JP2001353721A - Method for recycling plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recycling plastics, in which a paint film is released from plastic moldings in order to reutilize the same. SOLUTION: In a method for recycling the plastic to reutilize discarded plastic moldings with a paint film, the following respective processes are performed. (1) A process for fragmentating the plastic, in which the plastic moldings with the paint film are made to an aggregate consisting of platelike fine pieces (hereinafter 'fragmentated body'). (2) A process for releasing the paint film, in which a mixture of a fragmentated body/powder consisting of the fragmentated body releasing the paint film and coating powder is obtained by releasing the paint film from the plastic fragmentated body with the paint film by rubbing action due to mechanical force. (3) A process for separating the fragmentated body/powder, in which the mixture of the fragmentated body/ powder is separated into the fragmentated body releasing the paint film and coating powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling a plastic molded article by peeling off a coating film of the coated plastic molded article. For example, the present invention is suitable for recycling a plastic molded product, such as a PO bumper or a PO door side molding, which is generated in a manufacturing process of an automobile part, such as a defective plastic molded product, and a paint film removed from a market collection product. is there.

[0002] Hereinafter, description will be mainly given of an example of peeling off a coating film of a PO-based plastic molded article for automobiles. However, the present invention is not limited to this, and the present invention is applicable to peeling off a coating film of various other plastic molded articles. .

[0003]

2. Description of the Related Art Heretofore, most of painted automotive molded plastic rejects and products collected from the market have been treated as industrial waste. Usually, first, after cutting to an appropriate size to reduce the volume, treatments such as incineration and landfill were performed.

[0004] In recent years, however, attention has been paid to the reuse of plastic molded articles due to increasing awareness of environmental issues. The above plastic molded products are no exception,
Reuse methods are being considered. For example, a plastic molded product with a paint (coated surface) is ground to the size of a pellet and reused as a raw material plastic.

[0005]

However, when a plastic product with paint applied is crushed and reused,
The paint component is mixed into the recycled plastic, which may lead to quality deterioration of the recycled molded product (product). In addition, recycled products were also limited in coloration, and applicable products were limited.

[0006] Therefore, it is originally desirable that the coating film be reused after being separated from the plastic molded body. However, it has been said that the only way to peel the coating film from the plastic molded body is by manual work, which is usually troublesome and leads to an increase in cost. That is,
As far as the present inventor knows, there has been no simple method of peeling a coating film from a plastic product.

[0007]

Means for Solving the Problems The present inventors have conceived the following plastic recycling method in the course of intensive research and development to solve the above-mentioned problems.

A plastic recycling method for reusing discarded plastic molded products with a coating film, wherein the plastic molded products with a coating film are aggregated into plate-like strips (hereinafter referred to as “strips”). Plastic stripping process, a coating film is peeled from a coated plastic strip by a mechanical rubbing action to obtain a strip / powder mixture of the coating strip and the coating powder. It is characterized by passing through a film stripping step and a strip / powder separation step of separating a strip / powder mixture into a coating film strip and a coating powder.

Then, after the strip / powder separation step, a pulverizing step of appropriately pulverizing the peeled coating strip into granules having a particle size that can be easily recycled is performed.

[0010] The rubbing action by the mechanical force consists of rotation of at least a pair of outer mills (outer rolls) and inner mills (inner rolls). It is characterized in that it has a structure in which a compressive / frictional force can be applied to the surface of the strip introduced into the gap.

The coating film peeling step is performed by a continuous operation type coating film peeling apparatus having a charging hopper and a discharge port. A series of mechanisms that are introduced into the inner dies, and further moved by the rotation of the outer dies and / or the inner dies to the discharge port side while applying compression / frictional force between the external dies and the internal dies, and discharged from the discharge port. It is desirable that the workability is good because of good workability.

It is desirable to use a rotary cutter type crushing device in the plastic shredding step, because it can be easily shredded into strips having a predetermined shape.

In the strip / powder separation step, it is desirable to use a vibration sieving device because the coating strip and the coating can be easily separated.

Further, in the pulverizing step, it is desirable to use a rotary cutter type pulverizer generally used for plastic pulverization.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The plastic recycling method of the present invention will be described below in detail. Each step of the present invention can be easily performed as follows using a general-purpose device.

