JPH0222269Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a screw-type extrusion molding machine, and particularly to an improvement of a plasticizing section in an extrusion molding machine for polymeric materials (hereinafter simply referred to as resin).

[Conventional technology]

The mainstream of conventional single-screw extrusion molding machines is the full-flight type, in which a spiral flight is provided on the screw shaft. Various improved types have been put into practical use to improve stability. The reality is that they are used differently depending on the type of resin to be molded and the purpose of use, and each has advantages and disadvantages.

The biggest drawback of full-flight extrusion molding machines is that attempting to improve the extrusion rate leads to an increase in the length and size of the equipment, which is mechanically and economically limited.

Therefore, in order to increase the melting speed of the resin in the screw groove and improve the extrusion capacity, various extrusion molding machines equipped with specially shaped screws that separate the solid bed, which is a lump of unmelted resin, have been put into practical use. .

However, although these techniques can improve extrusion efficiency, they are improvements within the scope of changing the screw shape, and there are limits to the scope of improvement.

On the other hand, the most aggressive method, which focuses on improving the melting mechanism and forcibly destroys the solid bed from the outside, has been put into practical use in order to improve the melting rate.
This is different from a normal single-screw extrusion type machine, in that spiral blades are provided on both the surfaces of the screw and cylinder to create grooves, and both grooves constitute one flow path. During this process, resin is sheared and frictional heat is generated on the transfer circumferential surface, and the position of the resin is exchanged and the arrangement is rearranged.

However, since such a device was developed primarily for the purpose of mixing and coating rubber, it has various disadvantages when used as a resin molding machine.

Therefore, this device was developed as a screw-type extrusion molding machine with a structure suitable for resin molding.
The one described in Publication No. 48501 has been put into practical use.

This screw type extrusion molding machine is shown in Figures 4 and 5.
As shown in the figure, in the plasticizing section (melting section) of a single screw extruder, the entire plasticizing section (melting section) is used as a shearing/kneading section. expands conically along the cylinder axis, then contracts conically, the large diameter part inflow side widening gradient is larger than the large diameter part outlet side reducing gradient, and there is a conical wall on the outflow side parallel to the cylinder axis. The screw shaft 23 has a conical large diameter portion 24 which faces each other and has a slope approximately equal to the slope of the cylinder at a position approximately corresponding to the large diameter portion of the cylinder, and has a large diameter portion 24 which is disposed at a position substantially corresponding to the large diameter portion of the cylinder. A blade 25 twisted with respect to the cylinder axis is provided on the side conical slope, and the top diameter of the cylinder side blade 22 is slightly larger than the top diameter of the shaft side blade 25, and the flow rate is adjusted in the enlarged double conical flow path on the inlet side. The resin is completely transferred from the shaft-side flow path to the cylinder-side flow path, and then, on the large-diameter outflow side, while the resin is transferred from the cylinder-side flow path to the shaft-side flow path, the cylinder-side blade 2
The structure is such that the resin is sheared between the top part of the blade 2 and the top part of the shaft-side blade 25 to promote melting and kneading, thereby making it possible to improve the extrusion amount and quality.

[Problem that the invention attempts to solve]

However, in the method described in Utility Model Publication No. 56-48501, firstly, regarding the position of the shearing and kneading section, the entire melting section is used as the shearing and kneading section, which causes the following problems. ing.

First, in the shearing/kneading section, the cylinder side blade 22
The resin is mainly sheared between the top and the top of the shaft side blade 25, and the blade 25 has almost no propulsive force, so if the melting part disappears, the only propulsive force is the force of the supply part, which becomes extremely unstable. , it is difficult to obtain a stable extrusion state. In particular, the extrusion speed varies greatly depending on the type of resin.

Next, after the resin is sent from the supply section, it is preheated and immediately sheared in the shearing/kneading section without any melted parts, which requires a large amount of mechanical energy.

Furthermore, as mentioned above, since the propulsive force is weak, the extrusion capacity changes depending on the resistance of the die. For this reason, the weighing section must be made wider than the conventional machine, making the machine long and uneconomical.

Second, looking at the shape of the shearing/kneading section, the expansion slope of the cylinder inner wall and screw shaft (screw valley diameter) on the inflow side is larger than the contraction slope of the cylinder inner wall and screw shaft on the outflow side. Since there are no blades 22, 25 on the enlarged part on the inflow side, all the resin is once transferred to the cylinder side and then sheared when it is delivered to the screw side. Therefore,
The screw receives the shear from the part far from the inner wall of the cylinder (the part that is not sufficiently preheated).
The effect of kneading the molten resin and unmelted resin has been half destroyed.

