Twin screw extruder

Abstract

To provide a twin-screw extruder having a kneading disk, in which when a raw material containing a thermoplastic resin is kneaded and extruded, sufficient kneading performance of the raw material is obtained, temperature unevenness is suppressed, and a screw and a cylinder are not damaged by coming into contact with each other due to bending of the screw.SOLUTION: An intermeshing twin-screw extruder, wherein a cylinder has two Entsu hole connecting portions having a shape in which two mountain portions where two Entsu holes intersect each other are cut out in parallel to a line segment connecting centers of the Entsu holes in a cross section of the cylinder, A hole including the two Entsu holes and the two Entsu hole connecting portions in a cross section of the cylinder has a shape that is bilaterally symmetrical with respect to a vertical line at a midpoint of a line segment connecting centers of the two Entsu holes, and a vertical distance d1 between the two Entsu hole connecting portions, diameters D of the Entsu holes, and the distances d2 connecting the centers of the two Entsu holes have a specific ratio.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] When kneading two or more types 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 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. A twin-screw extruder is an extruder equipped with two screws inserted into a cylinder. The cylinder has two circular through-holes that run parallel to each other with portions of their inner wall surfaces overlapping. In a twin-screw extruder, the materials fed into the cylinder can be mixed by rotating the screws inserted into each circular through-hole.

[0003] In a twin-screw extruder, resins are mixed with each other or with powder particles by melting the solid raw materials fed in using the heat from the heater and the heat from the screws and cylinder, and then kneading them using 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 the 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. Also, in an intermeshing twin-screw extruder designed so that the two screws intermesh, the adjacent kneading discs are positioned with their phases shifted, which causes the long diameter part of the kneading disc to scrape off the raw materials adhering near the short diameter part of the other kneading disc, resulting in even more uniform kneading of the raw materials. As mentioned above, the kneading disc exhibits excellent kneading properties when kneading resins together or resins with powder particles, but due to its structure, there are large fluctuations in the pressure applied to the kneaded material, 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 through-holes are formed parallel inside a barrel so that parts of their inner wall surfaces overlap each other. The "contact avoidance section" prevents the tip of the kneading flight from contacting the inner wall surface of the circular through-hole of the barrel, and is formed as an inclined surface by cutting only the tip side of the ridge part diagonally, leaving the base end side of the ridge part. Patent Document 1 discloses in Figure 5 the pressure inside the barrel of a conventional twin-screw extruder in gray scale, and in the extremely high-pressure area shown in black at θ=30°, the problem of so-called "galling" where the kneading flights come into contact with the barrel is addressed by providing a contact avoidance section in the barrel where the peaks are offset diagonally, as disclosed in Figure 2(b) of Patent Document 1, thereby preventing contact between the kneading flights and the barrel, as disclosed in Figure 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 at the point where pressure rises to provide a contact avoidance section, thereby eliminating contact around the contact avoidance section. 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 section, and this contact could not be avoided even by the invention of Patent Document 1. Taking Patent Document 1 as an example, even when a contact avoidance section is provided, as shown at θ=30° in Figure 6, the pressure rises most when the tip of the kneading disc comes closest, and this pressure rise occurs in the direction perpendicular to the axial direction of the screw. Because the screw is connected to the power section with a cantilever structure, this pressure causes the screw to bend, and when viewed from the cross section of the barrel, the screw and 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 at θ=30° in Figure 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), causing problems such as damage to the cylinder, wear of the screw, and mixing of worn metal powder into the kneaded material.

[0006] Furthermore, in Patent Document 1, although the contact avoidance parts arranged above and below can be installed so as to be point symmetrical, the shape is not bilaterally symmetrical. Therefore, when raw materials are flowed from upstream to downstream 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 2(b) described in Patent Document 1, conventional cylinders with a cross-sectional shape like that of Figure 2(a) are symmetrical, and therefore 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 average over the time it takes for the screw to make one revolution, and the same thermal history is applied symmetrically to both the material flowing through the left cylinder and the material flowing through the right cylinder. However, in the case of a cylinder with a cross-sectional shape like that shown in Figure 2(b), the left cylinder at the upper ridge 6 has a wide flow path, while the right cylinder has a narrower flow path. As a result, 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 heating accumulates as the material flows downstream along the screw axis. Similarly, in the case of the lower ridge 6 at the lower right side, 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 achieve uniform kneading by shear while suppressing shear heat to a level that does not cause deterioration of the raw materials. However, if there are temperature variations in the raw materials due to different shear heat on the left and right sides as described above, sufficiently uniform kneading cannot be achieved, or if the screw rotation speed is increased to intensify the kneading, there is a problem that some 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, and this notch ensures 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 bending of the screw, and there remains the possibility that bending of the screw may cause contact between the kneading disc and the cylinder.

