Die set and extruder

Abstract

To provide a die set and an extruder which, when kneading and extruding a raw material containing a thermoplastic resin, suppress discoloration of the raw material and a decrease in molecular weight of the thermoplastic resin, stabilize discharge, and facilitate cleaning of a material adhering to the die.SOLUTION: There is provided a die set including a fitting die and a die flange, the die set being configured such that: a side surface of the fitting die has a cylindrical first fitting portion and a cylindrical second fitting portion having a diameter larger than that of the first fitting portion; the fitting die has, at a bottom of the second fitting portion, a breaker plate mounting hole, and a raw material flow path consisting of a raw material constriction portion having an inlet that is a circle with a diameter smaller than that of the breaker plate mounting hole, and a cylindrical nozzle portion; the fitting die has an annular fitting plane that is a plane perpendicular to a raw material inflow direction, and an annular mounting plane that is a plane perpendicular to the raw material inflow direction at a step between the breaker plate mounting hole and the inlet; and the die flange has a fitting hole for the fitting die and a die fastening portion for fastening with an extruder.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a die set used in an extruder for kneading a resin, and to an extruder. [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. In such extruder kneading, the heated and melted raw materials are thoroughly kneaded in the screw inside the extruder, coarse particles are removed using a screen inside a breaker plate installed downstream of the extruder, and thread-like strands are discharged from a die, and the cooled strands are then cut to obtain pellets. In mass-production processes for producing pellets by kneading using an extruder, the aforementioned heating and melting process is operated continuously for long periods of time. Therefore, the surfaces of the screws and dies that come into contact with the kneaded material can become coated with discoloration, a deterioration product of resins that have a high affinity for metal, and powder particles such as pigments. For this reason, when mixing a new product with a different formulation after a long period of operation, cleaning work is required, such as scrubbing the metal surfaces of the screws and dies with a brush to remove the adhered components, or placing these parts in a high-temperature bath to burn off the adhered components. However, because kneading using an extruder is performed under high pressures of several MPa to several tens of MPa, the dies and other components are heavy, made of thick metal to withstand the high pressure. Disassembling the parts for cleaning, as well as the need to lift and disassemble the dies with a chain block, requires a lot of time and effort.

[0003] Patent Document 1 proposes an extruder strand die in which a replaceable nozzle piece is screwed onto the die plate in order to reduce the occurrence of eye discharge caused by damage to the nozzle hole or the edge of its outlet, which occurs when the resin raw material contains components that are corrosive to metals or abrasive. However, when the invention of Patent Document 1 is viewed from the perspective of disassembly and cleaning after the aforementioned long-term operation, the screws seize due to the resin temperature and prolonged heating caused by friction between the metal and resin in the narrow flow passages, requiring a great deal of effort to remove them, and particularly when there are multiple nozzle holes, it is necessary to remove the screws from each hole, which requires a great deal of effort. Also, as shown in Figure 2 of Patent Document 1, a seam forms in the gap between the flow passages of the die plate and the nozzle piece, causing resin to accumulate at the seam and resulting in resin burn. Furthermore, when the screws are replaced multiple times, the end faces of the flow passages in the die plate are pressed by the screws, damaging some of the screw attachment points. As a result, the resin flow fluctuates, the strand flow becomes unstable, and the strand breaks before cooling. Furthermore, as disclosed in FIG. 2 of Patent Document 1, a throttle member is provided in the resin flow path, and after the resin is compressed and released, it is further compressed by the nozzle piece, which causes the problem of resin deterioration due to heat generated by compression and release.In addition, because parts other than the nozzle piece are also fastened with screws, it is necessary to remove each screw when disassembling and cleaning the extruder strand die, which is labor-intensive.

[0004] Furthermore, Patent Documents 2 and 3 propose providing each nozzle hole with a protruding nozzle or discharge nozzle that tapers toward the nozzle tip so that eye gunk that accumulates on the outside of the nozzle tip can be removed by air. Patent Document 2 describes fitting the protruding nozzle into a hole in the air blowing device, and Patent Document 3 describes that the nozzle has a discharge nozzle. While Patent Documents 2 and 3 do not specifically describe the fitting, when the drawings disclosed in Patent Documents 2 and 3 are applied from the perspective of cleaning after long-term operation, the protruding nozzles and discharge nozzles have a wedge-shaped outer surface that is pressed down by resin pressure from upstream, making the outer surface vulnerable to damage caused by the resin pressure. The resulting deformation of the nozzles causes fluctuations in the resin flow, and if there are multiple discharge holes, it is necessary to remove each nozzle one by one to clean them. Furthermore, both the protruding nozzles in Patent Document 2 and the discharge nozzles in Patent Document 3 require the provision of a narrow nozzle with a certain length of flow path to withstand the resin pressure. However, the resin is rapidly compressed at the entrance to each nozzle hole, and the compression and the heat generated by the resin in the narrow nozzles cause problems such as discoloration due to resin degradation and instability of the strand due to a decrease in molecular weight.

