JPH0120964B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recycling used plastic containers, particularly bottles, by crushing them and recycling them into useful uses.

Recently, a large amount of plastic has entered the field of containers, and plastic containers are now widely used for seasoning containers such as sauces, soy sauce, mayonnaise, salt, and sugar, and food containers such as edible oil, milk, alcoholic beverages, youth, flour, and rice. More recently, it has also been adopted in the field of pressure-resistant bottles for containing carbonated beverages such as beer and carbonated water.

By the way, used plastic containers discharged from these fields will become huge garbage if left unattended and will inevitably cause plastic pollution, and several states in the United States have already made their collection mandatory. There is. Therefore, there is an urgent need to collect and recycle these plastic containers.
This has several problems.

In other words, there are usually residues of the contents inside these containers, and there are also labels and labels on the surface.
The adhesive used to attach the label, dust, etc. are attached, and unless these are sufficiently removed, the product cannot be subjected to the recycling process. Furthermore, when recycling, it goes without saying that containers using the same type of resin are collected, but these containers are not necessarily the same in size, shape, hardness, etc.

Some proposals have already been made for recycling these plastic containers. For example, a method has been proposed in which the label is first mechanically peeled off, then crushed, washed, and dehydrated, but with this method, it is difficult to sufficiently remove the label by mechanical operations such as friction. This is difficult, and if the shape, size, hardness, etc. of the container changes, peeling becomes difficult, and if you are forced to adjust the device to match the external shape of each container, the mechanism has to be extremely complicated. .

The present invention improves these drawbacks of conventional devices and provides a highly efficient method for crushing and cleaning plastic containers that can be applied regardless of the shape, size, and hardness of the container. .

That is, in the method of the present invention, a waste plastic container to which a label made of the same kind of resin is attached is roughly crushed into slices with a width of 1 to 5 cm, and then mud,
This method of recycling waste plastic containers is characterized by separating and removing sand, metal powder, paper pieces, dust, etc., washing them, and then pulverizing them into fine particles.

By roughly crushing the container into strips or rounds, part of the label can be peeled off by itself, which not only simplifies subsequent processes, but also allows processing regardless of the shape, size, hardness, etc. of the container. becomes. In addition, since the crushed pieces are of appropriate size, it is easy to provide a mechanical cleaning effect during cleaning, making it easy to remove foreign substances adhering to the surface. Furthermore, since the product is pulverized into fine particles after washing, there is no problem of obstacles such as labels getting stuck in the pulverizer, and efficient pulverization is possible.

Containers to which the method of the present invention can be applied include crushing polyester, thermal containers.
The shape is not particularly limited and may be any type of bottle, tube container, square container, etc. Of course, there is no limit to the hardness.

In the coarse crushing step of the present invention, the container is preferably
The method is to cut the container into slices with a width of 5 cm, more preferably into slices with a width of 1 to 3 cm.This is usually done by cutting the container with a cutter having multiple rotating blades. A cutting method is used, but the method is not limited to this method.

After the crushing, it is preferable to roughly separate dust such as mud and sand, iron pieces, peeled labels, etc. adhering to the container. This separation facilitates the next cleaning step, and has the advantage of reducing the risk that the peeled paper or the like will stick to the stirring blades, rotating shaft, etc. and cause trouble. Preferably, a vibrating screen is used for this separation. Due to the large size of the polyester fragments, mud, sand, and iron pieces can be easily separated. In addition, when there are many iron pieces or iron powder, separation using a magnet may be used in combination. Further, an air separator or the like may be used to separate peeled paper pieces of the label. In other words, an air separator is effective for items that are easily blown away by wind, such as pieces of paper. This air separator blows air from below and separates crushed pieces of the container from paper, dust, etc. by the difference in sedimentation speed. Note that it is preferable to remove paper, dust, etc. separated by the air separator using a cyclone or the like to prevent them from being dispersed outside the system. In many cases, it is preferable to use the vibrating screen and air separator together.

