JPS61268407A - Granulating die for synthetic resin extruder - Google Patents

Abstract

PURPOSE:To enable to realize the low-temperature extrusion of an extruder by a method wherein a communicating space is interposed between a nozzle and a die main body and evacuated so as to control the heat transfer from resin to the wall surface of the bore of a nozzle in order to keep the tempera ture of the nozzle wall at the temperature of the discharged resin. CONSTITUTION:A communicating space portion 11c is provided by putting the outer end surfaces of projections 11b on the outer peripheral surface of a large diametral bore 11a portion into close contact with the inner peripheral surface of the bore 12 of a nozzle. In addition, a conical tubular space 11 is provided on the outer peripheral side of a small diametral bore 11a'' so as to communicate with the space portion 11c. The resin melted in the cylinder of an extruder is extruded from the respective nozzles 11 in the shape of a strand. During the process just mentioned above, the heat transfer from the resin to the wall surface of the bore 12 of the nozzle is checked by the space portions 11c and 11d, the temperature to the resin scarcely lowers even under the state that the heating by heating jackets is stopped.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to a granulation die used for producing pellets in a synthetic resin extruder, in which cooling of the synthetic resin while passing through the die is suppressed. This invention relates to a synthetic resin extruder granulation die designed to achieve the following.

(Prior Art) When a granulating die is used in the discharge section of an extruder to pelletize a thermoplastic and thermosetting synthetic resin (hereinafter simply referred to as resin), a large amount of synthetic resin is pelletized. for,
Generally, a so-called underwater cut method is used in which the resin is extruded into water through a number of nozzles provided on a granulation die and cut with a rotating cutter.

A conventional example generally used as such a granulation die will be explained with reference to FIGS. 3 and 4.

l is the die body, and the extruder cylinder and shaft I are not shown.
5! A large number of nozzle holes 2 are provided on a concentric circumference such that the nozzle holes 2 are almost coincident with each other, 2m is the nozzle hole inlet, and 2b is the nozzle hole outlet. 3 is the end face of the die where the nozzle hole outlet 2b is located. 4 is a heating jacket provided on the outer periphery of the 2 groups of nozzle holes, 5 is a heating jacket in the center of the 2 groups of nozzle holes, and the heat medium is supplied or discharged from the heat medium inlet/outlet 6m, 6b.

The die body 1' is fixed with bolts to the discharge part of an extruder cylinder (not shown) using a plurality of through holes 78, and cooling water is circulated over the die end face 38 using a threaded hole 8. The outer water channels are fixed, and a rotating cutter (not shown) is provided on the die end face 3 with a slight clearance.

Therefore, the resin extruded in the form of a strand from the nozzle hole outlet 2b is cut into pellets and cooled by cooling water, and the pellets are sent out together with the cooling water without causing mutual contact.

In this way, in order to pelletize the extruded resin in the form of a strand, it is necessary to cool the resin at the same time as cutting to completely prevent the intermelting layer of the pellets. However, since the die end face 3 is cooled by cooling water, the resin near the nozzle hole outlet 2b solidifies and adheres to the nozzle hole 2, resulting in a decrease in the apparent diameter of the nozzle hole 2 and an increase in the flow velocity. Therefore, irregularly shaped pellets are produced, and if the cooling effect is excessive, the nozzle holes 2 become clogged, and eventually blockage occurs, making it difficult to extrude the resin.

The first measures to avoid this M4i include increasing the temperature of the cooling water, increasing the resin discharge rate from the extruder, and increasing the amount of extrusion. An increase in the discharge temperature and an increase in the extrusion rate lead to deterioration of the physical properties of the sanitizing agent or an increase in power costs.

Further, as a second measure, there is a means for maintaining the resin temperature within the nozzle hole 2 so as not to drop.

In other words, there are heating jackets in which a large number of pores are provided close to the nozzle hole 2, but in both cases, the work is complicated and not only requires a large number of man-hours, but also causes problems in terms of strength. It also poses structural difficulties.

