Screw for single screw extruder, and single screw extruder

Abstract

To provide a screw and a single screw extruder having a high kneading performance and diffusibility while suppressing temperature increase of a raw material containing a thermoplastic resin when kneading and extruding the raw material.SOLUTION: Kneading components of a screw comprises: multiple forward spiral flights each comprising main flights that hold back resin, and cutout portions being protruded flights with a flight height lower than that of the main flights; grooves; and sub flights going over in the grooves between the main flights in the axial direction of the screw. The sub flight is connected to two main flights. The main flight has cutout portions each going over in the direction opposite to the spiralling of the main flight from the intersection on the downstream side of the screw among intersection portions at which the main flight and the sub flight are connected together. The main flight has a shape having a cutout angle smaller than a helix angle of the main flight when viewed from a side surface of the screw for a single screw extruder.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a screw for a single-screw extruder used for kneading raw materials containing a thermoplastic resin, and to a single-screw extruder. [Background technology]

[0002] When kneading two or more kinds of raw materials, such as kneading resins together or kneading resins with powder particles, particularly when a kneaded product is continuously produced using a thermoplastic resin as the resin, kneading is performed using an extruder equipped with a screw from the viewpoint of mass production. In kneading using such an extruder, it is required that the raw materials heated and melted in the extruder are sufficiently kneaded and the resin composition after kneading is discharged in a uniform state. If the kneading is insufficient and the material is extruded from the extruder in an uneven state, the physical properties of the kneaded product will be reduced due to bias in the concentration of each component, and when raw materials of different colors are kneaded, problems such as uneven coloring will occur in the kneaded product will occur.

[0003] One example of such screw-based kneading equipment is the single-screw extruder. A single-screw extruder has a single screw inside a cylinder, and by rotating the screw, the raw materials supplied from the upstream of the extruder are forcibly transferred to the flow path in the screw's helical direction, where they are kneaded while being melted and plasticized by the heat from the cylinder. However, with a single-screw extruder, there is a problem in that a high kneading effect cannot be obtained because the screw's helical direction is fixed. As a countermeasure against this, a process has been conventionally carried out to divert the flow of plasticized raw material into the screw in order to improve the kneading performance of the parts in the kneading portion of the screw.

[0004] For example, Patent Document 1 discloses a kneading rotating screw having a kneading structure in which a large number of kneading recesses are engraved along a virtual spiral direction on the outer peripheral surface of the kneading position of the rotating screw, and adjacent kneading recesses in the spiral width direction are connected by a flow passage. The engraved kneading structure splits and merges the raw materials through the flow passages, and at the same time, generates a turbulent pulsation phenomenon in the kneading section due to a turbulent phenomenon caused by pressure changes when passing through the flow passages and a pulsation phenomenon caused by flow resistance from the deep part to the shallow part of the kneading recess, and causes the raw materials to overcome the peripheral parts of the kneading recesses, causing a large flow change, stirring and kneading the raw materials uniformly. However, as the resin flows in a spiral shape in the recess, it passes through a flow passage provided in the width direction of the spiral, so the flow of the raw material is temporarily stopped, and then the raw material passes through a narrow flow passage, which generates heat due to a great deal of compression of the raw material. As a result, the raw material becomes very hot after passing through the kneading structure, and there is a problem in that the raw material deteriorates due to the heat.

[0005] In Patent Document 2, like the above patent, a large number of kneading recesses are engraved along a virtual spiral direction on the outer peripheral surface of the kneading position of the kneading rotating screw, and it is said that the same effect as in Patent Document 1 can be obtained. However, the diagram disclosed in Figure 1 of Patent Document 2 has an even narrower flow path than that of the above patent, and like the above patent, the raw material becomes hot due to heat generation caused by compression, which causes the raw material to deteriorate due to heat.

