JP3178095B2 - How to Recycle Painted Plastic - Google Patents

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 a surface treatment such as painting.

[0002]

2. Description of the Related Art Recently, plastic products have been frequently used for automobile parts. For example, in the case of a plastic bumper, if the bumper has no surface painted,
Defective molded products and recovered products from end-of-life vehicles are roughly pulverized to about 3 mm square, mixed with virgin material, and used again for bumper molding. This is possible because the physical properties of the recycled plastic hardly deteriorate, and in the case of a bumper whose surface is painted, the plastic recovered by the same method cannot be used again for the bumper. The reason is that, in the case of painted bumpers, the physical properties such as impact resistance, elongation, and surface quality of the plastic material are significantly reduced due to the incorporation of the crushed coating film into the recycled plastic, and the required performance as a bumper is reduced. This is because they cannot be satisfied. Therefore, painted plastic bumpers, such as defective molded products and recovered products from scrapped vehicles, are buried in the ground or burned except when reused for construction piles, etc., which do not require much physical properties. And there is a problem of environmental destruction.

JP-A-3-23909 proposes the following method for separating and recovering polyurethane and polyvinyl chloride from waste in which polyurethane and polyvinyl chloride are laminated. 20 to 5 of the above composite waste
Roughly pulverized into a lump of about 0 mm, and then finely pulverized by stirring with a high-speed stirrer, separated into polyurethane having a particle size of 1 to 2 mm and a sheet-like polyvinyl chloride having an outer dimension of about 30 mm by a sieve. Collect.

At present, for the recycling of painted plastic bumpers, the development of technology for separating the plastic portion and the coating film portion, recovering only the plastic portion, and reusing the plastic portion has been promoted. . A method of removing the coating film by blasting Abrasive is sprayed together with compressed air on the coated plastic bumper coating film, and the coating film is mechanically peeled off. Method of melting and separating the coating film with a screen The coated plastic bumper is roughly pulverized 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 outlet of the extruder to separate the coating film. A method of peeling a coating film from a plastic with a chemical agent A mixed solution of organic salts, polyhydric alcohol, water, etc. is used for about 100.
C. and the coated plastic bumper was immersed in this solution for several hours to remove the coating.

[0005]

In the above-mentioned 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. Then still, like a bumper 3
If the surface shape changes 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 finer and it is attempted to completely separate the crushed coating pieces, the extrusion pressure is increased and the screen is broken. Further, when the mesh of the screen is made coarse, it is impossible to remove fine pieces of the coating film. In the above method, since the organic salts are harmful to the human body, there is a problem such as wastewater treatment and industrialization is difficult. Therefore, the developed technology up to now has not been put to practical use. In addition, a laminate can be separated but a coated plastic film cannot be separated by a high-speed stirrer described in the above-mentioned Japanese Patent Application Laid-Open (Kokai) No. H11-27139.

The present invention makes it possible to remove a coating film from a plastic without using a chemical agent, so that there is no danger in a recycling process and that a recovered plastic having desired physical properties can be obtained at low cost. It aims to provide a recycling method.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a paint plastic.
Coarsely pulverized waste products and reduce the coarsely pulverized products to -20 ° C or lower.
This is a coated plastic recycling method in which the plastic is cooled, then finely pulverized in a low-temperature atmosphere until the average value of the particle size distribution of the plastic part becomes about 250 μm or less, and the finely pulverized product is classified into 75 μm or more to recover the plastic. .

[0008]

When the above-mentioned pulverization is performed, the coating film can be peeled off from the plastic part, and since the hardness of the coating film and the plastic are different, finely pulverized products having different particle size distributions of both can be obtained. The particle size is much smaller than that of the plastic. By classifying this finely pulverized product to 75 μm or more, a plastic from which the coating film has been removed is obtained.
If it is less than m, most of the film is finely pulverized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The outline of the recycling method of the present invention will be described with reference to recycling of a coated plastic bumper.
First, the waste plastic bumper is roughly pulverized to about 3 mm square, and then finely pulverized. In this pulverization, the average value of the particle size distribution of the plastic part was about 250 μm.
Perform until the following. When such fine grinding is performed,
The coating film can be peeled off from the plastic part, and since the hardness of the coating film and the plastic are different, finely pulverized products having different particle size distributions can be obtained, and the particle size of the coating film is much smaller than that of the plastic. By classifying this finely pulverized product to 75 μm or more, a plastic from which the coating film has been removed can be obtained. Almost 75 μm or less is a finely pulverized coating film. Plastic finely pulverized product classified to 75 μm or more,
Furthermore, if the floatation / sedimentation treatment is performed by using sound waves, the coating film can be completely removed from the plastic, and the floating / sedimentation separated plastic has no physical properties when used as a bumper material again because there is no contamination of the coating film. Without any decrease in
Practical use of plastic recycling.