[0005] Furthermore, although not a strand molding, Patent Document 4 discloses a method for extruding a ribbon-shaped molding, in which a bushing 2 as shown in FIG. 8 and an extrusion die 4 made of a wear-resistant material are held down by an outer tubular body 1 and a cylindrical body 8, as shown in FIG. 1. However, the invention of Patent Document 4 aims to be able to replace the extrusion channel even if the cross section of the extrusion channel suddenly changes, and from the viewpoint of cleaning, when removing the bushing or extrusion die, a very large torque is required to loosen the screws of the large structure such as the cylindrical body 8, which is labor-intensive, and there is also the problem that the screws may become seized due to heating.

[0006] Patent Document 5, like Patent Document 4, is an invention for a molding machine for extruding flat rubber. The invention kneads rubber inside a C-shaped die hole for escalator handrails by providing multiple protrusions in the die hole. However, Figure 3 of Patent Document 5 discloses a structure in which the nip holder 6, which holds the die 8, is inserted into the head body 5 to secure the nip holder 6 and nipple 7. However, because this structure kneads rubber using the protrusions in the die hole, providing protrusions in the die hole for creating strands can cause heat generation due to sudden friction of the resin in the flow path of the narrow protrusions, resulting in unstable strand discharge and discoloration of the extruded resin due to deterioration. Furthermore, the structure illustrated in Patent Document 5 requires a means for fastening the nip holder 6 to the head body 5 to resist resin pressure, but the specific fastening method is not described. For example, if a screw is fastened perpendicular to the resin flow to fasten the head body 5 and nipple holder 6, problems such as the screw bending due to high resin pressure can occur.

[0007] Patent Document 6 discloses an invention relating to a crosshead for a device for manufacturing plastic-insulated core wires, in which conductors such as cables are covered with plastic. This device is a crosshead that bends the flow of plastic extruded from the screw shown in the upper part of Fig. 1 at a right angle to coat the conductor with plastic, and describes that the nipple holder at the tip of the crosshead is separated into individual parts to improve processing accuracy so that the electric wire can be coated with a uniform thickness without adjustment, and that the extrusion die 22 is held down by a die fixing cap 29, and the die fixing cap is fixed to the sleeve 8 with a screw 30. However, while the above structure is effective when discharging small amounts of plastic, such as for cable covering, as shown by the raw material flow path between the extrusion nipple 18 and the die 22, when applied to the tip of an extruder that extrudes large amounts of resin, such as a die for creating strands, the threads cannot withstand the pressure of the resin, causing the die fixing cap 29 and the extrusion die 22 to shift downstream in the direction of resin flow, resulting in resin leakage. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-52403 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-136579 [Patent Document 3] WO2010 / 140310 publication [Patent Document 4] Special Publication No. 2005-516795 [Patent Document 5] Japanese Utility Model Application Publication No. 63-068420 [Patent Document 6] Japanese Patent Application Publication No. 56-9910 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a die set and an extruder which, when kneading and extruding raw materials containing a thermoplastic resin, suppress discoloration due to deterioration of the kneaded raw materials and a decrease in the molecular weight of the thermoplastic resin, enable stable extrusion of strands, and facilitate cleaning of material adhering to the die. [Means for solving the problem]

[0010] The present inventors have found that the above object can be achieved by forming a die set in which a mating die and a die flange are mated, as described below, and have thus completed the present invention.

