JP2000062002A - Retention-proof structure in apex part of biaxial extruder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve an inconvenience wherein in the conventional retention-proof structure at the apex part of a biaxial extruder, change in cross-sectional area in the axial direction is large and flow rate of a molten material is decreased and burning of a resin caused by retention is generated and physical properties are changed and this is mixed to result in decrease of quality sometimes. SOLUTION: A retention-proof structure at the apex part of a biaxial extruder has a constitution wherein the crosssectional shape of the flow path of a connection adaptor 14 mounted with a braker plate 15 between the apex of a cylinder and a pipeline 13 is made into a tapered shape narrowed toward the downstream side so as to be continuous to the flow path of the braker plate 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preventive structure for preventing retention at the tip of a twin-screw extruder for kneading and melting plastic materials.

[0002]

2. Description of the Related Art Conventionally, a twin-screw extruder is often used as an apparatus for melting and kneading a plastic material.
The twin-screw extruder is composed of a long cylinder and two screws that are inserted into an inner hole of the cylinder and driven to rotate. In the twin-screw extruder configured as described above, the plastic material supplied from the rear end portion is kneaded, melted and stirred by the screw and extruded from the front end surface.

More specifically, the tip of the twin-screw extruder is
It is configured as shown in FIGS. 5 to 8. Figure 5
5 is a cross-sectional view showing a tip portion of the twin-screw extruder, FIG. 5 is an axial cross-sectional view, FIG. 6 is a cross-sectional view taken along arrow A of FIG. 5, and FIG. 7 is a cross-sectional view taken along arrow B of FIG. FIG. 8 shows the tip of the screw of FIG. 5 in more detail. In FIG. 5, reference numeral 10 is a twin-screw extruder, and this twin-screw extruder 10 is composed of a cylinder 11 and a screw 12 rotatably inserted in an inner hole 11 a of the cylinder 11.

The two screws 12 are arranged in parallel in a direction perpendicular to the plane of the drawing and are overlapped with each other, and only one screw before the overlap is shown. Also, the inner hole 11
As shown in FIG. 6, the cross section perpendicular to the axial direction of a has a so-called spectacle shape in which two circles are partially overlapped and arranged side by side so that the two screws 12 can be inserted. It is configured.

A pipe 13 is provided in front of the tip of the cylinder 11.
Are located on the axis, between which the connection adapter 14
And the breaker plate 15 is interposed. The inner hole cross section of the pipe 13 is circular, the breaker plate 15 has a large number of fine holes formed in the circular cross section, and the connection adapter 14 is formed from the spectacle-shaped cross section of the inner hole 11a to the breaker plate 15. It is provided for connecting to the circular cross section of. Therefore, the inner hole 14a of the connection adapter 14 has an end face on the cylinder 11 side having the same spectacle shape as the inner hole 11a as shown in FIG. It has a circular shape and is smoothly changed into a circular cross section so that the plastic material does not stay.

Next, referring to FIG. 8, a screw cap 16a is fixed to the tip of the screw 12, and the screw cap 16a fixes the screw piece 12a constituting the tip of the screw 12.

In the structure for preventing stagnation at the tip of the twin-screw extruder 10 constructed as described above, the cylinder 11 is appropriately heated, and the screw 12 is rotationally driven and kneaded in the inner hole 11a. The molten plastic material is extruded from the tip of the cylinder 11, passes through the connection adapter 14 and the breaker plate 15, and the pipe 1
Flow to 3.

[0008]

Since the retention preventing structure at the tip of the conventional twin-screw extruder is constructed as described above, the following problems exist. That is,
In the conventional screw cap 16a, the cross-sectional area change in the axial direction is large, and as shown in FIG.
The flow velocity of the plastic material decreases at the hatched portion X downstream of the tip of a. As a result, a part of the molten plastic material stays in the X part, resin burning occurs and the physical properties change, and some plastic materials with changed physical properties are mixed to make the quality uneven, Lower.

The same applies to the structure of the tip portion, and the flow velocity of the plastic material decreases because the inner hole of the connection adapter 14 is constructed so as to sequentially increase the cross-sectional area in the downstream direction. In addition, at the joint surface between the connection adapter 14 and the breaker plate 15, the joint adapter 1
The inner hole 4 is larger than the flow path diameter of the breaker plate 15. As a result, the molten plastic material is likely to stay in the shaded portion Y of the inner wall. The plastic material staying in the Y portion is liable to be burnt with resin and its physical properties are changed, and a part of the plastic material whose physical properties are changed is mixed to make the quality non-uniform and deteriorate the quality.

The present invention has been made to solve the above problems, and in particular, in the tip portion of a twin-screw extruder that prevents the accumulation of plastic material and prevents deterioration of the quality of plastic material. It is intended to provide a retention preventing structure.

