JP2753669B2 - Separation and recovery method of waste plastic - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the separation of waste plastics in which a mixture of various waste plastics is separated into a high specific gravity substance and a low specific gravity substance by utilizing a specific gravity difference in a liquid, and these are separately collected. The present invention relates to a recovery method, and more particularly to a pretreatment thereof.

[0002]

2. Description of the Related Art When plastic waste containing polyvinyl chloride is collectively treated, when recycled plastic is recycled, various types of waste plastics are mixed, so that the quality of the recycled plastic deteriorates and the collected plastic is incinerated. In such a case, hydrogen chloride gas is generated along with incineration of the mixed polyvinyl chloride, which damages the incinerator and further causes pollution.

The present inventors have developed an apparatus for separating and recovering waste plastic as shown in FIG. This consists of a charging tank (1) for circulating the waste plastic mixture and a separation tank (2) for separating the waste plastic mixture into low specific gravity substances and high specific gravity substances based on the specific gravity difference. Is disposed such that a vertical cylinder (4) having a screw (3) sinks in the liquid. Vertical cylinder (4) by rotating screw (3)
A downward flow is generated therein, and by this downward flow, the waste plastic pieces are drawn into the vertical cylinder (4) and are forcibly dispersed, and the dispersed pieces are transferred to the separation tank in a short time.

[0004] In the separation tank (2) where there is almost no flow, waste plastic is separated into a low specific gravity substance (5) such as polyethylene and a high specific gravity substance (6) such as polyvinyl chloride due to a difference in specific gravity. The low specific gravity (5) floats on the surface of the separation tank (2), and the high specific gravity (6) deposits on the bottom of the separation tank (2). The deposit of the high specific gravity (6) is sent to the circulation path (9) equipped with the air lift (7) and the recovery device (8), and is recovered by the recovery device (8).

According to this waste plastic separation / recovery method, the apparatus is composed of a charging tank and a separation tank, and therefore, compared to a conventional method using a device including a charging tank, an intermediate tank and a separation tank.
The time required for waste plastic separation and recovery processing can be reduced, the size of the waste plastic separation and recovery device can be reduced, and the amount of liquid required for the processing can be reduced. A conventional method of generating a water flow for forcibly dispersing waste plastic pieces in a cylinder by a screw and transferring the dispersion pieces to a separation tank, so that a circulating flow is generated in water or salt water by blowing air from the bottom of the tank. As described above, air easily adheres to the surface of hydrophobic plastics such as polyvinyl chloride, so that this type of plastic hardly floats in the separation tank, improving the separation and recovery rate of waste plastics. Can be done.

[0006]

However, in the above-mentioned conventional method, when the waste plastic to be charged has a flat shape, a distorted shape, or an uneven shape, the rotation of the screw in the vertical cylinder causes the waste plastic to rotate. When the plastic is pulled into the cylinder, air adheres to the plastic surface,
Many high-density plastics also float in the separation tank.

SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for completely separating waste plastic into high specific gravity substances and low specific gravity substances in liquid according to the specific gravity difference, regardless of the shape. It is an object of the present invention to provide a method capable of separating and recovering the target in a high yield.

[0008]

The method of separating and recovering waste plastic according to the present invention has been devised to achieve the above-mentioned object, and comprises mixing a mixture of waste plastics with a high specific gravity material and a low specific gravity material in a liquid by a specific gravity difference. In separating into specific gravity,
By exposing the waste plastic to be treated to steam
The waste plastic is subjected to a wettability-imparting treatment in advance .

As the pretreatment for imparting wettability with water vapor , the following embodiments are possible.

A) Steam is added to the waste plastic to be treated.
Dedicate This removes air in the plastic pores.
I care.

Preferably, thereafter, water is further added to the pores.
Let it soak.

B) Waste plastic to be treated as described above
Water vapor to remove air in the plastic pores.
After that, the atmosphere is further cooled to liquefy water vapor and
Let the liquefied water soak in the holes.

The method of b) is preferred.

[0014]

According to the method for separating and recovering waste plastic according to the present invention, when a mixture of waste plastics is separated into a high specific gravity substance and a low specific gravity substance by a specific gravity difference in a liquid, the waste to be treated is removed.
Exposing waste to water by applying steam to plastics
Since the tic is pre-treated for imparting wettability , the affinity between the waste plastic and water in the separation / recovery device or a liquid in which salts or the like are dissolved in water to increase the specific gravity can be increased. As a result, air hardly adheres to the surface of the waste plastic, and the sedimentation speed of the high-density plastic can be increased. Therefore, regardless of the shape of the waste plastic, it can be completely separated into a high specific gravity substance and a low specific gravity substance in the liquid by a specific gravity difference, and these can be separated and recovered efficiently and with high yield.

[0015]

Next, the method for separating and recovering waste plastic according to the present invention will be described in detail with reference to examples.