[0011] That is, the present invention is (1) A die set provided in an extruder for extruding a thermoplastic resin composition into a strand shape, the die set being configured by fitting a fitting die and a die flange together, the side surface of the fitting die having a cylindrical first fitting portion and a cylindrical second fitting portion having a diameter larger than that of the first fitting portion, the inside of the fitting die having a breaker plate mounting hole at the bottom of the second fitting portion, and a raw material flow path consisting of a raw material constriction portion and a cylindrical nozzle portion, the raw material flow path having a circle as an inlet having a diameter smaller than that of the breaker plate mounting hole. the fitting die has an annular fitting plane which is a plane perpendicular to the raw material inflow direction at a step between side surfaces of a first fitting portion and a second fitting portion, and an annular mounting plane which is a plane perpendicular to the raw material inflow direction at a step between the breaker plate mounting hole and the inlet; the die flange has a fitting hole and an annular plane which mate with the first fitting portion, the second fitting portion, and the fitting plane of the fitting die; and the die flange has a die fastening portion which fastens to an extruder. (2) The die set according to (1), wherein the die set has, on its side surface between the first fitting portion and the second fitting portion, one or more additional fitting portions having a cylindrical side surface with a diameter intermediate between the diameters of the first fitting portion and the second fitting portion, and the die flange has one or more additional fitting holes that fit with the additional fitting portion of the fitting die; (3) An extruder equipped with the die set according to (1) or (2) and a breaker plate; It is related to. [Effects of the Invention]

[0012] According to the present invention, when raw materials containing a thermoplastic resin are kneaded and extruded, discoloration due to deterioration of the kneaded raw materials and a decrease in molecular weight of the thermoplastic resin are suppressed, discharge can be stably performed to extrude strands, and deposits on the die can be easily cleaned. [Brief explanation of the drawings]

[0013] [Figure 1] Cross-section of the extruder [Figure 2] Schematic diagram showing an example of the process for creating strands [Figure 3] 1 is an assembly diagram of a die set and a breaker plate according to a first embodiment of the present invention. [Figure 4] A diagram of the die set and the downstream side of the extruder according to the first embodiment of the present invention. [Figure 5] FIG. 1 is a diagram of a fitting die included in a die set according to a first embodiment of the present invention. [Figure 6] FIG. 1 is a diagram showing a die flange of a die set according to a first embodiment of the present invention; [Figure 7] Breaker plate diagram [Figure 8] FIG. 2 is a diagram showing the die set and the downstream side of the extruder according to the second embodiment of the present invention. [Figure 9] A diagram of a die set and the downstream side of an extruder according to a modified example of the present invention. [Figure 10] 10 is a diagram showing chamfering and R-machining in a die set according to a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Furthermore, in this specification, the expression "a to b" in the description of a range of values means not less than a and not more than b, unless otherwise specified.

[0015] <Extruder> FIG. 1 shows a cross-sectional view of an extruder for extruding a thermoplastic resin composition in the form of strands, and FIG. 2 shows a schematic diagram of an example of a process for forming strands using an extruder. FIG. 4-(a) is a plan view showing the extruder and die set of the present invention connected together. As shown in Figure 1, extruder 1 has a hollow cylinder 2 and a screw 3 housed within the cylinder. Rotational power from a motor and a reducer provided in the extruder is transmitted to the screw 3, which is connected to the reducer, causing the screw to rotate. Screw 3 transports raw materials (hereinafter also referred to as "raw materials") containing mixed thermoplastic resins supplied from raw material inlet 4 downstream 90 in the screw axial direction while supplying a fixed amount of the raw materials (hereinafter also referred to as "raw materials"), which are supplied in the forward spiral direction, into a flow path between the heated cylinder 2 and the roots of the screw 3. As the raw materials are transported downstream, they are heated by heat from a heater 5 wrapped around the cylinder and by shear heat between the raw materials and the cylinder and between the raw materials and the screw. This melts the thermoplastic resin (hereinafter also referred to as "resin") in the raw materials, plasticizing the raw materials and kneading them as they move. The raw materials heated and kneaded by the screw are further passed through a breaker plate 6 equipped with a screen, which is installed downstream of the extruder, to remove coarse particles and foreign matter that may have been mixed in when the raw materials were added. As shown in Figure 4-(a), the raw materials are then extruded as strands through a nozzle part installed in a die set 9, which is fastened to a cylinder end flange 8 installed downstream of the extruder. As shown in FIG. 2, the extruded strand is cooled in a cooling facility such as a cooling water tank 11, and then taken up by a take-up roll 13 attached to a strand cutter 12 while being cut to a predetermined length by a cutter 14, thereby producing pellets.

[0016] In the mass production process for producing pellets by kneading using an extruder, the kneading by heating and melting is operated continuously for a long period of time, so that the surfaces of the screw and die that come into contact with the kneaded material become coated with discoloration, which is a deterioration product of resin that has a high affinity for metal, and powder particles such as pigments. For this reason, when mixing using an extruder after a long period of operation and before mixing the next product with a different composition, cleaning work is carried out, such as scrubbing the metal surfaces of the screw and die with a brush to remove the adhering components, or placing these parts in a high-temperature bath to burn off the adhering components. In addition, during the cleaning work, the screen installed in the breaker plate is replaced to remove foreign matter trapped in the screen.

