Twin Screw Extruder

Abstract

To provide a twin-screw extruder having a kneading disk, which, when kneading and extruding a raw material containing a thermoplastic resin, can obtain sufficient kneading performance of the raw material, suppresses temperature unevenness, and prevents the screw and a cylinder from coming into contact with each other and being damaged due to bending of the screw. [Solution] An intermeshing type twin-screw extruder, wherein a cylinder in its cross section has two circular through hole connection parts shaped as two peaks where two circular through holes intersect, cut parallel to a line segment connecting the centers of the circular through holes, and a hole formed by the two circular through holes and the two circular through hole connection parts in the cross section of the cylinder has a shape that is symmetrical on either side of a vertical line at the midpoint of the line segment connecting the centers of the two circular through holes, and wherein the vertical distance d1 between the two circular through hole connection parts, the diameter D of the circular through hole, and the distance d2 connecting the centers of the two circular through holes have a specific ratio.

Description

[Technical field]

[0001] The present invention relates to a twin-screw extruder for kneading a resin. [Background technology]

[0002] When kneading two or more kinds of raw materials, such as kneading resins together or kneading resin with powder particles, particularly when a kneaded product is continuously produced using a thermoplastic resin as the resin, a method is used in which the raw materials are heated and kneaded using an extruder equipped with a screw, and then pelletized, from the viewpoint of mass productivity. One such extruder is the twin-screw extruder. The twin-screw extruder is an extruder equipped with two screws inserted into a cylinder, and the cylinder is perforated with two circular holes in parallel with parts of the inner wall surface overlapping each other. In the twin-screw extruder, the material fed into the cylinder can be kneaded by rotating the screws inserted into each circular hole.

[0003] In a twin-screw extruder, resins are mixed with each other, or with powder particles. The raw materials are added in solid form and melted by the heat of the heater and the heat of the screws and cylinder, while being kneaded by shear between the two screws and between the screws and cylinder. The screws in the twin-screw extruder have blades called screw elements that are tailored to various functions, such as feeding solid raw materials, kneading, and stably feeding molten resin. In particular, in a region called the kneading section where the most shear is applied immediately after melting, a screw element for kneading called a kneading disk is used in the screw. The kneading disc is a disc with a blade-shaped cross section with a long and short diameter, and the raw materials passing through the flow path between the kneading disc and the cylinder are kneaded by the blade-shaped kneading disc by rotating the two screws at the same speed. In an intermeshing type twin-screw extruder designed to have two screws intermesh, the adjacent kneading discs are arranged with their phases shifted, so that the long diameter part of the kneading disc scrapes off the raw materials adhering to the short diameter part of the other kneading disc, resulting in self-cleaning, whereby the raw materials can be more uniformly kneaded. As described above, the kneading disc exhibits excellent kneading properties in kneading resins together or resins with powder particles, but due to its structure, the pressure applied to the kneaded material fluctuates greatly, which has been problematic.

[0004] Patent Document 1 is a patent for a twin-screw extruder, and discloses an invention for such a twin-screw extruder, in which two circular holes are formed parallel inside a barrel so that parts of their inner wall surfaces overlap each other, and a "contact avoidance section" that prevents the tip of the kneading flight from contacting the inner wall surface of the circular holes of the barrel is formed as an inclined surface by cutting only the tip side at an angle, leaving the base end side of the peak portion. Patent Document 1 discloses in FIG. 5 the pressure inside the barrel of a conventional twin-screw extruder in gray scale. In response to the problem of so-called "galling" where the kneading flights come into contact with the barrel at the extremely high pressure points shown in black at θ=30° in the diagram, as disclosed in FIG. 2(b) of Patent Document 1, a contact avoidance section is provided in the barrel where the peaks are offset diagonally, thereby preventing contact between the kneading flights and the barrel as disclosed in FIG. 6 of Patent Document 1 at θ=30°.

[0005] The invention of Patent Document 1 avoids contact between the kneading disc (kneading flight) and the cylinder (barrel) by cutting out the contacting portion where the pressure rises to provide a contact avoidance portion, thereby eliminating contact around the contact avoidance portion. However, contact between the kneading disc and the cylinder in a normal twin-screw extruder can also occur in places other than the contact avoidance portion, and therefore, even the invention of Patent Document 1 could not avoid contact. Taking Patent Document 1 as an example, even if a contact avoidance unit is provided, as shown in θ=30° in Fig. 6, the pressure rises most when the tip of the kneading disk comes closest, and this pressure rise occurs in a direction perpendicular to the axial direction of the screw. Since the screw is connected to the power unit with a cantilever structure, this pressure causes the screw to bend, and when viewed from the cross section of the barrel, the screw and the cylinder come into contact at a point symmetrical with respect to the center of rotation of the screw at the point where the pressure rises (for example, in the diagram of θ=30° in Fig. 6 of Patent Document 1, the upper right tip of the right kneading flight and the upper left tip of the left kneading flight come into contact with the adjacent barrel), which causes problems such as damage to the cylinder, wear of the screw, and mixing of worn metal powder into the kneaded material.

[0006] In addition, in Patent Document 1, the contact avoidance parts arranged above and below can be installed so as to be point symmetrical, but the shape is not symmetrical on the left and right. Therefore, when raw materials are flowed from the upstream to the downstream direction of the screw axis into a twin-screw extruder having a cylinder with the cross-sectional shape disclosed in Patent Document 1 provided across a circular through hole, the history of shear heat acting on the raw materials differs between the left and right, resulting in a problem of temperature unevenness. Specifically, referring to Figures 1, 2(a) and (b) described in Patent Document 1, a conventional cylinder with a cross-sectional shape as shown in Figure 2(a) is symmetrical, so when screws of the same shape are arranged on the left and right, the flow path created by the gap between the screw and the cylinder is the same for both the left and right cylinders when viewed on the time average over one rotation of the screw, and the raw materials flowing through the left cylinder and the right cylinder are subjected to the same thermal history symmetrically. However, in the case of a cylinder with a cross-sectional shape as shown in Figure 2(b), in the upper ridge portion 6, the cylinder on the left has a wide flow path, and the cylinder on the right has a narrow flow path compared to the left. Therefore, the material flowing through the upper left side is subjected to weak shear and flows rapidly downstream along the screw axis, while the material flowing through the upper right side is subjected to strong shear and flows slowly downstream along the screw axis, generating shear heat. This tendency for shear heat accumulates as the material flows downstream along the screw axis. Similarly, in the lower ridge portion 6 of Figure 2(b), in contrast to the upper side, the material flowing through the lower right side is subjected to weak shear and flows rapidly downstream along the screw axis, while the material flowing through the lower left side is subjected to strong shear and flows slowly downstream along the screw axis, generating shear heat. Finally, at the downstream end of the screw on the right side of Figure 1, the raw materials with different thermal histories that have passed through the left and right cylinders join together, are mixed, and are discharged. When kneading raw materials containing thermoplastic resins in a twin-screw extruder, it is necessary to knead the raw materials uniformly by shearing while suppressing shear heat to a level that does not cause deterioration of the raw materials. However, if there are temperature unevenness in the raw materials due to different shear heat on the left and right as described above, sufficiently uniform kneading cannot be performed, or if the screw rotation speed is increased to intensify the kneading, there is a problem that part of the raw materials will deteriorate due to shear heat.