[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, which corresponds to the above-mentioned joint, gradually changes its curved shape toward the downstream side in order to prevent resin from accumulating at the tip (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 ensuring an escape route for the resin at the joint or contact with the cylinder due to bending of the screw, taking into account fluctuations in pressure applied to the kneaded material. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-192560 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-236831 [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 raw materials containing thermoplastic resins, can obtain sufficient kneading performance of the raw materials, suppress temperature unevenness, and prevent damage caused by contact between the screw and the cylinder due to 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 each having a kneading disc, 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 connecting portions shaped as if 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 formed by the two circular through holes and the two circular through hole connecting portions in the cross section of the cylinder has 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 the ratio shown in formula (1), 0.65 ≦ d1 / D ≦ 0.95 (1) Furthermore, the ratio of d1 to the distance d2 connecting 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), is. (2) 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 each having a kneading disk, 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 connecting portions shaped such that two peaks where the circular through-holes intersect are cut off with convex curves toward the holes of the cylinder, The hole formed by the two circular through holes and the two circular through hole connecting portions in the cross section of the cylinder has 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 distance d1 between the vertices of the two circular through-hole connection portions in the cross section of the cylinder and the diameter D of the circular through-hole are in the ratio shown in formula (1), 0.65 ≦ d1 / D ≦ 0.95 (1) Furthermore, the ratio of d1 to the distance d2 connecting 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), is. [Effects of the Invention]

[0013] The present invention can provide a twin-screw extruder having a kneading disc, which, when kneading and extruding raw materials containing a thermoplastic resin, can obtain sufficient kneading performance of the raw materials, suppress temperature unevenness, and prevent damage caused by contact between the screw and the cylinder due to bending of the screw. [Brief explanation of the drawings]

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

[0015] Hereinafter, embodiments 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 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 seen from the L-L cross section in Fig. 1 is shown in Fig. 2. As shown in Figs. 1 and 2, 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 below. In the following description, the reference numerals 31a and 31b will be used as necessary to distinguish between the two circular through-holes 31 in the drawings. As shown in Figure 1, the two screws 20 housed in the cylinder 30 are connected to a power section 2 having a motor and a reducer provided 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 into a hopper 4 provided at the top of the extruder 1 and supplied in a fixed amount in the forward spiral direction into a flow path between the screw 20 and the valleys of the cylinder 30, in a downstream direction 81 along the screw axis. The raw material in the hopper 4 is transferred in the downstream direction 81 in a supply section 11 and heated by heat from a 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 a kneading section 12, and the heated and kneaded raw material is pressurized in a metering section 13 to be stably discharged, and then passes through a nozzle provided in a die 6 at the tip of the extruder 1 and extruded as a strand. The melt viscosity of the raw materials during kneading is, for example, 0.01 to 50 g / 10 min in terms of melt flow rate (MFR) [230°C, 2.16 kg load]. The melt flow rate is measured in accordance with JIS K7210.

[0018] The screw 20 has screw elements shaped according 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 disc 22 for kneading shown in Fig. 2 in the kneading section 12. In the following description, the reference numerals 22a and 22b will be used as necessary to distinguish between the two kneading discs 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 its cross-sectional shape is approximately elliptical (rugby ball shape), and its external shape is composed of a convex surface. The kneading disc 22 has a major axis 25 and a minor axis 26, and in the major axis direction of the kneading disc 22, a narrow clearance flow path is formed between the disc 22 and the cylinder 30, and in the minor axis direction of the kneading disc 22, a wide clearance flow path is formed between the disc 22 and the cylinder 30. Therefore, the raw materials sent from the upstream of the twin-screw extruder (extruder 1) are kneaded by being sheared and stretched as the clearance changes with the rotation of the kneading disc 22.