The crushed pieces of the container from which paper pieces, dust, etc. have been removed are then washed, but the washing process can be selected as appropriate depending on the type of container, the type of contents, the type of adhesive on the label, etc. It is. For example, if the contents are water-soluble, such as youth or alcoholic beverages, and the adhesive is also water-soluble, you can wash them with warm water containing a surfactant and then rinse with water, but usually oil-based stains will adhere. Therefore, it is preferable to heat and wash the pieces in an alkaline aqueous solution having a pH of preferably 9 or higher, or to subject the crushed pieces to which the alkaline aqueous solution has been applied a wet heat treatment. Processing temperature is 40℃ or higher, preferably 60℃
C or higher and the treatment time is suitably 2 minutes or longer. If the contents or adhesive are hydrophobic, use trichlene,
Cleaning with an organic solvent such as percrene may also be used. In either case, the final step must be to thoroughly rinse with water to remove foreign matter. However, depending on the type of resin, the quality of the resin changes, so selection is necessary.

After washing, a separation step may be performed. This separation process separates the crushed pieces based on the difference in specific gravity, and includes metal powders such as iron and aluminum that are present in a small amount in the crushed pieces, and foreign resins that are slightly present in the crushed pieces of polyester. Remove polyethylene, polypropylene, etc. slightly attached to the surface. A hydrocyclone or the like is used for this separation operation. That is, by stirring the water in the water tank and rotating it gently, the water is separated based on the difference in specific gravity.

The crushed pieces are then dried or sent without drying to a grinding process. In the pulverizing step, it is preferable to use a rotary pulverizer with rotating blades to pulverize particles to a particle size of about 5 mm to 15 mm. That is, it is preferable that the particles have a particle size that passes through a sieve with a nominal size (JIS Z8801-1965) of 15.9 mm but does not pass through a sieve with a 4.0 mm diameter.

If the crushed pieces are not dried after crushing, they are dehydrated and dried. The dried crushed pieces may be washed again with a volatile organic solvent to remove adhesive, residual oil, etc., if necessary.

Although each of the above steps is carried out sequentially and continuously, there are various embodiments depending on the type of resin, the type of contents, the type of adhesive, etc. Some examples are as follows.

(1) When the contents and adhesive are water-soluble and there is little dirt: Crushing (round cutting) - Separating dust, etc. (vibration screen) - Separating paper pieces, etc. (air separator) - Hot water washing (surfactant included) - Water washing-grinding (rotary crusher)
- Dehydration (centrifugal separation) - Drying (2) When at least one of the contents and adhesive is hydrophobic and there is little dirt. Separator) Organic solvent cleaning (triclene, etc.) - Alkaline cleaning - Neutralization - Hot water washing (with surfactant) - Water washing - Grinding (rotary grinder) - Dehydration (centrifugal separation) - Drying (3) The contents and adhesive If at least one of these is hydrophobic and there is a lot of dirt Separation of dust, iron powder, etc. (washing with water and magnets) - Crushing (round cutting) - Separation of paper pieces, etc. (air separator)
- Organic solvent cleaning (triclene, etc.) - Alkali cleaning - Neutralization - Hot water washing - Water washing - Separation - Grinding - Dehydration (centrifugation) - Drying According to the method of the present invention, the size, shape, hardness and softness of waste plastic containers can be changed. Not only can it be processed independently, but it can also be easily and reliably washed, yielding extremely clean plastic particles, resulting in high-quality recycled products with extremely low impurities.
Therefore, it is an extremely useful invention in terms of processing waste plastics and saving resources.

Next, an example will be described based on process diagrams in the drawings.