[0006] Patent Document 3 is a patent related to a mixing and dispersing part for an extruder, and describes how the resin passing through the inlet groove flows between the blocking flights while overflowing the overflow flight, thereby achieving high mixing and dispersion even when the screw is rotated at medium to low speeds to prevent thermal degradation of the resin, and Fig. 2 of Patent Document 3 also shows a shape in which the resin flows into a spiral inlet groove, and then overflows the overflow flight and flows into the inlet groove on the downstream side. However, from the viewpoint of production, the screw is operated at high speed to increase the discharge amount, so this does not solve the problem of thermal degradation of the raw resin.

[0007] Patent Document 4 is a patent for a high-mixing extruder having a polygonal cross-sectional shape and a convex flight with a lead between the polygonal apexes shown in Figures 4 to 6 of Patent Document 4, and a polygonal cylinder, and it is said that high mixing and high dispersion can be expected. However, it only describes that a strong resin crushing effect is obtained when the resin overcomes the dam flight, and that the solid phase resin is dispersed by a mochi action caused by a complex flow with each rotation of the screw due to the shape of the screw and cylinder, which is effective before and during melting of the resin, such as improving heat conduction between the resins and making the resin temperature uniform. In addition, it can be used only in a polygonal cylinder extruder, and when the screw is used with a cylindrical cylinder that is common as a single-screw extruder, sufficient effects cannot be obtained, and there is also a problem that the raw material resin deteriorates due to heat generation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Utility Model Application Publication No. 63-119011 [Patent Document 2] Japanese Utility Model Application Publication No. 1-156005 [Patent Document 3] JP 2000-218619 A [Patent Document 4] Japanese Unexamined Patent Publication No. 54-73856 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a screw and an extruder which have high kneading performance and diffusibility while suppressing an increase in temperature of the raw material when kneading and extruding a raw material containing a thermoplastic resin. [Means for solving the problem]

[0010] The screw for a single screw extruder of the present invention is A screw for a single screw extruder equipped with a kneading element, The kneading element has multiple continuous spiral flights and grooves, the helical flight being a forward helical flight having a helix angle; The spiral flight includes a main flight that blocks the resin, and a cut portion that becomes a convex flight having a flight height lower than that of the main flight, A secondary flight extending in the axial direction of the single-screw extruder screw is provided in the groove between the main flights, The secondary flights are arranged at positions that evenly distribute the circumference of the single-screw extruder screw in a right-angle cross section, The secondary flight is connected to two main flights in the axial direction of the single-screw extruder screw, the convex flight is disposed from an intersection portion where the secondary flight and the main flight are connected to each other on the downstream side of the screw for a single screw extruder to a reverse direction of the spiral of the spiral flight, the main flight adjacent to the convex flight has a shape having a cut angle smaller than a helix angle of the main flight when viewed from a side surface of the screw for a single screw extruder, The structures of the main flight, the sub flight and the convex flight are engraved so as to be repeatedly arranged in the spiral direction of the spiral flight. The screw for a single screw extruder is characterized in that: The single-screw extruder of the present invention is characterized by comprising the above-mentioned screw for a single-screw extruder. Effect of the Invention

