JPH0129067Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an extrusion screw that can be applied to plastic extruders, rubber extruders, etc.

Figure 1 is a side sectional view of a conventional double-flight type extrusion screw, and Figure 2 is a cross-sectional view of D~ in Figure 1.
D sectional view, FIG. 3 is a sectional view taken along E to E in FIG. 1, and FIG. 4 is a sectional view showing the melted state of the resin in the screw groove.

In the figure, reference numeral 1 denotes an extrusion screw, which is composed of a first flight 2 and a second flight 3, which forms a first groove 4 and a second groove 5, as well as a feed section A, a compression section B, and a meter. Ring part C
It is divided into Further, the groove depths of the first groove 4 and the second groove 5 gradually decrease as shown in the figure. 6 is a cylinder, and 7 is a raw material inlet.

Here, the melting mechanism of the resin flowing in the first groove 4 between the first flight 2 and the second flight 3 will be explained (the explanation for the inside of the second groove 5 is the same and will be omitted), as shown in FIG. A collection of unmelted pellets, that is, a solid bed 8, is formed at the front in the direction of movement of the screw, and the portion of this bed near the cylinder 6 is exposed to the heat generated by the heat from the cylinder 6 and the shear between the resins caused by the rotation of the screw. The melt film 9 flows in a film shape on the solid bed 8 as shown by the arrow in FIG. 4, and flows into a pool of molten resin, that is, a melt pool 10. Typically, the width of the melt pool 10 increases as the resin progresses, and the width of the solid bed 8 decreases.

However, it is virtually impossible to maintain this molten state until the solid bed 8 disappears, and the solid phase resin and liquid phase resin separate in the compression part B, which is the so-called break up of the solid bed 8. A destructive phenomenon called .

After this phenomenon occurs, the solid phase resin and liquid phase resin form a large lump and are intermittent alternately, and as the screw advances further, the solid phase resin becomes suspended in the liquid phase resin. . The solid phase resin in this state is hardly subjected to effective shearing force due to screw rotation, and is melted mainly only by heat conduction from the liquid phase resin, so that melting of the solid phase resin becomes extremely slow. Further, the breakup of the solid bed 8 had a negative effect not only on kneading and dispersion, but also on defoaming, extrusion fluctuations, and galling phenomena between screws and cylinders.

The present invention was proposed to solve the above-mentioned conventional drawbacks, and in the synthetic resin extrusion screw,
A notch is formed intermittently on the top surface of the screw flight along the spiral direction, and the height of the notch is gradually increased toward the front of the screw. By arranging the notch portions so as to be inconsistent with the notch portions of adjacent flights, the solid phase and semi-molten resin are easily deformed by shearing, and efficient melting and kneading is performed. It is an object of the present invention to provide an extrusion screw which can prevent the occurrence of break-up, uniformly knead the material, maintain a uniform temperature, and obtain a high-quality material.

An embodiment of the present invention will be described below with reference to the drawings. Fig. 5 is a side sectional view of a double flight type extrusion screw showing an embodiment of the invention, Fig. 6 is a sectional view from F to F in Fig. 5, Fig. 7 is a sectional view of G to G in Fig. 5, and Fig. 8 is a sectional view of H to G in Fig. 5.
H sectional view, FIG. 9 is an I-I sectional view in FIG. 5, FIG. 10 is a developed view of the screw shown in FIG. 5,
FIG. 14 is a side sectional view of the top of the flight.

In the figure, 11 is an extrusion screw, which is composed of a first flight 12 and a second flight 13, with a first groove 14 and a second groove 15 formed between them.
It is divided into a feed section A, a compression section B, and a metering section C. Further, the groove depths of the first groove 14 and the second groove 15 gradually decrease as shown in the figure. 16 is a notch portion, and a feed portion A is formed on the top surface of the flight of the first flight 12 along the helical direction.
It is formed by intermittently cutting out a plane from the middle (the position where the resin starts melting, usually the 4th to 5th pitch from the base of the screw 11) to the tip of the screw, and has a notch height h. The notch height h is gradually increased toward the front, as shown by H in FIG. 14. In this embodiment, four notches are formed per circumference. Further, 17 is a notch, which is formed in the second flight 13 in the same manner as the notch 16, and is arranged in a positional relationship that is inconsistent with the notch 16, that is, in a staggered manner as shown in FIG. 6 is a cylinder, and 7 is a raw material inlet.