[0017] The strands produced by the extruder are extruded in a molten state, cooled and solidified, and then taken up and cut by a strand cutter. If the discharge of the raw material at the die set is unstable, the strand may break at the molten section, or the diameter of the strand may change due to instability in the take-up tension of the strand cutter, preventing uniform cutting and resulting in variations in the size of the pellets after cutting. Therefore, it is required that the strands be discharged stably and at a constant rate from the die set of the extruder.

[0018] The die set and extruder having the die set of the present invention have the structure described below, and by fastening the die set to the cylinder tip flange of the extruder, when raw materials containing a thermoplastic resin are kneaded and extruded, discoloration due to deterioration of the kneaded raw materials and a decrease in molecular weight of the thermoplastic resin are suppressed, strands can be stably extruded at a constant discharge rate, and material adhering to the die can be easily cleaned.

[0019] [Die set in the first embodiment] A schematic diagram of the assembly of the die set and breaker plate of the first embodiment is shown in Fig. 3, and a diagram of the die set attached to the extruder is shown in Fig. 4. In Fig. 4, (a) is a plan view, (b) is a right side view, and (c) is a cross-sectional view taken along the line L-L' shown in (b). Each part of the dice set will be explained below.

[0020] <Dice set> The die set of the present invention is constructed by fitting a fitting die 21 and a die flange 41 as shown in FIG. As shown in Figure 4-(a), the die set 9 is constructed by fitting a fitting die 21 and a die flange 41 together. After fitting the fitting die 21 and the die flange 41 together, a breaker plate 6 is inserted into a breaker plate mounting hole of the fitting die, which will be described later, and then the cylinder tip flange 8 provided at the tip of the extruder and the die flange 41 are fastened together with fastening bolts 78 so that the fastening force is uniform on both sides.

[0021] <Fitting dies> The fitting dies of the die set of the first embodiment are shown in Fig. 5. In Fig. 5, (a) is a plan view, (b) is a left side view, (c) is a cross-sectional view taken along line L-L' in (b), and (d) is a right side view. As shown in FIG. 5, the fitting die of the die set of the present invention has a first fitting portion 22 with a cylindrical side surface and a second fitting portion 23 with a cylindrical side surface and a larger diameter than the first fitting portion. As shown in Figure 5-(c), the inside of the fitting die has a breaker plate mounting hole 24 for fitting a breaker plate into the bottom of the second fitting part as seen from the right side, and a raw material flow path 27 consisting of a raw material constriction part 25 with an inlet 31 that is a circle with a smaller diameter than the breaker plate mounting hole, and a cylindrical nozzle part 26. The fitting die also has an annular fitting plane 28 at the step between the side surfaces of the first fitting portion and the second fitting portion, and an annular mounting plane 29 between the breaker plate mounting hole 24 and the inlet, and the fitting plane and the mounting plane are planes perpendicular to the raw material inflow direction 92.

[0022] As shown in FIG. 4, the depth of the breaker plate mounting hole 24 in the first embodiment is set to be smaller than the height at which the breaker plate 6 attached to the extruder protrudes from the cylinder tip flange 8 of the extruder. This provides a space between the fitting die 21 and the cylinder tip flange 8, allowing an equal clamping force to be applied between the die flange, breaker plate, and cylinder tip flange when the die set described below is fastened.

[0023] An example of a breaker plate provided in an extruder is shown in Figure 7. In Figure 7, (a) is a left side view in the direction in contact with the extruder, (b) is a front view, and (c) is a right side view in contact with the breaker plate mounting hole of the fitting die. As shown in Figure 7, the breaker plate is a cylindrical metal object that has an attachment section 61 for attaching a circular mesh screen on the side where the raw material flows in and a circular flat surface 62 on the side where the raw material flows out, and the raw material that passes through the screen passes through multiple through holes 63 provided in the breaker plate and is discharged.