Furthermore, since the expansion slope of the cylinder inner wall and screw shaft on the inflow side is larger than the contraction slope on the outflow side, there are no vanes 22 and 25 on the cylinder inner wall and screw shaft on the inflow side, making it difficult to scoop up the resin. Therefore, there is a problem that the inflowing resin encounters large resistance at that part and has difficulty advancing.

The technical objective of the present invention is to solve the above-mentioned problems and create a single-screw extrusion molding machine that can produce stable extruded products with excellent extrusion volume and quality.

[Means for solving problems]

In order to solve the above technical problem, the present invention takes the following technical measures.

That is, instead of using the entire melting section 7 as the shearing/kneading section 9, a part of the melting section 7 is left on the supply section 6 side, and while the driving force in the melting section 7 remains, the melting section 7 is
A shearing/kneading section 9 is provided in a portion extending over a part of the measuring part 8 and a part of the measuring part 8.

The diameter of the valley of the screw 3 in the remaining melting zone 7 gradually increases toward the extrusion side.

In addition, the structure of the shearing/kneading section 9 is such that when looking at the cylinder 1, the inner diameter of the cylinder 1 expands in a conical shape along the cylinder axis, and then decreases in a conical shape.
The expansion slope on the inflow side of the resin is smaller than the contraction slope on the outflow side, and a plurality of blades 11 parallel to the cylinder axis are provided on the conical inner walls of the inflow side and the outflow side, which are the inner wall surfaces of the cylinder 1 in this part. It has been established.

On the other hand, the screw 3 in the shearing/kneading section 9 is
The trough expands into a conical shape in the extrusion direction corresponding to the inner diameter of the cylinder 1 of the shearing/kneading section 9, and then contracts into a conical shape. Longer conical large diameter portion 12
The maximum diameter part of this large diameter part 12 is the flight 5.
The diameter is the same as the outer diameter of the screw 3 including the screw 3, and the flight 5 is excluded from the maximum diameter portion of the large diameter portion 12 to the reduced side.

[Effect]

The case of extrusion molding using the extrusion molding machine of the present invention will be described.

(a) The resin preheated in the supply section 6 is transported to the melting section 7.

(b) The groove diameter of the screw 3 in the melting zone 7 gradually increases as it goes toward the extrusion side (the depth of the screw groove gradually becomes shallower), so that the resin is formed between the inner wall of the cylinder 1 and the groove surface of the screw 3. It moves forward while being compressed in the radial direction.

(c) While moving forward, the resin begins to melt from the surface that is in contact with the inner wall of the cylinder 1. However, the portion far from the inner wall of the cylinder 1 (the portion close to the valley of the screw 3) is difficult to melt and remains as a solid bed.

(d) The melting section 7 plays an important role in stably advancing the resin, and for this purpose, the resin must be compressed between the inner wall of the cylinder 1 and the screw 3 to generate high pressure.

It is of course important to find ways to increase the melting rate, but for this purpose, it is absolutely essential to have a large, reliable, and stable force to move the resin forward.

(E) As the resin advances through the melting section 7, the resin gradually melts from the side that is in contact with the inner wall of the cylinder 1. In this area, the resin is in a mixed state of completely melted and unmolten solid bed.

The resin is then fed into a shearing and kneading section 9 based on the new technical concept of the present invention. Here, the molten resin is scooped up by the blades 11 provided on the inner wall of the cylinder 1 and the flights 5 of the screw 3 and transferred to the cylinder 1 side. As the resin advances further, an unmelted solid bed portion appears, and the blade 11 on the cylinder 1 side and the screw 3
The resin is sheared and fragmented between the resin and the flights 5 on the side, and then transferred to the cylinder 1 side, and eventually all of the resin is delivered to the cylinder 1 side.

(f) Then, by shearing and kneading as described above, the solid bed disappears and becomes completely molten.

That is, the shearing/kneading section 9 according to the present invention is characterized in that it transfers the resin in the three screw grooves from the melted portion to the cylinder 1 side, and sequentially transfers the unmelted portion to the high temperature cylinder 1 side while shearing. It is effective.

Since the shearing/kneading section 9 is located at a location that straddles the melting section 7 and the measuring section 8, the resin transported from the melting section 7 in the previous stage of the shearing/kneading section 9 is in one place. Parts are completely melted,
Some unmelted portions remain as solid beds. In such a situation,
Since the solid bed is sequentially delivered to the cylinder 1 side, the solid bed is sheared and divided into pieces and moved, and the unmelted resin and the molten resin are completely kneaded and a very high melting rate is obtained. .