[0011] The present invention provides a screw and an extruder which, when kneading and extruding a raw material containing a thermoplastic resin, have high kneading performance and diffusivity while suppressing an increase in the temperature of the raw material. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view of an extruder equipped with a single-screw extruder screw according to the present invention. [Diagram 2] A projection diagram of a kneading part in a screw for a single screw extruder according to the first embodiment of the present invention. [Diagram 3] FIG. 1 is a development view of a kneading part of a screw for a single-screw extruder according to a first embodiment of the present invention in the circumferential direction of the screw. [Figure 4] FIG. 1 is a development view of the kneading parts of the screw for a single-screw extruder according to the first embodiment of the present invention in the screw circumferential direction and a diagram showing the flow of raw materials. [Diagram 5] 1 is a cross-sectional view of a protruding flight and a cylinder according to a first embodiment of the present invention; [Figure 6] FIG. 2 is a development view of a kneading part of a screw for a single-screw extruder according to a second embodiment of the present invention in the circumferential direction of the screw. [Figure 7] FIG. 2 is a development view of the kneading part of the screw for a single-screw extruder according to the second embodiment of the present invention in the screw circumferential direction and a diagram showing the flow of the raw material. [Figure 8] FIG. 1 is a development view of a kneading part of a screw for a single-screw extruder in a modified example of the present invention in the circumferential direction of the screw. [Figure 9] FIG. 1 is a development view of a kneading part of a screw for a single-screw extruder in a modified example of the present invention in the circumferential direction of the screw. [Figure 10] 1 is a cross-sectional view of a convex flight according to a modified example of the present invention; [Figure 11] FIG. 1 is a partially enlarged development view of a kneading part of a screw for a single-screw extruder in a modified example of the present invention in the circumferential direction of the screw. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, in this specification, the expression "a to b" in the explanation of a numerical range means not less than a and not more than b, unless otherwise specified.

[0014] <Single screw extruder> FIG. 1 shows a cross-sectional view of a single-screw extruder equipped with a screw for a single-screw extruder (hereinafter also referred to as a "screw") of the present invention. As shown in FIG. 1, the single-screw extruder 1 has a cylinder 2 with a hollow interior and a screw 3 housed in the cylinder, and the rotational power of a motor and a reducer 9 equipped in the single-screw extruder is transmitted to the screw 3 connected to the reducer, causing the screw to rotate. The screw 3 has a forward spiral flight 5 and a valley portion 6, and by rotating the screw in the forward direction by the rotational power, a raw material containing a mixed thermoplastic resin (hereinafter also referred to as a "raw material") supplied from a hopper 4 is transferred to a downstream 34 in the screw axial direction while being supplied in a fixed amount to a flow path between the heated cylinder 2 and the valley portion 6 in the forward direction of the spiral. As the raw material is transported between the cylinder 2 and the valley portion 6, it is heated by the heat from the heater 8 wrapped around the cylinder, as well as by the shear heat between the raw material and the cylinder and between the raw material and the screw, causing the thermoplastic resin (hereinafter also referred to as "resin") in the raw material to melt, plasticizing the raw material as it moves and is kneaded, and the kneaded product is discharged through the die 10 installed downstream.

[0015] The screw 3 is divided into three zones: a supply section 31 that supplies a fixed amount of raw material supplied from a hopper 4; a kneading section 32 in which the resin in the raw material is melted and plasticized while the raw material is kneaded; and a metering section 33 that meters the plasticized raw material. The kneading section 32 is equipped with kneading parts 7 described below.

[0016] [Screw for a single-screw extruder equipped with the kneading part of the first embodiment] FIG. 2 is a projection view of the kneading parts provided on the screw for a single-screw extruder of the first embodiment, and FIGS. 3 and 4 are views of the kneading parts developed on a plane in the circumferential direction of the screw.

[0017] 3, the kneading part has multiple continuous helical flights and grooves 22, the helical flights being forward-direction helical flights having a helix angle 50, and the helical flights have main flights 20 that hold back the resin, and cut-out portions that become convex flights 24 whose flight height is lower than that of the main flights. The helix angle is defined as the angle at which the helical flights are inclined with respect to the screw axial direction. Furthermore, the kneading part is provided with a secondary flight 21 extending in the axial direction of the screw within the groove between the two main flights, the secondary flight 21 being connected to the two main flights 20 in the axial direction of the screw for the single-screw extruder, and the secondary flight 21 being positioned so as to evenly distribute the circumference of the screw in a perpendicular cross section.

[0018] The convex flight 24 is disposed from an intersection 26 at the downstream 34 side in the screw axial direction of the screw among the intersections where the secondary flight 21 and the main flight 20 are connected, to a reverse direction 58 of the spiral of the helical flight, and the convex flight 24 cuts into the main flight to form a convex portion having a lower flight height than the main flight. A cross-sectional view of the convex flight showing the L-L' cross section in Figure 3 is shown in Figure 5.

