JP7544769B2 - Extruder Die Plate - Google Patents

Description

The present invention relates to an extruder die plate, which is installed at the tip of an extruder used for extrusion molding of thermoplastic resin, and which increases the durability of the orifice through which the plasticized resin passes and reduces the occurrence of die marks, etc.

A conventional method for producing resin pellets for molding involves extruding molten thermoplastic resin to form string-like strands, which are then cut into short pieces to form pellets. In order to form strands of the desired diameter, a die plate with an orifice (nozzle) of a specified diameter is attached to the tip of the extruder. The plasticized molten resin is extruded into string-like strands by continuously passing through the orifice.

Die plates need to have multiple orifices with different diameters and numbers depending on the resin type and composition specifications of the strands to be produced. Furthermore, if the orifices of the die plate become worn or dirty, the entire die plate must be replaced.

In addition, when the molten resin composition is continuously extruded from an orifice during the extrusion molding process, wear and dirt on the inner wall surface of the orifice can cause resin lumps called "pit jelly" and carbonized matter to grow near the outlet of the orifice and adhere to the strand, or streaks and dirt can adhere to the strand, resulting in a deterioration in the quality of the pellets produced from the strand.

To solve these problems, a strand die for an extruder has been proposed that uses a die plate with a nozzle piece with nozzle holes formed therein, allowing maintenance without replacing the entire die plate and reducing the generation of die gunk (Patent Document 1).

In the extruder strand die disclosed in Patent Document 1, as shown in each figure of FIG. 2, a thin-diameter threaded nozzle hole is formed at the tip side of a wide resin flow path 7 formed in a die plate 5 (hereinafter, the reference numerals described in Patent Document 1 are cited). Furthermore, a nozzle piece 6, which is a feature of the invention, is attached by screwing from the downstream side of the die plate 5. In an extruder equipped with this die plate 5, the resin plasticized in the extruder passes from the wide resin flow path 7 in the die plate 5 through a thin-diameter nozzle hole and a nozzle hole 9 in the nozzle piece 6, and is discharged from the tip of the nozzle hole 9 to the outside of the extruder. And, if the inner surface of the nozzle hole is damaged, it can be restored at low cost by only replacing the nozzle piece without replacing the entire die plate, and it is said that the eye burr generated at the outlet of the nozzle hole can also be reduced.

JP 2000-52403 A

However, in the die plate of the strand die disclosed in Patent Document 1, a small-diameter nozzle hole is formed in the die plate body, and the nozzle hole of the nozzle piece is positioned so as to communicate with this nozzle hole. Therefore, the inner wall surface on the nozzle hole side formed in the die plate body, into which the molten resin flows under high pressure as if squeezed from the wide resin flow path 7 in which the molten resin is temporarily stored, is most susceptible to wear. If this part becomes worn or soiled, replacing the nozzle piece is not enough, and there is a problem that the entire die plate must be replaced.

The object of the present invention is to provide a die plate for an extruder that solves the problems of the conventional technology described above, has an orifice that is resistant to deterioration, can be used for a long period of time, and can be used to change the diameter of the strand to be molded by simply replacing the orifice pin with one of the appropriate size (inner diameter).

The die plate for an extruder of the present invention comprises a die plate main body which is attached to the discharge side of a molten resin in an extruder and has a flat, horizontally elongated recess with a semicircular convex inner part formed therein , in which the molten resin is stored, and an orifice pin which is fitted into a plurality of orifice pin holding holes which are formed side by side in the horizontal direction so as to be continuous with the inner part from the inflow direction of the molten resin, and has an orifice of a predetermined inner diameter formed in the axial direction through which the molten resin passes and is discharged, the orifice opening at the inlet end face of the molten resin, having a tapered surface which reduces in diameter to the predetermined inner diameter, and a land of a predetermined inner diameter and a predetermined length which is continuous with the small diameter side end of the tapered surface .