[0024] As shown in the cross-sectional view of Figure 4-(c), the fitting die has an inlet in the raw material flow path 27 that is circular in shape with a diameter that can include all of the through holes in the breaker plate, allowing all of the raw material that passes through the through holes to flow into the raw material flow path 27. Furthermore, as shown in the cross-sectional view of Figure 5-(c), the raw material flow path 27 integrally comprises a raw material constriction section 25, the flow path of which narrows toward the downstream side, and a plurality of cylindrical nozzle sections 26, each with an even narrower flow path, which are provided to form the resin into strands.The raw material flow path 27 integrally penetrates the raw material constriction section and nozzle sections from the bottom to the tip of the fitting die, so that the raw material that passes through the through holes in the breaker plate can be discharged and formed as cylindrical strands. The raw material constricting section 25 of the fitting die is arranged so that the raw material flow path narrows in the thickness direction as the raw material flows, as shown in the cross-sectional view of Fig. 5-(c). Note that, as shown in the plan view of Fig. 5-(a), the raw material constricting section is arranged in a shape that is flat in the width direction in order to connect with multiple nozzle sections.

[0025] As shown in Figures 5-(c) and 5-(b), the nozzle section in the die set of the first embodiment branches into multiple sections from the tip of the raw material constriction section, and the holes are arranged in two rows as shown in Figure 5-(d) so that strands are discharged from the multiple nozzle sections. In this embodiment, the nozzle portion is arranged to face downward with respect to the raw material inflow direction 92, as shown in the cross-sectional view of Figure 5-(c), so that the strand can be stably supplied to the cooling water tank illustrated in Figure 2. Furthermore, a convex portion is provided on a plane 30 adjacent to the first fitting portion of the fitting die, where the discharge outlet of the nozzle portion is provided, so that the discharge outlet of the nozzle portion arranged to face downward is aligned with the direction of the nozzle portion.

[0026] <Die flange> A diagram of the die flange of the die set of the first embodiment is shown in Fig. 6. In Fig. 6, (a) is a plan view, (b) is a left side view, (c) is a cross-sectional view taken along the line L-L' in (b), and (d) is a right side view. As shown in FIG. 6, the die flange of the die set of the first embodiment has a first fitting hole 42 cut out in a cylindrical shape at the center of the die flange on the downstream side of the raw material so as to fit with the side surface of the first fitting portion of the fitting die, and a second fitting hole 43 cut out in a cylindrical shape and having a larger diameter than the first fitting hole so as to fit with the second fitting hole of the fitting die, and the first fitting hole and the second fitting hole pass through the die flange. The die flange has an annular flat surface 44 perpendicular to the raw material inflow direction 92 between the first and second fitting holes, which contacts the fitting flat surface of the fitting die when fitted. The depth of the second fitting hole is set to the same height as the height of the second fitting portion of the fitting die, taking into consideration fitting tolerances and the thermal expansion coefficient of the material. In addition, the depth of the first mating hole in the first embodiment is the same height as the height of the first mating portion of the mating die, taking into account the mating tolerance and the thermal expansion coefficient of the material.

[0027] The die flange also has a bolt fastening portion 45 shown in Fig. 6-(d). As shown in Fig. 4, the bolt fastening portion 45 in the first embodiment is a bolt fastening portion in which a notch is provided in the flat surface of the die flange so that the die flange is fastened with an eyebolt, which is a fastening bolt 78 provided on the cylinder tip flange 8 of the extruder, and a nut.

[0028] Furthermore, the die flange in the first embodiment has a heater insertion hole 46 as shown in FIG. 6. As shown in FIG. 4, a cartridge heater 81 is inserted into the heater insertion hole and fixed with a bolt through a heater fixing screw provided in the heater fixing hole provided in the die flange. This also heats the fitting die that fits with the die flange, thereby preventing solidification of the raw material in the raw material flow path of the fitting die.

[0029] [Function and effect of the die set in the first embodiment] The effects of the die set of the first embodiment will be described below with reference to FIGS. 5 and 6, the die set described in the first embodiment is configured such that the annular mating plane 28 of the mating die, which is perpendicular to the raw material inflow direction, abuts the annular flat plane 44 of the die flange, and the annular mounting plane 29 of the mating die, which is also perpendicular to the raw material inflow direction, abuts the flat plane of the breaker plate. Therefore, when the die set is fastened to the extruder cylinder end flange in a state where the breaker plate 6, mating die 21, and die flange 41 are in contact as shown in FIG. 4, an equal fastening force is applied to each of the flat planes. This equal fastening force applied to each of the circular or annular flat planes prevents material leakage from the mating portions and the adjacent flat planes of the die set, even during long-term strand molding. Furthermore, the molten raw material discharged from the breaker plate passes through the raw material flow path 27, which is integrated into the mating die shown in Figure 5, so that the raw material does not deteriorate at the joints of the parts, and strands can be discharged from the nozzle at a stable rate.