[0019] The convex flight 24 is formed from the intersection portion 26 to the intersection portion 25 of the next main flight and secondary flight in the reverse direction 58 of the helix of the main flight, so that the convex flight is formed to leave a connection between the main flight 20 and the secondary flight 21 at the intersection portions 25 and 26.

[0020] The main flight 20 adjacent to the convex flight 24 has a shape having a cut angle 51 smaller than the twist angle of the main flight 20 on the reverse spiral direction 58 side of the main flight 20 and downstream 34 in the screw axial direction when viewed from the side of the screw for a single-screw extruder. The cutting angle is defined as the angle at which the main flight cuts with reference to the screw axial direction.

[0021] Furthermore, the main flight 20 is shaped to have a cut angle 52 smaller than the helix angle of the main flight on the helical forward direction 57 side of the main flight and on the upstream side 35 in the axial direction of the screw.

[0022] The kneading part is engraved so as to repeatedly arrange the structures of the main flight, the secondary flight and the convex flight in the helical direction of the helical flight.

[0023] <Function and effect of the kneading part in the first embodiment> The function and effect of the kneading parts provided in the screw for a single-screw extruder of the first embodiment will be described below with reference to Figs. The raw material flowing into this kneading part from the upstream side of the screw is distributed by the multiple main flights as shown in Figure 4, flows into each groove of the kneading part, and then flows along the forward direction 57 of the spiral of the main flight through the flow path consisting of the main flight, grooves, and cylinder of the extruder. As shown by arrow C in Figure 4, when the raw material flowing in the forward direction of the spiral reaches the convex flight 24, it overcomes the convex flight, which has a lower flight height than the main flight, and flows along the secondary flight 21 that holds back the raw material into the adjacent groove downstream of the screw, and then the raw material flows again in the forward direction 57 of the spiral, along the main flight 20. As shown in the cross-sectional view of Figure 5, the flow of the raw material before and after the convex flight is such that when the raw material flows between the cylinder 2 and the bottom 42 of the groove in the flow direction 46 and flows into the narrow flow passage between the top 41 of the convex flight 24 and the cylinder 2, the raw material is compressed and agitated in front of the convex flight 43 as the height of the flow passage changes, and the raw material exchanges position, and then the raw material that has been compressed and passed between the top 41 of the convex flight and the cylinder 2 is released into the adjacent flow passage. Furthermore, when the raw material flow path is viewed from the side of the screw as in Figure 4, the raw material exchanges its position due to changes in the flow path direction and flow path width as indicated by arrow C in Figure 4 due to the main flight, convex flight, and secondary flight. In the flow path indicated by arrow B in Figure 4, the raw material also exchanges its position on the convex flight and due to changes in the flow path direction and flow path width. The raw material is repeatedly exchanged in the same manner up to the downstream end of the kneading part. The kneading part kneads the raw material by repeatedly passing over the convex flights provided widely across the cutouts and gradually compressing and releasing the raw material multiple times. This allows the raw material to be kneaded without sudden compression like in conventional screws, while suppressing heat generation in the raw material.

[0024] In addition, as shown by arrows B and C in Figure 4, the raw material flows alternately in the forward spiral direction 57 and the downstream direction of the screw axis 34, and the raw material is mixed while exchanging positions due to changes in the direction and width of the flow path. Meanwhile, by repeatedly providing main flights with cut angles 51, 52 smaller than the twist angle of the main flights, a flow path can be secured in which the raw material flows linearly in the spiral direction while climbing over the convex flights, as shown by arrow A in Figure 4. This allows the raw material to be mixed without being suddenly compressed and with reduced heat generation.

