JPH0691727A - Extruder for recovering plastic - Google Patents

Abstract

PURPOSE:To provide the title extruder capable of sufficiently obtaining the biting, transfer and plasticizing capacities to a raw material and enhancing extrusion efficiency without increasing treatment cost even when the ground product of plastic foam is used as a raw material. CONSTITUTION:Projections each having a bottom surface 13 having a diameter larger than the inner diameter of the barrel EX of an extruder and having a conical surface 17 narrowing along the transfer direction of a raw material as a base bottom surface and having a shape protruding to the inside of the barrel and extending in the transfer direction and becoming narrow in width toward the leading end of the barrel and reduced in height in the downstream direction of the barrel are provided to the inner peripheral part of the upstream part in the transfer direction of the raw material of the barrel EX in two or more rows at a predetermined angle interval.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion method for recovering plastics, which is used when crushing waste plastic products or the like into an appropriate size as a part of waste recycling and extruding them in a molten state while compressing them for recycling. The present invention relates to a machine, and more particularly, to a machine suitable for treating a crushed product of a plastic foam such as expanded polystyrene having a low bulk density.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of effective use of resources and protection of the natural environment, a waste material made of a plastic foam such as expanded polystyrene or expanded polyethylene used as a packaging auxiliary material, a simple container, etc., for example, has a side length of 5 to 35 mm. It has been attempted to crush the material into pieces of a certain size and extrude the crushed material as a raw material while compressing and melting it with an extruder to regenerate it.

As an extruder for recovering plastic used for recovering and recycling such a plastic foam, at present, the extruder having substantially the same structure as a general-purpose machine used for extrusion molding a usual thermoplastic material is used. Things are being used.

[0004]

A conventionally used extruder for extrusion molding of plastic materials is usually a barrel (cylinder) having a supply port for supplying the raw material, and a raw material supplied into the barrel. And a screw for transferring the compressed air. Recently, as described in Japanese Patent Publication No. 62-30088, for example,
A plurality of pipes, which are rectangular in cross-section and have a shallower depth toward the downstream side, in parallel with the central axis of the barrel in the inner peripheral portion (near the inlet of the feed portion) of the upstream portion as viewed in the raw material transfer direction in the barrel. Has been developed in parallel with a predetermined angular interval.

According to the conventional extruder having the barrel with the groove, the groove having the above-described shape is formed in the barrel, so that it is formed between the inner surface of the barrel and the peripheral surface of the screw. Since the gap becomes smaller toward the downstream side, the frictional force and compression force of the barrel and screw acting on the raw material are increased compared to those without such concave groove, and the raw material is drawn in (bite), transferred and It can be expected that the plasticizing ability is improved and the extrusion rate is increased.

However, in such a conventional extruder, the size of the concave groove formed in the barrel is determined based on the size of the pellets used as the raw material, and the concave groove has a rectangular cross-sectional shape and a constant lateral width. Therefore, it is effective for raw materials of uniform size with a uniform grain size, but as mentioned above, plastic foam recovered for recycling, with irregular shape and large dimensional variation and small bulk density. When crushed body etc. is used as a raw material, the ability to bite / transfer and plasticize the raw material becomes insufficient, the extrusion efficiency decreases, a large extruder is required, and the processing cost rises. The problem of inviting arises.

In view of the above point, the present invention can sufficiently extrude and transfer the raw material and increase the extrusion efficiency without increasing the processing cost even when the crushed product of the plastic foam is used as the raw material. An object of the present invention is to provide an extruder for recovering plastic that can be improved.

[0008]

As a result of intensive studies, the inventors of the present application have found that the above object can be achieved by providing a protrusion of a specific shape in place of the above-mentioned concave groove of rectangular cross section in the barrel. It was The extruder for recovering plastic according to the present invention is based on such research results and consideration and trial production / experiment based on the research results. Specifically, it has a supply port into which raw materials such as crushed plastic products are put. A barrel and a screw for transferring the raw material supplied into the barrel while compressing the barrel are provided, and the inner peripheral portion of the upstream portion of the barrel in the transport direction of the raw material has a diameter larger than the inner diameter of the barrel. A conical surface having a bottom surface and narrowing along the transfer direction is used as a base surface to project inward of the barrel, extends along the transfer direction, and has a narrower width toward the tip side and further toward the downstream side. It is characterized in that a plurality of rows of projections each having a shape in which the height and the width thereof are gradually reduced are provided at predetermined angular intervals.