[0007] Patent Document 2 describes a twin-screw kneading extruder in which one or both of the tips of the upper and lower joints of the inner holes of two cylinders are removed to form a notch, which provides an escape route for the resin, thereby reducing energy consumption and suppressing an increase in resin temperature. However, the technology in Patent Document 2 does not take into consideration the bending of the screw, and there remains the possibility that the kneading disk and the cylinder may come into contact due to the bending of the screw.

[0008] Patent Document 3 describes a twin-screw kneading extruder in which the cross-sectional shape of the tip cylinder (cylinder head) at the tip of the screw, which corresponds to the above-mentioned joint, is gradually curved toward the downstream side in order to prevent resin retention at the tip of the screw (metering section). However, the cylinder head region is not the part where the kneading disk kneads the raw materials, and no consideration was given to the fluctuation in pressure applied to the kneaded material, securing an escape route for the resin at the joint, or contact with the cylinder due to bending of the screw. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2012-192560 A [Patent Document 2] JP 2003-236831 A [Patent Document 3] Japanese Utility Model Application Publication No. 1-137217 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, an object of the present invention is to provide a twin-screw extruder having a kneading disc, which, when kneading and extruding a raw material containing a thermoplastic resin, can obtain sufficient kneading performance of the raw material and suppress temperature unevenness, and which does not cause damage due to contact between the screw and the cylinder caused by bending of the screw. [Means for solving the problem]

[0011] The present inventors have discovered that the above object can be achieved by using the cylinder shape described below in an intermeshing twin-screw extruder equipped with two screws each having a kneading disc, and have thus completed the present invention.

[0012] That is, the present invention provides the following techniques. (1) A twin-screw extruder comprising a cylinder in which two circular through holes of the same diameter are formed in parallel so that parts of the inner wall surfaces of the circular through holes overlap each other, and two screws having kneading disks, the two screws rotating at the same rotation speed, The twin-screw extruder is an intermeshing extruder, The cylinder has, in its cross section, two circular through-hole connection parts that are shaped by cutting two mountain portions where the circular through-holes intersect parallel to a line segment connecting the centers of the circular through-holes, The two circular through holes and the two circular through hole connection parts in the cross section of the cylinder have a shape that is symmetrical with respect to a perpendicular line passing through the midpoint of a line segment connecting the centers of the two circular through holes, The vertical distance d1 between the two circular through-hole connection parts and the diameter D of the circular through-hole are in a ratio shown in formula (1), 0.65 ≦ d1 / D ≦ 0.95 (1) Furthermore, the ratio of d1 to the distance d2 between the centers of the two circular through holes is expressed by the following formula (2): Twin screw extruder. 0.82 ≦ d1 / d2 ≦1.10 (2), It is. (2) A twin-screw extruder comprising a cylinder in which two circular through holes of the same diameter are formed in parallel such that parts of the inner wall surfaces of the circular through holes overlap each other, and two screws having kneading disks, the two screws rotating at the same rotation speed, The twin-screw extruder is an intermeshing extruder, The cylinder has two circular through-hole connection parts in a cross section, the two mountain parts where the circular through-holes intersect each other are cut with a convex curve toward the hole of the cylinder, The two circular through holes and the two circular through hole connection parts in the cross section of the cylinder have a shape that is symmetrical with respect to a perpendicular line passing through the midpoint of a line segment connecting the centers of the two circular through holes, The ratio of the distance d1 between the vertices of the two circular through-hole connection parts in the cross section of the cylinder to the diameter D of the circular through-hole is shown in formula (1), 0.65 ≦ d1 / D ≦ 0.95 (1) Furthermore, the ratio of d1 to the distance d2 between the centers of the two circular through holes is expressed by the following formula (2): Twin screw extruder. 0.82 ≦ d1 / d2 ≦1.10 (2), It is. Effect of the Invention

[0013] The present invention can provide a twin-screw extruder having a kneading disc, which, when kneading and extruding a raw material containing a thermoplastic resin, can obtain sufficient kneading performance of the raw material and suppress temperature unevenness, and can prevent the screw and cylinder from coming into contact and being damaged due to bending of the screw. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view of a twin-screw extruder. [Diagram 2] FIG. 2 is a schematic diagram of a twin-screw extruder taken along the LL cross section of FIG. [Diagram 3] FIG. 1 is a cross-sectional view of a twin-screw extruder according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional view of a twin-screw extruder of a comparative example. [Diagram 5] FIG. 2 is a pressure distribution diagram of the raw material in a cross-sectional view of a twin-screw extruder of a comparative example. [Figure 6] FIG. 2 is a pressure distribution diagram of the raw material in a cross-sectional view of the twin-screw extruder according to the first embodiment of the present invention. [Figure 7] FIG. 4 is a cross-sectional view of a twin-screw extruder according to a second embodiment of the present invention. [Figure 8] FIG. 5 is a pressure distribution diagram of the raw material in a cross-sectional view of a twin-screw extruder according to a second embodiment of the present invention. [Figure 9] FIG. 2 is a cross-sectional view of a twin-screw extruder according to a modified example of the present invention. [Figure 10] 13 is a diagram illustrating the relationship between the radius of curvature R of the convex curve of the circular through-hole connection portion and the diameter D of the circular through-hole in the cross-sectional shape of a cylinder in a second embodiment of the present invention. FIG. [Figure 11]7(b) in the second embodiment of the present invention. [Figure 12] 10 is an enlarged view of region B of FIG. 9 in a modified example of the present invention. [Figure 13] FIG. 2 is a diagram illustrating the cylinder configuration of an extruder used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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 description of a numerical range means a or more and b or less unless otherwise specified. In addition, in this specification, "diameter" means a diameter.

[0016] [Extruder] A cross-sectional view of a twin-screw extruder of the present invention (hereinafter referred to as "extruder 1") is shown in Fig. 1, and a schematic view of the twin-screw extruder as viewed from the L-L cross section in Fig. 1 is shown in Fig. 2. As shown in Fig. 1 and Fig. 2, the extruder 1 has a cylinder 30 with a cylindrical hollow interior and two screws 20 housed in the cylinder. The cylinder 30 has a structure in which two cylindrical circular through holes 31 are connected in parallel in the longitudinal direction so as to have a cross-sectional shape described later. In the following description, the reference characters 31a and 31b are used as necessary to distinguish between the two circular through holes 31 in the drawings. As shown in FIG. 1, the two screws 20 housed in the cylinder 30 are connected to a power section 2 having a motor and a reducer equipped in the extruder 1 at two screw connection sections 21, and the rotational power of the motor and the reducer is transmitted to the connected screws 20, causing the screws 20 to rotate.

