JP5354535B2 - Cleaning method for steering wheel core - Google Patents

Description

  The present invention relates to a method for cleaning a mandrel for a steering wheel, wherein the coating is removed from a steering wheel in which the surface of a mandrel made of a magnesium alloy is covered with a film of a crosslinked polyurethane resin composition. The present invention also relates to a method for manufacturing an ingot and a method for manufacturing a steering wheel using the steering wheel core metal cleaned by such a method.

Magnesium alloys have the highest strength per unit weight among practical metals and can be recycled. In recent years, magnesium alloys have been widely used for automotive parts and electrical equipment. Especially, it is used suitably as components for motor vehicles in which both strength and lightness are required. Recycling of automobile parts is obligatory, and it is also important that energy consumption during recycling is low and CO ₂ emissions are low. However, since the magnesium alloy is not sufficiently recyclable as compared with iron or the like, a recycling method with low cost and high recycling efficiency is required. There is also a need for a recycling method that reduces the environmental burden caused by the discharge of waste liquid.

  When recycling metals used in automobile parts, etc., resin and rubber are often combined with the metal and paint is often applied, so organic components derived from such materials are removed from the metal. It is necessary to separate. In the case of iron, since the melting point is 1000 ° C. or higher, the organic component is decomposed prior to the melting of the iron at the time of melting. However, the melting point of a magnesium alloy is about 600 ° C., which is lower than that of iron and the like, and is easily oxidized. Therefore, there is a limit to increasing the temperature, and it is difficult to separate organic components by decomposition during melting. Moreover, since the specific gravity of molten magnesium is small, it is not easy to separate organic components and their decomposition products due to the difference in specific gravity. If an organic component or a decomposition product thereof remains in the molten metal, there is a risk that the product may be deteriorated in quality or yield due to the organic component being deposited on the surface of the molded product after cooling.

  Since the magnesium alloy is easily oxidized, when the magnesium alloy is melted and regenerated into an ingot, the furnace lid is usually closed. However, when the magnesium alloy in which the organic component remains is melted, the vaporized organic component may explode at the moment when the pan lid is opened.

  For this reason, normally, when recycling a magnesium alloy, it is melted and regenerated into an ingot after pretreatment for removing the adhering resin, rubber, or coating film. In Patent Document 1, a part of a coating film is removed by a cutter knife or wet blasting from a magnesium alloy material coated with an epoxy resin paint, a urethane resin paint, an acrylic resin paint, or the like, and then further with an alkaline stripping solution. A method for regenerating a magnesium alloy is described which melts after removing the coating. Patent Document 2 discloses a magnesium alloy in which a coating is removed from a coated magnesium alloy part by chemical treatment with a strong alkaline aqueous solution or organic solvent or by shot blasting, and then re-melted by adding chloride. A method for recycling parts is described. However, in the case of blasting, it is difficult to remove organic components adhering to fine uneven portions, and a large amount of dust is generated. The dust containing magnesium is easy to burn and has a safety problem. Moreover, when using an alkali liquid or an organic solvent, there was a problem that the waste liquid had to be treated.

  Magnesium alloys are increasingly used in automobile parts, but magnesium alloys are often used for steering wheels. A steering wheel usually has a structure in which a core metal made of a magnesium alloy is covered with a foam film made of a crosslinked polyurethane resin composition. The film can be formed by RIM molding (Reaction Injection Molding) or the like. Such a film often contains carbon black or the like in order to improve the strength. Since such a crosslinked polyurethane resin composition has high adhesion to the magnesium alloy, it is difficult to peel from the magnesium alloy. Moreover, since it has bridge | crosslinked, it cannot be melt | dissolved in an organic solvent, but it was also difficult to carry out dissolution removal using an organic solvent. In addition, the cored bar is often provided with a recess for preventing peeling or the spoke part is integrally formed, which makes peeling more difficult. In addition, since it is a foam containing air, its thermal conductivity is low, and heat decomposition by firing hardly transfers heat to the inside, so only the surface is carbonized first and internal decomposition is difficult to proceed. It was difficult to remove the film.

  On the other hand, a laser can be used to remove a coating film on a metal surface. Patent Document 3 describes a method for removing a coating film by irradiating a steel structural member coated with an epoxy-based paint, a polyurethane-based paint, a vinyl ester resin paint, or the like with a pulse laser. . Patent Document 4 describes a method for removing a coating film by irradiating an aluminum alloy plate having a synthetic resin coating film with an infrared laser.

JP 2004-99993 A JP 2002-356721 A JP 2000-263259 A JP 2007-105607 A

  The present invention has been made to solve the above problems, and provides a method for cleaning a mandrel for a steering wheel, which can easily remove a film, has excellent recyclability, and has a low environmental load. It is intended. It is another object of the present invention to provide a method for manufacturing an ingot and a method for manufacturing a steering wheel using the steering wheel core metal cleaned by such a method.