[0025] Furthermore, by arranging the sub-flights 21 at equal positions relative to the circumference of the screw, as shown by the extension line 29 of the sub-flight 21 in the screw axial direction and the distance N in the circumferential direction of the extension line 29 in Figure 4, the repeated changes in the flow of material between the main flight and the sub-flight and the changes in the width of the flow path, as well as the gradual compression and release of the material as it exchanges positions on the convex flight shown in Figure 5, occur at equal intervals per unit time that the material flows, thereby suppressing heat generation in the material and achieving excellent kneading properties.

[0026] [Screw for a single-screw extruder equipped with the kneading part of the second embodiment] 6 and 7 are views showing the kneading parts provided on the screw for a single-screw extruder of the second embodiment, developed on a plane in the circumferential direction of the screw.

[0027] In the first embodiment, the convex flight 24 is provided as a notch spanning two intersections formed by the main flight 20 and the sub flight 21, but the second embodiment differs from the first embodiment in that a notch is provided to leave the main flight on the forward spiral direction 57 side of the intersection 62 on the upstream 35 side in the axial direction of the screw among the intersections formed by the sub flight 21 and the main flight 20, as shown by the portion indicated by reference numeral 61 in Fig. 6, so as to allow further position exchange of raw material. The kneading parts in the second embodiment will be described below.

[0028] As shown in FIG. 6, the kneading part has multiple continuous helical flights and grooves 22, and the helical flights are forward-direction helical flights having a twist angle 50. The helical flights have a main flight 20 that blocks the resin and a cut portion that becomes a convex flight 24 whose flight height is lower than that of the main flight. Furthermore, the kneading part is provided with a secondary flight 21 extending in the axial direction of the screw within the groove between the two main flights 20, the secondary flight 21 being connected to the two main flights 20 in the axial direction of the screw for the single-screw extruder, and the secondary flight 21 being positioned so as to evenly distribute the circumference of the screw in a perpendicular cross section.

[0029] The convex flight 24 is disposed from an intersection 26 at the downstream 34 side of the screw axial direction of the screw among the intersections where the secondary flight 21 and the main flight 20 are connected, to a reverse direction 58 of the spiral of the helical flight, and the convex flight 24 cuts into the main flight to form a convex portion having a lower flight height than the main flight. The cross-sectional view of the convex flight showing the L-L' cross section in Figure 6 shows the cross-sectional shape of Figure 5, as in the first embodiment.

[0030] The convex flight 24 is disposed as a cut-out portion that leaves the main flight on the forward spiral direction 57 side of the intersection portion 62 toward the intersection portion 62 of the next main flight and secondary flight on the reverse spiral direction 58 side of the main flight as viewed from the intersection portion 26. Also, the secondary flight 21 connects the main flight and secondary flight at the intersection portion 26 and the intersection portion 62.

[0031] In addition, the main flight 20 adjacent to the convex flight 24 has a cut angle 51 that is smaller than the twist angle of the main flight on the reverse spiral direction 58 side of the main flight and downstream 34 in the screw axial direction when viewed from the side of the screw.

[0032] Furthermore, the main flight is shaped so that the helical forward direction 57 side of the main flight and the upstream side 35 in the axial direction of the screw also have a cut angle 52 that is smaller than the helix angle of the main flight.

[0033] The kneading part is engraved so as to repeatedly arrange the structures of the main flight, the secondary flight and the convex flight in the helical direction of the helical flight.