[0030] Furthermore, the raw material discharged from the breaker plate is first released into a large volume space on the inlet side of the raw material flow path, and then the raw material is constricted in the raw material constriction section and nozzle section. This allows strands to be discharged from the nozzle in a stable amount without being affected by fluctuations on the screw side during kneading.

[0031] Furthermore, because the fitting dies are lightweight, when disassembling the die set to clean adhering foreign matter, it is not necessary to clean all of the heavy dies as in the past. Instead, cleaning can be performed simply and easily by cleaning only the lightweight disassembled fitting dies or by replacing them with spare fitting dies, thereby shortening the time required to switch to a product with a different formulation. Furthermore, since the mating die has an integrated raw material flow path without the need to attach other parts, the raw material flow path can be shortened. In particular, when forming strands from raw materials with low heat resistance, shortening the raw material flow path can shorten the path time of the heated raw material.

[0032] [Die set in the second embodiment] A die set according to a second embodiment of the present invention will be described with reference to Fig. 8. In Fig. 8, (a) is a plan view, (b) is a right side view, and (c) is a cross-sectional view taken along the line L-L' in (b). The engaging die of the die set of the second embodiment differs from the first embodiment in that, as shown in Figure 8-(c), it has a third engaging portion 51 between the first engaging portion 22 and the second engaging portion 23 in the first embodiment, and the die flange of the die set of the second embodiment has a third engaging hole 54 that engages with the third engaging portion 51 of the engaging die, thereby forming a stepped engaging portion.

[0033] The third fitting portion 51 of the fitting die has a cylindrical side surface with a diameter larger than that of the first fitting portion 22 and smaller than that of the second fitting portion 23, and has annular first fitting planes 52 and second fitting planes 53 between the first fitting portion and the third fitting portion, and between the second fitting portion and the third fitting portion, respectively, and each of the fitting planes is perpendicular to the raw material inflow direction 92.

[0034] The die flange has a cylindrically cut through mating hole to mate with the first, second, and third mating portions of the mating die, and the third mating hole 54 of the die set, which mates with the third mating portion of the mating die, has a diameter larger than that of the first mating hole 42 and smaller than that of the third mating hole 43.The depth of the third mating hole is the same height as the height of the third mating portion of the mating die, taking into account the mating tolerance and the thermal expansion coefficient of the material.

[0035] As shown in Figure 8-(c), the die flange has a first annular flat surface 55 and a second annular flat surface 56 perpendicular to the raw material inflow direction 92 between the first fitting hole 42 and the third fitting hole 54, and between the third fitting hole 54 and the second fitting hole 43, respectively, which are in contact with the corresponding first and second fitting flat surfaces of the fitting die.

[0036] [Function and effect of the die set in the second embodiment] The die set in the second embodiment achieves the same effects as the first embodiment, but furthermore, the mating die contacts the die flange via a two-step circular ring formed by the first mating plane and the second mating plane, so that the fastening force applied to the mating plane and the resin pressure applied to the die set by the raw material can be evenly distributed over the ring. By distributing the resin pressure on the die set by the raw material evenly in a circular pattern, each fitting part is It does not bend under pressure and can be used with extruders with particularly large diameters, making it possible to scale up the extruder, which is effective in improving productivity.

[0037] [Variations] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted. Below, an example of a modification will be described based on the diagram shown in Figure 9. In Figure 9, (a) is a plan view, (b) is a right side view, and (c) is an L-L' cross-sectional view of (b).

[0038] The diameter of the nozzle portion of the mating die of the die set of the present invention can be set arbitrarily according to the strand to be produced, but is preferably 1.0 to 5.0 mm from the viewpoint of preventing the raw material from burning at the nozzle portion.

[0039] The number of nozzle portions that the fitting die has may be a plurality of nozzle portions as disclosed in the first and second embodiments, or may be one nozzle portion like the nozzle portion 26 shown in FIG. Furthermore, the depth direction of the nozzle portion may be angled with respect to the raw material flow path direction as disclosed in the first and second embodiments in order to prevent breakage of the extruded strand, but as shown in Figure 9-(c), the depth direction of the nozzle portion may also be parallel to the raw material flow path direction 92. The angle of the depth direction of the nozzle portion with respect to the raw material flow path direction 92 is preferably 0 to +75°, where the raw material flow path direction is 0° and the downward direction from the raw material flow path direction horizontal to the ground is +, from the viewpoint of preventing scorching of the raw material at the nozzle portion.

[0040] Furthermore, the plane 30 adjacent to the first mating portion of the mating die, where the discharge outlet of the nozzle portion is located, may have a convex portion so that the raw material is stably discharged from the nozzle portion, as shown in the first and second embodiments, but may also be a plane without a convex portion, as shown in Figure 9.