In such a structure, the cross-sectional outer shape of the protrusion is preferably an isosceles triangular shape, but a shape similar to that or a trapezoidal shape may be used. Further, it is preferable that the tops (apex and tip surfaces) of the protrusions are parallel to the central axis of the barrel and located on the inner peripheral surface of the barrel. If the cross-sectional outer shape of the protrusion is triangular or trapezoidal, the top or side edge thereof may be rounded. Particularly, the raw material is a crushed product of the plastic foam as described above (about 25 mm on average per side). Square piece)
Then, if the top of the protrusion is an acute angle, a radius of 10R or less is given. If the cross-sectional outer shape of the protrusion is trapezoidal, the flat width of the tip flat surface is 20mm or less and the side edge has a radius of 5R or less. Is preferably applied. In this case, if R is too large, the effect of crushing the raw material by the protrusions is reduced.

The height of the protrusions is preferably 1.5 times or less of the average size of the crushed product used as the raw material. If it is higher than that, the ability to bite the raw material is likely to decrease. However,
When a crushed product (width = X, length = Y, thickness = Z) is used as the raw material, the height of the protrusions should be 3Z or less, or the distance between the protrusions should be 2X or less than 2Y. It is desirable to do.

The length of the protrusion is L / D, where L is the length from the raw material inlet of the barrel to the extrusion port and D is the inner diameter of the barrel.
It is preferably about / 3 to 3 times, and if it is shorter than that, improvement in extrusion efficiency is hardly obtained, and if it is longer than that, the raw material is buried in the grooves formed between the protrusions, and it is meaningless to make it longer. The inclination angle of the protrusion (the inclination angle of the apex with respect to the conical surface serving as the base surface of the protrusion) is set according to the height and the length of the protrusion, but it is usually desirable to be 20 ° to 2 °.

The number of protrusions is determined in consideration of the inner diameter of the barrel of the protrusion, the lateral width of the protrusion, the size of the raw material, etc., but in the case of a barrel having a normal diameter, it is preferably about 4 to 20. Further, in the above-described configuration, a notch may be formed from the tip of the protrusion toward the base surface so as to divide the protrusion into several parts when viewed in the length direction. Such notches work particularly effectively when the size of the raw material is large.

[0013]

In the extruder for recovering plastic according to the present invention having the above-mentioned structure, since the projection is provided on the barrel with the specific shape as described above, the extruder having a concave groove is provided. Then, the crushing effect of the raw material by the projections and the frictional resistance to the raw material of the barrel are increased, and even if the size of the raw material is relatively large, it sufficiently digs in, sufficient pulling-in / transporting and plasticizing ability for the raw material is obtained, , A plastic foam recovered for recycling, which can effectively respond to changes in the bulk density of the raw material (0.1 to 0.007 g / cc), has an irregular shape and has large dimensional variation and small bulk density. It is possible to improve the extrusion efficiency even when the pulverized product or the like is used as a raw material.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. In the following, Examples 1 to 5 and Comparative Example 1
Table 3 shows the specifications of the extruder, the processing conditions, the properties of the raw materials, and the extrusion amount per unit time showing the effects of the present invention in Tables 1 to 3.
The second and subsequent embodiments will be described focusing on the differences from the first embodiment, and redundant description of each example will be omitted.

[0015]

[Table 1]

[Embodiment 1] FIGS. 1 to 5 The extruder 10 of this example is of a two-stage type, and the first barrel EX located at the upper stage has an extrusion opening 12a of a hopper 12.
Is provided with a first supply port 14 for feeding a raw material, which is rotated by a drive source 16 inside the first supply port 14,
A screw 20 for displacing the raw material supplied from No. 2 into the first barrel EX to the first extrusion port 18 side while compressing the raw material is arranged. Although not shown, the first barrel EX
Also, a heating means such as a band heater for heating and melting the raw material in an appropriate manner is provided on the outer periphery of the second barrel EY described later.

Below the first barrel EX, the first barrel EX
A second barrel EY provided with a second supply port 24 connected to the extrusion port 18 via a connecting pipe 19 is arranged, and the second barrel EY is rotated by a drive source 26 to provide a second supply. The screw 3 for transferring the raw material supplied from the port 24 into the second barrel EY to the second extrusion port 28 side while compressing the raw material.
0 is allocated.