[0034] <Function and effect of the kneading part in the second embodiment> The function and effect of the kneading parts provided in the screw for a single-screw extruder according to the second embodiment will be described below with reference to Figs. The raw material flowing into this kneading part from the upstream side of the screw is distributed by the multiple main flights as shown in Figure 7, flows into each groove of the kneading part, and then flows through the flow path consisting of the main flights, grooves, and the cylinder of the extruder along the forward direction 57 of the spiral of the main flight. As shown by arrow B in Figure 7, when the raw material flowing in the forward direction of the spiral reaches the convex flight 24, it overcomes the convex flight, which has a lower flight height than the main flight, and flows along the secondary flight 21 that holds back the raw material into the adjacent groove on the downstream side of the screw, and then the raw material flows again in the forward direction 57 of the spiral, following the main flight. On the other hand, when the raw material gets over the convex flight, it is also distributed to a flow path 63 consisting of two main flights and a sub flight, as shown by arrow D in Fig. 7. The distributed raw material is blocked by the sub flight 21 in the flow path 63, but because the screw is rotating in the forward direction (rotating from bottom to top in Fig. 7), the blocked raw material is pushed out to the side of the flow path 64 before distribution, where the raw material is redistributed while exchanging its position, and the redistributed raw material gets over the convex flight so as to flow to the downstream side of the kneading parts. As shown in the cross-sectional view of Figure 5, the flow of the raw material before and after the convex flight is such that when the raw material flows between the cylinder 2 and the bottom 42 of the groove in the flow direction 46 and flows into the narrow flow passage between the top 41 of the convex flight 24 and the cylinder 2, the raw material is compressed and agitated in front of the convex flight 43 due to the change in the height of the flow passage, and the raw material exchanges position, and then the raw material that has been compressed and passed between the top 41 of the convex flight and the cylinder 2 is released into the adjacent flow passage. When viewed from the side of the screw as shown in Figure 7, the raw material is exchanged between the main flight, convex flight, and secondary flight as the flow path direction and width change, as indicated by arrows B and D in Figure 7. From here on, all the way to the downstream end of the kneading part, the raw material is kneaded by repeatedly exchanging its three-dimensional position through similar changes in the flow path direction and width, stirring before the convex flight, and position exchange in the flow path 63 consisting of the two main flights and the sub flight. Since kneading in each part is repeated multiple times, excellent kneading is achieved while suppressing heat generation in the raw material.

[0035] In addition, while the raw material is kneaded while exchanging positions as shown by arrows B and D in the groove in Figure 7, by repeatedly providing main flights with cut angles 51, 52 smaller than the twist angle of the main flights, as in the first embodiment, a flow path is secured in which the raw material also flows linearly in the spiral direction as shown by arrow A in Figure 7, and kneading is achieved with reduced heat generation without the raw material being suddenly compressed.

[0036] Furthermore, as in the first embodiment, the sub-flights 21 are evenly arranged around the screw circumference, so that the repeated changes in the flow of the raw material between the main flight and the sub-flight, the changes in the width of the flow passage, and the position exchanges on the convex flights gradually compress and release the raw material at equal intervals per unit time that the raw material flows, thereby suppressing heat generation in the raw material and achieving excellent kneading properties.

[0037] <Modification> Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

[0038] In the screw of the present invention, the sub-flights, the convex flights, and the main flights having a shape with a cutting angle constituting the kneading parts may be repeatedly arranged in the configurations of the above-mentioned embodiments, and the number of the sub-flights may be set arbitrarily. For example, from the viewpoint of further suppressing heat generation, as shown in FIG. 8, by reducing the number of the sub-flights in the kneading parts of the second embodiment and making the convex flights long, it is possible to obtain a linear flow of the raw material in the helical direction while performing position exchanges in which the raw material flows alternately in the forward helical direction 57 and downstream in the screw axial direction 34, position exchanges by the wide convex flights, and position exchanges by the effect of dividing the flow between the two main flights. Also, as in the above-mentioned embodiment, the changes accompanying the flow of the raw material and compression and release are performed at equal intervals per time the raw material flows, so that high kneading properties can be obtained while suppressing heat generation of the resin.

[0039] The secondary flights in the kneading parts may be arranged at positions that evenly distribute the circumference in a cross section perpendicular to the screw, and the number of evenly distributed grooves can be set arbitrarily, but is preferably 2 to 8. The term "groove" in the secondary flights refers to the number of grooves that are evenly distributed around the circumference of the kneading parts in a cross section perpendicular to the screw axial direction.

