JP2012187466A - Coating film peeling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently peeling a coating film from a coated vehicle bumper made of resin.SOLUTION: This coating film peeling method includes a press process for pressing the vehicle bumper made of the resin between rolls and a blast process for blasting the pressed object obtained in the press process. By this method, the coating film can be efficiently peeled from the coated vehicle bumper made of the resin and the base material resin can be efficiently recovered.

Description

  The present invention relates to a method for peeling a coating film from a painted resin automobile bumper.

  An automobile bumper is generally composed of a plastic base layer, an adhesive layer, and a surface coating layer. The base material layer is composed of, for example, a raw material in which a filler such as elastomer or talc is blended based on a polypropylene resin, and has a thickness of about 2 mm to 4 mm. The adhesive layer is a primer layer having a thickness of about 10 μm, such as chlorinated polyolefin, and is a layer for enhancing the adhesion between the base material layer and the surface coating layer. The surface coating layer is a layer formed by applying a paint using a polyurethane resin, an alkyd melamine resin, or an epoxy thermosetting resin as a raw material, and has a thickness of about 40 μm to 100 μm.

  Such plastic paint bumpers are often recycled and reused. However, if the bumper is melted and remolded without peeling off and removing the coating layer (surface coating layer and adhesive layer) formed on the bumper, it is resistant to the effects of the unmelted surface coating layer and adhesive layer. The physical properties such as impact properties are degraded, and the product may have a problem of uneven color. In addition, if the surface coating layer remains, the surface coating component deteriorates and decomposes due to heat during re-molding, causing appearance defects and off-flavor generation of the re-molded material, which hinders recycling.

  On the other hand, in Patent Document 1, the coated product is pulverized by jet eddy current, and the pulverized product is collided with each other to peel the base material layer and the surface coating film layer. A method for selecting a component and a surface coating component is disclosed. Patent Document 2 discloses a method of decomposing and removing a coating film with an enzyme. This method has been devised for the purpose of improving the burden on the environment such as harmfulness to the human body and difficulty in post-treatment of the liquid agent, which has been a drawback of the conventional liquid agent treatment. Furthermore, Patent Document 3 discloses a method of removing the coating film by generating a peeling stress due to shear by applying pressure to the coating film with a roll at a temperature of less than 70 ° C.

JP-A-5-237410 Japanese Unexamined Patent Publication No. 7-040344 JP 7-214558 A

  In the method of Patent Document 1, the surface coating film is firmly bonded to the base material layer by the adhesive layer and is almost integrated, and when the surface coating layer and the adhesive are to be removed, the entire surface including the base material layer is included. Must be pulverized as finely as possible, and if pulverized as finely as possible, the accuracy of sorting due to the difference in specific gravity in the subsequent process will deteriorate, and the recovery rate of the base material components that will be recycled materials will decrease. In addition, even if the surface coating layer is removed, the adhesive layer remains on the base material, which leads to a decrease in physical properties when reused as a recycled material. In the method of Patent Document 2, the effect on the human body and the environmental load are reduced, while the effect on the coating film is mild, and a very long decomposition treatment time is required, the processing capacity is poor, and the volume for processing is also low. Is also required. The treatment using such a liquid agent is effective for removing only the surface coating layer and the adhesive layer, but there are many problems in terms of the liquid agent treatment and processing ability after the treatment, and the practical application has progressed. Not in. In the method of Patent Document 3, it is difficult to completely separate the coating film because only pressure by a roll is applied.

  It is an object of the present invention to provide a method for efficiently peeling a coating film from a painted resin automobile bumper.

In order to solve the above-mentioned problems, the present invention provides the following coating film peeling method.
(1) A method of peeling a coating film from a coated resin automobile bumper, a pressing step of pressing the bumper between rolls, and a blasting step of blasting a pressed product obtained in the pressing step A coating film peeling method comprising:
(2) The coating film peeling method according to (1), wherein the resin is a polypropylene resin.
(3) The coating film peeling method according to the above (1) or (2), wherein the clearance between the rolls is 40% or more and 70% or less of the bumper thickness.

