JPH09109150A - Volume reducing treatment apparatus for waste plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attempt to simplify the pretreating step for removing foreign matter of waste plastic before introducing to a hopper. SOLUTION: The volume reducing treatment apparatus for waste plastic heats to melt the waste plastic introduced into a hopper 3 while feeding it by a screw shaft 2 inserted into a heating cylinder 1 to extrude it, and comprises an annular space 4 for surrounding the shaft 2 in the cylinder 1 on the way of feeding by the shaft 2 to communicate the downstream with the upstream of the space 4 or the space 4 with the cylinder 1 of the upstream side from the space 4 via an annular channel 5, and a foreign matter outlet 8 at the channel 5. Further, the depth (b) of the groove of the shaft 2 at the downstream side of the space 4 is made shallower than the depth (a) of the groove of the shaft 2 at the upstream side from the space 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste plastic volume reduction apparatus for melting waste plastic mixed with foreign matter such as metal, sand, wood, and paper to reduce its capacity.

[0002]

2. Description of the Related Art As an apparatus of this kind, Japanese Patent Laid-Open No. 5-245
As disclosed in Japanese Patent No. 463, a screw extrusion type is known. In this conventional device, the crushed waste plastic put into the hopper is heated and melted while being transferred in the heating cylinder by the bidirectional screw of different rotation type.

This molten plastic is uniformly mixed in the reaction chamber provided at the tip of the heating cylinder, and the outflow pressure is further adjusted by the adjusting valve, so that the gas component and the molten plastic are discharged in the separation chamber leaving this adjusting valve. And are to be separated.

[0004]

In the case of using the above-mentioned screw type heating cylinder, since the gap between the outer peripheral flight part of the screw of the two biaxial screws facing each other and the screw valley bottom part is small, the waste plastic is If the foreign matter that is not melted by heating is mixed, the foreign matter is caught in the gap and a screw lock is generated, which often causes a stop in continuous operation, which is a serious problem in safe operation of the device. . Also, in the case of the conventional single-screw type extruder, since the depth of the screw groove generally becomes shallower toward the downstream side, there is a problem that foreign matter is caught as in the case of the above-mentioned twin-screw screw. .

In order to prevent such a problem from occurring, it is necessary to remove foreign matter from the waste plastic in advance by using a pretreatment device such as a magnetic separator, a wind separator, a specific gravity separator, etc., resulting in an increase in cost. There is.

On the other hand, the structure for separating the hydrogen chloride gas generated by the decomposition of vinyl chloride mixed as a foreign substance from the molten plastic in the above-mentioned prior art is such that a reaction chamber and a regulating valve are provided at the tip of the heating cylinder. It is a configuration provided,
And since it was designed to take out the molten plastic separated from the hydrogen chloride gas under normal pressure, if you intend to reuse the vinyl chloride-removed waste plastic for molded products, after crushing it after curing, Since it had to be molded again using another extrusion molding machine or injection molding machine, the utilization efficiency of waste plastic was poor.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the structure of the first invention is a screw in which waste plastic put in a hopper is inserted into a heating cylinder. In a volume reduction device for waste plastic that is heated and melted and extruded while being transferred by a shaft, an annular space portion surrounding the screw shaft is provided in the heating cylinder during the transfer by the screw shaft. The downstream portion and the upstream portion of the space portion, or the annular space portion and the inside of the heating cylinder upstream of the annular space portion are communicated with each other through an annular flow path, and a foreign matter discharge port is provided in the return passage, and the annular space portion The depth b of the groove of the screw shaft on the downstream side is shallower than the depth a of the groove of the screw shaft on the upstream side of the annular space.

With this configuration, the waste plastic put in from the hopper is melted and reduced in volume while being transferred as the screw shaft rotates. Since the depth of the groove of the screw shaft on the downstream side of the annular space is shallower than that on the upstream side, the molten waste plastic is retained here and is recirculated to the upstream side in the recirculation flow path, during which it was mixed. Metal, sand,
Foreign matter such as wood and paper is accumulated in this ring flow path, and is continuously removed from the foreign matter discharge port in an open state, or is periodically removed by removing the plug.