[0017] The screw 20 transfers the mixed thermoplastic resin-containing raw material (hereinafter also referred to as "raw material"), which is introduced and supplied to a hopper 4 provided at the top of the extruder 1, in a downstream direction 81 in the screw axial direction while supplying a fixed amount in the forward direction of the spiral to a flow path between the screw 20 and the valley of the cylinder 30. The raw material in the hopper 4 is transferred in the downstream direction 81 in the supply section 11, and is heated by heat from the heater 5 wrapped around the cylinder 30 and by shear heat between the raw material and the cylinder 30 and between the raw material and the screw 20, melting the thermoplastic resin (hereinafter also referred to as "resin") in the raw material and plasticizing the raw material. The plasticized raw material is kneaded in the kneading section 12, and the heated and kneaded raw material is pressurized in the metering section 13 to be stably discharged, and then passes through a nozzle section provided in a die 6 at the tip of the extruder 1 and extruded as a strand. The melt viscosity of the raw material during kneading is, for example, 0.01 to 50 g / 10 min in terms of melt flow rate (MFR) [230° C., load 2.16 kg]. The melt flow rate is measured in accordance with JIS K7210.

[0018] The screw 20 has screw elements having shapes corresponding to the functions of raw material supply, kneading, and metering in the supply section 11, the kneading section 12, and the metering section 13. In this embodiment, the extruder 1 has a kneading disk 22 for kneading shown in Fig. 2 in the kneading section 12. In the following description, the reference characters 22a and 22b will be used as necessary to distinguish between the two kneading disks 22 in the figure.

[0019] Figure 3 shows a cross-sectional view of the kneading disc 22 and the cylinder 30 as seen from the LL cross section of Figure 1. As shown in Figure 3(c), the kneading disc 22 is a screw element formed so that the cross-sectional shape is substantially elliptical (rugby ball shape), and the external shape is constituted by a convex surface. The kneading disc 22 has a long diameter 25 and a short diameter 26, and in the long diameter direction of the kneading disc 22, a narrow clearance flow path is formed between the kneading disc 22 and the cylinder 30, while in the short diameter direction of the kneading disc 22, a wide clearance flow path is formed between the kneading disc 22 and the cylinder 30. Therefore, the raw material sent from the upstream of the twin-screw extruder (extruder 1) is kneaded by being sheared and stretched as the clearance changes with the rotation of the kneading disc 22.

[0020] In addition, the extruder 1 of the present embodiment is an intermeshing extruder, and has an excellent pump function of sending the raw material to the downstream side of the extruder 1 without causing it to stagnate in the cross-sectional direction of the cylinder 30. In addition, in a screw element having two kneading discs 22 (22a, 22b), when the phase of the kneading discs 22 is combined at 90° as shown in Figure 3, a kneading effect due to a self-cleaning effect can be obtained in which the long diameter side tip 29 of one kneading disc 22 scrapes off the raw material near the short diameter side of the other kneading disc 22.

[0021] FIG. 4 shows a cross-sectional view of a conventional cylinder 30 and kneading disc 22 as a comparative example of the present invention. The conventional cylinder 30 has a structure in which two cylindrical circular through holes 31a, 31b are connected in parallel in the longitudinal direction, and therefore has two vertices 92 at the connecting portion. In addition, the two kneading discs 22a, 22b are assembled so that the phase difference is 90°, and they rotate in the same direction at the same speed. Figure 5 shows the pressure distribution of the raw material when the kneading disc 22 in the conventional cylinder 30 in Figure 4 is rotated. In Figure 5, (a) is set as the reference 0°, and the angle of rotation of each kneading disc 22 in the direction of the arrow is shown as θ, and the pressure applied to the raw material in the cylinder 30 shown in Figure 5 is shown in order of increasing pressure with black, diagonal lines, halftone dots, and white. In this specification, the rotation angle θ indicates the angle rotated in the clockwise direction based on the reference 0° shown in Figure 5(a), that is, based on the state in which the major axis 25 of the kneading disc 22a on the right side in the figure is parallel to the line connecting the centers 32 of the two circular through holes 31a, 31b, and the major axis 25 of the kneading disc 22b on the left side is perpendicular to the line. As shown in the black areas of Figures 5(c) and 5(f), when the long diameter side tips 29 of the two kneading discs 22a, 22b come closest to the apex 92, the raw material is compressed between the two kneading discs 22a, 22b and the cylinder 30, and high pressure is applied to the raw material. As shown in Fig. 1, the screw 20 having the kneading disc 22 has a cantilever structure connected to the power unit 2 only at the screw connection part 21, and the kneading disc 22 is configured at a location away from the screw connection part 21, so that the screw 20 bends in the direction indicated by the arrow 90 in Fig. 5(c) and (f) due to the high pressure of the raw material, and if the bending is large, the kneading disc 22 and the cylinder 30 come into contact and wear at the location indicated by the symbol 93 in Fig. 5(c) and (f). Therefore, in the conventional cylinder 30, the raw material flow path formed by the kneading disc 22 and the cylinder 30 changes due to wear, so that the kneading effect designed at the beginning cannot be obtained, and there is a problem that the worn metal powder is mixed into the raw material as a foreign matter.

[0022] [cylinder] In response to the above-mentioned problems of the prior art, the present invention provides an extruder 1 (twin-screw extruder) in which the screw 20 is not damaged due to contact between the screw 20 and the cylinder 30 caused by bending of the screw 20, by using the following cylinder shape. The cylinder 30 in the first and second embodiments will be described below, followed by modified examples.

[0023] [Cylinder of the first embodiment] The cross-sectional shape of the cylinder 30 of the twin-screw extruder in the first embodiment of the present invention is shown in Fig. 3. Fig. 3 shows a cross-sectional view seen from the LL cross section of Fig. 1. In the cylinder 30, two circular through holes 31a, 31b of the same diameter and having a circular cross section are formed in parallel so that parts of the inner wall surfaces of the circular through holes 31 overlap each other. Furthermore, in the cross section of the cylinder 30, between the two circular through holes 31a, 31b, the cylinder 30 has two circular through hole connection parts 40 shaped to cut out two peaks where the circular through holes 31 of the cylinder 30 intersect, parallel to the line segment 33 connecting the centers 32 of the circular through holes 31, as shown by reference numeral 41 (hereinafter referred to as "cutout parts 41") in Fig. 3(b). The perpendicular line passing through the midpoint of the line segment 33 connecting the centers 32 of the two circular holes 31a, 31b is set as the center line of symmetry 34, and the hole consisting of the two circular holes 31 (31a, 31b) and the two circular hole connection portions 40 in the cross section of the cylinder 30 has a shape that is symmetrical on both sides of the center line of symmetry 34. The cylinder 30 has circular hole connection parts 40 at two locations where the circular holes 31 overlap, and the vertical distance d1 between the two circular hole connection parts 40 and the diameter D of the circular holes is, for example, in the ratio shown in formula (1). 0.65 ≦ d1 / D ≦ 0.95 (1) Moreover, the ratio of the vertical distance d1 between the two circular through-hole connecting portions 40 and the distance d2 connecting the centers 32 of the two circular through-holes 31a, 31b is, for example, the ratio shown in formula (2). 0.82 ≦ d1 / d2 ≦1.10 (2)