Example 1 (for reference) First, as an aqueous solution of a nonionic surfactant, 250 pp
m of an aqueous solution of polyoxyethylene octyl phenyl ether was prepared and stored in a chemical solution tank (10). As a waste plastic to be treated, 100 g of a 1 mm thick polyvinyl chloride plate crushed to about 15 × 15 mm is prepared, and the crushed pieces are subjected to nonionic surface activity in a chemical solution tank (10) with a stirrer (15). It was immersed in the agent aqueous solution for 10 seconds. Thereafter, the plastic crushed pieces were collected and lightly drained with a dehydrator (11) to form a surfactant thin film on the surface of the plastic crushed pieces.

The filtrate discharged from the dehydrator (11) is supplied to a filtrate tank (12).
The sludge was removed from the bottom of the tank (12) by a pump (13) through a filter device (14), and then returned to a chemical solution tank (10).

After such pretreatment, the treated plastic crushed pieces were put into water in the charging tank (1) of the separation and recovery apparatus shown in FIG. The waste plastic separation and recovery device is a charging tank (1) for circulating the waste plastic mixture
And a separation tank (2) that separates the waste plastic mixture into low-specific gravity substances and high-specific gravity substances based on the specific gravity difference.In the charging tank (1), a vertical cylinder (4) equipped with a screw (3) is equipped with a liquid. It is arranged to sink in. A downward flow is generated in the vertical cylinder (4) by the rotation of the screw (3), and the plastic flow is drawn into the vertical cylinder (4) by this downward flow and is forcibly dispersed, and the dispersion pieces are dispersed. Transfer to the separation tank in a short time.

In the separation tank (2) where there is little flow, waste plastic is separated into a low specific gravity substance (5) such as polyethylene and a high specific gravity substance (6) such as polyvinyl chloride due to a difference in specific gravity. The low specific gravity (5) floats on the surface of the separation tank (2), and the high specific gravity (6) deposits on the bottom of the separation tank (2). The deposit of the high specific gravity (6) is sent to the circulation path (9) equipped with the air lift (7) and the recovery device (8), and is recovered by the recovery device (8).

Example 2 Instead of the pretreatment with the nonionic surfactant aqueous solution of Example 1, steam was previously applied to the waste plastic to be treated, and the air in the pores of the waste plastic was degassed. Water was soaked in the holes.

After this pre-processing, as in the first embodiment, FIG.
The treated plastic crushed pieces were charged into water in the charging tank (1) of the separation and recovery apparatus shown in (1), and the same operation as in Example 1 was performed.

Example 3 Instead of the pretreatment with a nonionic surfactant aqueous solution of Example 1, water vapor (temperature
After applying air at a temperature of 150 ° C. and a pressure of 5 kgf / cm ² G) to evacuate the air in the pores of the waste plastic, the atmosphere is cooled to liquefy water vapor and impregnate liquefied water into the pores. Was.

After this preprocessing, as in the first embodiment, FIG.
The treated plastic crushed pieces were charged into water in the charging tank (1) of the separation and recovery apparatus shown in (1), and the same operation as in Example 1 was performed.

COMPARATIVE EXAMPLE 1 100 g of plastic crushed pieces obtained by crushing a polyvinyl chloride plate having a thickness of 1 mm into a size of about 15 × 15 mm were not subjected to the above-mentioned pretreatment, and the water in the charging tank (1) of the separation and recovery apparatus shown in FIG. And the same operation as in Example 1 was performed.

Comparative Test Separation and recovery experiments of waste plastic were performed on the pretreated product according to Example 3 and the non-pretreated product according to Comparative Example 1.
Table 1 shows the experimental results.

[0026]

[Table 1] From Table 1, it can be seen that the method for separating and recovering waste plastic according to the present invention significantly improves both the transfer time and the recovery rate.

[0027]

The method for separating and recovering waste plastic according to the present invention has the following advantages since it is configured as described above.

1) The separation and recovery rate of waste plastic can be improved.

2) The time required for the separation and recovery of waste plastic can be reduced.

3) By pre-treating the waste plastic, the dirt on the surface of the waste plastic can be removed before the waste plastic is introduced.

Thus, according to the apparatus of the present invention, the mixture of waste plastics can be completely separated into low specific gravity substances and high specific gravity substances according to the specific gravity difference, and these can be separated and recovered efficiently and with high yield. .

[Brief description of the drawings]

FIG. 1 is a vertical sectional view showing a device for separating and recovering waste plastic.

FIG. 2 is a flow sheet showing the method of the present invention.

[Explanation of symbols]

 (1)… Input tank (2)… Separation tank (3)… Screw (4)… Vertical cylinder (5)… Low specific gravity (6)… High specific gravity (9)… Circulation path (10)… Chemical tank (11) Dehydrator

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Chitose Takakura 5-28 Nishikujo, Konohana-ku, Osaka-shi Inside Tachibashi Shipbuilding Co., Ltd. (56) References JP-A-48-97155 (JP, A) 50-5037465 (JP, A) JP-A-50-96773 (JP, A) JP-B 52-5065 (JP, B2)

Claims (1)

(57) [Claims] The method according to claim 1 mixture of waste plastics Upon separated into a high density product and low specific gravity thereof by a difference in specific gravity in the liquid processing
By applying steam to the waste plastics
And separating and collecting the waste plastic in advance by subjecting the waste plastic to a wettability imparting treatment .