In the drawing, by feeding bottles made of polyethylene terephthalate into a hopper 1, the bottles are sequentially conveyed by a conveyor 2 and fed into a crusher 3. In this crusher 3, the bottle is cut into slices about 3 cm wide by a rotating blade, which fall from the bottom and are sent onto a vibrating screen 4. This vibrating screen 4 removes sand, mud, iron powder, etc. adhering to the crushed pieces, and the crushed pieces from which these have been removed are sent to a screw feeder 6 via a conveyor 5, and sequentially supplied to an air separator 7. be done. In this air separator 7, the blower 8
This blows air up from the bottom, blowing light objects such as paper pieces and dust attached to the crushed pieces up to the top and separating them. The blown up pieces of paper, dust, etc. are sent to the cyclone 9 and captured, and the air is discharged outside the system.

On the other hand, the crushed pieces are sent to an alkali cleaning tank 11 via a conveyor 10. This alkaline cleaning tank 11 contains a 3% aqueous solution of caustic soda at a temperature of 40°C.
Wash with stirring for 10 minutes. The washed fragments are
It is supplied to a neutralization tank 13 by a conveyor 12.
In this neutralization tank 13, the alkali from the previous step is neutralized with a dilute aqueous hydrochloric acid solution. The crushed pieces are sent to a hot water washing tank 15 via a conveyor 14 after being neutralized. In the hot water washing tank 15 , the pieces are washed with hot water at 70° C. for 10 minutes, and the washed crushed pieces are sent to the separation tank 17 via the conveyor 16 . In the separation tank 17, water is slowly rotated by a stirrer, thereby separating the crushed pieces from sand, mud, foreign resin powder, etc. adhering to the crushed pieces.

The crushed pieces from which foreign matter has been removed are then conveyed to conveyor 1.
8 and sent to a crusher 19. This crusher 19
In this case, the amount of crushed pieces is usually 5 mm or more due to the rotation of the rotary blade.
It is crushed into particles with a diameter of 15 mm. The crushed pieces are conveyor 2
0 and then sent to the dehydrator 21. This dehydrator 21
is of a centrifugal dewatering type, and the dehydrated crushed pieces are sent to a fluidized fluidized dryer 23 via an air conveyor 22.

In the fluidized fluid dryer 23, hot air is blown up from the bottom, the crushed pieces are dried, and attached dust and the like are separated and sent along with the wind to the cyclone 24, where they are separated from the air. On the other hand, iron powder etc. are separated from the crushed pieces by a magnet etc. on the way they fall, and finally they pass through an air conveyor 25 to a volatile organic solvent cleaning tank 26.
and sent to the receiver 27.

Through this process, waste plastics can be efficiently made into clean fine particles, which can be used as is or as new plastics of the same or different type, or recycled products by mixing and melting various organic or inorganic additives or fillers as desired. For example, it can be used as a molding material, and various molded parts, films, bands, fibers, pipes, etc. can be obtained. In addition, polyesters can be directly polymerized in a solid state, or modified resins can be produced by blocking treatment of terminal carboxy groups, depolymerization in the presence of unsaturated carboxylic acids, and the like.

[Brief explanation of drawings]

The drawings are process charts showing an example of the method of the present invention. 1: Hopper, 2, 5, 10, 12, 14, 1
6, 18, 20: conveyor, 3: crusher, 6: screw feeder, 7: air separator,
8: Blower, 9, 24: Cyclone, 11: Alkali cleaning tank, 13: Neutralization tank, 15: Hot water cleaning tank, 17: Separation tank, 19: Pulverizer, 21: Dehydrator, 22, 25: Air conveyor , 28: Fluidized dryer, 26: Organic solvent cleaning tank, 27: Receiver.

Claims (1)

[Claims] 1. A waste plastic container with a label made of the same kind of resin attached is roughly crushed into slices with a width of 1 to 5 cm, and mud, sand, metal powder, paper pieces, dust, etc. are separated and removed. A method for recycling waste plastic containers, which comprises removing, cleaning and then pulverizing them into fine particles. 2. The method for recycling waste plastic containers according to claim 1, wherein the cleaning is washing with hot water containing a surfactant, washing with an organic solvent followed by alkaline washing, or washing with water. 3. The method for recycling waste plastic containers according to claim 1, wherein the waste plastic containers are made of polyester whose main repeating unit is ethylene terephthalate.