screw is: C = 2Rcos(β / 2)

[0062] Then the inner diameters r of the first and second screws satisfy the following relationship: r = 2Rcos(β / 2) - R

[0063] For the first screw, on the one hand, as shown in Figure 2, the top diameter and root diameter of the first screw are connected by a curved arc BC, connecting the rotation center O and the root diameter starting point B as the polar diameter starting position Ox, counterclockwise is positive, given the auxiliary angle θ, then the polar angle corresponding to any position of the BC arc is The polar diameter is ρ1(θ),

[0064] at this time, Among them, CD and C'D' are arcs of radius R, and the central angle corresponding to CD and C'D' is α. AB and A'B' are arcs of radius r, and the central angle corresponding to AB and A'B' is also α. The curved arcs BC and B'C' are centrosymmetric about the rotation center O, and the central angle corresponding to BC and B'C' is both B.

[0065] On the other hand, the top diameter and the root diameter of the first screw are connected by a curved arc A′D, which connects the rotation center O and the root diameter starting point A′ as the polar diameter starting position Ox′. Clockwise is positive. Given the auxiliary angle θ, the polar angle corresponding to any position of the A′D arc is The polar diameter is ρ1′(θ),

[0066] at this time, As shown in FIG2 , A′D and AD′ are centrally symmetrical about the rotation center O, and the corresponding central angles are both β; AB, BC, CD, A′D, A′B′, B′C′, C′D′, and AD′ form a closed curve arc, forming the end face of the first screw thread element.

[0067] Given that the total axial (z-direction) length of the threaded element of the first screw is L, mm, 0.5 ≤ L, and given the parameter t, the z-coordinate of any cross section of the threaded element satisfies:

[0068] Here, 0≤t≤2π. At the same time, the closed curve arc of the thread end face composed of AB, BC, CD, A′D, A′B′, B′C′, C′D′, and AD′ rotates clockwise or counterclockwise around the rotation center by an angle γ1(t):

[0069] Corresponding to the second screw, as shown in Figure 3, on the one hand, the top diameter and root diameter of the second screw are connected by a curved arc B1C1, and 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 the auxiliary angle θ, the polar angle corresponding to any position of the B1C1 arc is The polar diameter is ρ2(θ),

[0070] at this time, Thus, as shown in Figure 2, C1D1 and C1′D1′ are arcs with a radius of R, and the corresponding central angle is α; A1B1 and A1′B1′ are arcs with a radius of r, and the corresponding central angle is also α; and the curved arcs B1C1 and B1′C1′ are centrosymmetric about the rotation center O1, and the corresponding central angles are both β;

[0071] On the other hand, as shown in Figure 3, the top diameter and root diameter of the second screw are connected by a curved arc A1D1′, connecting the rotation center O1 and the root diameter starting point A1 as the polar diameter starting position Ox1′, clockwise is positive, and given the auxiliary angle θ, the polar angle corresponding to any position of the A1D1′ arc is The polar diameter is ρ2′(θ),

[0072] at this time, As shown in FIG2 , A1′D1 and A1D1′ are centrally symmetrical about the rotation center O1, and the corresponding central angles are both β; the curved arcs A1B1, B1C1, C1D1, A1′D1, A1′B1′, B1′C1′, C1′D1′, and A1D1′ form a closed curved arc, forming the end face of the second screw thread element.

[0073] Similarly, given that the total axial (z-direction) length of the threaded element of the second screw is L, mm, 0.5 ≤ L, and given the parameter t, the z-coordinate of any cross section of the threaded element satisfies:

[0074] Where, 0≤t≤2π, and at the same time, the closed curve arc of the second screw thread end face composed of the curve arcs A1B1, B1C1, C1D1, A1′D1, A1′B1′, B1′C1′, C1′D1′, and A1D1′ rotates clockwise or counterclockwise around the rotation center by an angle γ2(t):

[0075] In addition, the embodiment of the present invention can also increase the center distance C of the two screws to increase the flow rate of the material passing through the gap between the two screws and improve the randomness of the movement in the meshing area to further enhance the melt plasticization effect.

[0076] In some embodiments, the top diameters of the first screw and the second screw are tangent to the inner wall of the barrel.

[0077] In some embodiments, the screw mechanism divides the inner cavity of the barrel into a conveying section, a melting section, an exhaust section and a mixing and extrusion section in sequence; a feed port is provided on the barrel corresponding to the conveying section, an exhaust port is provided on the barrel corresponding to the exhaust section, and a discharge port is provided at the end of the barrel corresponding to the mixing and extrusion section.

[0078] In some embodiments, the screw mechanism further includes a third screw having the same structure as the first screw, the third screw and the second screw are always meshed with each other; the third screw and the first screw have the same rotation direction.