The plastic molded article applicable to the present invention is not particularly limited as long as it is a plastic molded article having a coating film and is capable of delamination between the plastic and the coating film. For example, a thermoplastic resin such as polypropylene (PP), polyethylene (PE), ABS resin, thermoplastic resin such as acryl and vinyl chloride, or a thermosetting resin such as polyester resin, epoxy resin, phenol resin and melamine resin (fiber reinforced) Plastics (including FRP) are coated with a general-purpose coating film. The effect of the present invention is easily exerted in the case of a nonpolar thermoplastic such as polyolefin, in which delamination between the coating film and the plastic easily occurs due to a difference in SP value. Also, in the case of a plastic material which is not brittle even if it is not nonpolar and which is rich in ductility (toughness) and hard to be broken by a rubbing action,
By the rubbing action, the peeling of the coating film and the plastic substrate is mechanically ensured mechanically, and the effect of the present invention is easily exerted.

Specific examples of the molded product include an automobile bumper and an automobile door side molding. It is desirable to apply the present invention to a plate-shaped molded product so that a strip having a predetermined shape is easily formed in a stripping step described later. In addition, a three-dimensional shape which is not a plate shape can be applied by shaving a plastic surface having a coating film as a pre-treatment to form a plate shape.

The plastic recycling method of the present invention comprises:
The basic feature is to go through the following procedure (see FIG. 1).
The following steps can be applied to both a dry state and a wet state.

Slicing Step This is a step of crushing (crushing) a plastic molded article with a coating film to prepare a treated article into a strip having a predetermined shape. Crush the plastic molded product to a size that easily peels the coating film. Here, crushing (crushing) means from the order of meters to several tens of cm.
(Refer to "Chemical Engineering Handbook, Revised Fourth Edition", edited by the Society of Chemical Engineers, Japan). 53-10-25) Maruzen, p. 1264 ").

The shape of the plastic product after crushing is substantially the same, and is 10 to 100 mm square, preferably 20 to 50 mm.
It is desirable that the front and rear thin pieces (leaf shape) be used, and furthermore that they have a flat plate (piece shape) without curved portions and corner portions. This is because the direction in which the strips are introduced into the peeling mechanism of the peeling device in the subsequent coating film peeling step is easily stabilized, and further, the peeling is easy.

The crushing may be performed using a general-purpose crushing device capable of crushing plastic. In particular, it is possible to suitably use a cutter mill type, a shredder type mainly focusing on a shearing action and a cutting action, a crusher type crushing apparatus mainly focusing on an impact action, and the like.

Further, although it is not efficient, if there is no crusher, it is of course possible to carry out manually by using a cutter or the like. Further, it is also possible to use a pulverizer described below instead.

FIG. 2 is a schematic cross-sectional view of a crushing mechanism of a crushing apparatus that can be used in the fragmenting step. FIG. 2 shows a crushing mechanism of the rotary cutter type crushing device. The rotary cutter type crushing device is suitable for the present invention because the shape of the crushed product can be made substantially constant.

The crushing mechanism 12 has rotary blades (rotary cutters) 14a and 14b, and performs crushing by strong shearing force generated by the engagement of the rotary blades. The plastic molded product introduced from above is drawn into the interior by the claw blades 15a and 15b of a plurality of rotary blades set on two shafts 16a and 16b which rotate inward each other. Then, while being slit by the continuously acting shearing force between the outer peripheral edges of the blade rotating in the engaged state, the blade is crushed into a flake shape (leaf shape) by receiving the shearing force. The whole of the crushed plastic molded article is immediately discharged as a strip by rotation, and is scraped off by the scraper 18. The size of the strip is determined by the distance (gap) between the rotating blades.
Can be adjusted by changing

In this step, the rotary blades 14a, 14b
Some of the coating films may be peeled off due to contact with the plastic molded product.

The coating film peeling step The coating film is peeled off from the strip obtained in the fragmenting step by a rubbing action by mechanical force,
This is a step of obtaining a strip / powder mixture with the coating powder. In the present coating film peeling step, a coating film peeling device having a peeling mechanism section basically having the following rubbing action is used. This device is
It has the same structure as a mill usually used for milling cereals and the like. When used in the field of plastic film peeling, which is different from milling, a remarkable peeling effect is produced as described below.