Next, the operation will be described. As the screw 11 rotates, the resin in the first groove 14 and the second groove 15 is pushed forward, and melting starts in the middle of the feed section A. In addition to the melting mechanism shown in FIG. 4, the resin flows over the notches 16 and 17 from the front groove to the rear groove as shown by the arrow in FIG. The inside of the groove 15 becomes turbulent and a good mixing effect is performed, and efficient melting and kneading is performed, and the solid bed 8
This accelerates the collapse of the structure and prevents break-ups from occurring. In addition, the resin that has become non-uniform due to shearing within the groove flows into the adjacent groove and is kneaded, resulting in even more uniform kneading.
A uniform temperature can be maintained and high quality materials can be obtained. In this case, the flight notch 1
6, 17 and the inner surface of the cylinder 6, when the unmolten or semi-molten resin p passes in the backward direction as shown by the arrow in FIG. Since the resin is gradually enlarged, the resin passing through it is easily deformed by shearing. Therefore, the lump of resin passing through the notch becomes smaller, making it easier for the resin to pass through, and subsequent melting and homogenization of the mixture become easier.

In addition, the notch height h is set appropriately, and the notch part 1
By alternately arranging the 6 and the circular arc portions 18 and the notch portions 17 and the circular arc portions 19 up to the tip of the screw 11, it is possible to increase the extrusion amount (melting amount) without sacrificing the melting performance. . Note that since the notch can be formed by simple machining, an increase in cost can be avoided.

FIG. 11 shows another embodiment, in which the extrusion screw 1
The cutout portion 21 may be formed in one single flight 20 so that adjacent cutout portions 21 may be inconsistent with each other. In addition, in the above embodiment, as shown in FIGS. 12 and 13, the notch 1
It is also conceivable that 6 and 17 are formed at three or two locations per circumference. Further, the arrangement distribution of the notches may be set from coarse to dense from the rear to the front.

Since the present invention is configured as described in detail above, efficient melting and kneading can be performed and the occurrence of breakup can be prevented. In addition, by adding even more uniform kneading and maintaining a uniform temperature to obtain a high-quality material, and by forming the notch all the way to the tip of the screw, the extrusion amount (melting amount) can be increased. This is possible without sacrificing performance. In addition, the present invention intermittently provides the top surface of the flight along the spiral direction.
In addition to forming a flat notch, the height of the notch is gradually increased toward the front of the screw, so that the gap between the inner circumferential surface of the cylinder and the notch increases toward the rear. The unmelted or semi-molten resin passing through the notch is easily deformed by shearing, and the lump of resin passing through the notch becomes smaller and has an increased surface area, which facilitates subsequent melting and homogenization of the mixture. In addition, the force that acts when the resin passes through the notch is not due to the pressure flow that flows due to the pressure difference between the front and back of the notch, as in conventional screws with a slit-like notch. Since the flow is caused by shear in which one plane is moving, more efficient melt plasticization can be achieved than in the past.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of a conventional double flight type extrusion screw, Figure 2 is a sectional view from D to D in Figure 1, Figure 3 is a sectional view from E to E in Figure 1, and Figure 4 is a sectional view of the screw. Cross-sectional view showing the molten state of the resin in the groove, No. 5
The figure is a side sectional view of an extrusion screw showing an embodiment of the present invention, FIG. 6 is a sectional view from F to F in FIG. 5, FIG. 7 is a sectional view from G to G in FIG. 5, and FIG. 9 is a sectional view from I to I in FIG. 5, FIG. 10 is a developed view of the screw shown in FIG. 5, and FIG. 11 is a cross-sectional view of the screw shown in FIG. 5. Side view, 12th
13 and 13 are front sectional views of the screw showing another embodiment, and FIG. 14 is an enlarged side sectional view showing one embodiment of the flight top in the present invention. Explanation of the main parts of the figure, 11... Extrusion screw,
12...First flight, 13...Second flight,
14...first groove, 15...second groove, 16,17...
...Notch part, A...Feed part, p...Unmelted or semi-molten resin.

Claims (1)

[Scope of utility model registration request] In a synthetic resin extrusion screw, a notch is formed intermittently on the top surface of the screw flight along the helical direction, and the height of the notch is adjusted in the forward direction of the screw. 1. An extrusion screw characterized in that the notches are gradually enlarged toward each other, and the notches are arranged so as to be inconsistent with the notches of adjacent flights.