[0079] As shown in FIG8 , an embodiment of the present invention further provides a processing method for a co-rotating twin-screw extruder with a periodically changing speed ratio, which is applied to the above-mentioned co-rotating twin-screw extruder with a periodically changing speed ratio, and the method comprises at least the steps of:

[0080] Step S101: adding materials;

[0081] Step S102: The first screw and the second screw rotate in the same direction, the speeds of the first screw and the second screw vary periodically over time, the average speeds of the first screw and the second screw are the same, the pulsation period and the pulsation amplitude of the speeds of the first screw and the second screw are the same, and the material is propelled forward by the first screw and the second screw;

[0082] Step S103: 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, this process can produce an extrusion and stretching effect in the meshing area to accelerate the melting process of the material and form a melt. The melt is efficiently exhausted through the exhaust port under the periodic transient disturbance.

[0083] Step S104: mixing and building up pressure under periodic transient disturbance by the first screw, the second screw, and the barrel, and finally extruding from the outlet to form.

[0084] In some embodiments, the processing method includes adding material, the first screw and the second screw rotate in the same direction, the speed of the two screws changes periodically with time, the average speed is the same, the pulsation period and pulsation amplitude of the two screw speeds are the same, and the material is pushed forward by the first screw and the second screw; the material is melted by the heat generated by the rotation of the first screw and the second screw and external heating. Due to the periodic transient disturbance effect and the different geometric shapes of the screw grooves, this process can produce extrusion and stretching effects in the meshing area, which can effectively enhance the melting and dispersion mixing effects of the multiphase system materials, accelerate the material melting process, and form a melt; the melt is exhausted efficiently through the exhaust port under the periodic transient disturbance effect; finally, the first screw, the second screw, and the barrel are mixed and pressurized under the periodic transient disturbance effect, and finally extruded from the outlet.

[0085] Based on this, the present invention has at least the following technical effects: (1) The two screws rotate around their respective axes, and the speed changes periodically with time, and the pulsation period of the two screws is the same, resulting in a periodic change in the screw speed ratio, with a periodic alternation of left fast to right slow, left slow to right fast, and then left fast to right slow. The introduction of a periodic transient disturbance effect enhances the melt mixing effect and devolatilization efficiency. (2) In order to increase production, the present invention can appropriately increase the screw center distance, and even operate at a speed ratio of 1:1, which can achieve a periodic expansion and contraction of the meshing zone gap, thereby generating an extrusion and stretching effect in the meshing zone to enhance the melt mixing effect, enhance the dispersion mixing and accelerated melting of multiphase system materials, and be more suitable for high-speed, high-output and low-temperature extrusion processing. (3) The present invention ensures that the screws can still mesh with each other and rotate under the premise of a variable speed ratio. The superposition of the periodic pulsation effect can more effectively achieve a self-cleaning effect.

[0086] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above implementation. Those skilled in the art can also make various equivalent modifications or substitutions under the shared conditions that do not violate the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present invention.

Claims

1. A co-rotating twin-screw extruder with a periodically changing speed ratio, characterized in that: include: The barrel adopts an 8-shaped structure with cylindrical holes with parallel axes interpenetrating each other; A screw mechanism, wherein the screw mechanism is located in the barrel, and 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 rotation speeds of the first screw and the second screw are equal, the rotation speeds of the first screw and the second screw both pulsate periodically with time, and the pulsation change periods are the same, and the first screw and the second screw are always meshed with each other during operation.

2. The co-rotating twin-screw extruder with periodically changing speed ratio according to claim 1, characterized in that: The first screw and the second screw rotate in the same direction, and the angular velocity of the first screw is set to: ω1=ω0(1+ε1sin(2πω0t / α)) is the rotational speed of a screw, ω0 is the average angular velocity, 0<ω0<50000; ε1 is the rotational speed disturbance amplitude of the first screw, and 0≤ε1≤1; t is time; α is the screw top angle, the rotational speed of the second screw is: ω2=ω0(1-ε2sin(2πω0t / α)), ε2 is the rotational speed disturbance amplitude of the second screw, and 0≤ε2≤1; the rotational speed ratio of the first screw and the second screw is (1+ε1sin(2πω0t / α)) / (1-ε2sin(2πω0t / α)).

3. The co-rotating twin-screw extruder with periodically changing speed ratio according to claim 1, characterized in that: The rotation center of the first screw is O, the top diameter and root diameter of the first screw are composed of arc AB and arc CD, the radii of arc AB and arc CD are R and r respectively, and the corresponding central angles are α; the top diameter and root diameter of the first screw are connected by a curved arc, and the corresponding central angle is β. Given an integer k, k=1, 2, ... 100, then, The rotation center of the second screw is O1, the top diameter and the root diameter of the second screw are both composed of arc A1B1 and arc C1D1, the radii of arc A1B1 and arc C1D1 are R and r respectively, and the corresponding central angles are both α; the top diameter and the root diameter of the second screw are connected by a curved arc, and the corresponding central angle is β, then the center distance C between the first screw and the second screw is: C=2Rcos(β / 2) The inner diameters r of the first screw and the second screw satisfy the following relationship: r=2Rcos(β / 2)-R The top diameter and the root diameter of the first screw are connected by a curved arc BC, and the rotation center O and the root diameter starting point B are connected as the polar diameter starting position Ox. Counterclockwise is positive. Given an auxiliary angle θ, the corresponding polar angle of any position of the BC arc is The polar diameter is ρ1(θ), in, CD and C′D′ are arcs with radius R, and the corresponding central angles of CD and C′D′ are α. AB and A′B′ are arcs with radius r, and the corresponding central angles of AB and A′B′ are also α. The curved arcs BC and B′C′ are centrally symmetrical about the rotation center O, and the corresponding central angles of BC and B′C′ are both β. The top diameter and the root diameter of the first screw are connected by a curved arc A′D, and the rotation center O and the root diameter starting point A′ are connected as the polar diameter starting position Ox′, clockwise is positive, and the auxiliary angle θ is given, then the polar angle corresponding to any position of the A′D arc is The polar diameter is ρ1′(θ), in, A′D and AD′ are centrally symmetrical about the rotation center O, and the corresponding central angles are β; AB, BC, CD, A′D, A′B′, B′C′, C′D′, and AD′ form a closed curve arc to form the end face of the first screw thread element.