The peeling mechanism of the coating film peeling device comprises at least a pair of outer mills (outer rolls) and inner mills (inner rolls). The outer mill and the inner mill are configured to be rotatable about the same rotation axis, and an adjustable gap is provided between the two mills at regular intervals. As the outer mill and / or the inner mill rotate, the strip is introduced (drawn) into the gap between the outer mill and the inner mill, and a compressive / frictional force generated by the rotation of the mill is applied to the surface of the strip. It was made possible.

FIG. 3 shows an example of the peeling mechanism. The peeling mechanism 23 includes an outer mill (a donut-shaped outer roll) 25 and an inner mill (a disk-shaped inner roll) 27.
The peeling mechanism 23 is an enlarged view of the bottom surface of the coating film peeling apparatus 21 shown in FIG.
The inner mill 27 is rotatable around the shaft 29. In addition, the outer mill 25 and the inner mill 27 may be configured to rotate in opposite directions to each other, or may be designed to rotate only one of the mills. Further, in the drawing, the peeling mechanism 23 is in a vertical state, but can be used in a horizontal state.

The opposing surfaces (the inner peripheral surface and the outer peripheral surface) of the outer mill 25 and the inner mill 27 are formed as uneven tooth-shaped surfaces as shown in the figure. This is because the compressive / frictional force is effectively applied to the strip, which is the object to be processed, and the strip introduced into the gap S can be effectively discharged from the opposite side of the gap S. is there. The contact surface can be variously changed in design, such as a smooth type or a corrugated type, as long as a compressive / frictional force can be applied to the strip.

The width of the gap S is adjusted according to the thickness of the strip so that a suitable compressive / frictional force can be applied to the strip. The width of the gap S is adjusted by rotating the adjustment handle 37 shown in FIG. Appropriate compressive / frictional force means that the peeling of the coating film will occur by overcoming the delamination strength between the plastic and the coating film of the strip, and will not give deformation such as breakage to the shape of the strip. A degree is desirable.

For example, when the thickness of the strip is about 3 mm, the gap S is about 2.5 mm. By adjusting the gap S to an appropriate width, only the coating film can be satisfactorily peeled off from the strip. If the width of the gap S is too narrow, the strips extend and lose their shape, or the strips themselves are crushed. On the other hand, if the width is too wide, sufficient compression / shearing force is not applied to the strips, so that peeling of the coating film is incomplete.

The peeling of the coating film here is caused by peeling between the plastic and the coating film due to compression / frictional force applied to the strip by rotation of the mortar (roll). It is thought to be due to polishing both sides of the body.

The outer and inner dies and other parts are usually made of cast iron, high manganese cast steel or the like so as to maintain strength, wear resistance and the like. In addition, the temperature of the peeling mechanism unit 23 is likely to increase due to the operation of the apparatus. Therefore, a separate cooling means may be provided to control the temperature so as not to affect the processing of the strip.

The coating film peeling device 21 having the above-described peeling mechanism 23 has a charging hopper 31 and a discharge port 33 in the illustrated example. That is, the strips fed from the loading hopper 31 are subsequently introduced between the outer mill and the inner mill,
Further, by rotating the outer mill and / or the inner mill, the outer mill and the inner mill are moved to the discharge port 33 side while applying compression / frictional force,
A series of mechanisms for discharging from the discharge port 33 are provided.

When using the above-mentioned apparatus, a strip is introduced from the upper part of the input hopper 31. Although it is not inevitable, it is desirable to remove the crushed pieces and the powdery plastic that have been crushed to the desired size or more in the crushing step before putting them into the coating film peeling device 21. This is because even if the plastic having a small particle size enters the coating film peeling device 21, the coating film is not easily peeled off due to the clearance. Furthermore, when plastics having a small particle size are mixed, the peeling efficiency may be reduced.

The above-mentioned small-grain plastic can be removed by using a mesh feeder or the like.

An adjusting means (not shown) for adjusting the amount of the strip to be introduced into the peeling mechanism 23 is provided below the input hopper 31. The amount of the strip introduced into the peeling mechanism 23 is adjusted according to the size of the apparatus, the processing capacity, and the like.

The strip introduced into the mortar moves under the compression / frictional force while passing through the gap S.

The strip having passed through the gap S between the outer mill and the inner mill is discharged from the discharge port 33 to the outside of the coating film peeling device 21. At this time, due to the rotation of the mortar, the strip is discharged in a state of being separated into the coating powder and the coating strip.