(g) The molten resin that has completely moved to the cylinder 1 side advances to the measuring section 8 by the large, reliable, and stable propulsive force generated in the supply section 6 and the melting section 7, and is further extruded.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

A hopper 2 is provided on the inlet side of the cylinder 1, and a screw 3 is inserted into the cylinder 1. This screw 3 is formed by providing a spiral flight 5 around a screw shaft 4.

The cylinder 1 has a supply section 6, a melting section 7, and a measuring section 8 at the tip from the inlet side to the extrusion port side, and a shearing/kneading section 9 spanning between the melting section 7 and the measuring section 8. is formed.

To explain these in order from the inlet side to the extrusion side of the cylinder 1, first, the feed section 6 is a place where the groove depth of the screw 3 is constant and has the function of reliably conveying the resin forward while preheating it. , where the resin remains solid.

The diameter of the molten part 7 gradually increases as the root diameter of the screw 3 goes toward the extrusion side, so the groove depth of the screw 3 becomes shallower at a constant rate, and the resin is compressed toward the inner wall of the cylinder 1. This is where the resin is compressed and melted by the friction with the inner wall of the cylinder 1 and the heat from the cylinder 1. Then, the resin gradually melts from the part in contact with the inner wall of the cylinder 1, but the resin in the valley of the screw groove remains solid, called a solid bed. Here, since the diameter of the valley of the screw 3 is enlarged, the resin is compressed in the radial direction, and therefore the propulsive force due to the friction between the wall surface of the cylinder 1 and the resin becomes large and reliable. This driving force is extremely important for extrusion molding machines, and is an important function that is indispensable for stabilizing extrusion capacity.

The shearing/kneading section 9 has a cylinder 1 in that section.
The inner diameter is formed so that it expands conically in the extrusion direction along the cylinder axis and then contracts conically, and the slope on the expanding side is smaller than that on the contracting side, and the length on the expanding side is longer than that on the contracting side. ing.

Further, on the inner wall surface of the cylinder 1 of the shearing/kneading section 9, a plurality of blades 11 are provided which are parallel to the cylinder axis and have the same diameter as the inner diameter of the cylinder 1.

Furthermore, the root diameter of the screw 3 in the shearing/kneading section 9 expands conically in the extrusion direction and then shrinks conically, corresponding to the fact that the inner wall surface of the cylinder 1 expands conically and then shrinks. However, the slope on the enlarged side is smaller than that on the reduced side, and the length thereof is longer than that on the reduced side, forming a conical large diameter portion 12. A plurality of flights 5 with large pitches are provided on the outer periphery of the screw shaft 4 in this portion, separately from the supply section 6, melting section 7, and measuring section 8. Also,
The maximum diameter portion of the large diameter portion 12 is the same as the outer diameter of the screw 3 including the flights 5, and the flights 5 are removed from this maximum diameter portion.

Then, the cylinder 1 side blade 11 and the screw 3
A shearing and kneading action is performed between the flight 5 and the flight 5. What is important here is that the resin is sufficiently preheated, that the portion in contact with the cylinder 1 wall is already molten, and that it is transferred from the screw 3 side to the cylinder 1 side. This makes it possible to obtain very high melting rates.

In addition, since the slope of the inner wall of the cylinder 1 and the valley diameter of the screw 3 on the enlarged side is smaller and gentler than the slope of the reduced slope side, there is no resistance to the flow of resin here, and moreover, there is no resistance to the flow of the resin here. Since the flights 5 are provided and the blades 11 are provided on the inner wall of the cylinder 1, as the screw 3 rotates, the resin is scooped toward the extrusion side by the flights 5 and the blades 11, and the flow becomes smooth. Moreover,
Since there is no flight 5 from the maximum diameter portion to the reduction side and the slope on the reduction side is large, the resin is conveyed to the measuring section 8 without any resistance.

In addition, the effective area of the shearing/kneading section 9 is the actual area L/D when the L/D of the extrusion molding machine is 25 to 32 times.
D=4 to 6 times was effective. Also, the position of the shearing/kneading section 9 is L/D=12 counting from the hopper 2 side.
~15 times the amount is transferred to the supply section 6 and melting section 7, and then sheared and
Basically, a kneading section 9 is provided.

