JPH06198712A - Extruder screw cooling system - Google Patents

Abstract

(57) [Summary] [Purpose] An extruder that allows the slew cooling length to be adjusted to an optimum value without stopping the operation of the extruder, and that it is not necessary to place blind plugs or screw cooling pipes of different lengths in line. To provide a screw cooling device of. A screw cooling pipe 12 having a refrigerant discharge hole 13 is inserted into a cooling center hole 4 formed inside a screw 3 of an extruder so as to be movable in the axial direction of the screw 3. Is connected to the stroke adjusting mechanism 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw cooling device for an extruder, which is capable of continuously adjusting the substantial length of screw cooling without stopping the operation of the extruder. Regarding the device.

[0002]

2. Description of the Related Art In a single-screw extruder or a single-screw vent type extruder, in order to prevent an unstable operation phenomenon such as surging and an operation stop due to winding of a raw material resin around the screw surface, the screw of the extruder is I'm trying to cool from.

FIG. 4 is a longitudinal sectional view showing a prior art of a screw cooling device of an extruder.

In the screw cooling device of the extruder shown in FIG. 4, a cooling center hole 4 is formed inside the screw 3. A screw cooling pipe 5 is inserted into the cooling center hole 4. This screw cooling pipe 5
The outer end of is connected to a rotary joint 6 having a refrigerant inlet 7 and a refrigerant outlet 8. Note that FIG.
Inside, 1 is a barrel, 2 is a raw material resin inlet, and 11 is a refrigerant.

In the prior art, when the substantial screw cooling length S ₁ is changed, the operation of the extruder is temporarily stopped, the screw cooling pipe 5 used up to now is pulled out, and the tapping hole for pulling out is used. The replaceable blind plug 9 is pulled out or added using 10 to adjust the effective length of the cooling center hole 4. Then, the screw cooling pipe 5 having a length S ₂ corresponding to the adjusted cooling center hole 4 is replaced.

[0006]

By the way, the solid transfer capacity and operation stability of a single-screw extruder depend on the friction resistance between the barrel surface and the screw surface of the extruder due to the powder characteristics of the raw material resin. large. In particular, in the case of high-mix low-volume production, it is often the case that various lubricants, dyes, and pigments are added as auxiliary materials by changing the prescription, or the raw material resin itself is changed. In that case, the frictional resistance changes significantly. Further, the friction coefficient has temperature dependence. Therefore, in order to obtain the above-mentioned operational stability, the temperature of the extruder and the temperature of the screw cooling are adjusted. However, since the latter screw cooling has a limit, the screw cooling length S
₁ needs to be adjusted and optimized. In such a case, in the conventional technique, the operation of the extruder is once stopped,
Parts of both the blind plug 9 inserted in the cooling center hole 4 of the screw 3 and the screw cooling pipe 5 will be replaced.

However, it is impossible to know in advance the optimum values of the lengths of the blind plug 9 and the screw cooling pipe 5, and in some cases, in order to find the optimum screw cooling length S ₁ , the trial and error is performed. As a result of repeated parts replacement, there is a problem that the resin raw material is wasted a lot and requires a lot of labor.

Further, in the case of a single-screw extruder used for coextrusion molding of a sheet and a film, the combination of the layer ratios of the intended product is wide, so that the same extruder can stably operate in a wide discharge flow range. Being able to do so is a necessary condition. Here, the discharge flow rate of the extruder can be variably adjusted by both the screw design and various operating conditions such as the screw rotation speed, but the change of the screw design means replacement with a screw having a different screw dimension. Therefore, the latter is actually adjusted by adjusting the screw rotation speed, and accordingly, it is possible by mutual adjustment of various operating conditions such as adjustment of the barrel temperature of the extruder or the screw cooling temperature.

As described above, in order to optimize the cooling of the squeeze in accordance with the demand for operational stability in a wide range of discharge flow rates in the same extruder, as described above, the blind plug 9 and screw of appropriate length are used. There is no alternative but to replace the parts in the cooling pipe 5. Therefore, there has been a problem that the operation of the extruder has to be stopped and the production efficiency is significantly reduced.