(4) In the coating film peeling method according to any one of (1) to (3) above, the pressure between rolls is 4900 N / cm or more and 19600 N / cm or less with respect to the roll length direction. A coating film peeling method characterized by the above.
(5) In the coating film peeling method according to any one of (1) to (4) described above, the nozzle angle at the time of spraying the abrasive in the blasting step is relative to the surface of the pressed article. The coating film peeling method characterized by being an angle of 10 ° or more and 70 ° or less.
(6) The coating film peeling method according to any one of (1) to (5), wherein water is dropped or sprayed between rolls in the pressing step. .

  According to the present invention, the coating film can be efficiently peeled from the coated resin bumper, and the base resin can be regenerated. Therefore, it is effective for the recovery (recycling) of the base resin from the coating bumper using polypropylene resin or the like as the base material.

The figure which shows typically the high pressure roll (2 rolls) used at the press process which concerns on this embodiment.

  Hereinafter, an embodiment of the present invention will be described. The coating film peeling method according to the present embodiment includes a pressing step of pressing a coating resin bumper between rolls, and a blasting step of blasting a pressed product obtained in the pressing step. The painted resin bumper in the present embodiment is a painted polypropylene resin bumper.

[Pressing process]
(Configuration of high pressure roll)
FIG. 1 schematically shows a high-pressure roll (two rolls) used in the pressing step. The roll diameter is about 200 mm to 400 mm, and the roll length is about 300 mm to 500 mm.
One end of each end of the roll is fixed, and the other end is slidably supported by the bearing block. The bearing block is pressurized by hydraulic pressure or a spring.
The roll interval (clearance) of the high-pressure roll is preferably 40% to 70%, more preferably 50% to 60% of the bumper thickness. If the roll interval is less than 40% of the bumper thickness, the coating film may sink into the bumper material during the press treatment described later, and may be difficult to peel in the next step. On the other hand, if the roll interval exceeds 70% of the bumper thickness, the coating film peeling effect may not be sufficiently exhibited during the press treatment.

(Press processing)
The most pressurized shear force is applied to the material where the rolls are closest to each other, and the material is stretched according to the hardness of the material by the applied pressure while moving at the same speed as the circumferential speed of the roll. At that time, the base material (polypropylene resin) of the coating bumper made of polypropylene resin is softer than the surface coating layer and is stretched by the applied pressure, but the surface coating layer does not stretch, so there is a difference in elongation speed between materials. At the same time, the surface coating layer is cracked in a certain direction due to the shearing force between the rolls.
Here, the pressure between rolls is preferably 4900 N / cm or more and 19600 N / cm or less, and more preferably 4900 N / cm or more and 14700 N / cm or less with respect to the roll length direction. In particular, about 9800 N / cm is most preferable.

Further, since the roll generates heat due to the pressure shear force, the material is also heated, and shaving occurs on the surface coating layer side which is difficult to extend, and the roll is wound. Therefore, it is preferable that the inside of the roll has a structure capable of circulating the cooling water. In addition, a small amount of water is dropped into the material supply zone and pressed while cooling the material itself to suppress warping of the material due to heat generation, and a flat material that is easy to blast in the next process (pressed product) ) Can be obtained.
If the roll rotation is too fast, the time for exposure to the pressure shear force in the gap between the rolls is short, so it is difficult for the substrate and the surface coating film to be misaligned, so the number of cracks generated in the surface coating layer is reduced. . Further, since friction with the roll is increased, frictional heat is easily generated. Therefore, it is preferable to rotate the roll at as low a speed as possible according to the production capacity.

