JPS62176819A - Dice for preparing resin pellets - Google Patents

Abstract

PURPOSE:To give no heat influence from cooling water filled on the surface of a dice to a molten resin of high temp. being sent under pressure into nozzle holes and to enable the smooth extrusion of the molten resin by providing a space between a part of a smaller diameter of a pipe forming a nozzle of a dice and an inserting hole of the dice main body. CONSTITUTION:A resin blended and molten by means of an extruder is transferred under pressure in a nozzle hole 5 and extruded into cooling water from the surface cured layer 4 of a dice 1 and cut into pellets by means of a rotating cutter. In this process, the temp. of the dice is controlled by a heating medium introduced and exhausted in/from heating jackets 8, 9. A space 7 is set between a part of a smaller diameter 6d of a pipe and an inserting hole 6 of the dice main body 2 and this space 7 performs a heat insulating function of depressing the heat influence from the surface of the dice. The molten resin in the nozzle hole 5 thereby shows little temp. decrease and neither adherence inside of the nozzle hole 5 nor clogging due to hardening occur. The molten resin is therefore smoothly extruded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a die used in a resin pellet manufacturing apparatus for manufacturing synthetic resin pellets.

(b) Prior Art Generally, synthetic resin materials are transported after kneading raw materials and processing them into pellets. Such resin pellets are produced by continuously extruding a kneaded molten synthetic resin through a nozzle hole of a die, and cutting the resin into small pieces using a rotating cutter provided on the front surface of the die. Therefore, resin pellets for that! The Il production equipment includes:
A die with multiple resin extrusion nozzle holes is used.

By the way, even if molten synthetic resin is simply extruded through the nozzle hole of a die and cut with a rotating cutter,
Synthetic resins in a high temperature state weld together and form a lump. Therefore, the surface of the die is usually filled with cooling water, and the synthetic resin is extruded into the cooling water and is cooled and hardened at the same time as it is cut by the cutter.

In that case, the cooling water comes into contact with the surface of the die body, and the surface side of the nozzle hole is cooled by the cooling water, so the molten resin inside the nozzle hole hardens and adheres to the inside of the nozzle hole. However, by decreasing the apparent inner diameter of the nozzle hole and increasing the resin extrusion flow rate,
Irregularly shaped pellets may be produced, and if the cooling is excessive, the nozzle holes may become clogged with the hardened resin. Conventionally, various types of dies have been proposed to prevent such clogging phenomenon, but the clogging prevention means can be roughly classified into the following two types. That is, A: A jacket structure is provided around the nozzle hole of the die, and a heating medium is supplied to this to heat the area around the nozzle hole.

B: In order to prevent heat dissipation from the tip of the nozzle hole on the die surface side due to cooling water, the tip of the nozzle hole is protected with a heat insulating material.

An example of a die using the Δ method is Japanese Patent Publication No. 60-106976, which was previously filed by the present applicant. Also B
As an example of a die using the method of
65 can be raised.

(C) Problems to be Solved by the Invention As mentioned above, methods for preventing clogging of the nozzle holes of dies can be roughly divided into methods A and B, but this method, which has been conventionally used, is This method also has the following problems. However, in method A, if a die with good thermal efficiency is to be manufactured, the structure becomes complicated, the conduit cutting is required to be at a high degree, and the manufacturing process is complicated and takes a long time. However, the production cost increases. In addition, in method B,
Materials with low thermal conductivity, such as ceramics, heat-resistant plastics, or asbestos molded products, are used as protective materials to prevent heat dissipation from the die surface.
These low thermal conductive materials inevitably have inferior mechanical strength properties compared to metal materials, and are especially difficult to use under severe temperature conditions such as heating and cooling as in dies.
It was difficult to ensure adequate strength and lifespan.

In addition, the above-mentioned Special Publication Publication No. 56-25365 taken as an example
Because the extruded raw material is in direct contact with the heat insulating material in a part of the nozzle hole, the heat insulating material is subject to severe wear.
A fully satisfactory lifespan has not been obtained. Furthermore, regarding the structure of the washer that holds down the heat insulating material, it is advantageous to have a smaller washer thickness at the nozzle hole to prevent clogging at the nozzle hole. The longer it is attached, the greater the distortion caused by bolting or thermal deformation, the hardened layer on the surface may crack or peel off, or the washer deformation may change the cutting conditions of the rotating cutter blade, making it difficult to obtain a good quality pellet shape. Therefore, the thickness of the washer could not be reduced unnecessarily, and as a result, the nozzle portion of the washer could become clogged. The present invention improves these shortcomings in the prior art and provides resin pellets that prevent clogging in the nozzle hole due to heat dissipation from the die surface.
The purpose is to provide dies for manufacturing.