Furthermore, as described in Japanese Patent Publication No. 56-25365 (Perforated Plate for Extruded Synthetic Resin Pelletization) J, in order to make the temperature distribution of the nozzle hole uniform, insulation is provided at the nozzle hole and around the nozzle hole. - The insulating layer crosses multiple nozzle holes near the outlet to form a part of the nozzle hole, and the insulating layer is made of resin. requires a certain thickness for strength and structure, and is located downstream of the insulating layer, so it is cooled by cooling water. Even a good insulating layer is involved in heat transfer.

(Problems to be Solved by the Invention) As described above, in the conventional synthetic resin extrusion imitation core die, cooling water prevents the resin in the nozzle hole from decreasing in temperature and adhering to the inner wall of the nozzle hole. Various measures have been taken to prevent this, and among them, means for maintaining the resin temperature within the nozzle hole is the most clever. However, since many small-diameter nozzle holes are formed on a fixed die surface, providing temperature maintenance means in a limited area is often a problem in terms of strength and workmanship, and good countermeasures have not yet been established. By the way, the resin passing through the nozzle hole is cooled by heat transfer from the resin to the nozzle hole wall surface.
It is necessary to cut off this flow of heat.

(Means for Solving the Problems) The present invention is a die for granulating a synthetic resin extruder, in which cooling of the synthetic resin while passing through the die is suppressed, and the structure thereof is as follows. be.

In the synthetic resin extrusion imitation core die, a cavity 11Ji communicating with the die body is interposed between a nozzle fitted and fixed in a nozzle hole provided in the die body, and this space is used as a vacuum chamber.

As an advantageous embodiment, a part of the vacuum chamber is formed to be inclined from the outer periphery of the nozzle toward the tip of the small diameter hole of the nozzle.

(Function) A vacuum chamber is provided between the die body and the nozzle, and heat transfer from the resin to the nozzle hole wall surface is significantly suppressed, so the resin passing through the die is It is extruded from the nozzle while maintaining almost the same temperature.

By forming a part of the hollow vacuum leg slanting from the outer periphery of the nozzle toward the tip of the small-diameter hole of the nozzle, the required strength of the nozzle tip is maintained and heat transfer from the small-diameter hole of the nozzle is maintained. The amount can be reduced.

(Embodiment) An embodiment of the synthetic resin extrusion imitation core die according to the present invention will be described based on FIGS. 1 and 2, and with reference to FIGS. 3 and 4.

In FIG. 1, 1 is a die main body, 4 is a heating jacket provided around the outer periphery of a group of nozzles 11 to be described later, and 6a is a heat medium inlet/outlet.

The die body 1 is provided with a nozzle hole 12 in which a nozzle 1 made of a pipe material is inserted, and the nozzle hole 12 is arranged concentrically with the die body 1 in the same manner as shown in FIG. The nozzle 11 includes a large diameter hole 11m for reducing pressure loss of the resin and a small diameter hole 11m' connected to the tip side through a constricted portion 11a'. A plurality of protrusions 11b8 are provided on the outer circumferential surface of the large diameter hole 11a, and a space 1 is provided in which the outer end surface of the protrusion 11b is brought into close contact with the inner circumferential surface of the nozzle hole 12.
It is provided with 1c.

A conical cylindrical space 411d is provided on the outer peripheral side of each of the small diameter holes 11m' and communicated with the space 11c.

The conical cylindrical space lid is formed into a conical cylindrical shape whose diameter decreases from the outer peripheral surface of the nozzle 11 toward the tip side of the small diameter hole 11a#. That is, the thickness of the outer periphery of the small diameter hole 11a' in the axial direction becomes gradually thinner from the rounded side toward the center. In this way, the conical cylindrical space lid and the small diameter hole 11
The reason why the small diameter hole 11a' of the nozzle 11 is inclined toward the tip side is to ensure the thickness of the cross section perpendicular to the axis of the small diameter hole 11a' of the nozzle 11 as much as possible to maintain strength, and to maintain the strength of the small diameter hole 11a'.
By reducing the wall thickness in the axial direction near the exit of the small diameter hole 11a
This is to suppress as much as possible the heat radiation from the passing resin.