Next, test examples will be described. Material of sample plastic bumper Plastic: Polypropylene resin Coating: Baking paint of polyester melamine resin for both primer and base Ultra-low temperature pulverization Crusher: Pin mill Temperature: Cooling to -20 to -60 ° C with liquid nitrogen Rough pulverization Before the sample is put into the pin mill, it is immersed in liquid nitrogen and cooled, and the sample is pulverized at a peripheral speed of the pin mill of 190 / sec.
Continue grinding until In the obtained finely pulverized product, the coating film was completely peeled off from the plastic part. 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. And the distribution ranges of those particle sizes are separated.

The material properties of the above-mentioned mixture of the finely pulverized coating film and the plastic are remarkably improved as compared with those of the roughly pulverized film. Table 1 shows the results of the comparison test of the physical properties. 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 a part that does not require much physical properties, even if it cannot be used as a material for a 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, an axial flow type or a vortex type which can be crushed at a low temperature can be used. In the fine pulverization, the coarsely pulverized material may be cooled in a range of -20 to -250 ° C and finely pulverized in a range of a peripheral speed of 50 to 300 m / sec.

[0012]

[Table 1] Note Sample 1: Virgin material made of plastic only Sample 2: A material obtained by roughly pulverizing a painted plastic bumper and reshaping it Sample 3: A mixed and finely pulverized material obtained by roughly pulverizing a painted plastic bumper and then pulverizing under the above-mentioned conditions. Reformed material

When the above-mentioned finely ground material is classified using a 200-mesh (mesh coarseness: about 75 μm) screen, the coating particles pass through the screen, and the plastic particles remain on the screen, and are almost finely ground. Can be removed. However, this plastic grain has
As shown in (1), fine coating particles 4 having an average particle size of 20 μm are attached around the plastic particles 3 having an average particle size of 250 μm due to static electricity, so that the coating particles cannot be completely removed from the plastic particles. In order to completely remove the coating film grains, float separation is performed as described below. Table 2 shows that the above pulverized product was 75 μm or less, 75 to 250 μm and 2 μm.
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 coating films, and materials of 75 to 250 μm and 250 μm or more are
Most of them are finely pulverized plastic products. As is evident from Table 2, the materials classified to 75 to 250 μm can be reused for parts having high physical properties even if they cannot be used for bumpers. Materials classified to 250 μm or more have very little contamination in the coating film, and do not cause any problems when reused for bumpers.

[0014]

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

In order to completely remove the coating particles from the plastic particles, the following flotation separation is performed. 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 using the difference in specific gravity between the two. In order to carry out the flotation efficiently, it is effective to agitate the liquid and add a surfactant. Particularly, it is effective to use ultrasonic waves. The finely pulverized product classified to 75 to 250 μm is further separated by flotation by ultrasonic waves. Table 3 shows the physical properties of the obtained materials. The physical properties of the recycled plastic material from which the coating has been completely removed are:
It is almost the same as the physical properties of the virgin material (Sample 1 in Table 1).

[0016]

[Table 3] Note Sample 7: Finely pulverized product classified to 75 to 250 μm
Recycled plastic material from which the coating is completely removed by floating separation using ultrasonic waves

In the above embodiment, a painted plastic bumper has been described. However, in the case of automobile-related parts, the present invention can also be applied to recycling of a foil cover, and in addition to automobiles, plastic can be recovered from plastic parts subjected to surface treatment such as painting. And can be recycled.

[0018]

According to the present invention, it is possible to peel a coating film or the like from a plastic without using a chemical agent.
Recycling at a factory without a wastewater treatment facility becomes possible, and there is no danger in work and no problem of environmental destruction. In addition, it is easy to obtain recovered products of various physical properties from plastics with completely removed paint film to plastics with some paint film mixed in. Plastics can be recycled at low cost.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 3 Finely ground resin particles 4 Finely ground coating particles

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryomitsu Suyama 8 Tsuchiya, Fujisawa City, Kanagawa Prefecture Isuzu Central Research Institute Co., Ltd. (56) References JP-A-3-23909 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) B29B 17/00 C08J 11/00-11/28

Claims (1)

(57) [Claims] [Claim 1] a waste of painted plastic and rough grinding, this
Rough ground product was cooling to -20 ° C. or less, and then to an average value of the particle size distribution of the plastic portion is approximately 250μm following
A method for recycling coated plastics, comprising finely pulverizing in a low-temperature atmosphere, and collecting the plastic by classifying the finely pulverized product to 75 μm or more.