[0040] Furthermore, the height of the secondary flight may be any height that blocks the raw material so as to move the raw material to the adjacent groove, and it is preferable to set the height of the secondary flight such that df / D=0.920 to 0.999, where D is the cylinder bore of the single screw extruder and df is the diameter of the secondary flight. The width of the top of the secondary flight can be set as desired as long as it connects the main flight and the secondary flight to block the raw material, and the width of the secondary flight may be varied as desired in the axial direction of the screw from the standpoint of cutting the screw.

[0041] The helical flight in the kneading part may be a forward spiral multiple flight, the helix angle of which may be set arbitrarily within a range of 10° to 85°, and the number of grooves is preferably 2 to 8. The side surface of the main flight may have a structure in which the groove is cut up, as is applied to a typical screw for an extruder. The height of the main flight relative to the groove can be set arbitrarily depending on the diameter of the cylinder and screw of the single-screw extruder and the desired resin discharge amount, but it is preferable that the diameter of the main flight is about -0.5 to -0.2 mm relative to the cylinder diameter. Furthermore, the width of the top of the main flight can be set arbitrarily as long as the main flight and the secondary flight can be connected at the intersection of the main flight and the secondary flight while having a cut-in angle.

[0042] In Figures 3 and 6, the cutting angle 51 on the reverse spiral side of the main flight and downstream in the axial direction of the screw, and the cutting angle 52 on the forward spiral side of the main flight and upstream in the screw, can be set arbitrarily as long as they are smaller than the twist angle of the main flight, but from the viewpoint of allowing the raw material to flow linearly, the two cutting angles may be the same.

[0043] Fig. 11 shows a partially enlarged development of the kneading parts of a screw for a single screw extruder in the circumferential direction of the screw. As shown by reference numerals 51 and 52 in Fig. 11, when the twist angle of the main flight is large and the cut angle of the main flight is small, the secondary flight can be cut off together with the main flight along the cut angle to the extent that the connection between the secondary flight and the main flight remains.

[0044] The height of the convex flight in the kneading part can be set to any height so as to gently compress the passing raw material, but it is preferable to set it to ds / D = 0.85 to 0.98, where D is the cylinder diameter of the single-screw extruder and ds is the diameter of the convex flight. The height of the apex of the convex flight in the forward spiral direction may be constant along the forward spiral direction of the main flight, but can be set arbitrarily. For example, the apex may be higher in the forward spiral direction, or lower in the forward spiral direction.

[0045] As shown in the cross-sectional shape of the convex flight in Figure 10, the shape of the top of the convex flight may be any shape. It may have a shape with a certain width as shown in Figure 10(a), or, from the perspective of suppressing compression, it may have a shape with no width as shown in Figure 10(b), or may be further cut into two peaks as shown in Figure 10(c). In addition, from the viewpoint of stirring the raw material in front of the convex flight, the shape of the side slope in the cross section of the convex flight is preferably a convex curve cutting upward from the groove direction as shown in Figures 10(a) to (c), similar to the main flight cutting upward from the groove, but the curvature and shape can be set arbitrarily.

[0046] From the viewpoint of further increasing the position exchange of the raw material, the kneading part of the screw of the present invention may be provided with a new convex flight for exchanging the position of the raw material in addition to the above-mentioned convex flight, within the scope of not impairing the function of the present invention, and for example, a new convex flight 55 extending in the screw axial direction may be provided in addition to the above-mentioned secondary flight, as shown in Figure 9. The convex flights 55 provided separately in the screw axial direction are preferably arranged at equal intervals in the flow path of the kneading part from the viewpoint of suppressing heat generation of the raw material.

[0047] The screw of the present invention may be a screw for a single screw extruder equipped with the kneading parts, and the screw bore, screw shape of the supply section, and screw shape of the metering section may be any shape as long as they have the functions of each section. The screw may be equipped with the kneading parts in the kneading section of the screw, and may be equipped with parts of other shapes before and after the kneading parts in the kneading section.