4. The co-rotating twin-screw extruder with periodically changing speed ratio according to claim 2, characterized in that: The total axial length of the threaded element of the first screw is L, mm, 0.5≤L. Given the parameter t, the z coordinate of any cross section of the threaded element satisfies: Among them, 0≤t≤2π, at the same time, the closed curve arc of the thread end face composed of AB, BC, CD, A′D, A′B′, B′C′, C′D′, AD′ rotates clockwise or counterclockwise around the rotation center. Angle γ1(t) is:

5. The co-rotating twin-screw extruder with periodically changing speed ratio according to claim 4, characterized in that: The top diameter and the root diameter of the second screw are connected by a curved arc B1C1, and 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 the auxiliary angle θ, the polar angle corresponding to any position of the B1C1 arc is The polar diameter is ρ2(θ), in, C1D1 and C1′D1′ are arcs with a radius of R, and the corresponding center angle is α. A1B1 and A1′B1′ are arcs with a radius of r, and the corresponding center angle is also α. The curved arcs B1C1 and B1′C1′ are in a centrally symmetrical relationship about the rotation center O1, and the corresponding center angles are both β. The top diameter and the root diameter of the second screw are connected by a curved arc A1D1′, and the rotation center O1 and the root diameter starting point A1 are connected as the polar diameter starting position Ox1′, clockwise is positive, and the auxiliary angle θ is given, then the polar angle corresponding to any position of the A1D1′ arc is The polar diameter is ρ2′(θ), in, A1′D1 and A1D1′ are centrally symmetrical about the rotation center O1, and the corresponding central angles are both β; the curved arcs A1B1, B1C1, C1D1, A1′D1, A1′B1′, B1′C1′, C1′D1′, A1D1′ form a closed curved arc to form the end face of the second screw thread element.

6. The co-rotating twin-screw extruder with periodically changing speed ratio according to claim 5, characterized in that: The total axial length of the threaded element of the second screw is L, mm, 0.5≤L. Given the parameter t, the z coordinate of any cross section of the threaded element satisfies: Among them, 0≤t≤2π, the curve arcs A1B1, B1C1, C1D1, A1′D1, A1′B1′, B1′C1′, C1′D1′, The closed curve arc of the second screw thread end face composed of A1D1′ rotates clockwise or counterclockwise around the rotation center at an angle γ2(t):

7. The co-rotating twin-screw extruder with periodically changing speed ratio according to claim 1, characterized in that: The top diameters of the first screw and the second screw are both tangent to the inner cavity wall of the barrel.

8. The co-rotating twin-screw extruder with periodically changing 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, an exhaust section and a mixing and extruding section in sequence; a feed port is arranged on the barrel corresponding to the conveying section, an exhaust port is arranged on the barrel corresponding to the exhaust section, and a discharge port is arranged on the barrel corresponding to the end of the mixing and extruding section.

9. The co-rotating twin-screw extruder with periodically changing speed ratio according to claim 1, characterized in that: The screw mechanism further comprises a third screw having the same structure as the first screw, the third screw and the second screw are always meshed with each other; the third screw and the first screw have the same rotation direction.

10. A processing method of a co-rotating twin-screw extruder with a periodically changing speed ratio, characterized in that: Applied to a co-rotating twin-screw extruder with a periodically changing speed ratio as claimed in any one of claims 1 to 9, the method comprising: Add materials; The first screw and the second screw rotate in the same direction, the rotation speeds of the first screw and the second screw change periodically with time, the average rotation speeds of the first screw and the second screw are the same, the pulsation period and the pulsation amplitude of the rotation speeds of the first screw and the second screw are the same, and the material is pushed forward by the first screw and the second screw; The material is melted by the heat generated by the rotation of the first screw and the second screw and external heating. Due to the periodic transient disturbance, this process can produce an extrusion and stretching effect in the meshing area to accelerate the melting process of the material and form a melt; the melt is exhausted efficiently through the exhaust port under the periodic transient disturbance; The first screw, the second screw and the barrel are used to mix and build up pressure under periodic transient disturbance, and finally extruded from the outlet to form the product.

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