JPH06819A - Recycling method of coated plastic - Google Patents

Abstract

PURPOSE:To inexpensively obtain recovered plastic having desirable CONSTITUTION:Coated plastic material being a waste thing is pulverized coarsely, then a plastic part is pulverized finely until a mean value of a grain size distribution becomes at the most 250mum, the plastic is recovered by classifying the pulverized article at 75mum or larger. Since a citing and the plastic differ in their hardness, the pulverized article wherein the grain size distributions of both of them differ from each other is obtained. Since the grain size becomes particularly small as compared with that of the plastic. Since the pulverized article is classified at 75mum or larger, the plastic from which the coating is removed is obtained and almost all of the pulverized article of at the most 75mum becomes the pulverized article of the coating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recycling method for recovering and reusing plastics from waste plastics whose surfaces have been subjected to surface treatment such as painting.

[0002]

2. Description of the Related Art Recently, plastic products have been widely used for automobile parts. For example, in the case of a plastic bumper, if the bumper is not painted on the surface,
Defective molded products and recovered products from scrapped cars can be roughly crushed into 3 mm square pieces, mixed with virgin material, and used again for molding bumpers. This is possible because the physical properties of recycled plastics are hardly deteriorated, and with a bumper whose surface is coated, the plastics recovered by the same method cannot be used again for the bumper. The reason for this is that in the case of painted bumpers, the properties of the plastic material such as impact resistance, elongation, surface quality, etc. are significantly reduced by mixing the crushed coating film into the recycled plastic, and the performance required as a bumper is reduced. This is because we cannot be satisfied. Therefore, painted plastic bumpers such as defective molded products and recovered products from scrapped cars are buried in the ground or burned, except when reused as construction piles that do not require physical properties. There is a problem of environmental destruction.

Japanese Unexamined Patent Publication No. 3-23909 proposes the following method as a method for separating and recovering polyurethane and polyvinyl chloride from a waste product in which polyurethane and polyvinyl chloride are laminated. 20 to 5 of the above composite waste
Coarsely crushed to a lump of about 0 mm, then stirred with a high-speed stirrer and pulverized to separate it into a polyurethane with a particle size of 1 to 2 mm and a sheet-like polyvinyl chloride with an external dimension of about 30 mm, and then polyvinyl chloride. Collect.

At present, for the recycling of painted plastic bumpers, technical development is in progress to separate the plastic part and the paint film part and to recover and reuse only the plastic part. . Method of removing coating film by blasting The coated film of the plastic bumper is sprayed with an abrasive together with compressed air to mechanically remove the coating film. Method of melting and separating the coating film with a screen A coated plastic bumper is roughly crushed and put into an extruder to melt the plastic part. Since the coating film is thermosetting and does not melt in the extruder, a screen is installed at the exit of the extruder to separate the coating film. Method of peeling coating film from plastic with chemicals Approximately 100 parts of mixed solution of organic salts, polyhydric alcohol, water, etc.
After heating to ℃, the rough crushed product of the plastic bumper coated with this liquid is immersed for several hours to peel off the coating film.

[0005]

In the above method, it is very difficult to adjust the distance between the abrasive spray nozzle and the object, the spray angle, the air pressure, the diameter and the shape of the nozzle, and the object has a planar shape. If so, still like a bumper 3
If the surface shape changes three-dimensionally, the above adjustment is very difficult. In the above method, if the mesh of the screen installed at the outlet of the extruder is made fine and the crushed coating film pieces are to be completely separated, the extrusion pressure becomes high and the screen is damaged. Further, if the mesh of the screen is made coarse, it becomes impossible to remove fine coating film pieces. The above method is difficult to industrialize because organic salts are harmful to the human body and have problems such as wastewater treatment. Therefore, the above-mentioned developed technology to date has not been put to practical use. Further, even if the laminate can be separated, the coating film of the coated plastic cannot be separated only by agitating with the high-speed agitator described in the above publication and finely pulverizing.

The present invention enables the coating film to be peeled off from the plastic without using chemicals, does not pose a risk in the recycling process, and is a coated plastic from which the recovered plastic having the desired physical properties can be obtained at low cost. The purpose is to provide a recycling method.

[0007]

According to the present invention, a waste painted plastic material or the like is roughly crushed, and then finely crushed until the average value of the particle size distribution of the plastic part becomes about 250 μm or less. This is a method for recycling coated plastics in which plastics are collected by classifying them to 75 μm or more.

[0008]

When the above pulverization is carried out, the coating film can be peeled from the plastic part, and the hardness of the coating film and that of the plastic are different, so that a pulverized product having a different particle size distribution is obtained. The particle size is much smaller than that of plastic. By classifying this finely pulverized product to 75 μm or more, a plastic with the coating film removed can be obtained.
Most of m or less are finely pulverized coating films.

[0009]

EXAMPLES The outline of the recycling method of the present invention will be described with respect to recycling of painted plastic bumpers.
A scrapped painted plastic bumper is first roughly crushed into about 3 mm square and then finely crushed. The average value of the particle size distribution of the plastic part is about 250 μm.
It is carried out until it becomes the following. With such fine pulverization,
Since the coating film can be peeled off from the plastic part and the hardness of the coating film and that of the plastic are different, a finely pulverized product having different particle size distributions of the two can be obtained, and the particle size of the coating film is significantly smaller than that of the plastic. By classifying this finely pulverized product to 75 μm or more, a plastic with the coating film removed can be obtained. When the thickness is 75 μm or less, most of the coatings are finely pulverized products. Finely pulverized plastic products classified to 75 μm or more
Further, if the float-sink separation treatment is performed with a sound wave, the coating film can be completely removed from the plastic, and the plastic that has been float-sink separated does not contain the coating film. There is no decrease in
Practical use of plastic recycling.