It is preferable that the orifice pin has a collar portion that is expanded in diameter from the main body portion via a haunch portion on the inlet side of the molten resin, and is held in position within the orifice pin holding hole by the haunch portion.

It is preferable that the orifice pin has a tapered surface formed on the inlet side end surface of the collar portion for guiding the molten resin to the orifice.

It is preferable that the material strength of the orifice pin is greater than the material strength of the die plate body.

The tapered surface preferably has a taper angle set to 90 to 150 °.

It is preferable that the length of the land of the orifice is set to 10 to 20 mm.

The present invention has the effect of increasing the durability of the orifice through which the plasticized molten resin passes during molding, simplifying part replacement work, and reducing the generation of resin and other defects that accompany molding during molding.

FIG. 2 is a front view showing the box body of the extruder die plate of the present invention, and a cross-sectional view taken along the line Ib-Ib. 1A to 1C are a front view, an end view, and a longitudinal sectional view showing the overall shape of an orifice pin of a die plate for an extruder of the present invention. FIG. 4 is a partially enlarged cross-sectional view showing the orifice pin mounted in the pin accommodating portion of the box body of the die plate. IVb-IVb cross-sectional view showing a state in which the orifice pin is attached to the pin accommodating portion of the box body of the die plate and a molten resin flow path is formed in the die plate. FIG.

The configuration of one embodiment of the extruder die plate of the present invention will be described below with reference to the attached drawings.

The configuration of one embodiment of the extruder die plate of the present invention will be described below with reference to the attached drawings. FIG. 1(a) is a front view of the extruder die plate 10 of the present invention (hereinafter, simply referred to as die plate 10) viewed from the front end side of the extruder. This die plate 10 has four mounting bolt holes 11 when viewed from the front, and is attached to the downstream end face of the extruder body through the mounting bolt holes 11 using fixing bolts (not shown), forming a die section that serves as an outlet for the molded resin. High-hardness stainless steel (SUS440C) is used for the die plate 10 of this embodiment. Other materials such as chromium molybdenum steel (SCM material), aluminum chromium molybdenum steel (SACM material), and alloy tool steel (SKD material) can also be used as appropriate.

The molten resin heated and plasticized in the extruder passes continuously through orifices (described later) of a predetermined inner diameter formed in the die plate 10 of the die section and is discharged outside the extruder, forming a string-like strand (FIG. 4(b)) of a predetermined diameter. In this embodiment, the orifice is a small-diameter through hole formed in an orifice pin 20 (described later in FIG. 2) that is incorporated as a separate member from the main body of the die plate 10. In addition, in the die plate 10 of this embodiment, as shown in FIG. 1(a), four orifice pins 20 are attached to the die plate 10 side by side at a predetermined interval so that, as an example, four strands can be molded in parallel at the same time (after attachment: FIG. 4(a)).

On the inner surface side (upstream side in the resin flow direction) of the die plate 10 to which the orifice pin 20 is attached, as shown in Figs. 1(a) and (b), a flat horizontally elongated recess 12 with a semicircular convex inner portion 12a is formed. This flat horizontally elongated recess 12 functions as a buffer section for temporarily storing the molten resin transported by a screw or the like (not shown) and allowing the molten resin to flow uniformly into each orifice. Furthermore, in the semicircular convex inner portion 12a, four orifice pin holding holes 13 are formed side by side at a predetermined interval along the longitudinal direction of the flat horizontally elongated recess 12. The orifice pin 20 (Fig. 2(a)) is attached so as to be fitted closely into each orifice pin holding hole 13 as shown in Figs. 3(a) and (b). Therefore, the inner wall surface shape of the orifice pin holding hole 13 is set to follow the overall outer shape of the orifice pin 20. Furthermore, the orifice diameter through which the plasticized resin passes can be set as desired to suit the characteristics of the various thermoplastic resins being extruded, and it goes without saying that the size of the die plate 10 and the number of orifice pins 20 attached to the die plate 10 can also be set appropriately depending on the scale and specifications of the molding machine.