[0024] The diameter D of the circular through hole 31 is, for example, not less than 60 mm and not more than 80 mm, and preferably not less than 65 mm and not more than 75 mm. The vertical distance d1 between the two circular through-hole connections 40 is, for example, 35 mm or more and 50 mm or less, and preferably 40 mm or more and 45 mm or less. A distance d2 connecting the centers 32 of the two circular through holes 31a, 31b is, for example, not less than 50 mm and not more than 75 mm, and preferably not less than 55 mm and not more than 65 mm. The lower limit of d1 / D is preferably 0.7 or more, and more preferably 0.75 or more. The upper limit of d1 / D is preferably 0.9 or less, and more preferably 0.85 or less. The lower limit of d1 / d2 is preferably 0.85 or more, and more preferably 0.88 or more. The upper limit of d1 / d2 is preferably 1.05 or less, and more preferably 1.00 or less. By setting the value of d1 / D to be equal to or greater than the lower limit, the length of the cut-out portion 41 in the vertical direction (d1 direction) in the figure can be secured, and the space for the cut-out portion 41 can be secured. As a result, even under the condition where the long-diameter side tips 29 of the two kneading disks 22a and 22b are closest to each other (rotation angle θ=45°) as shown in FIG. 6(c) described later, the compression of the raw material at the cut-out portion 41 is suppressed compared to the conventional case (e.g., FIG. 5(c)), the vibration of the screw 20 caused by large pressure fluctuations of the screw 20 is suppressed, and the bending of the screw 20 supporting the kneading disks 22 is suppressed. Furthermore, by setting d1 / D within the above-mentioned lower and upper limit numerical range and setting d1 / d2 to be equal to or greater than the lower limit of the above-mentioned numerical range, the raw material can flow to the adjacent circular through hole 31 without remaining at the cut-out portion 41, and the flowed-out raw material can also be efficiently kneaded between the kneading discs 22a, 22b and between the kneading discs 22a, 22b and the cylinder 30, thereby obtaining a sufficient kneading effect. In addition, by setting d1 / D within the above-mentioned lower and upper limit numerical ranges and setting d1 / d2 to be equal to or less than the upper limit of the above-mentioned numerical range, a sufficient kneading effect can be obtained, compression of the raw materials can be suppressed, and bending of the screw 20 can be suppressed. As a result, the kneading discs 22 are prevented from coming into contact with the inner wall of the cylinder 30 (more specifically, the circular through hole 31), and the raw material can be sufficiently kneaded.

[0025] The extruder 1 of this embodiment has two kneading discs 22a and 22b shown in Figure 3(c) as screw elements in the kneading section 12 of the screw, and the kneading disc 22 is a screw element formed so that the cross-sectional shape is approximately elliptical (rugby ball shape), and its external shape is composed of a convex surface and has a major axis 25 and a minor axis 26. The two kneading discs 22a, 22b are arranged to be out of phase with each other and rotate at the same speed, so that the material fed into the extruder 1 is kneaded by the change in the major axis 25 and minor axis 26 of the kneading disc 22 while passing through the clearance formed between the kneading disc 22 and the cylinder 30 formed by the circular through hole 31 and the circular through hole connection part 40. Note that Fig. 3 illustrates an example in which the two kneading discs 22a, 22b are arranged with a phase difference of 90° and the kneading discs 22 rotate in the same direction.

[0026] The extruder 1 of this embodiment is an intermeshing twin-screw extruder, and the distance d2 connecting the centers 32 of the two circular through holes 31a, 31b of the cylinder 30 is greater than the sum of the major and minor radiuses of the kneading disc 22 and is smaller than twice the major radius of the kneading disc 22. By using an intermeshing twin-screw extruder, a strong kneading action and a pumping action for sending the raw material downstream can be obtained in the kneading disc 22 of the kneading section 12.

[0027] [Effects of the first embodiment] Hereinafter, the operation and effect of the first embodiment of the present invention will be described with reference to FIG. 6, in comparison with FIG. 5 which shows a comparative example of the cylinder 30 having the above-mentioned conventional shape. Fig. 6 shows the pressure distribution of the raw material when the kneading disc 22 in Fig. 3 is rotated in the same direction. In Fig. 6, (a) is set as the reference 0°, and the angle by which the kneading disc 22 is rotated in the direction of the arrow is shown as θ, and the pressure applied to the raw material in the cylinder 30 is shown in descending order of pressure by solid black, diagonal lines, halftone dots, and white, as in Fig. 5. The kneading discs 22 in the kneading section 12 of the intermeshing twin-screw extruder knead the raw material by changing the clearance between the cylinder 30 and the kneading discs 22 as the kneading discs 22 rotate. As shown in Fig. 6(a) and Fig. 6(e), when the long-diameter end 29 of one of the two kneading discs 22a and 22b comes closest to the other kneading disc 22 in the short-diameter direction, the long-diameter end 29 scrapes off the raw material on the short-diameter side of the other kneading disc 22, a self-cleaning effect is obtained, and kneading is promoted.

[0028] On the other hand, the cylinder 30 of the extruder 1 of the present invention has a circular through hole connection part 40 between the circular through holes 31, which is cut parallel to the line segment connecting the centers of the circular through holes 31. By having the shape of the circular through hole connection part 40, in other words, the shape of the cutout part 41 determined by d1 / D in the above formula (1) and d1 / d2 in the formula (2), as shown in Figures 6(c) and 6(f), even when the long diameter side tip parts 29 of the two kneading disks 22a and 22b are closest to each other, the clearance between the two kneading disks 22a and 22b and the cylinder 30 is wide, and the raw material flows to the adjacent circular through hole 31 along the circular through hole connection part 40 provided in parallel, so that the black areas where the raw material pressure is high as seen in Figures 5(c) and 5(f) in the comparative example do not occur. As a result, bending of the screw 20 due to the high pressure between the kneading disc 22 and the cylinder 30 is suppressed, so that the kneading disc 22 and the screw 20 do not come into contact with the cylinder 30 on the side that is point-symmetrical to the high pressure point based on the center of the circular through hole 31 in the cross-sectional view of Figure 6, and kneading can be performed without damaging the cylinder 30 or wearing out the screw 20, and without the worn metal powder being mixed into the kneaded material.

[0029] As shown by the diagonal lines and dots in Figures 6(a) to (f), the increase in pressure of the raw material to the extent that the screw 20 does not bend occurs at the long diameter end 29 of the kneading disc 22 and the circular through hole 31 of the cylinder 30, where the clearance is compressed as the kneading disc 22 rotates. However, when the pressure change is observed in one rotation of the screw 20, it occurs over the entire wall surface of the circular through hole 31, so the screw 20 does not bend due to a localized pressure increase. As a result, the cylinder 30 is not damaged or the screw 20 is not worn, and kneading can be performed without the worn metal powder being mixed into the kneaded material. On the other hand, if d1 / D in the above formula (1) and d1 / d2 in the above formula (2) are outside the above ranges, the kneading property decreases and the effect of the self-cleaning property (kneading disc 22) of scraping off the raw material deteriorates.