The diameter of the second barrel EY is smaller than that of the first barrel EX, and the rotation speed of the screw 30 incorporated therein is set to be low. And
A protrusion 1 as shown in detail in FIGS. 2 and 3A, which is a characteristic part of the present invention, is provided on the inner peripheral portion of the upstream portion (feed portion) as viewed in the raw material transfer direction in the first barrel EX. The sleeve member 15 is inserted and fixed by appropriate means.

In addition to FIGS. 2 and 3A, the projection 1 also includes FIGS. 4 and 5 showing a cross section (AA) near the upstream end and a cross section (BB) near the downstream end of the sleeve member 15, respectively. As can be seen from the reference, the bottom surface 1 having a diameter (Db) larger than the diameter of the first barrel EX (diameter Da of the barrel inner surface 11).
3 has a conical surface 17 that is narrowed along the raw material transfer direction as a base surface and projects inward in the radial direction of the first barrel EX, extends along the raw material transfer direction, and has a narrower width toward the tip end side. Moreover, the height and the width of the projection are reduced toward the downstream side, and the cross-sectional outer shape is an elongated triangular pyramid having an isosceles triangle shape. The sleeve member 15 is provided with eight such projections 1 at a predetermined angular interval. The respective vertices are located on the inner surface 11 of the barrel.

As shown in Table 1, the height a, the lateral width b, and the length c (FIG. 3A) of the projection 1 are 20, 4 respectively.
It is set to 0,300 mm. In this case, a crushed product FS having an average size of 25 mm and consisting of 60 times as many as the recovered polystyrene foam is used as the raw material, and the raw material is extruded while being heated and melted under the conditions as shown in Table 1. Then, a pellet of 3 × 3 mm was granulated by a cutting means such as a rotary cutter.

The protrusion 1 has an apex angle of 90 ° and has a pointed tip. However, as in the protrusion 1'shown in FIG. 3B, the apex is rounded. May be. [Embodiment 2] FIG. 6 The protrusion 2 of this embodiment has a shorter length (c = 50 mm) than that of Embodiment 1, and other conditions are substantially the same as those of Embodiment 1.

[Embodiment 3] FIG. 7 The protrusion 3 of this example has a trapezoidal shape in which the top portion of the protrusion 1 of Embodiment 1 is cut off, and the lateral width d of the tip end face (top face) thereof.
Is 5 mm, and the overall length is longer than that of Example 1 (c
= 450 mm), and from the tip of the protrusion 3 to the base surface 1
Five notch portions 3a having a notch width e of 20 mm are formed at regular intervals toward 7 and the protrusion 3 is divided into six small protrusions (n = 6) when viewed in the length direction. . Other conditions are substantially the same as those in the first embodiment.

[Embodiment 4] FIG. 8 In this example, the number of the protrusions 4 is twice as large as that of the embodiment 1 (16).
And the height a and width b thereof are made shorter than those of the protrusion 1 of Example 1, and a sheet-shaped polystyrene foam 8 is used as a raw material.
Double piece (thickness: 2.5 mm, vertical, horizontal: 4 x 4 m
m) is used. Other conditions are substantially the same as those in the first embodiment.

[Fifth Embodiment] FIG. 9 In this example, unlike the first embodiment, the extruder is a vented single (single stage), and the number of the protrusions 5 is the same as that of the fourth embodiment (16). However, the height a and the width b thereof are made shorter than those of the protrusion 1 of the fourth embodiment, and further, the wedge-shaped notches 5a having the notch width e of 20 mm from the tip of the protrusion 5 toward the base surface 17 are spaced at regular intervals. Are formed at 7 positions apart from each other, and the protrusions 5 are divided into 8 sections (n = 8) as viewed in the length direction.

Here, a small piece of polystyrene-based unfoamed film (PSP) (thickness: 0.35) is used as a raw material.
mm, vertical, horizontal: 5 × 5 mm) is used. Other conditions are as described in the table. The notch 5a is cut into a ring shape for each protrusion 5 here,
The cutouts 5a may be formed spirally or randomly.

Comparative Example 1 In this comparative example, the conditions are substantially the same as in Example 1 except that no protrusion is provided on the barrel. [Comparative Example 2] This comparative example has substantially the same conditions as in Example 4 except that the barrel is not provided with a protrusion.

Comparative Example 3 In this comparative example, the conditions are substantially the same as in Example 5 except that no protrusion is provided on the barrel. Comparing the extrusion amounts per unit time according to Examples 1 to 5 and Comparative Examples 1 to 3 on the basis of Table 1, the present example in which the protrusions 1 to 5 were provided although the individual condition settings were slightly different It will be readily appreciated that the extruder capabilities of the 1 to 5 extruders outperform the conventional ones.