In addition, since the extruder of the present invention is intended to extrude super engineering plastics (such as PEEK resin), a heater (not shown) is provided in the die plate 10 to prevent the resin temperature from dropping as it passes through the die plate 10. The heater is stored in a heater storage section 14 in the shape of a circular hole that runs through the die plate 10, and is heated by passing electricity from an external power source. By raising the die plate 10 to a predetermined temperature, the temperature of the molten resin passing through the die plate 10 can be maintained at a predetermined temperature. Needless to say, the present invention can be applied to the efficient production of high-quality molded products of various engineering plastics and filler-filled general-purpose plastics, in addition to the molding of the above-mentioned super engineering plastics.

Here, the configuration of the orifice pin 20 attached to the die plate 10 shown in FIG. 1 will be described with reference to each of the drawings in FIG. 2. The orifice pin 20 of this embodiment has a generally cylindrical shape in which a main body portion 20a (length 11 mm, outer diameter Φ7 mm) with a total length of 15 mm, a haunch portion 20b (length 1 mm, haunch angle 45°) that widens the outer diameter of the main body portion 20a, and a collar portion 20c (length 3 mm, outer diameter Φ9 mm) whose outer diameter is wider than that of the main body portion 20a are integrated, and a through hole 21 (inner diameter Φ3 mm) is formed along the central axis direction. This through hole 21 functions as an orifice (nozzle) through which the molten resin passes. In addition, a gentle taper portion is formed on the end face of the through hole 21 on the molten resin inlet side. Hereinafter, this through hole will be referred to as the "orifice 21" as a functional name. In order to form a uniform strand, the length of the land is set to approximately 13.6 mm to define the diameter of the strand and maintain its shape, out of the total length of the orifice 21.

Of the overall shape of the orifice pin 20, the haunch portion 20b connecting the main body portion 20a and the collar portion 20c is set so that its taper angle is 90° (haunch angle 45°). This haunch portion 20b and the enlarged collar portion 20c are closely fitted against the haunch portion 13b and the enlarged portion 13c formed on the inner wall surface of the orifice pin holding hole 13 formed in the die plate 10. This makes it possible to prevent the orifice pin 20 fitted into the die plate 10 from rotating or falling off during resin molding.

In addition, by setting the length (thickness) of the collar part of the orifice pin 20 to about 3 mm, it can adequately withstand the internal pressure (resin pressure) of the molten resin acting on the orifice pin 20 during resin molding.

Furthermore, a gentle tapered surface 22 is formed on the molten resin inlet side of the orifice 21. In this embodiment, the angle θ of the tapered surface 22 is set to θ = 120°. By providing this gentle tapered surface 22 on the resin inlet side end face, it is possible to prevent a sudden increase in pressure of the molten resin that reaches the orifice 21 and the associated decomposition of the resin. This also makes it possible to suppress the generation of gas associated with resin decomposition, which causes corrosion of the orifice 21. It is preferable that the taper angle θ at which this effect is obtained is approximately θ = 90° to 150°.

In addition, it is preferable to set the land length of the orifice 21 in the orifice pin 20 to 10 to 20 mm. Within this range, the shear rate experienced by the molten resin passing through the orifice 21 can be mitigated, and the temperature rise of the molten resin can be suppressed. It is preferable to set the dimensional values of each part of the orifice pin 20 described above (total length, collar thickness, taper angle, land length, etc.) appropriately depending on the characteristics of the thermoplastic resin used and the specifications of the strand to be molded (size, material).