[0030] In addition, the holes consisting of the two circular holes 31 and the circular hole connection parts 40 in the cross section of the cylinder 30 have shapes that are symmetrical on either side of the symmetric center line 34 shown in Figure 3. Therefore, the thermal history of the shear heat applied to the raw material passing through the two cylinders 30 on the left and right is the same on both the left and right, and temperature unevenness of the raw material inside the cylinder 30 and when it is discharged can be suppressed.

[0031] [Cylinder of the second embodiment] Next, the cross-sectional shape of the cylinder 30 of the extruder 1 (twin-screw extruder) in the second embodiment of the present invention is shown in Fig. 7. Fig. 7 shows a cross-sectional view seen from the LL cross section of Fig. 1. In the cylinder 30, two circular through holes 31a, 31b of the same diameter and having a circular cross section are formed in parallel so that parts of the inner wall surfaces of the circular through holes 31 overlap each other. Furthermore, in the cross section of the cylinder 30, between the two circular through holes 31a, 31b, the cylinder 30 has two circular through hole connection parts 50 shaped to cut out two peaks where the circular through holes 31 of the cylinder 30 intersect with each other, as shown by reference numeral 51 (hereinafter referred to as "cutout parts 51") in Fig. 7(b) by a convex curve toward the hole direction of the cylinder 30. As shown in Figure 7(a), a perpendicular line passing through the midpoint of a line segment 33 connecting the centers 32 of the two circular holes 31a, 31b is set as a center line of symmetry 34, and the convex curves of the two circular hole connection portions 50 form curves that are symmetrical on both sides of the center line of symmetry 34. As a result, the hole consisting of the two circular holes 31a, 31b and the two circular hole connection parts 50 in the cross section of the cylinder 30 has a shape that is symmetrical on both sides of the symmetric center line 34, and the vertex 52 of the convex curve of the two circular hole connection parts 50 in the cross section of the cylinder 30 is formed at the intersection of the curve and the symmetric center line 34. The cylinder 30 has circular hole connection portions 50 at two locations where the circular holes 31 overlap, and the distance d1 between the vertices 52 of the two circular hole connection portions 50 in the cross section of the cylinder 30 and the diameter D of the circular hole 31 is, for example, the ratio shown in equation (1). 0.65 ≦ d1 / D ≦ 0.95 (1) Moreover, the ratio of the distance d1 between the vertices of the two circular through-hole connecting portions 50 and the distance d2 connecting the centers 32 of the two circular through-holes 31a, 31b is, for example, the ratio shown in formula (2). 0.82 ≦ d1 / d2 ≦1.10 (2)

[0032] The diameter D of the circular through hole 31 is, for example, not less than 60 mm and not more than 80 mm, and preferably not less than 65 mm and not more than 75 mm. The vertical distance d1 between the two circular through-hole connections 50 is, for example, 35 mm or more and 50 mm or less, and preferably 40 mm or more and 45 mm or less. A distance d2 connecting the centers 32 of the two circular through holes 31a, 31b is, for example, not less than 50 mm and not more than 75 mm, and preferably not less than 55 mm and not more than 65 mm. The lower limit of d1 / D is preferably 0.7 or more, and more preferably 0.75 or more. The upper limit of d1 / D is preferably 0.9 or less, and more preferably 0.85 or less. The lower limit of d1 / d2 is preferably 0.85 or more, and more preferably 0.88 or more. The upper limit of d1 / d2 is preferably 1.05 or less, and more preferably 1.00 or less.

[0033] The conditions for a preferable shape of the convex curve of the circular through-hole connecting portion 50 can be defined by the relationship between the radius of curvature R and the diameter D of the circular through-hole 31. Specifically, the ratio between the radius of curvature R and the diameter D of the circular through-hole 31 is, for example, as shown in the following formula (3). 0.115 ≦ R / D ≦1.74 (3) The lower limit of R / D is preferably 0.12 or more, more preferably 0.15 or more, and the upper limit of R / D is preferably 1.7 or less, more preferably 1.5 or less.

[0034] FIG. 10 is a diagram illustrating the relationship between the radius of curvature R of the convex curve of the circular through-hole connecting portion 50 and the diameter D of the circular through-hole 31 with respect to the cross-sectional shape of the cylinder 30. FIG. 10(a) shows the cross-sectional shape when the circular through-hole connecting portion 50 is not provided. FIG. 10(b) shows the cross-sectional shape when R / D=0.116. FIG. 10(c) shows the cross-sectional shape when R / D=0.174. FIG. 10(d) shows the cross-sectional shape when R / D=0.232. FIG. 10(e) shows the cross-sectional shape when R / D=1.000.

[0035] By setting the value of d1 / D in the above formula (1) to be equal to or greater than the lower limit, the length of the cut-out portion 51 in the vertical direction (d1 direction) in the figure can be secured, and the space for the cut-out portion 51 can be secured. As a result, even under the condition where the long-diameter side tips 29 of the two kneading disks 22a and 22b are closest to each other (rotation angle θ=45°) as shown in FIG. 8(c) described later, the compression of the raw material at the cut-out portion 51 is suppressed compared to the conventional case (e.g., FIG. 5(c)), the vibration of the screw 20 caused by large pressure fluctuations of the screw 20 is suppressed, and the bending of the screw 20 supporting the kneading disks 22 is suppressed. Furthermore, by setting d1 / D within the above-mentioned lower and upper limit numerical range and setting d1 / d2 in the above formula (2) to be equal to or greater than the lower limit of the above-mentioned numerical range, the raw material can flow to the adjacent circular through hole 31 without remaining at the cut-out portion 51, and the flowed-out raw material can also be efficiently kneaded between the kneading discs 22a, 22b and between the kneading discs 22a, 22b and the cylinder 30, thereby obtaining a sufficient kneading effect. In addition, by setting d1 / D within the above-mentioned lower and upper limit numerical ranges and setting d1 / d2 to be equal to or less than the upper limit of the above-mentioned numerical range, a sufficient kneading effect can be obtained, compression of the raw materials can be suppressed, and bending of the screw 20 can be suppressed. As a result, the kneading discs 22 are prevented from coming into contact with the inner wall of the cylinder 30 (more specifically, the circular through hole 31), and the raw material can be sufficiently kneaded.

[0036] By setting the lower limit of R / D within the above range, the radius of curvature R of the convex curve with respect to the diameter D of the cylinder 30 (degree of convex curvature) becomes sufficiently large, and even when the long-diameter side tips 29 of the two kneading discs 22a, 22b are closest to each other (see Fig. 8(c) and Fig. 8(f) described later), the clearance between the two kneading discs 22a, 22b and the cylinder 30 can be sufficiently secured, and the raw material can smoothly flow along the circular through-hole connection part 50 to the adjacent circular through-hole 31. In addition, by setting the upper limit of R / D within the above range, the raw material can be appropriately compressed at that location and can be prevented from stagnation at that location.