The shape of the protrusion is not limited to that of the above-described embodiment, but may be the shape as shown in FIGS. 10 and 11, for example. The projections 6 shown in FIG. 10 have an obtuse apex angle so that both ends in the width direction of the projections 6 overlap, and the projections 7 shown in FIG. 11 have curved side surfaces. It is a thing.

Further, as described above, in the plastic recovery extruder embodying the present invention, when the crushed pieces of the plastic foam are used as the raw material, the extrusion amount per unit time is higher than that of the conventional one. Since it increases, it is necessary to improve the raw material supply capacity of the hopper. In that case, as shown in FIG. 12, the hopper previously proposed by the applicant of the present application (Japanese Patent Application No. 4-147758). Described in the specification) can be used. This hopper will be described in brief. A cylindrical portion expanded upwardly at a position eccentric from the central axis of the substantially funnel-shaped first hopper 110 whose lower outflow end is connected to the supply port 14 of the extruder 10 is described. Have second
The hopper 50 is provided, and the rotary screw for feeding is arranged on the central axis of the first hopper 110.

[0030]

As can be understood from the above description, in the extruder for recovering plastic according to the present invention, since the projection is provided on the barrel with the specific shape as described above, the extruder with the conventional groove is provided. Compared to the ones, the crushing effect of the raw material by the protrusions and the frictional resistance to the raw material of the barrel are increased. Moreover, even if the bulk density of the raw material changes, it is possible to effectively cope with it, and the bulk density is small with an irregular shape and large dimensional variation.
Even when the crushed product of the plastic foam recovered for recycling is used as a raw material, the effect of improving the extrusion efficiency can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an extruder for recovering plastic according to a first embodiment.

FIG. 2 is a partially cutaway perspective view showing a first barrel of the extruder according to the first embodiment.

FIG. 3 is an enlarged perspective view showing the shape of protrusions of the extruder of Example 1.

FIG. 4 is a sectional view taken along the line AA of FIG.

5 is a cross-sectional view taken along the line BB of FIG.

FIG. 6 is a partially cutaway perspective view showing a first barrel of an extruder according to a second embodiment.

FIG. 7 is an enlarged perspective view showing the shape of protrusions of the extruder of Example 3.

FIG. 8 is a partial cutaway perspective view showing a first barrel of an extruder according to a fourth embodiment.

FIG. 9 is an enlarged perspective view showing the shape of protrusions of the extruder of Example 5.

FIG. 10 is a cross-sectional view showing a modified example of the protrusion.

FIG. 11 is a cross-sectional view showing a modified example of the protrusion.

FIG. 12 is a diagram showing an example of a hopper suitable for the extruder of the present application.

[Explanation of symbols]

 1 to 7-Protrusions 10-Extruder 11-Barrel inner peripheral surface 12-Hopper 14,24-Supply port 15-Sleeve member 17-Cone surface 18,28-Extrusion port 20,30-Screw EX-First barrel EY- 2nd barrel

Claims (6)

[Claims] 1. A transfer direction of the raw material in the barrel, comprising: a barrel having a supply port into which a raw material such as waste plastic crushed product is charged; and a screw for transferring the raw material supplied in the barrel while compressing the raw material. In the inner peripheral portion of the upstream portion as viewed in, while protruding toward the inner side of the barrel with a conical surface having a bottom surface having a diameter larger than the inner diameter of the barrel and narrowing along the transfer direction as a base surface, A plurality of rows of protrusions having a shape that extends along the transfer direction and has a width that is narrower toward the front end side and that is lower toward the downstream side, and the protrusions are provided at predetermined angular intervals. Extruder for plastic recovery. 2. The extruder for recovering plastic according to claim 1, wherein the projection has a triangular cross-section. 3. The extruder for recovering plastic according to claim 1, wherein the top of the protrusion is arranged on the inner peripheral surface of the barrel in parallel with the central axis of the barrel. 4. The extruder for recovering plastic according to claim 1, wherein the lateral width of the protrusion is narrowed toward the downstream side. 5. The extruder for recovering plastic according to claim 1, wherein a notch is formed from the tip of the projection toward the base surface so as to divide the projection into several pieces when viewed in the length direction. 6. The extruder for recovering plastic according to claim 1, wherein a crushed product of a plastic foam is used as a raw material.