In this embodiment, the orifice pin 20 is made of a cemented carbide (VM10 to 50 or so). Instead of a cemented carbide such as a WC-Co alloy, a cemented carbide steel having the same strength may be used. For example, the strength of the cemented carbide is higher than that of the die plate 10, and it has high resistance to wear, corrosion, and dirt, and is less likely to deteriorate than the die plate 10. Therefore, the surface of the inner wall of the orifice 21 is less likely to become rough due to wear caused by the generated decomposition gas and the molten resin passing through the orifice 21, and the smoothness of the inner wall surface of the orifice 21 can be maintained. This allows the thermoplastic resin passing through the orifice 21 to flow uniformly, and the occurrence of burrs at the outlet of the orifice 21, which impairs the stability of production and the quality of the obtained product, can be significantly reduced. It can be effectively used even in cases where the thermoplastic resin contains reinforcing fibers, fillers, additives, flame retardants, etc., and burrs are likely to occur as a specification of the molded product.

In this way, the material of the orifice pin 20 in this embodiment is more durable than the die plate 10 and deteriorates more slowly, so the orifice pin 20 has a long life and can be used for a long period of time, and the replacement period of the orifice pin 20 can be extended.

The figures in Figure 3 are partial enlarged views showing the state in which the orifice pin 20 is attached to the flat, horizontally elongated recess 12 of the die plate 10. As shown in Figure 3(a), the overall external shape of the orifice pin 20 is substantially the same as the shape of the inner wall surface of the orifice pin holding hole 13 formed in the flat, horizontally elongated recess 12 of the die plate 10. As a result, the orifice pin 20 attached to the orifice pin holding hole 13 on the die plate 10 side is held in close contact with the inner wall surface of the orifice pin holding hole 13 (Figure 3(b)).

Figure 4 shows a longitudinal cross section of the orifice pin 20 mounted in the flat, elongated recess 12 of the die plate 10. As indicated by the arrows in the figure, the molten resin R flows smoothly from the flat, elongated recess 12 along the resin path formed in the die plate 10 through the tapered surface 22 of the orifice pin 20 into the orifice 21, and strands S of a specified diameter are discharged from the discharge side.

As described above, in extrusion molding operations using the orifice pin 20 of the present invention, even if the inner wall surface of the orifice 21 deteriorates as a result of molding operations over a long period of time, or if the diameter of the strand being molded changes, it is sufficient to simply replace the orifice pin 20 with a new orifice pin 20 or an orifice pin 20 with an inner diameter of the orifice 21 that corresponds to the change, while leaving the die plate 10 as it is, thereby greatly simplifying and streamlining maintenance operations.

The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the claims. In other words, embodiments obtained by combining technical means that are appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

10 Die plate 12 Recess 13 Orifice pin holding hole 14 Heater storage hole 20 Orifice pin 21 Orifice 22 Tapered surface R Molten resin S Strand

Claims (5)

a die plate body attached to a discharge side of a molten resin in an extruder , the die plate body having a flat, horizontally elongated recess with a semicircular convex inner portion formed therein, the molten resin being stored therein ;
an orifice pin that is fitted from an inflow direction of the molten resin into a plurality of orifice pin holding holes that are formed side by side in a horizontal direction so as to be continuous with the inner portion, and that has an orifice with a predetermined inner diameter formed in an axial direction through which the molten resin passes and is discharged;
Equipped with
The orifice is opened at an end surface on the inlet side of the molten resin, and a tapered surface is formed so as to reduce in diameter to the predetermined inner diameter, and a land having a predetermined inner diameter and a predetermined length is set continuously to the small diameter side end of the tapered surface.
A die plate for an extruder. 2. The die plate for an extruder according to claim 1, wherein the orifice pin has a collar portion which is expanded in diameter from a main body portion via a haunch portion and is formed on the inlet side of the molten resin, and the collar portion is positioned and held within the orifice pin holding hole. The extruder die plate according to claim 1, wherein the material strength of the orifice pin is greater than the material strength of the die plate body. 2. The die plate for an extruder according to claim 1 , wherein the tapered surface has a taper angle set to 90 to 150 degrees. 2. The die plate for an extruder according to claim 1 , wherein the length of the land of the orifice is set to 10 to 20 mm.

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