According to this construction, minute metal, sand, wood, etc. mixed in the waste plastic put in from the hopper,
Non-melting foreign matter such as paper can be removed while the molten waste plastic is accumulated and refluxed in the annular space, which makes it possible to strictly perform pretreatment for foreign matter separation of the waste plastic before being put into the hopper. This pretreatment step can be simplified by eliminating the need to perform it. In this configuration, if water is injected into the annular space 4 from a water injection port (not shown), the wood and paper are hydrolyzed therein and the volume is reduced.

Further, foreign matter is not caught on the screw shaft downstream from the annular space, and screw lock due to foreign matter can be eliminated.

Further, the structure of the second invention is such that a deaeration port is provided in the heating cylinder in the middle of transfer downstream of the annular space in the structure of the first invention.

With this structure, hydrogen chloride gas, which is a decomposition gas of vinyl chloride mixed in the waste plastic during the transfer by the screw shaft, is degassed.

Therefore, the waste plastic whose volume has been melted and reduced in the heating cylinder can be extruded from the tip of the heating cylinder through a check valve or the like directly under the condition that the extruding pressure is applied, and the molding die is applied to this heating cylinder. The device can be directly connected and molded, and the utilization efficiency when reusing waste plastic as a molded product can be significantly improved.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. In the figure, reference numeral 1 denotes a heating cylinder, and a screw shaft 2 is fitted in the heating cylinder 1. The heating cylinder 1 is provided with a hopper 3 on the upstream side in the transfer direction of the screw shaft 2.

The heating cylinder 1 is, for processing reasons,
It is divided into two in the axial direction, and an annular space portion 4 which constitutes an annular space surrounding the screw shaft 2 is provided at the downstream end portion of the upstream member 1a. The lower side of the annular space 4 and the inside of the cylinder on the upstream side communicate with each other through an annular flow path 5. The ring 6 has a filter 6
Is a diaphragm 7, and the portion communicating with the inside of the cylinder is a diaphragm 7. An exhaust port 8 communicating with the outside is provided on the annular space 4 side of the annular flow path 5, and the exhaust port 8 is closed by a plug 9.

A degassing port 10 communicating with the inside of the heating cylinder 1 is provided at an axially intermediate portion of the downstream side member 1b. The degassing port 10 communicates with a depressurizing cylinder 11 fixed to the downstream side member 1b. I am doing it. The check valve 12 is provided at the downstream end of the downstream member 1b.
Is installed. A filter (not shown) is provided on the upstream side of the check valve 12 so that minute foreign matters in the molten waste plastic can be removed on the upstream side of the check valve 12.

Upper and lower stream side members 1a and 1b of the heating cylinder 1
Are provided with heating devices 13a and 13b on the outer periphery thereof, and the upstream side of the annular space portion 4 has a temperature (200 to 250) at which the waste plastic in this portion is melted to a fluid degree.
Temperature), and at the downstream side, the temperature at which vinyl chloride mixed in the waste plastic is decomposed into hydrogen chloride gas (300-
It is designed to be heated to 340 ° C.).

The screw shaft 2 has a drop port 3a of a hopper 3 attached thereto.
A screw groove is provided from the portion facing to the tip to the tip, and the depth of the screw groove is changed in the length direction.

That is, the depth a of the groove in the section from the portion of the hopper 3 facing the drop opening 3a to the portion of the hopper 3 facing the annular space 4 is such that the required transfer amount is obtained. On the other hand, a certain length on the downstream side of the annular space portion 4, for example, the depth b of the groove for two peaks is a> b, which is smaller than the depth a of the groove on the upstream side of the annular space portion 4. ing. The depth b of the groove on the downstream side is set to a depth that prevents foreign matter from entering this portion.

The depth c of the groove in the portion facing the degassing port 10 is a <c, which is sufficiently deep.

A plurality of axially engraved grooves 14 are circumferentially provided on the inner surface of the cylinder between the hopper 3 and the annular space 4. The downstream end wall 4a of the annular space 4 is angular with respect to the axis of the cylinder, and the inner end of the downstream end wall 4a is gate-shaped with the screw shaft 2 in the transfer direction. There is.