Here, when the present apparatus is operated in a state where one of the outer mill and the inner mill is a fixed mill and the other is rotating at a rotation speed of 200 to 500 rpm, good peeling can be performed. When the present invention is applied to a relatively hard material other than the PO-based plastic, both the outer mill and the inner mill are rotated in directions opposite to each other to increase the rubbing action. .

Since the surface of the fixed mortar has a smaller frictional force than the surface of the rotating mortar, the powder of the coating film after peeling is likely to adhere. When the peeling step is performed while rotating the mortar to which a large amount of the coating film powder adheres, the surface of the fixed mortar can be cleaned. Low-speed rotation is sufficient for cleaning.

In FIG. 4, reference numeral 39 denotes a pulley,
40 is a motor. Further, the plastic coating film peeling device of the present invention is not limited to the illustrated configuration, and various design changes can be made within the scope of the present invention. Although it is conceivable that the coating film is peeled off by barrel polishing or the like, in the case of barrel polishing, not only the coating film but also the plastic is polished, and the efficiency of collecting the plastic is low.

Strip / Powder Separation Step This is a separation step of separating the coating film powder separated in the coating film peeling step and the coating film strip.

Any method may be used as long as the method can separate the coated film strip from the coated film. Generally,
It is desirable to use a sieving apparatus that can be easily separated by utilizing the difference in size between the peeled coating film and the coating film strip.

As the sieving apparatus, there are a vibrating sieve, an in-plane motion sieve and the like, and any of them can be used. The size of the sieve may be determined as appropriate according to the size of the strip fragmented in the fragmentation step.

When the vibrating sieving apparatus is used, the paint powder that has already been peeled off from the strips is naturally removed, but the powder that has been peeled off and adheres to the strips due to static electricity or the like can be efficiently removed by vibration. Can be removed.

FIG. 5 shows an example of a circular vibrating sieve apparatus applicable to the present invention.

In the vibration sieving apparatus 41, a vibration generating mechanism including a motor 45 and a vibrating body 47 is housed in a mount 43. The motor 45 and the vibrating body 47 are connected by a V-belt 49 and a drive spring 51. Vibrator 4
Weights 53a and 53b are attached to the upper and lower sides of 7, and by rotating the weights 53a and 53b, the vibrator base 57, the lower frame 59, and the middle frame 60 supported by the frame receiving spring 55 vibrate. Is a structure that generates

The strip / powder mixture is put on the sieving surface 61 to generate vibration. Due to the generated vibration, the mixture moves on the sieve surface, and the fine coating powder is discharged from the discharge port 63a attached to the lower frame 59 and from the discharge port 63b of the large film peeling strip body frame, respectively. You. In addition,
The phase and amplitude of the vibration are controlled by adjusting the weight.

The coating film powder (paint residue) separated in the strip / powder separation step is separately reused. For example, it can be used as an alternative energy auxiliary material. Hard paint scum can also be used as a decorative material for decorative surfaces such as abrasives and outer walls.

Pulverization Step This is a step of pulverizing the separated coating film strip. Here, pulverization refers to further subdividing a breakage of about several cm. (“Chemical Engineering Association,“ Chemical Engineering Handbook Revised Fourth Edition ”)
(Showa 53-10-25) Maruzen, p. 1264 ").

The pulverized plastic powder can be recycled as a raw material. For example, when the pellets are used again in a manufacturing process such as a factory, the pellets are finely divided in the pulverizing process, and the pellets may be used in the same manner as ordinary pellets. In the case of thermosetting resins,
Instead of being used as a recycled material, it can be used as an abrasive, a coating film sub-element (filler for paint), and the like.

In the above-mentioned fragmentation step, when the plastic molded product has been crushed to a size suitable for recycling, this crushing is not an essential step.

In this pulverizing step, a general-purpose pulverizer capable of pulverizing plastic may be used. As a pulverizer, for example, an impact shear mill (Victory mill) or a turbo mill can be suitably used.

FIG. 6 shows a rotary cutter type pulverizer as an example of a specific pulverizer.

The crushing device 64 has a basic structure including a main body 65, a rotary cutter 67, a fixed cutter 68, and a screen 70. The coating film peeling strip supplied from above is drawn into the grinding chamber by the rotation of the rotary cutter 67, and is crushed by the shearing force acting between the rotary cutter 67 and the fixed cutter 68 serving as the main crushing force. You. The powder that has reached the particle size equal to or smaller than the opening hole diameter of the screen 70 by the pulverization is discharged downward by its own weight or blower suction. Pulverization of a large powder piece having a diameter larger than the opening diameter is repeated until it is lifted by the rotary cutter 67 and passes through the screen 70.