After the nozzle 11 is fitted into the nozzle hole 12, the outer circumferential surface of the end on the large diameter hole 11a side is fixed to the die body 1 at the welding part A, and the rain space parts 11c, lld;fi- are kept in a vacuum. Meanwhile, the outer peripheral surface of the end on the side of the small diameter hole 11 m' is vacuum welded to the die body 1 and fixed at the welding part B. Therefore,
The rain space 11c and the lid are a vacuum chamber.

In addition, since vacuum welding is performed, before inserting the nozzle 11 into the nozzle hole 12, the outer circumferential surface of the nozzle 11 and the inner cylindrical surface of the nozzle hole 12 are thoroughly washed and dried.

13 is a wear-resistant material having a small diameter hole 13m having the same diameter as the small diameter hole 11- of the nozzle, and is fixed to the end face of the nozzle.

The die main body 1 constructed as described above is attached to the discharge section of a synthetic resin extruder cylinder, as in the conventional example.

Next, the effect will be explained.

When operating the synthetic resin extruder, the heating jacket 4,
A heat medium is passed through 5 to heat the die body 1 and nozzle 11. When the extruder is operated, the resin melted in the extruder cylinder is extruded into strands from each nozzle 11, cut by a rotary cutter, cooled with cooling water, and pelletized.

In this process, the heat transfer from the resin to the wall surface of the nozzle hole 12 is suppressed in the space (JIC empty room) 11c and lid, so even if heating by the heating jacket 4.5 is stopped, the resin remains at a temperature of Nozzle 1 with almost no decrease in
1.

The nozzle 11 may be fitted into the nozzle hole 12 by using a spiral protrusion or a protrusion extending in the axial direction of the nozzle 11 instead of the plurality of protrusions 11b. It is preferable to have a smaller fitting area to the nozzle hole 12. Further, the conical cylindrical space] 1d can be divided by providing partition walls radially, but by doing so, although the strength is increased, the heat radiation suppressing effect is slightly reduced.

FIG. 2 shows a case in which one nozzle is provided with two discharge ports.

1 is the die body, 4 is a heating jacket provided on the outer periphery of the nozzle 11' group, 6a is a heating medium inlet/outlet, 1r is a nozzle h
, "lra is a large diameter hole, each 1ra' is a constriction part, each 11
'a' is a small diameter hole, 11'b is a protrusion, 11'c is a space,
11'd is a conical cylindrical space, 12' is a nozzle hole, 13 is a wear-resistant material, A and B are welded parts, and the conical cylindrical space It'd surrounds two small diameter holes 11'a''. Even if such a granulation die is used, there is no substantial difference in operation and effect.

(Effects of the Invention) As can be understood from the above explanation, if the synthetic resin extruder granulation die according to the present invention is used, heat transfer from the resin to the nozzle hole wall surface is suppressed in the vacuum chamber. Therefore, it is possible to suppress the temperature drop of the resin passing through the nozzle due to the cooling water, and it is possible to maintain the nozzle wall near the temperature of the discharged resin. Therefore,
Low-temperature extrusion using an extruder is also possible, and mutual fusion of pellets can be sufficiently prevented by setting the cooling water temperature low.

[Brief explanation of the drawing]

Figures 1 and 2- are sectional views of essential parts of a synthetic resin extruder granulating die according to the present invention, Figure 3 is a sectional view of a conventional synthetic resin extruder granulating die, and Figure 4 is a sectional view of a conventional synthetic resin extruder granulating die. , is a front view of the same. 1: Dice body 11, rr: Nozzle lla,
lra: Large diameter hole 11a', ll'a': Restricted part 11a", lra": Small diameter hole 1lb, ll'b:
Projection 11c, ll'c: Empty I1tlW<(X vacancy)
11d, lrd: Conical cylindrical space (vacuum chamber) 12.1
2' Nozzle hole, Patent attorney Toshiyuki Maeda Figure 3 JP-A-6L-268407 (5) Figure 4

Claims (1)

[Claims] 1. In a synthetic resin extruder granulation die, a space communicating with the die body is interposed between a nozzle fitted and fixed in a nozzle hole provided in the die body, and the space is A synthetic resin extruder granulation die featuring a vacuum chamber. 2. The synthetic resin extruder granulation die according to claim 1, wherein a part of the vacuum chamber is formed to be inclined from the outer periphery of the nozzle toward the tip of the small diameter hole of the nozzle.