[0020] Furthermore, the extruder 1 of this embodiment is an intermeshing extruder, and has an excellent pumping 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 of two kneading discs 22 (22a, 22b), when the phase of the kneading discs 22 is combined at 90° as shown in Figure 3, the tip 29 on the major axis side of one kneading disc 22 scrapes off the raw material near the minor axis side of the other kneading disc 22, thereby achieving a kneading effect due to a self-cleaning effect.

[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 there is a phase difference of 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 discs 22 in the conventional cylinder 30 of Figure 4 are rotated. In Figure 5, (a) is set as the reference 0°, and the angle θ is shown as the angle at which each kneading disc 22 is rotated in the direction of the arrow. The pressure applied to the raw material in the cylinder 30 shown in Figure 5 is indicated in order of increasing pressure by black, diagonal lines, halftone dots, and white outline. In this specification, the rotation angle θ indicates the angle of clockwise rotation from the reference 0° shown in Figure 5(a), that is, from 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 in the figure is perpendicular to said line. As shown in the black areas in Figures 5(c) and 5(f), when the long diameter side tips 29 of the two kneading discs 22a, 22b come closest to the vertex 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 Figure 1, the screw 20 having the kneading disc 22 has a cantilever structure that is connected to the power unit 2 only at the screw connection part 21, and the kneading disc 22 is located at a distance from the screw connection part 21. Therefore, due to the high pressure of the raw material, the screw 20 bends in the direction indicated by the arrow 90 in Figures 5(c) and (f). If the bending is large, the kneading disc 22 and the cylinder 30 come into contact and wear at the part indicated by the symbol 93 in Figures 5(c) and (f). Therefore, with the conventional cylinder 30, the raw material flow path formed by the kneading disc 22 and the cylinder 30 changes due to wear, making it impossible to achieve the kneading effect originally designed, and there was also the problem that worn metal powder was mixed into the raw material as foreign matter.

[0022] [cylinder] In response to the above-mentioned conventional problems, the present invention provides an extruder 1 (twin-screw extruder) that prevents the screw 20 from being damaged by contact between the screw 20 and the cylinder 30 due to 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 taken along the line LL in Fig. 1. The cylinder 30 has two circular through holes 31a, 31b of the same diameter, each having a circular cross section, formed in parallel such that parts of the inner wall surfaces of the circular through holes 31 overlap each other. Furthermore, the cross section of the cylinder 30 has two circular through hole connecting portions 40, which are shaped to cut out two peaks where the circular through holes 31 of the cylinder 30 intersect, between the two circular through holes 31a, 31b, parallel to a line segment 33 connecting the centers 32 of the circular through holes 31, as shown by reference numeral 41 in Figure 3(b) (hereinafter referred to as "cutout portions 41"). 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 through-hole connection portions 40 at two locations where the circular through-holes 31 overlap, and the vertical distance d1 between the two circular through-hole connection portions 40 and the diameter D of the circular through-holes is, for example, in the ratio shown in equation (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 and 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, 60 mm or more and 80 mm or less, and preferably 65 mm or more and 75 mm or less. The vertical distance d1 between the two circular through-hole connecting portions 40 is, for example, 35 mm or more and 50 mm or less, and preferably 40 mm or more and 45 mm or less. The distance d2 connecting the centers 32 of the two circular through holes 31a and 31b is, for example, 50 mm or more and 75 mm or less, and preferably 55 mm or more and 65 mm or less. The lower limit of d1 / D is preferably 0.7 or more, more preferably 0.75 or more, and the upper limit of d1 / D is preferably 0.9 or less, more preferably 0.85 or less. The lower limit of d1 / d2 is preferably 0.85 or more, more preferably 0.88 or more, and the upper limit of d1 / d2 is preferably 1.05 or less, more preferably 1.00 or less. By setting the value of d1 / D to be equal to or greater than the above-mentioned lower limit, it is possible to ensure the length of the cut-out portion 41 in the vertical direction (d1 direction) in the figure, and to ensure the space for the cut-out portion 41. As a result, even under the condition where the major diameter side tips 29 of the two kneading discs 22a, 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)), and vibration of the screw 20 due to large pressure fluctuations in the screw 20 is suppressed, and bending of the screw 20 supporting the kneading discs 22 is suppressed. Furthermore, by setting d1 / D within the above-mentioned lower and upper limit numerical ranges and 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. Furthermore, by setting d1 / D within the above-mentioned lower and upper limits and d1 / d2 equal to or less than the upper limit of the above-mentioned range, a sufficient kneading effect can be similarly obtained, and compression of the raw material can be suppressed, thereby suppressing bending of the screw 20. 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 its 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 so that they are out of phase with each other and rotate at the same speed, so that the material fed into the extruder 1 is kneaded by changes in the major axis 25 and minor axis 26 of the kneading disc 22 while passing through a clearance formed between the kneading disc 22 and the cylinder 30 formed by the circular through-hole 31 and the circular through-hole connecting portion 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 radius in the major axis direction and the radius in the minor axis direction of the kneading disc 22, but is smaller than twice the radius in the major axis direction of the kneading disc 22. By using an intermeshing twin-screw extruder, it is possible to obtain a strong kneading action and a pumping action that sends the raw material downstream in the kneading disc 22 of the kneading section 12.