Further, in the prior art, there was also a problem that many parts such as blind plugs having different lengths and screw cooling pipes had to be placed together.

An object of the present invention is to provide an extruder in which the slew cooling length can be adjusted to an optimum value without stopping the operation of the extruder and it is not necessary to arrange blind plugs and screw cooling pipes having different lengths in line. It is to provide a screw cooling device.

[0012]

In order to achieve the above object, in the present invention, a screw cooling pipe having a refrigerant discharge hole is provided in a cooling center hole formed inside a screw of an extruder in the axial direction of the screw. It is movably inserted and this screw cooling pipe is connected to a stroke adjusting mechanism.

[0013]

In the present invention, the screw cooling pipe inserted in the cooling center hole formed inside the screw is moved to an arbitrary position in the axial direction of the screw by the stroke adjusting mechanism. Thereby, the screw cooling length can be adjusted to the optimum value without stopping the operation of the extruder. In addition, it is possible to eliminate the need for aligning blind plugs and screw cooling pipes having different lengths as in the prior art.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view showing a first embodiment of the present invention, and FIG. 2 is an enlarged view of a portion P of FIG. 1, which is an enlarged sectional view of a screw cooling pipe and a slide plug portion.

In the first embodiment shown in FIGS. 1 and 2, the screw cooling pipe 12 is inserted into the cooling center hole 4 formed inside the screw 3.

At one end of the screw cooling pipe 12,
A refrigerant discharge hole 13 and a slide plug 14 are provided, and the other end is a refrigerant inlet 12 '. A plurality of the refrigerant discharge holes 13 are provided at equal intervals in the circumferential direction. An oil-free bearing 15 is fitted around the outer periphery of the slide plug 14. This oil-free bearing 15
Is formed to have a small clearance between the cooling center hole 4 and a flange provided on one end side of the slide plug 14 and a bearing abutted on the other end side. The stopper 16 and the bolt 17 make the slide stopper 1
It is fixed at 4. The slide plug 14 plays a role of defining the screw cooling length. The refrigerant inlet 12 'is a refrigerant supply source (not shown) through a hose or the like.
It is connected to the.

An outer portion of the screw 3 in the screw cooling pipe 12 is connected to a rotary joint 18. The rotary joint 18 includes a body portion 19 having a refrigerant outlet 20 and a flange 24, a rotary shaft 21 connected to the screw 3 and inserted into the body portion 19, an outer periphery of the rotary shaft 21 and a half of the body portion 19. And a mechanical seal 23 installed between the inner periphery of the other half of the body 19 and the end of the rotary shaft 21.
And have. The refrigerant outlet 20 communicates with the cooling center hole 4 of the screw 3 through the inside of the rotary joint 18, and discharges the used refrigerant.

The other end of the screw cooling pipe 12 is connected to a stroke adjusting mechanism 26. The stroke adjusting mechanism 26 includes a mount 27 fixed to the outside of the barrel 1 of the extruder, a feed shaft 28 rotatably supported by the mount 27, a handle 29 attached to the feed shaft 28, and the feed unit. Guide shaft 3 arranged parallel to shaft 28 and fixed to mount 27
0, the other end of the screw cooling pipe 12 and the feed shaft 2
8 and a guide shaft 30, and an arm 31 provided across the guide shaft 30. The arm 31 is welded to the other end of the screw cooling pipe 12, and
It is screwed to the feed shaft 28 via 2 and is fitted to the guide shaft 30 via the guide hole. Then, the stroke adjusting mechanism 26 operates the handle 29 to rotate the feed shaft 28, so that the screw cooling pipe 12 together with the arm 31 moves in the axial direction X of the screw 3 by the screw action of the feed shaft 28 and the female screw 32.
It is configured to move to -X '. A coolant drain 33 is provided on the arm 31.

On the outer periphery of the screw cooling pipe 12, a flange 24 provided on the body portion 19 of the rotary joint 18 and an arm 31 of the stroke adjusting mechanism 26.
An expansion joint 25 is attached between and.

Next, the operation of the screw cooling device according to the first embodiment will be described.