[0037] FIG. 11 is an enlarged view of region A in FIG. 7(b). However, FIG. 11 shows the state where the rotation angle θ of the kneading disk 22 is 45° (the state of FIG. 8(c) described later) where the raw material is most compressed. With reference to this figure, the escape route of the raw material under the condition where the long-diameter side tips 29 of the two kneading disks 22a and 22b are closest to each other (rotation angle θ=45°) will be described. A line 75 is drawn from the screw axis through the center 29 of the screw flight (short-diameter part), and the point where the line 75 intersects with the cylinder 30 (circular through hole 31) is defined as point 72. In a state where the cutout portion 51 is not provided (cross-sectional shape corresponding to FIG. 4; shown by a dashed line in FIG. 11), the point where the above line 75 intersects with the cylinder 30a is defined as point 71. When the distance between center 29 and point 71 is db (hereinafter also referred to as the "reference clearance distance") and the distance between center 29 and point 72 is dα (hereinafter also referred to as the "clearance distance"), the clearance distance dα and the reference clearance distance db are, for example, the ratio shown in the following equation (4). 2.0 ≦ dα / db ≦21 (4) The lower limit of dα / db is preferably 2.5 or more, and more preferably 3.0 or more. The upper limit of dα / db is preferably 15 or less, and more preferably 10 or less. By setting dα / db as described above, even when the long diameter side tips 29 of the two kneading discs 22a, 22b are closest to each other (see Figures 8(c) and 8(f) described below), sufficient clearance can be secured between the two kneading discs 22a, 22b and the cylinder 30, and the raw material can flow smoothly along the circular hole connection part 50 to the adjacent circular hole 31.

[0038] The extruder 1 (twin-screw extruder) having a cylinder 30 of the second embodiment has two kneading discs 22a, 22b shown in Figure 7(c) as screw elements in the kneading section 12 of a screw 20 similar to that of the first embodiment, and the kneading disc 22 is a screw element formed so that the cross-sectional shape is approximately elliptical (rugby ball shape), and the external shape is composed of a convex surface and has a major axis 25 and a minor axis 26.

[0039] The extruder 1 having the cylinder 30 of the second embodiment is an intermeshing type twin-screw extruder like the first embodiment, and the distance d2 between the two circular through holes 31a, 31b of the cylinder 30 is larger than the sum of the radius in the major axis direction and the radius in the minor axis direction of the kneading disc 22, and is smaller than twice the radius in the major axis direction of the kneading disc 22. By using an intermeshing type twin-screw extruder, a strong kneading action and a pumping action for sending the raw material downstream can be obtained in the kneading disc 22 of the kneading section 12.

[0040] [Functions and Effects of the Second Embodiment] Hereinafter, the effects of the second embodiment of the present invention will be described with reference to Fig. 8. Fig. 8 illustrates the pressure distribution of the raw material when the kneading disc 22 in Fig. 7 is rotated in the same direction. In Fig. 8, (a) is set as the reference 0°, and the angle at which the kneading disc 22 is rotated in the direction of the arrow is indicated as θ, and the pressure applied to the raw material in the cylinder 30 is indicated in descending order of pressure by solid black, diagonal lines, halftone dots, and white, as in Figs. 5 and 6.

[0041] The cylinder 30 of the second embodiment has the same action and effect as the cylinder 30 of the first embodiment, and has a circular through hole connection part 50 that is shaped symmetrically on both sides of the symmetric center line 34, which is a perpendicular line passing through the midpoint of the line segment 33 connecting the centers 32 of the two circular through holes 31a, 31b.As a result, as shown in Figures 8(c) and 8(f), even when the long diameter side tips 29 of the two kneading discs 22 are closest to each other, the clearance between the two kneading discs 22a, 22b and the cylinder 30 is wide, and the raw material flows to the adjacent circular through hole 31 along the circular through hole connection part 50 arranged in parallel, so that no blackened area where the raw material pressure is high is generated. As a result, bending of the screw 20 due to the high pressure between the kneading disc 22 and the cylinder 30 is suppressed, so that the kneading disc 22 and the screw 20 do not come into contact with the cylinder 30 on the side that is point-symmetrical to the high pressure point based on the center of the circular through hole 31 in the cross-sectional view of Figure 8, and kneading can be performed without damaging the cylinder 30 or wearing out the screw 20, and without the worn metal powder being mixed into the kneaded material.

[0042] As in the first embodiment, as shown by the diagonal lines and dots in Figures 8(a) to (f), a rise in the pressure of the raw material to the extent that the screw 20 does not bend occurs at the long diameter end 29 of the kneading disc 22 and the circular through hole 31 of the cylinder 30 where the clearance is compressed as the kneading disc 22 rotates. However, when the pressure is observed as a change in one rotation of the screw 20, it occurs over the entire wall surface of the circular through hole 31, so the screw 20 does not bend due to a localized pressure rise. As a result, the cylinder 30 is not damaged or the screw 20 is not worn, and kneading can be performed without the worn metal powder being mixed into the kneaded material.

[0043] In particular, in the cylinder 30 of the second embodiment, compared to the cylinder 30 of the first embodiment in which the diameter D of the circular hole 31 and the distance d2 between the centers of the circular holes 31 are the same, and the distance d1 of the circular hole connection part 50 is also the same, the clearance through which the raw material flows around the convex curve formed by the circular hole connection part 50 is wider than in the first embodiment, so that an increase in pressure can be suppressed and contact between the screw 20 and the cylinder 30 due to bending of the screw 20 can be suppressed.

[0044] Furthermore, similar to the cylinder 30 of the first embodiment, the hole consisting of the two circular holes 31 and the circular hole connection portion 50 in the cross section of the cylinder 30 has a shape that is symmetrical on both sides of the symmetric center line 34 shown in FIG. 7. Therefore, the thermal history of the shear heat applied to the raw material passing through the two cylinders 30 on the left and right is the same on both sides, and temperature unevenness of the raw material inside the cylinder 30 and when discharged can be suppressed.

[0045] [Variations] Although the embodiment of the present invention has been described above, these are merely examples of the present invention, and various configurations other than those described above may also be adopted. Modification examples will be described below.

[0046] [Cylinder in modified example] A modified example of the cylinder 30 of the first embodiment of the twin-screw extruder of the present invention will be described with reference to Fig. 9 and Fig. 12. Fig. 9 is a cross-sectional view of the extruder 1 (twin-screw extruder) of the modified example. Fig. 12 is an enlarged view of region B in Fig. 9.