[0027] [Operation and effect of the first embodiment] Hereinafter, the effects 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 at which the kneading disc 22 is rotated in the direction of the arrow is shown as θ, and the pressures applied to the raw material in the cylinder 30 are shown in descending order of pressure by solid black, diagonal lines, halftone dots, and white outline, as in Fig. 5. The kneading discs 22 in the kneading section 12 of the intermeshing twin-screw extruder knead the raw materials by changing the clearance between the cylinder 30 and the kneading discs 22 as the kneading discs 22 rotate. Also, as shown in Figures 6(a) and 6(e), when the long-diameter side tip 29 of one of the two kneading discs 22a and 22b comes closest to the other kneading disc 22 in the short-diameter direction, a self-cleaning effect is achieved in which the long-diameter side tip 29 scrapes off the raw materials on the short-diameter side of the other kneading disc 22, and kneading is promoted.

[0028] On the other hand, the cylinder 30 of the extruder 1 of the present invention has circular through-hole connecting portions 40 between the circular through-holes 31, which are cut out parallel to the line segment connecting the centers of the circular through-holes 31. The shape of the circular through-hole connecting portions 40, in other words, the shape of the cutout portions 41 determined by d1 / D in the above-mentioned formula (1) and d1 / d2 in the formula (2), ensures a wide clearance between the two kneading discs 22a, 22b and the cylinder 30 even when the long-diameter side tips 29 of the two kneading discs 22a, 22b are closest to each other, as shown in Figures 6(c) and 6(f). Furthermore, the raw material flows into the adjacent circular through-hole 31 along the parallel circular through-hole connecting portions 40, so that the blackened areas of high raw material pressure seen in Figures 5(c) and 5(f) for 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 worn metal powder getting mixed into the kneaded material.

[0029] Furthermore, as shown by the diagonal lines and dots in Figures 6(a) to (f), an increase in the pressure of the raw material to the extent that it does not bend the screw 20 occurs at the point where the clearance is compressed as the kneading disc 22 rotates at the long diameter end 29 of the kneading disc 22 and the circular through hole 31 of the cylinder 30. However, when observing the change in the pressure during one rotation of the screw 20, the pressure occurs over the entire wall surface of the circular through hole 31, so the screw 20 does not bend due to a localized increase in pressure. As a result, the cylinder 30 is not damaged or the screw 20 is not worn, and kneading can be performed without 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 formula (2) are outside the above ranges, the kneading property will decrease and the effect of the self-cleaning property (kneading disc 22) of scraping off the raw material will deteriorate.

[0030] Furthermore, the holes consisting of the two circular through-holes 31 and the circular through-hole connecting portions 40 in the cross section of the cylinder 30 have a shape that is symmetrical on both sides of the symmetrical center line 34 shown in Figure 3, so the thermal history of shear heat applied to the raw material passing through the two left and right cylinders 30 is the same on both sides, making it possible to suppress temperature unevenness in the cylinders 30 and when the raw material is discharged.