(d) Means for Solving the Problems In order to solve the above-mentioned problems, the die of the present invention has a diameter of 1Φ larger than the hole in the die body from the upstream side of the die body.
A manhole is provided concentrically with the nozzle hole, and a pipe material having a nozzle hole with a large diameter part on the upstream side and a small diameter part on the downstream side is inserted into the insertion hole, and the small diameter part of the pipe material and the die are inserted. The gist is to provide a space between it and the insertion hole of the main body.

(E) Function As described above, in the die of the present invention, by providing a space between the small diameter portion of the pipe material and the insertion hole of the die body,
Since this space serves as a heat insulator, the high-temperature molten resin that is pumped through the nozzle hole is not affected by the heat from the cooling water filling the die surface, so the molten resin changes its viscosity and passes through the nozzle. It is extruded smoothly without sticking to the holes or clogging due to hardening.

(f) Practical ftI Examples The present invention will be described in detail below with reference to the drawings without showing examples thereof. FIG. 1 is a longitudinal sectional view of a die for resin pellet VU according to the present invention, FIG. 2 is a front view thereof, and FIG. 3 is an enlarged longitudinal sectional view of the same main part.

In the figure, the main components of the die 1 of the present invention are composed of a die body 2, a pipe material 3, and a hardened surface layer 4. In the die 1, a large number of nozzle holes 5, which are resin passages, are formed on a concentric circumference, penetrating the pipe material 3, the die body 2, and the hardened surface layer 4, with the axis almost coinciding with the extruder cylinder (not shown). It is provided. The shape of the nozzle hole 5 is from the upstream side (left side in Fig. 3) to a large diameter part 5a and a tapered part 5b.
, and a small diameter portion 5C on the outlet side. Nozzle hole 5
A hardened surface layer 4 having high wear resistance is provided on the surface of the die body 2 on the exit side by means such as welding. The pipe material 3 is inserted from the upstream side to the downstream side with its outer diameter part fitted into a stepped insertion hole 6 provided in the die body 2 so as to coaxially communicate with the nozzle hole 5. The outer diameter of the pipe material 3 and the shape of the insertion hole 6 are, from the upstream side, a flange portion 6a1, a large diameter portion 6b, a tapered portion 6c corresponding to the tapered portion 5b of the nozzle hole 5, and a tapered portion 6c corresponding to the tapered portion 5b of the nozzle hole 5. A small diameter portion 6d is formed first. Note that the tapered portion 6c' on the side of the insertion hole 6 is provided as close to the hardened surface layer as possible in terms of strength, and therefore the axial length of the large diameter portion 6b is made to be larger than that of the pipe material 3. I'm in the middle of the day. The fitting length of the small diameter portion 6d is such an axial length that the fitting will not come off even if an imbalance of axial expansion/contraction times occurs between the die body 2 and the pipe material 3 due to the influence of thermal expansion. Just take the dimensions. With the above configuration, when the pipe material 3 is inserted into the fixed position of the stepped insertion hole 6 provided in the die body 2, the outer diameter part of the small diameter part 5C of the nozzle hole 5 of the pipe material 3, A space 7 is formed between the tapered portions 6C and 6c'. Furthermore, similarly to the die in the prior art, 8 is a heating jacket provided on the outer periphery of the nozzle hole group, 9 is a heating jacket provided in the center of the nozzle hole group, heating medium population 10, heating medium A heat medium is supplied and υ1 is discharged from the outlet 11. Further, the die 1 is fixed to a discharge portion of an extruder cylinder (not shown) with bolts using a plurality of bolt holes 12 provided in the die body 2. In addition, a cooling water circulation box (not shown) in which cooling water circulates is attached to cover the surface of the die 1 on the surface hardening layer 4 side using a plurality of screw holes 13 provided in the die body 2. A rotary cutter (not shown) is provided on the surface of the hardened surface layer 4 in contact or with a small gap.