[0047] The connection between the two circular through holes 31a, 31b of the cylinder 30 and the circular through hole connection part 40 may be a curved surface part 45 that is R-processed at the connection point between the circular through holes 31a, 31b and the linear circular through hole connection part 40 from the viewpoint of preventing the raw material from burning at the corners, as shown in FIG. 9. In this case, it is preferable to perform R processing so as to be symmetrical with respect to the symmetric center line 34. From another viewpoint, this modified example can be said to have a shape in which the tip part 155 of the convex curve of the circular through hole connection part 50 in FIG. 7 provided at the intersection part of the two circular through holes 31a, 31b in the second embodiment is cut off, as shown in FIG. 12. The circular through hole connection part 150 (40) has a flat part 151 formed perpendicular to the symmetric center line 34 and linearly, and curved parts 152 formed at both ends of the flat part 151. The circular through-hole connection portion 150 (40) is symmetrical with respect to the center line of symmetry 34.

[0048] The diameter D of the circular through hole 31 of the cylinder 30 of the extruder 1, which is a twin-screw extruder, need only have the above-mentioned ratio relationship with the vertical distance d1 of the circular through hole connection part 40, and can be set arbitrarily depending on the discharge capacity and kneading capacity required of the twin-screw extruder. Furthermore, the distance d2 connecting the centers of the two circular holes 31 of the cylinder 30 only needs to have the above-mentioned ratio relationship with the vertical distance d1 of the circular hole connection portion 40, and can be set arbitrarily within the range of d1 / d2 = 0.82 to 1.10.

[0049] From the viewpoint of processing, the cylinder 30 in the extruder 1, which is a twin-screw extruder, is preferably a combination of cylindrical circular through holes 31 having the same diameter along the screw axis direction, but the cross-sectional shape of the cylinder 30 in contact with the kneading disc 22 may be any shape disclosed in the embodiments and modifications, and the cross-sectional shape of the cylinder 30 in other places may be any diameter depending on the functions required in the supply section 11, the kneading section 12, and the metering section 13. In addition, the inner surface of the circular through holes may be processed, such as by providing slits, for example, for the purpose of improving the kneading effect.

[0050] As shown in FIG. 1, the twin-screw extruder of the present invention may be provided with a vertical hole communicating with cylinder 30 through which the raw material from hopper 4 is introduced into cylinder 30, and may also be provided with a vertical hole for mounting vacuum pump 91 for discharging volatile components of the molten raw material. Any hole can be provided depending on the characteristics of the raw material.

[0051] [Kneading disc and screw in modified example] The two kneading discs 22 of the twin-screw extruder of the present invention can be assembled with their phases at 90° to each other as disclosed in the embodiment, but even when assembled with other phases, the pressure of the raw material around the circular through-hole connection part 40 of the cylinder 30 can be reduced, and the phase between the kneading discs 22 can be changed arbitrarily.

[0052] The kneading disc 22 may be any kneading screw element having a cross-sectional shape formed of a convex curved surface having a major axis 25 and a minor axis 26, and is not limited to a structure in which multiple discs having a thickness as disclosed in Figure 2 are stacked and shifted by 90°, but may be configured by stacking discs shifted at any angle. The thickness of the kneading disc 22 can be set arbitrarily as long as the kneading disc 22 does not bend due to the pressure of the raw material, and is not limited to the blade-shaped disc shape shown in Figure 2, but may also be a twist kneading disc having a continuous curved surface structure in which the blade shape of the cross section changes spirally.

[0053] The kneading disc 22 may be a kneading screw element having a cross-sectional shape of a convex curved surface with a major axis 25 and a minor axis 26, but from the viewpoint of improving kneading and improving the self-cleaning function, the major axis side tip 29 may be a curved surface or a flat surface having a certain width as disclosed in Fig. 3(c). From the viewpoint of pressure rise when approaching the circular through hole connection part 40, the width of the major axis side tip 29 is preferably 0.01D to 0.2D with respect to the diameter D of the circular through hole 31.

[0054] The clearance between the long diameter end 29 of the kneading disc 22 and the circular through hole 31 of the cylinder 30 is preferably 0.5 to 3 mm from the viewpoint of kneading the raw material and preventing contact between the kneading disc 22 and the cylinder 30. In general, it is set according to the diameter D of the circular through hole 31, and for example, when the diameter D is large, the clearance is set large. Note that the clearance corresponds to the "reference clearance distance db" in the second embodiment.

[0055] In order to suppress localized pressure increases by keeping the pressure fluctuations of the raw materials at constant intervals, it is preferable that the center of rotation of the kneading disc 22, the midpoint of the major axis 25 and the midpoint of the minor axis 26 of the kneading disc 22, and the center 32 of the circular hole 31 disclosed in Figure 3(b) are all located at the same position. However, for the purpose of further improving the kneading performance, the center of rotation of the kneading disc 22 may be shifted within a range where bending of the screw 20 does not occur.

[0056] The screw 20 of the extruder 1, which is a twin-screw extruder, is required to have the kneading disc 22 as a screw element, and the other screw elements can be configured as desired depending on the functions required for the areas of the supply section 11, the kneading section 12, and the metering section 13, and the functions of the areas into which each of the above sections is further subdivided. The phase of adjacent screw elements including the kneading discs 22 can be set arbitrarily, but from the viewpoint of suppressing temperature unevenness, it is preferable that adjacent screw elements have the same cross-sectional shape.

[0057] The two screws 20 (20a, 20b) of the extruder 1, which is a twin-screw extruder, preferably rotate at the same speed. The two screws 20 (20a, 20b) may rotate in the same direction as disclosed in the embodiment, but even if they rotate in opposite directions, there are arrangements similar to the kneading disks 22a and 22b disclosed in Figures 6(c) and 6(f) that have high pressure distribution, so the extruder 1 can be suitably used even when operating in opposite directions.

[0058] The extruder 1, which is a twin-screw extruder, has high mixing performance when mixing and extruding a raw material containing a thermoplastic resin that has high viscoelasticity when melted and is easily deteriorated by shear heat, and does not come into contact with the cylinder 30 and is not damaged due to bending of the screw 20. In particular, the extruder 1 can be suitably used in applications in which fine particles are mixed with a thermoplastic resin, in which the pressure of the raw material is likely to increase during mixing, without bending of the screw 20 even with an increase in pressure. EXAMPLES

[0059] The present invention will be described in detail below with reference to examples. The following examples are provided to better explain the present invention, but are not intended to limit the present invention. In addition, "parts" refers to parts by weight unless otherwise specified.