[0011]

A stagnation prevention structure at a tip portion of a twin-screw extruder according to the present invention is a twin-screw extruder constituted by a cylinder and two screws rotatably driven in an inner hole thereof. In, the cross-sectional shape of the flow path of the connection adapter mounted together with the breaker plate between the tip of the cylinder and the pipe is tapered so as to be tapered toward the downstream side so as to be continuous with the flow path of the breaker plate. The screw cap fixed to the tip of the screw gradually reduces the cross-sectional area toward the tip, and the tip is sharpened.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the retention preventing structure at the tip of a twin-screw extruder according to the present invention will be described below in detail with reference to the drawings. It should be noted that the same or equivalent portions as those of the conventional example are designated by the same reference numerals and described.
1 to 3 are sectional views showing a tip portion of a twin-screw extruder according to the present invention, FIG. 1 is an axial sectional view, and FIG. 2 is A in FIG.
FIG. 3 is a sectional view taken along the arrow B in FIG. FIG. 4 shows the screw tip of FIG. 1 in more detail. In FIG. 1, reference numeral 10 is a twin-screw extruder, which is composed of a cylinder 11 and a screw 12 rotatably inserted in an inner hole 11a of the cylinder 11.

The two screws 12 are arranged in parallel in the direction perpendicular to the plane of the drawing and overlap each other, and only one screw before the overlap is shown. Also, the inner hole 11a
As shown in FIG. 2, the cross-section perpendicular to the axial direction of is configured in a so-called spectacle shape in which two circles are partially overlapped and arranged side by side so that the two screws 12 can be inserted. Has been done.

A pipe 13 is provided in front of the tip of the cylinder 11.
Are located on the axis, and the connection adapter 1
4 and breaker plate 15 are interposed. The inner hole cross section of the pipe 13 is circular, the breaker plate 15 has a large number of fine holes formed in the circular cross section, and the connection adapter 14 is formed from the spectacle-shaped cross section of the inner hole 11a to the breaker plate 15. It is provided for connecting to the circular cross section of.

The inner hole 14a of the connection adapter 14 has an end surface on the cylinder 11 side as shown in FIG.
The same spectacle shape as 1a is formed into an oval shape in the middle as shown in FIG. 3, and further smoothly changes to a circular cross section. Further, even if the cross-sectional shape changes, the cross-sectional area changes smoothly, and the shape of the joint surface with the breaker plate 15 is the same. Therefore, the connection adapter 1
The cross-sectional shape of the inner hole 14a of the flow path 4 is the breaker plate 1
5 is formed in a taper shape that becomes thinner toward the downstream side so as to be continuous with the flow path 15a.

Next, in FIG. 4, a screw cap 16a is fixed to the tip of the screw 12, and the screw cap 16a fixes the screw piece 12a constituting the tip of the screw 12. The screw piece 12a has a so-called cannonball shape in which the cross-sectional area is gradually reduced from the end surface perpendicular to the axis toward the tip, and the tip is sharpened.

In the retention preventing structure at the tip portion of the twin-screw extruder 10 constructed as described above, the cylinder 11 is appropriately heated and the screw 12 is rotationally driven to be kneaded in the inner hole 11a. And is extruded from the tip of the molten plastic material cylinder 11, and flows into the pipe 13 through the tapered inner hole 14a of the connection adapter 14 and the flow path 15a of the breaker plate 15.

The plastic material extruded from the tip of the twin-screw extruder 10 flows through the inner hole of the connection adapter 14 having no stagnation portion without abrupt change in flow velocity, and then flows through the breaker plate 15 to the pipe 13. To do. Further, it flows from the tip of the screw 12 along the shell-shaped screw cap 16a that smoothly reduces the cross-sectional area without staying.

[0019]

As described above, the structure for preventing the retention at the tip portion of the twin-screw extruder according to the present invention has the following effects. That is,
There is no plastic material retention area downstream of the tip of the screw cap. In addition, there is no sudden change in the flow rate of the plastic material at the tip portion, and there is no stagnant portion. As a result, the plastic material is prevented from accumulating at the tip portion of the twin-screw extruder, and it is possible to prevent deterioration in quality due to resin burning.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a retention preventing structure at a tip portion of a twin-screw extruder according to the present invention.

FIG. 2 is a view on arrow A ′ of FIG.

FIG. 3 is a view on arrow B ′ of FIG.

FIG. 4 is a cross-sectional view showing another form of the tip portion of the screw shown in FIG.

FIG. 5 is a sectional view showing a tip portion of a conventional twin-screw extruder.

6 is a view on arrow A of FIG.

FIG. 7 is a view on arrow B of FIG.

8 is a cross-sectional view showing the conventional example of FIG.

[Explanation of symbols]

10 twin screw extruder 11 cylinders 11a inner hole 12 screws 13 Piping 14 Connection adapter 15 breaker plate 16a screw cap

Claims (2)

[Claims] 1. A twin-screw extruder comprising a cylinder (11) and two screws (12) rotatably inserted into an inner hole (11a) of the cylinder (11), the tip of the cylinder (11) and a pipe. The cross-sectional shape of the flow path of the connection adapter (14) mounted together with the breaker plate (15) between (13) becomes narrower toward the downstream side so as to be continuous with the flow path of the breaker plate (15). A retention preventing structure at a tip portion of a twin-screw extruder characterized by being configured in a tapered shape. 2. The screw cap (16a) fixed to the tip of the screw (12) is configured such that the cross-sectional area gradually decreases toward the tip and the tip is sharpened. The structure for preventing retention at the tip of the twin-screw extruder according to claim 1.