[0041] The raw material constricting section 25 in the raw material flow path of the fitting die may have a circular inlet and a narrower flow path in either the thickness or width direction of the raw material flow path so that the raw material narrows as it advances downstream, and may have a shape that narrows only in the thickness direction of the raw material flow path and is flat in the width direction, as in the first and second embodiments, or may have a shape that narrows in both the thickness and width directions, as shown in Figure 9. Furthermore, from the viewpoint of preventing scorching of the raw material in the raw material constricting section, it is preferable that the tip 73 of the raw material constricting section has a curved surface, as shown in Figure 9-(c).

[0042] The diameter of the circular inlet of the raw material constriction portion of the fitting die can be set to any diameter as long as it can accommodate the raw material flowing through all of the through holes in the attached breaker plate. From the viewpoint of equalizing the resin pressure of the raw material and the clamping force of the die set, it is preferable that the raw material flow path be located in the center as viewed from the right side of the die set, and that the inlet of the raw material flow path be a perfect circle.

[0043] The diameter and length of the entire fitting die can be made to any size so as to withstand the resin pressure of the number of strands to be produced. The overall size of the die flange can be any size as long as it is designed to be able to fit the mating die, be able to fasten to the cylinder tip flange, and be able to transmit heat from the heater to the mating die.

[0044] Furthermore, the mating portions on the side of the mating die may be two, a first mating portion and a second mating portion, as in the first embodiment, or three, a first mating portion, a second mating portion, and a third mating portion, as in the second embodiment, and further cylindrical mating portions of different diameters may be provided so that the side of the mating die has a stepped shape.

[0045] In addition, the fit tolerance between the breaker plate and the breaker plate mounting hole of the mating die can be set so that the fit is a "transition fit" or "loose fit" taking into account the thermal expansion of the mating die and the material of the breaker plate when heated by the heater. Furthermore, the depth of the breaker plate mounting hole can be set arbitrarily within the range that provides a space between the die set and the extruder cylinder tip flange when fastened, so that the fastening force is transmitted to the breaker plate mounting hole and the breaker plate when the die set and the extruder cylinder tip flange are fastened together.

[0046] As disclosed in the first and second embodiments, the depth of the first fitting hole of the die flange of the die set of the present invention may be the same as the height of the first fitting portion of the fitting die, from the viewpoint of efficiently conducting the heat of the die flange heated by the heater installed on the die flange to the fitting die; however, the depth of the first fitting hole of the die flange may also be shallower than the height of the fitting die so that the raw material extruded from the fitting die does not come into contact with the die flange. Furthermore, it is preferable that the depth of the fitting holes other than the first fitting hole is the same as the height of the side surface of the fitting portion of the corresponding fitting die. However, the depth of the fitting hole may be fine-tuned after taking into account the fitting tolerance and taking into account the thermal expansion due to the materials and shapes of the die flange and the fitting die, respectively. Furthermore, the depth of the second fitting hole may be set arbitrarily within the range that provides a space between the die set and the extruder cylinder tip flange when fastened, so that the fastening force is transmitted to the die flange and the fitting die when the die set and the extruder cylinder tip flange are fastened together.

[0047] The mating portions of the mating dies of the die set of the present invention, the breaker plate mounting holes, and the mating holes of the die flanges can be chamfered or rounded at the edges of each mating surface as shown in Figure 10 to prevent damage caused by contact between the parts during mating and installation, and to prevent damage to the contacting parts due to thermal expansion of the corners of each part. In addition, Figure 10 shows (a) a cross-sectional view of the die set, and (b) an enlarged view of part A formed by the second mating plane of the mating die and the bottom surface of the die flange shown in (a), showing chamfering as an example, and (c) an enlarged view of part A formed by the second mating plane of the mating die and the bottom surface of the die flange shown in (a), showing chamfering as an example, and R machining as an example.

[0048] The die set of the present invention and the cylinder end flange of the extruder may be fastened together using eyebolts as in the first and second embodiments from the viewpoint of ease of disassembly, but multiple bolt holes may be drilled in the cylinder flange, and corresponding holes for the bolts and counterbore holes may be drilled in the die flange, and then the die flange and cylinder flange may be fastened together using multiple bolts. From the viewpoint of obtaining a uniform fastening force, it is preferable that each bolt fastening portion be evenly spaced from the center of the fitting hole in the die flange.