When the handle 29 of the stroke adjusting mechanism 26 is rotated in the forward direction or the reverse direction while the operation of the extruder is continued, the guide shaft is screwed by the feed shaft 28 and the screw 32 so that the guide shaft is rotated. The screw cooling pipe 12 along with the arm 31 moves forward or backward in the cooling center hole 4 formed inside the screw 3.

The adjustment of the screw cooling length toward the optimum value is performed, for example, while observing the resin pressure gauge (not shown) provided at the discharge part of the extruder, and the position where the vibration of the resin pressure gauge is stopped is set. It becomes possible by asking. As a result, the screw cooling length can be adjusted to the optimum value steplessly and easily and in a short time without stopping the operation of the extruder.

In this way, the screw cooling length can be adjusted without stopping the operation of the extruder.
It is possible to eliminate the decrease in production efficiency. Also, since the screw cooling length can be adjusted steplessly to the optimum value, in the case of high-mix low-volume production, it is possible to add various lubricants and dyes and pigments as auxiliary raw materials by changing the prescription or changing the raw material resin itself. In this case, stable operation conditions can be satisfied. Furthermore, since the screw cooling length can be easily adjusted to the optimum value while observing the resin pressure gauge, it is possible to eliminate waste of the resin raw material for adjusting the screw cooling length and to save labor. Moreover, it is possible to eliminate the need for aligning parts of different lengths to change the screw cooling length.

The refrigerant 11 is supplied to the cooling center hole 4 inside the screw 3 through the refrigerant supply source → the other end of the screw cooling pipe 12 which is the refrigerant inlet 12 ′ → the screw cooling pipe 12 → the refrigerant discharge hole 13. By doing. At this time, the slide plug 14 provided at one end of the screw cooling pipe 12 plays a role of limiting the outflow of the refrigerant 11 to the outside of the area partitioned by the slide plug 14 and defining the screw cooling length. Air, cooling water, refrigerant oil, or the like is used as the refrigerant 11. Also, screw 3
After cooling the refrigerant, the refrigerant is discharged from the rear end of the cooling center hole 4 → the inside of the rotary joint 18 → the refrigerant outlet 20 provided in the body portion 19 of the rotary joint 18.
Through. Then, the refrigerant outlet 20 is connected to a heat medium temperature controller, and is circulated for use after adjusting the temperature, or in the case of industrial water, it is directly guided to the drain port in one pass.

Next, FIG. 3 is a vertical sectional view showing a second embodiment of the present invention.

In the second embodiment shown in FIG. 3, O is formed on the outer circumference of the slide plug 14 provided on the screw cooling pipe 12.
A ring 34 is attached to prevent the refrigerant 11 from flowing out of the area defined by the slide plug 14 as much as possible. Is provided with a clearance necessary for moving the slide plug 14.

The portion of the screw cooling pipe 12 protruding from the screw 3 is attached to the first and second rotary joints 35 and 36. The first rotary joint 35 includes the screw cooling pipe 1
A cylinder having a rotary shaft 37 fitted to the outer circumference of 2 and pressed against the end of the screw 3, and a half of which is fitted to the outer circumference of the rotary shaft 37 and has a refrigerant outlet 46 and a flange 47 on the other half side. The part 39, the bearing 41 interposed between the outer circumference of the rotary shaft 37 and the inner circumference of the one half of the body 39, and the bearing 39 installed between the inside of the other half of the body 39 and the end of the rotary shaft 37. And a mechanical seal 43. The second rotary joint 36 has a rotary shaft 38 which is hollow and integrally connected to the screw cooling pipe 12, a body 40 having a half part fitted to the outer periphery of the rotary shaft 38, and the rotary shaft 38.
4 interposed between the outer periphery of the body and the inner periphery of the half of the body 40
2 and a mechanical seal 44 incorporated between the other half of the body 40 and the end of the rotary shaft 38. A refrigerant inlet pipe 45 is inserted from the outside to the inside of the second rotary joint 36, and the refrigerant 11 is fed from the refrigerant inlet pipe 45 to the screw cooling pipe 12.