[0048] The single screw extruder of the present invention may be a single screw extruder having the screw of the present invention. The rotation direction of the screw by the rotational power of the single screw extruder is clockwise if the forward direction of the spiral of the flight of the screw and the main flight of the kneading part is clockwise, and counterclockwise if the forward direction of the spiral is counterclockwise. The cross-sectional shape of the cylinder of the single screw extruder can be set arbitrarily, but is preferably cylindrical, and a groove may be provided in the cylinder.

[0049] By being configured as described above, the screw for a single-screw extruder and the single-screw extruder of the present invention provide a screw and a single-screw extruder that have high kneading performance and diffusivity while suppressing an increase in the temperature of the raw material when kneading and extruding a raw material containing a thermoplastic resin. In addition, since the structure is such that the position of the raw material is repeatedly exchanged, the raw material is excellent in diffusibility. In particular, since the screw and single screw extruder of the present invention have a mechanism for gradually compressing and releasing, even in applications where particles with a high aspect ratio such as glass fiber or mica are kneaded with a thermoplastic resin, suitable kneading can be performed without applying a strong force to the particles to crush them. Furthermore, in the single-screw extruder of the present invention, even when kneading is performed at a high screw rotation speed in order to achieve a high output rate, the structure of the kneading parts makes it possible to perform suitable kneading while suppressing heat generation in the raw materials. [Explanation of symbols]

[0050] 1. Single screw extruder 2 Cylinder 3. Screw for single screw extruder 4. Hopper 5 Flights 6 Valley 7 Mixing parts 8. Heater 9 Motors and reducers 10 Dice 20 Main Flight 21 Secondary Flight 22 Groove 24 Convex Flight 25 Intersection of main and secondary flights 26 Intersection of main and secondary flights 29 Extension line of the secondary flight in the screw axial direction 31 Screw supply section 32 Screw mixing section 33 Screw metering section 34 Downstream in the axial direction of the screw 35 Screw axial direction upstream 41 Convex flight top 42 Bottom of the groove 43 Raw material upstream of the convex flight 45 Width of the top of the convex flight 46 Resin flow direction 50 Main flight twist angle 51 Angle of intrusion of the main flight in the forward spiral direction and downstream of the screw axis 52 Angle of intrusion of the main flight in the reverse spiral direction and upstream of the screw axis 55 In the modified example, a convex flight extending in the screw axial direction is provided separately from the cut portion. 57 Spiral forward direction 58 Spiral reverse direction 62 Intersection of main flight and secondary flight in second embodiment 63 A flow path consisting of two main flights and a secondary flight 71 Secondary flight cut off with main flight 72 Secondary flight cut off with main flight

Claims

1. A screw for a single screw extruder equipped with a kneading element, The kneading element has multiple continuous spiral flights and grooves, the helical flight being a forward helical flight having a helix angle; The spiral flight includes a main flight that blocks the resin, and a cut portion that becomes a convex flight having a flight height lower than that of the main flight, A secondary flight extending in the axial direction of the single-screw extruder screw is provided in the groove between the main flights, The secondary flights are arranged at positions that evenly distribute the circumference of the single-screw extruder screw in a right-angle cross section, The secondary flight is connected to two main flights in the axial direction of the single-screw extruder screw, the convex flight is disposed from an intersection portion where the secondary flight and the main flight are connected to each other on the downstream side of the screw for a single screw extruder to a reverse direction of the spiral of the spiral flight, the main flight adjacent to the convex flight has a shape having a cut angle smaller than a helix angle of the main flight when viewed from a side surface of the screw for a single screw extruder, The structures of the main flight, the sub flight and the convex flight are engraved so as to be repeatedly arranged in the spiral direction of the spiral flight. A screw for a single screw extruder.

2. A single-screw extruder comprising the screw for a single-screw extruder according to claim 1.

Images