[0031] [Cylinder of the second embodiment] Next, the cross-sectional shape of the cylinder 30 of the extruder 1 (twin-screw extruder) according to the second embodiment of the present invention is shown in Fig. 7. Fig. 7 shows a cross-sectional view taken along the line LL in Fig. 1 . Cylinder 30 has two circular through holes 31a, 31b of the same diameter, each having a circular cross section, formed in parallel such that parts of the inner wall surfaces of circular through holes 31 overlap each other. Furthermore, in the cross section of cylinder 30, between two circular through holes 31a, 31b, two circular through hole connecting parts 50 are provided, which are shaped to cut out two peaks where circular through holes 31 of cylinder 30 intersect, with convex curves toward the hole of cylinder 30, as shown by reference numeral 51 in Figure 7(b) (hereinafter referred to as "cutout parts 51"). As shown in Figure 7(a), the perpendicular line passing through the midpoint of the line segment 33 connecting the centers 32 of the two circular through holes 31a, 31b is set as the symmetrical center line 34, and the convex curves of the two circular through hole connection portions 50 form curves that are symmetrical on both sides of the symmetrical center line 34. As a result, the hole consisting of the two circular through holes 31a, 31b and the two circular through hole connecting portions 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 through hole connecting portions 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 through-hole connection portions 50 at two locations where the circular through-holes 31 overlap, and the distance d1 between the vertices 52 of the two circular through-hole connection portions 50 in the cross section of the cylinder 30 and the diameter D of the circular through-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 and 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, 60 mm or more and 80 mm or less, and preferably 65 mm or more and 75 mm or less. The vertical distance d1 between the two circular through-hole connecting portions 50 is, for example, 35 mm or more and 50 mm or less, and preferably 40 mm or more and 45 mm or less. The distance d2 connecting the centers 32 of the two circular through holes 31a and 31b is, for example, 50 mm or more and 75 mm or less, and preferably 55 mm or more and 65 mm or less. The lower limit of d1 / D is preferably 0.7 or more, more preferably 0.75 or more, and the upper limit of d1 / D is preferably 0.9 or less, more preferably 0.85 or less. The lower limit of d1 / d2 is preferably 0.85 or more, more preferably 0.88 or more, and the upper limit of d1 / d2 is preferably 1.05 or less, more preferably 1.00 or less.

[0033] The preferable shape of the convex curve of the circular through-hole connecting portion 50 can be determined 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 for 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 above lower limit, it is possible to ensure the length of the cut-out portion 51 in the vertical direction (d1 direction) in the figure, and to ensure the space for the cut-out portion 51. As a result, even under the condition where the major diameter side tips 29 of the two kneading discs 22a, 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)), and vibration of the screw 20 due to large pressure fluctuations in the screw 20 is suppressed, and bending of the screw 20 supporting the kneading discs 22 is suppressed. Furthermore, by setting d1 / D within the above-mentioned lower and upper limit numerical ranges and 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. Furthermore, by setting d1 / D within the above-mentioned lower and upper limits and d1 / d2 equal to or less than the upper limit of the above-mentioned range, a sufficient kneading effect can be similarly obtained, and compression of the raw material can be suppressed, thereby suppressing bending of the screw 20. 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 Figures 8(c) and 8(f) described later), a 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 through-hole connecting part 50 to the adjacent circular through-hole 31. Furthermore, by setting the upper limit of R / D within the above range, the raw material is appropriately compressed at that location and can be prevented from accumulating at that location.

[0037] FIG. 11 is an enlarged view of region A in FIG. 7(b). However, FIG. 11 shows the state in which the rotation angle θ of the kneading disc 22 is 45° (the state in FIG. 8(c) described later), in which the raw material is most compressed. With reference to this figure, the escape route of the raw material when the long-diameter side tips 29 of the two kneading discs 22a, 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 this line 75 intersects with the cylinder 30 (circular through hole 31) is designated as point 72. In a state in which no cutout portion 51 is provided (a 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 designated as point 71. When the distance between the center 29 and point 71 is db (hereinafter also referred to as the "reference clearance distance") and the distance between the 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, more preferably 3.0 or more, and the upper limit of dα / db is preferably 15 or less, 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 the cylinder 30 of the second embodiment has two kneading discs 22a and 22b shown in Figure 7(c) as screw elements in the kneading section 12 of the screw 20 similar to that of the first embodiment, and the kneading disc 22 is a screw element formed so that its 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.

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

[0040] [Operation and effect of the second embodiment] The effects of the second embodiment of the present invention will be described below 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. The pressures applied to the raw material in the cylinder 30 are indicated in descending order of pressure by solid black, diagonal lines, halftone dots, and white outline, as in Figs. 5 and 6.