An arm 28 is fixed to the outer circumference of one half of the body 40 of the second rotary joint 36 with a screw. A drain 49 is provided on the arm 28.

An expansion joint 48 is attached between the arm 28 and a flange 47 provided on the body 39 of the first rotary joint 35.

The other structure of the second embodiment is similar to that of the first embodiment, and the same members are designated by the same reference numerals.

Next, the operation of the screw cooling device according to the second embodiment will be described.

First, in the case of adjusting the screw cooling length, the stroke adjusting mechanism 2 with the operation of the extruder continued.
The handle 26 of 3 is rotated in the forward direction or the reverse direction.
As a result, the arm 28, the second rotary joint 36, and the screw cooling pipe 12 move together in the forward or backward direction along the guide shaft 27 by the screw action of the screw 29 provided on the feed shaft 25 and the arm 28. To do. Also in this embodiment, the adjustment of the screw cooling length toward the optimum value is performed while observing the resin pressure gauge provided in the discharge part of the extruder and determining the position where the deflection of the resin pressure gauge is settled. . As a result, according to the second embodiment as well, the screw cooling length can be adjusted to the optimum value steplessly and easily and in a short time without stopping the operation of the extruder.

The refrigerant is supplied from the refrigerant supply source → the refrigerant inlet pipe 4
5 → Screw cooling pipe 12 → Discharge to the cooling center hole 4 through the refrigerant discharge hole.

After cooling the screw 3, the cooling medium is discharged through the cooling center hole 4 → the inside of the first rotary joint 35 → the body 3 of the first rotary joint 35.
9 is the same as that of the first embodiment except that it is carried out through the refrigerant outlet 46 provided at 9. In the second embodiment, the O-ring 34 is attached to the outer peripheral surface of the slide plug 14 provided at one end of the screw cooling pipe 12,
The gap between the cooling center hole 4 and the O-ring 34 is slightly suppressed. Therefore, the cooling center hole 4 has O
The ring 34 comes into contact, and the frictional force at that time may cause the slide stopper 14 and the screw cooling pipe 12 to rotate together with the screw 3. The rotation of the screw cooling pipe 12 at this time is performed by the first and second rotary joints 3
5,36.

The other operation of the second embodiment is the same as that of the first embodiment.

In the present invention, the stroke adjusting mechanism 23
Is not limited to the structure shown in FIGS. 1 and 4, and any structure may be used as long as it can exhibit a desired function.

Here, in the first and second embodiments, the points to be noted are the member provided on the outer periphery of the slide plug 14 connected to the tip of the screw cooling pipe 12 and the cooling center hole 4. The sealability with the center hole for cooling 4
It is not intended to positively prevent the refrigerant from leaking into the hollow portion existing between the end portion of the cooling plug and the slide plug 14, but rather the screw cooling pipe 12 can be easily provided in the long cooling center hole 4. The purpose of this is to provide a gap that allows the screw cooling pipe 12 connected to the slide stopper 14 to be easily slid. More specifically, when oil is used as a coolant for screw cooling, this hollow portion is filled with oil and becomes dead.When water is used, once water that has penetrated evaporates and internal pressure is reduced. It has been confirmed that the water cooling rate is increased and the water that tries to penetrate further is automatically blocked, and that neither has any adverse effect on the screw cooling function.

Next, more specific examples and comparative examples will be given.

Example 1 In a single-screw vent type extruder for p-MMA pellet extrusion molding, the existing screw cooling pipe and blind plug were removed, and the screw cooling device of the present invention shown in FIG. 1 was installed. The screw cooling length is p-MM in advance.
Extrusion was carried out after setting the length suitable for the production of A transparent pellets. First, as a raw material for p-MMA transparent pellets, a bead-shaped p-MMA resin having an average particle diameter of 0.2 to 0.3 mmφ was supplied to an extruder and extrusion molding was performed, and stable operation was performed without any problems. However, the extrusion amount did not decrease.