The opening of the screen 70 is adjusted according to the required size of the pulverized material to obtain a desired size of the pulverized material.
The obtained pulverized material can be used again as a plastic raw material.

Between the above devices (between the crushing device and the coating film removing device, between the coating film removing device and the sieving device, and between the sieving device and the crushing device), a transfer device such as a belt, a vibration, and a bucket conveyor is separately installed. Then, it can be automated. .

[0059]

According to the present invention, the coating film can be easily separated from the plastic molded article with the coating film by using the rubbing action by the mechanical force. for that reason,
Recycling of plastic molded products has become possible, and it has become possible to provide higher quality recycled plastic raw materials than before.

By the way, the present inventor has made PP
As a result of peeling off the coating film of the bumper, it was confirmed that the coating film was peeled off favorably and 60% or more of the plastic could be recovered.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a procedure of a plastic recycling method of the present invention.

FIG. 2 is a schematic cross-sectional view showing a crushing unit of a crushing apparatus usable in the present invention.

FIG. 3 is an enlarged view showing a peeling mechanism of a coating film peeling apparatus usable in the present invention.

4 is an overall side view of the coating film peeling device shown in FIG.

FIG. 5 is a partial sectional view showing a vibrating sieve device usable in the present invention.

FIG. 6 is a cross-sectional view showing a crushing device that can be used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Rough crushing mechanism part 14a, 14b of a crushing apparatus 14 Rotary blade 21 Coating peeling apparatus 23 Peeling mechanism part of a coating film peeling apparatus 25 Outer mill (outer roll) 27 Inner mill (inner roll) 31 Input hopper 33 Discharge port 41 Vibration Sieving equipment 64 Crushing equipment

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 55:00 B29K 55:00 F term (Reference) 4D021 AA01 CA03 CB09 CB12 DA13 EA10 4D065 CA12 CB10 CC01 CC08 DD04 EB14 ED01 ED11 ED21 4D075 BB01X BB20Z DA23 DB31 4F301 AA12 AB01 BA12 BA21 BD05 BE30 BE31 BE32 BF02 BF08 BF12 BF31

Claims (8)

[Claims] 1. A plastic recycling method for reusing a discarded plastic molded article with a coating film, wherein the plastic molded article with a coating film is aggregated into plate-like strips (hereinafter referred to as a "strip body"). A) a plastic stripping step, wherein the coating is peeled from the coated plastic strip by a rubbing action by mechanical force, and a strip / powder of the coating strip and the coating powder; A coating stripping step of obtaining a mixture; and a strip / powder separation step of separating the strip / powder mixture into a coating strip and a coating powder. Plastic recycling method. 2. The method according to claim 1, further comprising, after the strip / powder separating step, a pulverizing step of further pulverizing the coating film peeling strip into particles having a particle size that is easily recyclable. Plastic recycling method. 3. The rubbing action by the mechanical force comprises the rotation of at least a pair of an outer mill (outer roll) and an inner mill (inner roll), and the outer mill and / or the inner mill is rotated by rotation of the outer mill. The surface of the strip introduced into the gap between the inner mills
The plastic recycling method according to claim 1, wherein the method has a structure capable of applying a frictional force. 4. The coating film peeling step is performed by a continuous operation type coating film peeling apparatus having a charging hopper and a discharge port, wherein the strips supplied from the charging hopper are successively removed from the outside. A series of steps that are introduced between the mortar and the inner mill, and further moved by the rotation of the outer mill and / or the inner mill to the discharge port side while applying a compression / frictional force between the outer mill and the inner mill, and discharged from the discharge port. 4. The plastic recycling method according to claim 3, wherein the plastic recycling method is provided. 5. The plastic recycling method according to claim 1, wherein a crusher of a rotary cutter type is used in the plastic fragmenting step. 6. The plastic recycling method according to claim 1, wherein a vibrating sieve is used in the strip / powder separation step. 7. The plastic recycling method according to claim 2, wherein a rotary cutter type pulverizer is used in the pulverization step. 8. The method according to claim 1, wherein the plastic is polyolefin (P).
O) type | system | group, Claim 1, 2, 3, 4,
The plastic recycling method according to 5, 6, or 7.