[Blasting process]
Examples of blasting include air blasting (suction type, direct pressure type, blower type), shot blasting, and the like, but air blasting suitable for abrasives having a low specific gravity is preferable.
The abrasive preferably has a Mohs hardness of 3 or more and 6 or less. When the Mohs altitude is higher than 6, the peeling ability of the surface coating layer and the adhesive layer is improved, but the abrasive is driven into the base material itself to cause contamination. May cause this. If the Mohs hardness is less than 3, the hardness may be insufficient compared to the surface coating layer and the peeling ability may be poor. Examples of abrasives having a Mohs hardness of 3 or more and 6 or less include melamine resin, urea resin, polycarbonate resin, nylon resin, and silica sand. Among them, melamine resin (Mohs hardness, which is the same resin system used for the surface coating layer) About 4.0) is most preferred.

The particle size of the abrasive may be appropriately selected depending on the type of abrasive and injection conditions, but those having an average particle size of 150 μm or more and 850 μm or less are preferably used from the viewpoint of the grinding effect. In addition, what is necessary is just to measure an average particle diameter by the sedimentation method, for example.
What is necessary is just to set suitably the nozzle diameter and the injection pressure which inject a grinding material according to the particle size and material of a grinding material, and the material which becomes an injection partner. Since the abrasive material coming out of the injection nozzle is subjected to air resistance as soon as it comes out of the nozzle, in the case of the suction type, the distance between the injection nozzle and the material is about 10 to 20 times the nozzle diameter, direct pressure type In this case, it is preferable to set a value of about 35 times to 45 times as a guide.

Examples of the injection nozzle include a wide-angle type and a straight type. In general, in the case of a straight nozzle, most of the abrasive is sprayed in a range of 3 degrees each with respect to the line (0 degrees) extending the nozzle injection port, and is thinly blasted concentrically on the outer periphery. The
Such spray nozzles are preferably arranged so that both sides of the material can be processed simultaneously (eg 5 or more on each side). Further, the injection nozzle preferably has an angle of 10 ° to 70 °, more preferably 20 ° to 40 ° with respect to the material surface (the surface of the press) when the abrasive is injected. Installed. The coating layer of the pressed product is in a cracked state, and the abrasive can be effectively acted between the coating layer and the substrate by injecting the abrasive at an angle in this range. .

[Crushing process, pelletizing process]
When pelletizing the regenerated resin, it is preferable to pulverize the material after the blasting process into a size that can be charged into a melt extruder. In that case, it is only necessary to be able to pulverize to a size that can be charged into the melt extruder used for pelletization, so a general pulverizer such as a cutter mill may be used. Further, for the purpose of making the material cleaner, a washing step may be provided either before or after the pulverization.
An ordinary melt extruder may be used to form the pulverized product into pellets.

  According to the embodiment described above, the coating film can be efficiently peeled from the coated polypropylene resin bumper, and the polypropylene resin as the base material of the bumper can be efficiently regenerated. The recycled polypropylene resin can be suitably used as a raw material for producing bumpers themselves and various molded products.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In each of the embodiments described above, a polypropylene resin-made bumper is used as the paint bumper. However, the present invention can be applied to any resin bumper that has been painted. For example, a bumper made of polyurethane resin may be used.

Next, the present invention will be described in more detail with reference to examples. In addition, this invention is not restrict | limited to the description content of these Examples at all.
[Example 1]
(Pressing process)
A coated polypropylene resin automobile bumper having an average thickness of 2.6 mm (minimum 2.4 mm to maximum 2.8 mm) was put into a high-pressure roll press apparatus. Here, the high-pressure roll of this apparatus consists of a set of rolls having a roll diameter of 300 mm and a roll length of 300 mm. And roll rotation number 5rpm, roll cooling, a small amount of water is sprayed on the gap between rolls, roll pressure 1t (9.8kN) / cm, clearance between rolls 1.3mm (50% of bumper material thickness). The bumper was pressed to obtain a pressed product. The surface coating layer had cracks on the entire surface, the crack width was wide, and the coating film was lifted.