[0041] The cylinder 30 of the second embodiment has the same 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, there is a wide clearance between the two kneading discs 22a, 22b and the cylinder 30, and the raw material flows to the adjacent circular through hole 31 along the circular through-hole connection part 50 that is arranged in parallel, so no blackened areas with high raw material pressure are 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 worn metal powder getting mixed into the kneaded material.

[0042] Furthermore, as in the first embodiment, as shown by the diagonal lines and dots in Figures 8(a) to (f), an increase in the pressure of the raw material to the extent that it does not bend the screw 20 occurs at the point where the clearance is compressed as the kneading disc 22 rotates at the long diameter side tip 29 of the kneading disc 22 and the circular through hole 31 of the cylinder 30. 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 increase in pressure. As a result, the cylinder 30 is not damaged or the screw 20 is not worn, and kneading can be performed without 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, which has the same diameter D of the circular through hole 31 and the same distance d2 between the centers of the circular through holes 31, and which also has the same distance d1 of the circular through hole connecting portion 50, the clearance through which the raw material flows around the convex curve formed by the circular through hole connecting portion 50 is wider than in the first embodiment, so that pressure increases 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 holes consisting of the two circular through-holes 31 and the circular through-hole connection parts 50 in the cross section of the cylinder 30 have a shape that is symmetrical on both sides of the symmetrical center line 34 shown in Figure 7, so the thermal history of shear heat applied to the raw material passing through the two left and right cylinders 30 is the same on both sides, and temperature unevenness of the raw material inside the cylinder 30 and when it is discharged can be suppressed.

[0045] [Variations] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may also be adopted. Modified 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 Figs. 9 and 12. Fig. 9 is a cross-sectional view of the modified extruder 1 (twin-screw extruder). Fig. 12 is an enlarged view of region B in Fig. 9.

[0047] As shown in FIG. 9, the connection between the two circular through-holes 31a, 31b of the cylinder 30 and the circular through-hole connecting portion 40 may be formed as a curved portion 45 where the circular through-holes 31a, 31b and the linear circular through-hole connecting portion 40 are connected, from the viewpoint of preventing the raw material from burning at the corners. In this case, it is preferable to perform the rounding so that the connection is symmetrical with respect to the symmetry center line 34. From another perspective, as shown in FIG. 12, this modified example can be said to have a shape in which the tip portion 155 of the convex curve of the circular through-hole connecting portion 50 in FIG. 7, which is provided at the intersection of the two circular through-holes 31a, 31b in the second embodiment, is cut off. The circular through-hole connecting portion 150 (40) has a flat portion 151 formed linearly and perpendicular to the symmetry center line 34, and curved portions 152 formed at both ends of the flat portion 151. The circular through-hole connecting 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, may be in the above-mentioned ratio relationship with the vertical distance d1 of the circular through-hole connection portion 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 through holes 31 of the cylinder 30 only needs to have the above-mentioned ratio relationship with the vertical distance d1 of the circular through hole connecting 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 of the same diameter along the screw axis, but it is sufficient that the cross-sectional shape of the cylinder 30 in contact with the kneading disc 22 has a shape disclosed in the embodiments and modifications, and the cross-sectional shape of the cylinder 30 in other parts can have 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 surfaces of the circular through-holes can be processed, for example, by providing slits, 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 raw materials from hopper 4 are introduced into cylinder 30, or with a vertical hole for attaching vacuum pump 91 that removes volatile components from the molten raw materials. The holes can be arbitrarily provided depending on the properties of the raw materials.

[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 as desired.

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

[0053] The kneading disc 22 may be a kneading screw element having a cross-sectional shape formed of a convex curved surface with a major axis 25 and a minor axis 26, but from the viewpoint of improving kneading and self-cleaning function, the major axis side tip 29 may be formed as a curved surface or a flat surface having a certain width, as shown in Fig. 3(c). From the viewpoint of pressure increase when approaching the circular through-hole connecting 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 side tip 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 this diameter D is large, the clearance is also set large. Note that this clearance corresponds to the "reference clearance distance db" in the second embodiment.