  The above-mentioned subject is a cleaning of a core metal for a steering wheel, in which the surface of the core metal made of a magnesium alloy is removed from the steering wheel formed by covering with a film of a crosslinked polyurethane resin composition containing a laser light absorber. A method of mechanically peeling the film from the steering wheel in advance, and decomposing the crosslinked polyurethane by irradiating the crosslinked polyurethane resin composition remaining on the surface of the core metal with a laser beam. This is solved by providing a method for cleaning a mandrel for a steering wheel, characterized by comprising the step of:

  At this time, it is preferable that the crosslinked polyurethane resin composition is a foam. It is also preferable that the wavelength of the laser beam is 350 to 11000 nm. It is also preferable that the laser beam is a pulse wave. Moreover, it is also suitable to have the process of wash | cleaning or wiping off the polyurethane which decomposed | disassembled and liquefied following the process of decomposing | disassembling the said crosslinked polyurethane.

  A preferred embodiment of the present invention is a method for producing an ingot made of a magnesium alloy in which a steering wheel core bar cleaned by the above method is heated and melted and then cooled. A steering wheel manufacturing method in which the steering wheel core metal cleaned by the above method is covered with a crosslinked polyurethane resin is also a preferred embodiment of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the film | membrane can be easily removed from the core metal which consists of magnesium alloys, the recyclability is excellent, and the cleaning method of the core metal for steering wheels with little environmental impact is provided. Therefore, the steering wheel core bar cleaned by such a method can be suitably used for manufacturing an ingot made of a magnesium alloy or manufacturing a steering wheel.

It is an external appearance photograph of the mandrel for steering wheels after shaving off a coat with a blade in Example 1. It is a cross-sectional photograph of the adhesion interface between the film remaining after mechanically peeling the film and the core metal for the steering wheel in Example 1. It is an external appearance photograph of the core metal for steering wheels after laser irradiation in Example 1. In Example 1, it is the external appearance photograph of the metal core for steering wheels, after wiping off the liquefied film | membrane component and irradiating a laser with a frequency of 1 kHz after that. It is an external appearance photograph of the core metal for steering wheels after baking with the atmospheric furnace in the comparative example 1.

  The method for cleaning a mandrel for a steering wheel according to the present invention removes the film from the steering wheel in which the surface of the mandrel made of a magnesium alloy is covered with a film of a crosslinked polyurethane resin composition containing a laser light absorber. To do.

  A steering wheel used for cleaning is formed by covering the surface of a cored bar made of a magnesium alloy with a film of a crosslinked polyurethane resin composition containing a laser light absorber. The shape of the steering wheel is not particularly limited. Usually, it consists of a rim part, a spoke part, and a boss part to be attached to the vehicle body. The core metal for the steering wheel made of a magnesium alloy may be formed by integrally forming the rim portion, the spoke portion and the boss portion with the magnesium alloy, or the core metal made of the magnesium alloy is used only for a part of the steering wheel. May be. The rim portion is usually circular. The steering wheel used for cleaning may be covered entirely with a coating or may be covered only with a coating. Usually, the entire rim portion is covered with a film. Further, in order to improve the adhesion between the coating and the core metal and to prevent displacement, the rim portion of the core metal often has a groove (concave portion) formed on the surface. The magnesium alloy of the core metal only needs to have magnesium as a main component, and the content of magnesium element is usually 50% by weight or more, and preferably 80% by weight or more. Examples of magnesium alloys include Mg-Al alloys, Mg-Al-Zn alloys, Mg-Al-Mn alloys, Mg-Zn-Zr alloys, Mg-rare earth elements alloys, Mg-Zn-rare earth elements alloys. Etc. Usually, an Mg-Al alloy is used for the core for the steering wheel.

  The film of the crosslinked polyurethane resin composition containing the laser light absorbent of the present invention is not particularly limited as long as it contains a laser light absorbent and contains a crosslinked polyurethane resin as a main component. The cross-linked polyurethane resin composition referred to here is usually a polymer obtained by reacting polyisocyanate and polyol. A crosslinked structure can be introduced by using a polyisocyanate or polyol having a valence of 3 or more. The laser light absorber contained in the crosslinked polyurethane resin composition is not particularly limited, but usually an infrared absorber, particularly a black pigment such as carbon black is preferably used. By containing carbon black in the crosslinked polyurethane resin composition, the strength of the film is improved. The crosslinked polyurethane resin composition may contain an additive such as an antioxidant, a light stabilizer, a foaming agent or a filler alone or in combination of two or more. The thickness of the coating covering the mandrel is not particularly limited, but is usually about 1 to 30 mm. The crosslinked polyurethane resin composition has good adhesion to a magnesium alloy and is suitably used as a coating film for a steering wheel.