Next, the operation of the embodiment will be described. The die configured as described above is attached to the discharge part of the extruder cylinder (not shown) with bolts, and the resin sufficiently kneaded and melted in the extruder is delivered to the back of the die 1, that is, to the large diameter part of the nozzle hole 5. It is pressurized and supplied to the 5a side. Then, the pressurized resin is transferred to the nozzle hole 5.
The material is forced into cooling water and extruded from the surface side of the die 1, that is, from the surface hardened layer 4 side, and is cut into pieces by a rotary cutter and pelletized. In this process,
The die 1 is a heating jacket 1 provided on the die body 2.
-8.9, the overall temperature is controlled by the heat medium introduced and discharged from the heat medium inlet 10 and heat medium outlet 11. Further, in the small diameter portion 5C of the nozzle hole 5, which is most susceptible to the cooling water filling the surface of the die 1, the small diameter portion 6d of the pipe material and the insertion hole 6 of the die body 2 are located close to the hardened surface layer 4. By providing a space 7 between them, this space 7 performs a heat insulating function to suppress the heat influence from the die surface due to the cooling water, so that the high temperature molten resin pumped through the nozzle hole 5 is It causes almost no temperature drop, and therefore changes its viscosity and adheres to the inside of the nozzle hole 5.
It hardens and extrudes smoothly without clogging. Note that the pipe 4A3 is always pressed forward by the molten resin supplied under pressure from the extruder, so it is simply inserted into the stepped insertion hole 6 provided in the die body 2 from the upstream side. Therefore, it can be manufactured extremely easily. Further, when fitting the pipe material 3 and the die body 2, it is acceptable even if a small gap is formed on the side surface of the tip of the small diameter portion 6d. This is because even if a small gap is created and molten resin enters there, it will be the exact same resin as the resin being extruded, and the resin that entered the gap will act as a heat insulator, and the cooling water will This is because the effect of further suppressing the heat influence from the die surface is exhibited. Therefore, the axial length dimension of the pipe material 3 does not require much machining precision, making machining even easier. In addition, the stepped insertion hole 6 provided in the die body 2 is formed with a tapered portion 6C' from the large diameter portion 6b to the small diameter portion 6d, thereby increasing the strength of the die body 2 against the molten resin supplied under pressure. Since the space 7 can be formed at a position extremely close to the hardened surface layer 4 side without any damage, the thermal influence of the cooling water can be suppressed at a position extremely close to the tip of the nozzle hole 5. Further, in the portion forming the space 7, it is desirable to make the wall thickness of the pipe material 3 as small as possible in terms of strength. This is because it is advantageous in reducing the size of the hot canister that attempts to move in the axial direction through the thick portion of the pipe material 3. This is because while the molten resin is being pumped through the nozzle hole 5, its retained pressure is significantly reduced due to pressure loss, so by forming the space 7 as close to the tip of the nozzle hole 5 as possible, It is advantageous to make the wall thickness of the small diameter portion 6d of No. 3 small.

(G) Effects of the Invention As described above, according to the die for making resin pellets L-':J according to the present invention, the tip of the nozzle hole, which is most easily affected by the cooling water filling the die surface, has a hardened surface. By providing a space close to the layer and between the small diameter part of the pipe material and the insertion hole of the die body, this space can
Since the cooling water acts as a heat insulator to suppress the heat effect from the die surface, the high temperature molten resin that is pumped through the nozzle hole hardly experiences a drop in temperature, changing its viscosity and preventing it from adhering to the inside of the nozzle hole or hardening. It is extruded smoothly without clogging. Moreover, its structure requires no complicated machining compared to conventional dies and chairs, and is extremely easy to manufacture, as the pipe material is simply inserted into the insertion hole provided concentrically with the nozzle hole in the die body. The result was that the strength was sufficiently satisfactory.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of a die for producing resin pellets according to the present invention, FIG. 2 is a front view of the same, and FIG. 3 is an enlarged longitudinal cross-sectional view of the same main part. DESCRIPTION OF SYMBOLS 1...Dice, 2...Die body, 3...Pipe material, 4...Surface hardening layer, 5...Nozzle hole, 6...
Insertion hole and pipe material outer diameter, 7... Space, 8.9...
・Heating jacket, 10...Heat medium inlet, 11...
Heat medium outlet, 12... bolt hole, 13... screw hole. Patent applicant: Japan Steel Works, Ltd. Representative: Naohiko Yagi Figure 1 Figure 2 Figure 3 Flash

Claims (1)

[Claims] A die for producing resin pellets, which is a die attached to the tip of an extruder, and extrudes molten resin into cooling water from a number of nozzle holes of the die, and cuts the resin into pellets with a rotating cutter provided on the front of the die. An insertion hole having a diameter larger than the nozzle hole is provided in the die body from the upstream side of the die body, concentrically communicating with the nozzle hole, and the insertion hole has a large diameter part on the upstream side and a small diameter part on the downstream side. 1. A die for resin manufacturing, characterized in that a pipe material having a diameter of 100 mm is inserted therein, and a space is provided between a small diameter portion of the pipe material and an insertion hole of a die body.