(Blasting process)
Using an air blasting apparatus, both surfaces of the press product were simultaneously blasted using a melamine resin abrasive (particle size range of about 425 μm to about 600 μm) at an air pressure of 0.7 MPa and a nozzle angle of 30 ° with respect to the material. Polypropylene resin (base material) was recovered with a separation accuracy of 99.95% between the surface coating layer and the adhesive layer under the condition of a treatment capacity of 500 kg / hr. The separation accuracy was determined by the mass ratio of polypropylene to the total mass.

[Example 2]
(Pressing process)
This was carried out in the same manner as in Example 1 except that the clearance between rolls of the high-pressure roll press apparatus was 1.9 mm (70% of the bumper material thickness). Although the coating layer partially cracked, the number of cracks was smaller than that in Example 1.
(Blasting process)
The same operation as in Example 1 was performed except that the nozzle angle with respect to the pressed product of the air blast apparatus was 45 ° and the treatment capacity was 250 kg / hr. The polypropylene resin (base material) was recovered with a separation accuracy of 99.93% of the surface coating layer and the adhesive layer.

Example 3
(Pressing process)
The same operation as in Example 1 was performed.
(Blasting process)
This was carried out in the same manner as in Example 1 except that the nozzle angle with respect to the pressed product of the air blasting apparatus was 0 °, and the processing capacity was 250 kg / hr. The polypropylene resin (base material) was recovered with a separation accuracy of 99.75% between the surface coating layer and the adhesive layer.

Example 4
(Pressing process)
This was carried out in the same manner as in Example 1 except that the clearance between rolls of the high-pressure roll press apparatus was 0.8 mm (30% of the bumper material thickness).
(Blasting process)
Although there were things that caused the surface coating layer to bite into the base resin in the pressed product, although various air blast conditions were examined, there was biting into the base resin of the abrasive and there was a reduction in processing capacity, It was somewhat difficult to find suitable conditions. However, the separation accuracy of the surface coating layer and the adhesive layer of the collected polypropylene resin (base material) exceeded 95%.

Example 5
(Pressing process)
This was performed in the same manner as in Example 1 except that the clearance between rolls of the high-pressure roll press apparatus was 2.0 mm (80% or more of the bumper material thickness). Since there was a portion where the pressure of the high-pressure roll press was not sufficiently applied to the base resin, there was a case where the phenomenon of the coating layer not being lifted occurred. Still, the separation accuracy of the surface coating layer and the adhesive layer of the recovered polypropylene resin (base material) exceeded 95%.

[Comparative Example 1]
For the same automobile bumper as in Example 1, the same material as in Example 1 was used without using the high-pressure roll press device, and the melamine resin abrasive of Example 1 was used. The air blasting process was carried out. Even when the treatment capacity was reduced to 50 kg / hr, which was 1/10 of Example 1, the separation accuracy of the surface coating layer and the adhesive layer of the recovered polypropylene resin (base material) was 95% or less.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as a method for peeling a coating film from an automotive resin coating bumper.

Claims (6)

A method of peeling a coating film from a painted resin automobile bumper,
A pressing step of pressing the bumper between rolls;
And a blasting step of blasting the pressed product obtained in the pressing step. In the coating film peeling method according to claim 1,
The method for removing a coating film, wherein the resin is a polypropylene resin. In the coating film peeling method of Claim 1 or Claim 2,
The clearance between the rolls is 40% or more and 70% or less of the bumper thickness. In the coating film peeling method according to any one of claims 1 to 3,
The pressure between rolls is 4900 N / cm or more and 19600 N / cm or less with respect to the roll length direction. The coating film peeling method characterized by the above-mentioned. In the coating film peeling method according to any one of claims 1 to 4,
A coating film peeling method, wherein a nozzle angle at the time of spraying the abrasive in the blasting step is an angle of 10 ° to 70 ° with respect to the surface of the press product. In the coating film peeling method according to any one of claims 1 to 5,
A coating film peeling method, wherein water is dropped or sprayed between rolls in the pressing step.

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