[0049] In order to prevent the mating die from rotating during assembly, the die set of the present invention can be provided with a mating die rotation stopper 74, as shown in Figure 9, which has a hole or groove in the mating die and a corresponding hole or groove in the die flange.

[0050] The fitting die of the die set of the present invention can be provided with a hole for a withdrawal screw 79 as shown in FIG. 9 so that the fitting die and the die flange can be disassembled for cleaning.

[0051] From the viewpoint of workability during disassembly and assembly, the die flange of the die set of the present invention may be provided with a bolt holder 75 on the side of the die flange to hold down the eye bolt to be fastened, as shown in Figure 9, so that the die set can be opened in a one-sided manner. Furthermore, from the viewpoint of workability during disassembly and assembly, the die flange may be provided with an opening / closing handle 76 to be used when opening and closing the die set, as shown in Fig. 9. The opening / closing handle is connected to the die flange by, for example, bolting or welding a rod-shaped object to the side surface of the die flange.

[0052] The heater for heating the die flange of the die set of the present invention may be a cartridge heater inserted into the die set as shown in the first and second embodiments, but any other heater may be used, such as a plate heater screwed to the side of the die flange.

[0053] The extruder of the present invention may be any extruder that can melt-knead raw materials containing a thermoplastic resin to form strands, and may be, for example, a single-screw extruder, a twin-screw extruder, or the like.

[0054] The die set and extruder of the present invention are effective from the viewpoint of disassembly and cleaning of the die set, particularly when raw materials containing solid particles together with thermoplastic resin are processed into strands and pellets, but are also effective from the viewpoint of cleaning of burn marks when raw materials containing only thermoplastic resin are used. Examples of the solid particles include known particles such as pigments, dyes, additives for plastics, and plasticizers.

[0055] The cylinder end flange of the extruder of the present invention may be of any size and any fastening means as long as it can fasten the die set. Furthermore, as shown in Figure 9, the cylinder tip flange can be provided with a die set guide 77 to prevent the die set from falling, from the viewpoint of ease of disassembly and assembly, and the die set guide can be connected to the cylinder tip flange by any method, such as welding or screwing to the cylinder tip flange.

[0056] As shown in FIG. 7, the side of the breaker plate of the extruder of the present invention may or may not have a groove 65 for removing the breaker plate from the cylinder tip flange, from the viewpoint of ease of disassembly. [Explanation of symbols]

[0057] 1. Extruder 6 Breaker Plate 8 Cylinder tip flange 9 Dice Sets 21 Mating Dies 22 First fitting portion 23 Second fitting portion 24 Breaker plate mounting hole 25 Raw material squeezing section 26 Nozzle section 27 Raw material flow path 28 Mating plane 29 Mounting plane 31 Inlet 41 Die flange 42 First fitting hole 43 Second fitting hole 44 Circular Plane 45 Bolt fastening part 51 Third fitting part 52 First mating plane 53 Second mating plane 54 Third fitting hole 55 First Circular Plane 56 Second Circular Plane 63 Through hole 78 Fastening bolt 92 Raw material inflow direction

Claims

1. A die set provided in an extruder for extruding a thermoplastic resin composition into a strand shape, The die set is configured by fitting a fitting die and a die flange together, a side surface of the fitting die having a cylindrical first fitting portion and a cylindrical second fitting portion having a diameter larger than that of the first fitting portion; the inside of the fitting die has a breaker plate mounting hole at the bottom of the second fitting portion, and a raw material flow path consisting of a raw material constriction portion having an inlet that is a circle with a diameter smaller than that of the breaker plate mounting hole, and a cylindrical nozzle portion; the fitting die has an annular fitting plane which is a plane perpendicular to the raw material inflow direction at a step between a side surface of the first fitting portion and a side surface of the second fitting portion, and an annular mounting plane which is a plane perpendicular to the raw material inflow direction at a step between the breaker plate mounting hole and the inlet, the die flange has a fitting hole and an annular flat surface that mate with the first fitting portion, the second fitting portion, and the fitting flat surface of the fitting die, The die flange has a die fastening portion that fastens to an extruder. A dice set characterized by:

2. 2. The die set according to claim 1, The die set has, between the first fitting portion and the second fitting portion, one or more further fitting portions each having a cylindrical side surface with a diameter intermediate between the diameter of the first fitting portion and the diameter of the second fitting portion, The die flange has one or more additional fitting holes that mate with additional fitting portions of the fitting die. Dice set.

3. An extruder comprising the die set according to claim 1 or 2 and a breaker plate.

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