[0060] (Test confirmation machine) The following equipment was used for the measurements in the examples. Japan Steel Works TEX65 (twin-screw extruder) L / D=28 L: Screw length D: Cylinder diameter

[0061] (Test confirmation cylinder) Fig. 13 shows the screw configuration of the extruder used in the examples. The upper row shows the cylinder configuration, and the lower row shows the structure of the screw in each cylinder. Cylinders C1 to C8 are mounted in order from the left side of the figure. The left side of the figure is upstream, and the right side of the figure is downstream. Cylinder C1 is a material inlet, cylinder C5 is an open vent for air venting, and cylinder C7 is a forced vent for vacuum degassing. Cylinders C3 and C4 correspond to the first kneading section, and C6 corresponds to the second kneading section. In Comparative Examples 1 and 2, a cylinder (standard cylinder) with a conventional cross-sectional structure as shown in FIG. 4 was used. In Examples 1 and 2, the first kneading section (cylinders C3 and C4) of the cylinders was replaced with a cylinder (special cylinder) processed to a cross-sectional structure having a convex curved circular through-hole connection portion 50 shown in the second embodiment. The specific specifications are as follows: d1 / D=0.717 d1 / d2=0.868 dα / db = 4.422 R / D=0.174 d1: Vertical distance between two circular hole connections D: Cylinder diameter (circular hole diameter) d2: The distance between the centers of the two circular holes dα: Clearance distance db: Reference clearance distance

[0062] (Test confirmation materials) The raw materials used in the measurements were as follows: The raw materials in the following composition were dry blended and then fed into the hopper of the extruder by a weight-controlled feeder. (1) Polypropylene resin (density 0.9 g / cm 3 ) 70 parts by weight (2) Filler: talc (average particle size 3 μm) 20 parts by weight (3) Ethylene propylene rubber 10 parts by weight

[0063] The extruder was operated under the conditions of screw rotation speed and raw material supply rate shown in Table 1, and at the cylinder set temperature shown in Table 2 to knead and extrude the raw materials. The extruded raw materials were discharged as strands from the die at the tip of the extruder, and the strands were then cut to create pellet-shaped test products measuring 3φ x 3 mm in length. [Table 1]

[0064] The measurement results are shown in Tables 2 to 4. Table 2 shows the indicated temperature of each cylinder when the extruder was in operation. Table 3 shows the vibration displacement (μm) when the extruder was in operation. The vibration displacement was measured using a portable vibration meter (type: DigiVibro MODEL1332B, manufacturer: Showa Sokki Co., Ltd.). The displacement was measured at four points, top, bottom, left and right, at the middle position of each block cylinder, and the average value was calculated.

[0065] The physical properties of the test samples were measured as follows. The physical properties were measured in the following (1) to (8), and for (1), the physical properties of the obtained test specimens were measured, and for the physical property measurements in (2) to (8), the obtained test specimens were prepared from the obtained test specimens using an injection molding machine (machine name: IS55EPN, manufactured by Toshiba Machine Co., Ltd., mold temperature 40°C, cylinder temperature 200°C, injection speed 20 mm / sec) under conditions of an injection molding temperature of 240°C and a mold temperature of 40°C, and the physical properties were evaluated. In Table 4, Comparative Example 1 is used as the standard, and physical properties within 95 to 105% of the standard are marked with "○". (1) MFR (Melt Flow Rate) was measured in accordance with JIS K7210 with test samples at 230°C and a load of 2.16 kg (21.18 N). (2) Specific gravity was measured in accordance with JIS K7112. (3) The tensile yield strength was measured at 23°C in accordance with JIS K7161. (4) The tensile breaking strength was measured at 23°C in accordance with JIS K7161. (5) Flexural strength was measured at 23°C in accordance with JIS K7171. (6) Flexural modulus was measured at 23°C in accordance with JIS K7171. (7) The heat distortion temperature (load temperature) was measured in accordance with JIS K7191 under the condition of applying a load of 0.45 MPa. (8) Izod impact strength was measured in accordance with ASTM D256 Method A (notched).

[0066] (Summary of Examples) From the measurement results of Comparative Examples 1 and 2 and Examples 1 and 2, the following was confirmed. (1) The vibration displacement data showed that the vibration displacement was clearly smaller when Examples 1 and 2 were installed. (2) After the test was completed, the screw was removed and the condition of the cylinder and screw was checked. In the cases of Comparative Examples 1 and 2, contact marks of the cylinder and screw were confirmed in the first kneading section. On the other hand, in the cases of Examples 1 and 2, no screw marks were confirmed in the cylinder and screw. (3) No difference was observed in the physical properties between Examples 1 and 2 and Comparative Examples 1 and 2. In Examples 1 and 2, no decrease in strength of the kneaded product was observed, and it was confirmed that the kneaded product was sufficiently kneaded.

[0067] [Table 2] [Table 3] [Table 4] [Explanation of symbols]

[0068] 1. Extruder (twin screw extruder) 2 Power section 4. Hopper 5. Heater 6 Dice 11 Supply section 12 Mixing section 13 Measuring part 20 Screw 21 Screw connection 22, 22a, 22b Kneading disc 25 Long diameter of kneading disc 26 Minor diameter of kneading disc 29 Long-diameter tip of kneading disc 30 Cylinder 31 Circular through hole 32 Center of circular through hole 33 Line segment connecting the centers of circular holes 34 Symmetry centerline 40, 50 circle through hole connection 41 Cut-out portion in the first embodiment 45 Curved surface in modified example 51 Cut-out portion in the second embodiment 52 Vertex 81 Downstream direction 82 Upstream direction 90 Screw bending direction 91 Vacuum Pump 92 Top of cylinder in comparative example 93 Contact area between kneading disc and cylinder in comparative example

Claims

1. A twin-screw extruder comprising a cylinder in which two circular through holes of the same diameter are formed in parallel such that parts of the inner wall surfaces of the circular through holes overlap each other, and two screws having kneading disks, the two screws rotating at the same rotation speed, The twin-screw extruder is an intermeshing extruder, The cylinder has, in its cross section, two circular through-hole connection parts that are shaped by cutting two mountain portions where the circular through-holes intersect parallel to a line segment connecting the centers of the circular through-holes, The hole consisting of the two circular through holes and the two circular through hole connection parts in the cross section of the cylinder has a shape that is symmetrical on both sides of a perpendicular line passing through the midpoint of a line segment connecting the centers of the two circular through holes, The vertical distance d1 between the two circular through-hole connection parts and the diameter D of the circular through-hole are in a ratio shown in formula (1), 0.65≦d1 / D≦0.95...(1) Furthermore, the ratio of d1 to the distance d2 between the centers of the two circular through holes is expressed by the following formula (2): Twin screw extruder. 0.82 ≦ d1 / d2 ≦1.10 (2)

2. A twin-screw extruder comprising a cylinder in which two circular through holes of the same diameter are formed in parallel such that parts of the inner wall surfaces of the circular through holes overlap each other, and two screws having kneading disks, the two screws rotating at the same rotation speed, The twin-screw extruder is an intermeshing extruder, The cylinder has two circular through-hole connection parts in a cross section, the two peaks where the circular through-holes intersect are cut with a convex curve toward the hole of the cylinder, The hole consisting of the two circular through holes and the two circular through hole connection parts in the cross section of the cylinder has a shape that is symmetrical on both sides of a perpendicular line passing through the midpoint of a line segment connecting the centers of the two circular through holes, The ratio of the distance d1 between the vertices of the two circular through-hole connection parts in the cross section of the cylinder to the diameter D of the circular through-hole is shown in formula (1), 0.65≦d1 / D≦0.95...(1) Furthermore, the ratio of d1 to the distance d2 between the centers of the two circular through holes is expressed by the following formula (2): Twin screw extruder. 0.82 ≦ d1 / d2 ≦1.10 (2)

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