[0055] In order to suppress local pressure increases by maintaining pressure fluctuations of the raw materials at regular 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 through hole 31 disclosed in Figure 3(b) are all at the same position.However, for purposes such as further improving 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 provided in the extruder 1, which is a twin-screw extruder, is only 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 in the supply section 11, kneading section 12, and metering section 13 regions, and the functions of the regions into which each of the above sections is further subdivided. The phase of adjacent screw elements including the kneading disc 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 twin-screw extruder 1 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 discs 22a and 22b shown in Figures 6(c) and 6(f) that have a high pressure distribution, so the extruder 1 can also be suitably used when operating in opposite directions.

[0058] By configuring the extruder 1 as a twin-screw extruder as described above, when kneading and extruding a raw material containing a thermoplastic resin that has high viscoelasticity when melted and is prone to deterioration due to shear heat, the extruder 1 has high kneading performance and does not cause damage due to contact between the screw 20 and the cylinder 30 caused by bending of the screw 20. In particular, the extruder 1 can be suitably used even in applications where fine particles are kneaded with a thermoplastic resin, in which the pressure of the raw material is likely to increase during kneading, because bending of the screw 20 does not occur even when the pressure increases. [Example]

[0059] The present invention will be described in more detail below with reference to examples. The following examples are provided to better illustrate the present invention, but are not intended to limit the present invention. Note that "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) Figure 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 screw structure in each cylinder. Cylinders C1 to C8 are mounted in this order from the left side of the figure. The left side of the figure is upstream, and the right side is downstream. Cylinder C1 is the 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, cylinders (standard cylinders) with a conventional cross-sectional structure as shown in Figure 4 were 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 convexly curved circular through-hole connecting portion 50 as 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 the two circular through-hole connections D: Cylinder diameter (circular through 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 for the measurements were as follows: The raw materials in the following composition were dry blended and then fed into the hopper of the extruder using 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 feed 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 test samples in the shape of pellets measuring 3φ x 3mm in length. [Table 1]

[0064] The measurement results are shown in Tables 2 to 4. Table 2 shows the indicated temperatures of each cylinder while the extruder was in operation. Table 3 shows the vibration displacement (μm) while 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 midpoint of each block cylinder, and the average value was calculated.

[0065] The physical properties of the test sample were measured as follows. The physical properties (1) to (8) below were measured. For (1), the physical properties of the obtained test specimens were measured. For the physical property measurements (2) to (8), 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) at an injection molding temperature of 240°C and a mold temperature of 40°C according to the standard, 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 the test sample 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 strength at break was measured at 23°C in accordance with JIS K7161. (5) The bending strength was measured at 23°C in accordance with JIS K7171. (6) The 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) From the vibration displacement data, 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 between the cylinder and screw were confirmed in the first kneading zone. On the other hand, in 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 kneading was sufficient.

[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 screws 21 Screw connection 22, 22a, 22b Kneading disc 25 Long diameter of kneading disc 26 Minor diameter of kneading disc 29 Long diameter end of kneading disc 30 cylinders 31 Circular through hole 32 Center of circular through hole 33 Line segment connecting the centers of circular holes 34 Symmetry centerline 40, 50 circular through-hole connection 41 Cut-out portion in the first embodiment 45 Curved surface in modified form 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 the cylinder in the 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 each having a kneading disc, wherein the two screws rotate at the same rotation speed; the twin-screw extruder is an intermeshing extruder, The cylinder has, in its cross section, two circular through-hole connecting portions shaped as if two mountain portions where the circular through-holes intersect are cut parallel to a line segment connecting the centers of the circular through-holes, a hole formed by the two circular through holes and the two circular through hole connecting portions in a cross section of the cylinder has a shape that is symmetrical with respect to a perpendicular line passing through a 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 portions and the diameter D of the circular through-hole are in the ratio shown in formula (1), 0.65≦d1 / D≦0.95...(1) Furthermore, the ratio of d1 to the distance d2 connecting 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 each having a kneading disc, wherein the two screws rotate at the same rotation speed; the twin-screw extruder is an intermeshing extruder, The cylinder has, in its cross section, two circular through-hole connecting portions shaped such that two peaks where the circular through-holes intersect are cut off by curves that are convex toward the holes of the cylinder, a hole formed by the two circular through holes and the two circular through hole connecting portions in a cross section of the cylinder has a shape that is symmetrical with respect to a perpendicular line passing through a 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 portions in the cross section of the cylinder to the diameter D of the circular through-hole is expressed by the following formula (1), 0.65≦d1 / D≦0.95...(1) Furthermore, the ratio of d1 to the distance d2 connecting 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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