Next, when gradually changing to a raw material for p-MMA colored pellets in which a pigment and a lubricant were added to the p-MMA transparent raw material resin in an amount of 6% by weight, surging started to occur. When stroke adjustment was performed back and forth, as a result of lengthening 1.25 pitch (ratio to screw diameter) from the initial position, surging could be eliminated in a few minutes.

Example 2: p-MMA type two-kind two-layer coextrusion In a single-screw vent type extruder for coextruding upper and lower skin layers used for sheet forming, equipped with the screw cooling device of the present invention shown in FIG. , A bead-shaped p− containing 10% by weight of mica as a raw material resin and having an average particle diameter of 0.2 to 0.3 mmφ
MMA transparent resin was supplied and the extrusion rate was controlled by adjusting the screw rotation speed to extrude various products with different skin layer thicknesses. Since the surging started when the temperature was lowered, when the stroke was adjusted to adjust the screw cooling length, the surging subsided, and stable extrusion molding became possible even when the rotational speed was reduced to 30% of the usual maximum rotational speed.

Comparative Example 1 In the above Example 1, when the screw cooling device according to the prior art is used, p-MMA is fixed in the fixed screw cooling pipe and the blind plug even if the refrigerant flow rate and the refrigerant temperature are controlled. Transparent pellet manufacturing,
It is impossible to achieve stable operation at the same time as the production of p-MMA colored pellets containing 6% by weight of pigment and lubricant, and there is no choice but to replace parts. Production loss occurred.

Comparative Example 2: Prior to the above Example 1, a pigment,
In order to enable stable production of p-MMA colored pellets containing 6% by weight of lubricant, a blind plug of 0.5 and 1.0 pitch and a plurality of screw cooling pipes corresponding to this blind plug were prepared in advance and trial and error. I tried to replace the parts, but one part replacement causes a production loss of about 1 hour and 0.5 pitc
Since the stroke is adjusted in increments of h, the optimization cannot be achieved, and it is unavoidable to operate in a state in which the discharge flow rate is reduced by about 25% with respect to the maximum working extrusion amount.

Comparative Example 3: In Example 2, the screw cooling device according to the prior art was replaced, and the barrel temperature, the screw cooling water amount, and the cooling water inlet temperature were adjusted to each other. As for the lower limit of the above, when the screw rotation speed was reduced with respect to the usual maximum extrusion amount of 100% and the extrusion amount was reduced, the lower limit of the stable extrusion amount could not be set to 50% or less because of the occurrence of surging.

[0046]

As described above, according to the present invention, the cooling center hole formed inside the screw of the extruder,
A screw cooling pipe having a refrigerant discharge hole is inserted so as to be movable in the axial direction of the screw, and this screw cooling pipe is connected to a stroke adjusting mechanism, so that the slew cooling length can be reduced without stopping the operation of the extruder. There is an effect that it can be adjusted to an optimum value, and there is also an effect that it is possible to eliminate the need to arrange parts such as blind plugs and screw cooling pipes of different lengths in line.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is an enlarged view of a P portion of FIG. 1, and is an enlarged sectional view of a screw cooling pipe and a slide plug portion.

FIG. 3 is a vertical cross-sectional view showing a second embodiment of the present invention.

FIG. 4 is a vertical sectional view showing a conventional technique.

[Explanation of symbols]

 3 ... Screw of extruder 4 ... Center hole for cooling screw 11 ... Refrigerant 12 ... Screw cooling pipe 12 '... Refrigerant inlet 13 ... Refrigerant discharge hole 14 ... Slide stopper 15 ... Oil-free bearing XX' ... Screw cooling pipe Stroke adjusting direction 18 ... Rotary joint 20 ... Refrigerant outlet 26 ... Stroke adjusting mechanism 34 ... O-ring 35, 36 ... First and second rotary joint 45 ... Refrigerant inlet pipe 46 ... Refrigerant outlet

Claims (1)

[Claims] 1. A screw cooling pipe having a refrigerant discharge hole is inserted into a cooling center hole formed inside a screw of an extruder so as to be movable in the axial direction of the screw, and the screw cooling pipe has a stroke adjusting mechanism. A screw cooling device for an extruder, which is characterized by being connected to.