In the above structure, by rotating the screw shaft 2 with the upstream side and the downstream side of the heating cylinder 1 being heated to a predetermined temperature, the waste plastic in the crushed state, which has been put in from the hopper 3, has an annular space portion. It is sufficiently melted during the period of reaching 4.

At this time, since the groove depth b of the screw shaft 2 on the downstream side of the annular space 4 is shallower than the groove depth a of the upstream side, the transfer amount by the screw shaft 2 is narrowed at this portion. The melted waste plastic stays in the annular space 4, and due to this staying pressure, it is circulated through the annular flow path 5 to the upstream side of the annular space 4 through the filter 6 and the throttle 7.

The molten waste plastic transferred to the annular space 4 is filtered by the filter 6 so that particulate foreign matters such as metal, sand, wood, paper mixed in the molten waste plastic are in the ring flow path 5. Accumulated in. This foreign substance is removed from the discharge port 8 by removing the plug 9. It should be noted that the plug 9 may be removed in an open state to remove it continuously.

During this time, the molten waste plastic retained in the annular space 4 is transferred to the downstream side of the annular space 4 by the rotation of the screw shaft 2.
The downstream end of the gate is gate-shaped with respect to the transfer direction, and the depth of the screw groove in this gate-shaped portion prevents the transfer of particulate foreign matter, and the molten waste plastic from the annular space 4 is blocked. Then, a minute foreign matter having a depth of the shallow groove or less is transferred, and the minute foreign matter is removed by a filter installed upstream of the check valve 12 at the tip of the screw.

Next, since the depth c of the screw groove at the portion facing the degassing port 10 becomes deep, the transfer pressure is lowered at this portion, and hydrogen chloride gas in the molten waste plastic is separated and degassed. It is discharged to the outside through the mouth 10 and the de-cylinder 11. Although not shown, the de-cylinder 11 is connected with a hydrogen chloride gas recovery device or a neutralizer, if necessary.

The molten waste plastic that has passed through the degassing port 10 is again transferred by the shallow screw groove and extruded through the check valve 12. The extrusion pressure at this time is the pressure extruded by the screw shaft 2.

At the time of the above operation, since the groove 14 in the axial direction is formed on the inner surface of the cylinder between the hopper 3 and the annular space 4, the resistance between the waste plastic and the inner surface of the cylinder is increased, and the screw is screwed. The feed capacity by the axis 2 increases.

As a measure against vinyl chloride in the molten waste plastic, a calcium salt supply device 1 is provided upstream of the degassing port 10.
5, a calcium salt may be continuously supplied to the upstream side of the degassing port 10 to neutralize the hydrogen chloride gas in the molten waste plastic.

In the above embodiment, the example in which the downstream portion of the annular flow passage 5 is opened in the cylinder upstream of the annular space portion 4 is shown, but the downstream side of the annular flow passage 5 is upstream of the annular space portion 4. You may open to the part.

Further, water may be added to the annular space portion 4 to hydrolyze wood or paper at this portion.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view taken along the line AA of FIG. 1 and omitting the screw shaft.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heating cylinder 2 ... Screw shaft 3 ... Hopper 4 ... Annular space part 5 ... Annular flow path 6 ... Filter 7 ... Restriction 8 ... Discharge port 9 ... Plug 10 ... Degassing port 11 ... De-cylinder 12 ... Check valve 13a, 13b … Heating device 14… Groove

Claims (2)

[Claims] 1. In a waste plastic volume reduction processing apparatus, which heats and melts and extrudes waste plastic while it is being transferred by a screw shaft inserted in a heating cylinder, the waste plastic being transferred by the screw shaft. An annular space portion surrounding the screw shaft is provided in the heating cylinder, and a downstream portion and an upstream portion of the annular space portion, or an annular space portion and an inside of the heating cylinder upstream of the annular space portion are formed by an annular flow path. Communication,
A foreign matter discharge port is provided in the annular flow passage, and the groove depth b of the screw shaft downstream of the annular space portion is shallower than the groove depth a of the screw shaft upstream of the annular space portion. Waste plastic volume reduction processing equipment. 2. The apparatus for reducing volume of waste plastic according to claim 1, wherein a deaeration port is provided in the heating cylinder on the downstream side of the annular space during transfer.