Also, the resin on the cylinder 1 side is formed by the outflow part provided on the screw shaft 4 again by the large and reliable driving force of the supply part 6 and the melting part 7, and the conical reduction part on the cylinder 1 side. It is sent to the screw 3 side through the flow path. Since the resin is almost completely melted in this flow path, there is no need to particularly reduce the cross-sectional area of the flow path, and this plays an effective role in improving extrusion capacity.

The measuring section 8 has a constant groove depth in the screw 3, and has a function of stably extruding a fixed amount of melted resin corresponding to the die resistance per screw rotation speed.

[Effect of idea]

According to the present invention, the position of the shearing/kneading section 9 remains in the conventional melting section 7, and a part of the melting section 7 and a part of the measuring section 8 are newly formed as the shearing/kneading section 9. and the melting section 7 are the same as in the conventional machine, and the propulsive force is as large and stable as in the conventional machine.

In addition, the resin sent to the shearing/kneading section 9 is
Part of it has completely melted, and the solid bed has been sufficiently preheated and is in a considerably softened state. Therefore, the mechanical energy required for shearing and kneading can be small.

In addition, the shape of the shearing/kneading section 9 is such that the expansion slope on the inflow side of the cylinder 1 is smaller than the contraction slope on the outflow side, and the blades 11 on the cylinder 1 side are uniform from the inflow side to the outflow side. When transferring from the side to the cylinder 1 side, it is sheared. Then, it is sufficiently preheated and the part in contact with the inner wall of the cylinder 1 is completely melted, and it is transferred from this part to the cylinder 1 side and sequentially sliced until it becomes a solid bed.
The next time the screw 3 receives the resin again for transfer to the side, the unmelted resin will be completely melted and thoroughly kneaded with the molten resin. In this way, the resin is melted and kneaded extremely smoothly, and the melting speed is also fast.

Therefore, it is not necessary to make the length of the cylinder 1 very long, and therefore the extrusion molding machine can be made small, and the manufacturing cost can be lowered.
It is convenient and can be installed in a narrow space.

In addition, since the slope of the inner wall of the cylinder 1 and the valley diameter of the screw 3 on the enlarged side is smaller and gentler than the slope of the reduced slope side, there is no resistance to the flow of resin here, and moreover, there is no resistance to the flow of the resin here. Since the flights 5 are provided and the blades 11 are provided on the inner wall of the cylinder 1, the resin is scooped toward the extrusion side by the flights 5 and the blades 11 due to the rotation of the screw 3, and the flow becomes smooth. Moreover,
Since there is no flight 5 from the maximum diameter portion to the reduction side and the slope on the reduction side is large, the resin is conveyed to the measuring section 8 without any resistance, and extrusion can be performed smoothly.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing one embodiment of the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. 1, Fig. 3 is a sectional view taken along line B-B in Fig. 1, and Figs. The figure is a longitudinal sectional view showing a conventional example. 1... Cylinder, 3... Screw, 4... Screw shaft, 5... Flight, 6... Supply section, 7...
Melting section, 8... Measuring section, 9... Shearing/kneading section, 1
1...Blade, 12...Large diameter part.

Claims (1)

[Claims for Utility Model Registration] A single-shaft screw that is equipped with one screw 3 in the cylinder 1, and has a supply section 6, a melting section 7, and a metering section 8 from the inlet side to the extrusion port side of the cylinder 1. In the type extrusion molding machine, a shearing/kneading section 9 is provided spanning a part of the melting part 7 and a part of the measuring part 8, and the remaining melting part 7 is
The diameter of the root of the screw 3 is gradually increased toward the extrusion side, and the inner diameter of the cylinder 1 of the shearing/kneading section 9 is expanded conically in the extrusion direction along the cylinder axis, and then reduced to a conical shape. The slope on the expansion side is made smaller than that on the contraction side, and the length thereof is made longer than that on the contraction side.
In the shearing/kneading section 9 of the screw 3, a plurality of blades 11 are provided on the inner wall surface, parallel to the cylinder axis, and having the same diameter as the inner diameter of the cylinder 1, and a spiral flight 5 is provided around the periphery. The valley diameter of the part is expanded conically in the extrusion direction in accordance with the inner diameter of the cylinder 1 of the shearing/kneading section 9, and then reduced conically, and the slope on the expanding side is made smaller than on the contracting side to reduce its length. It is made longer than the reduced side to form a conical large diameter part 12, and the maximum diameter part of this large diameter part 12 is the same diameter as the outer diameter of the screw 3 including the flight 5, and from the maximum diameter part of the large diameter part 12. A screw type extrusion molding machine characterized in that the flight 5 is removed from the reduction side.