Next, a test example will be shown. Material of plastic bumper of sample Plastic: Polypropylene resin Paint: Baking paint of polyester melamine resin for both primer and base Fine grinding in ultra-low temperature atmosphere Crusher: Pin mill Temperature: Cooling to -20 to -60 ° C with liquid nitrogen Treatment rough crushing Before the sample is put into the pin mill, it is immersed in liquid nitrogen and cooled, and the sample is crushed at a peripheral speed of 190 / sec of the pin mill so that the average particle size of the plastic part is about 250 μm.
Continue crushing until. The finely pulverized product obtained had the coating film completely peeled off from the plastic part, and as shown in FIG. 1, the average value of the particle size distribution of the coating film 2 was about 20 μm and the average value of the particle size distribution of the plastic 1 was about 250 μm. Therefore, the distribution range of the particle diameters is deviated.

The material properties of the mixture of the finely pulverized coating film and the plastic are remarkably improved as compared with the as-roughly pulverized one. Table 1 shows the results of the physical property comparison test. Table 1
Therefore, the mixture of the coating film and the plastic finely pulverized under the above-mentioned conditions can be used as it is for the parts which are not required to have much physical properties, even if it cannot be used as it is as a material for the bumper. The plastic may be a thermoplastic resin, and the paint may be a normal baking paint. As the crusher, a disk mill, a hammer mill, or an axial flow type / vortex flow type crusher capable of crushing at low temperature can be used. In the fine pulverization process, the coarsely pulverized material is cooled in the range of 0 to -250 degrees, and the peripheral speed is 5
You may make it pulverize in the range of 0-300 m / sec.

[0012]

[Table 1] Note Sample 1: Virgin material containing only plastic Sample 2: Coated plastic bumper was crushed and re-molded. Sample 3: Painted plastic bumper was crushed and then finely crushed under the above conditions. Material remolded

When the finely pulverized material was classified using a screen of 200 mesh (mesh coarseness of about 75 μm), the coating particles passed through the screen, the plastic particles remained on the screen and were almost pulverized. The coated film can be removed. However, in this plastic grain,
As shown in (1), since the fine coating particles 4 having an average particle size of 20 μm adhere to the periphery of the plastic particles 3 having an average particle size of 250 μm due to static electricity, the coating particles cannot be completely removed from the plastic particles. In order to completely remove the coating particles, the floating-settling separation described below is performed. In Table 2, the above finely pulverized products are 75 μm or less, 75 to 250 μm and 2
The physical properties of the material classified into three types of 50 μm or more are shown. 75
Most of the materials classified to μm or less are finely pulverized products of the coating film, and materials of 75 to 250 μm and 250 μm or more are
Most are finely crushed plastic products. As is clear from Table 2, the material classified to have a thickness of 75 to 250 μm can be reused for parts having high physical properties even if it cannot be used for bumpers. The material classified to 250 μm or more has a very small amount of the mixed material in the coating film, and no problem occurs even if it is reused in the bumper.

[0014]

[Table 2] Note Sample 4: Reformed material of finely pulverized product classified to 75 μm or less Sample 5: Material of reformed molded finely pulverized product to 75 to 250 μm Sample 6: Material of reformed finely pulverized product classified to 250 μm or more

In order to completely remove the coating particles from the plastic particles, the following floating-settling separation is carried out. Since the specific gravity of the plastic is about 0.9 and the specific gravity of the coating film is about 1.4, the finely pulverized product is immersed in a liquid having a specific gravity of about 1 and separated by utilizing the difference in specific gravity between the two. In order to efficiently carry out this floating-settling separation, it is effective to stir the liquid and to add a surface active agent, and it is particularly effective to use ultrasonic waves. The finely pulverized product classified to 75 to 250 μm is further separated by the ultrasonic floating-sink separation. Table 3 shows the physical properties of the obtained materials. The physical properties of the recycled plastic material from which this coating film has been completely removed are
The physical properties of the virgin material (Sample 1 in Table 1) are almost the same.

[0016]

[Table 3] Note Sample 7: Finely pulverized product classified to 75 to 250 μm
Recycled plastic material that is completely separated from the coating film by ultrasonication

Although the painted plastic bumper has been described in the above embodiment, it can be applied to the recycling of the wheel cover for automobile-related parts, and the plastic can be recovered from the plastic parts which have been subjected to a surface treatment such as painting outside the automobile. And can be recycled.

[0018]

INDUSTRIAL APPLICABILITY According to the present invention, a coating film or the like can be peeled from a plastic without using a chemical agent.
Recycling can be performed in a factory without a wastewater treatment facility, there is no danger of work, and no environmental damage is caused. In addition, since it is easy to obtain recovered products with various physical properties, from those with a small amount of mixed coating to plastic with the coating completely removed, it is cheap to select the classification and separation method according to the object to be reused. Recycling of plastic is possible at a cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a particle size distribution of a finely pulverized resin and a coating film according to the present invention.

FIG. 2 is a view showing a state of finely pulverized resin particles and coating film particles according to the present invention.

[Explanation of symbols]

 3 Finely crushed resin particles 4 Finely crushed coating particles

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryomitsu Suyama 8 Tsutana, Fujisawa City, Kanagawa Prefecture Isuzu Central Research Institute

Claims (1)

[Claims] 1. A scrapped painted plastic material or the like is roughly crushed, and then finely crushed until the average value of the particle size distribution of the plastic part becomes about 250 μm or less.
A method for recycling coated plastics, characterized in that the plastics are recovered by classifying them to 5 μm or more.