  A foam of a crosslinked polyurethane resin composition is preferably used for the coating of the steering wheel. By being a foam, a soft hand can be obtained and the material can be reduced in weight. Moreover, the heat insulation is also high. RIM molding is suitably used as a method for forming a film made of a foamed product of a crosslinked polyurethane resin composition. This is a method in which two or more types of monomers are mixed and injected into a mold together with a catalyst, a crosslinking agent, a foaming agent, and the like to cause a polymerization reaction and foam at the same time to obtain a foam molded product. Since the raw material enters the mold in the state of a monomer having a low viscosity, the injection pressure may be low, and it is suitably used for manufacturing a steering wheel.

  The cleaning method of the present invention includes a step of mechanically peeling the film from the steering wheel in advance. In this step, the coating is roughly removed from the cored bar in a short time. The method is not particularly limited as long as it is a mechanical peeling method. For example, in the case of manual work, there are a method of cutting a film and then roughly peeling it off, a method of scraping with a blade, or a combination thereof. Before peeling, the film of the crosslinked polyurethane resin composition may be swelled or softened by dipping in hot water so that it can be easily peeled off. The cored bar surface after the work may be in a state where a thin film is left almost entirely. According to the study of the inventors of the present invention, it has been found that when the coating is mechanically peeled from the cored bar, the coating tends to remain on almost the entire surface of the cored bar. This is presumably because the magnesium alloy core and the crosslinked polyurethane resin composition are firmly bonded. Moreover, when the film | membrane of a crosslinked polyurethane resin composition is a foam, since the said crosslinked polyurethane resin composition is easy to tear, it can become a factor in which a film | membrane remains easily on the metal core surface.

  Subsequent to the mechanical peeling step, the crosslinked polyurethane resin composition remaining on and attached to the surface of the metal core is irradiated with laser light. The crosslinked polyurethane irradiated with a laser is vaporized or liquefied by thermally decomposing and reducing its molecular weight. At this time, since the crosslinked polyurethane resin composition contains a laser light absorber, the laser light can be efficiently absorbed. And since the laser beam irradiation is a high energy density light for a very short time, there is no partial carbonization, and the molecular chain is cut all at once in the surface layer or inside, and the whole Liquefies or vaporizes. Further, by employing laser light that is easy to scan, the coating can be easily removed even in intricate portions such as a groove in the rim portion or a connection portion between the rim portion and the spoke portion.

  As a kind of laser used by this invention, all well-known, such as a gas laser, a solid state laser, a semiconductor laser, can be used, and it does not specifically limit. Further, the laser light is not limited to one having a single wavelength, and may be a mixture of two or more wavelengths. Decomposition of the film of the crosslinked polyurethane resin composition by laser light can remove the remaining film more efficiently by using a laser having a wavelength of 350 to 11000 nm. Since the film of the crosslinked polyurethane resin composition contains a laser light absorber, the film efficiently absorbs laser light in the wavelength region. More preferably, the wavelength of the laser light is 500 to 1100 nm.

  Even when a laser having a low energy output is used, the film is satisfactorily removed. Further, if a laser having a low energy output can be used, damage to the core metal due to laser irradiation can be suppressed. In the present invention, the remaining film can be more efficiently removed by pulsed laser irradiation. By irradiating with a pulse, even a low-power laser can instantaneously thermally decompose the crosslinked polyurethane to reduce the molecular weight, and the temperature rise of the core metal can be suppressed. Therefore, a laser marker having a low output, a high scanning accuracy, and a relatively low price such as a laser marker can be suitably used.

  The laser scanning method is not particularly limited, but there are a method of scanning the laser light with the steering wheel fixed, a method of moving the steering wheel with the laser light fixed, a method of moving the steering wheel simultaneously with the scanning of the laser light, etc. Can be adopted. The irradiation angle of the laser beam is not particularly limited as long as energy is sufficiently transmitted to the film. The irradiation energy can be controlled by either current or voltage. In the case of pulse irradiation, it can also be controlled by its frequency and duty ratio. In the case of pulse irradiation, the amount of energy per pulse changes by changing the pulse frequency. That is, if the energy amount per unit time is constant, the energy per pulse increases as the pulse frequency decreases. The intensity | strength of a laser beam should just be intensity | strength required for the membrane | film | coat of a crosslinked polyurethane resin composition to make low molecular weight. The film component after low molecular weight is vaporized or liquefied. When it is desired to irradiate a laser with a lower output, such as when it is desired to suppress damage to the core metal, the coating can be liquefied and washed or wiped off in a later step. Further, when it is desired to omit the post-process, all the film components can be vaporized by laser irradiation at a higher output than in the case of liquefaction. The portion to be irradiated with the laser may be irradiated only on the remaining film, or may be irradiated on the entire surface of the core metal. As described above, since the coating can be removed with a low-power laser beam by irradiating the crosslinked polyurethane resin composition with a laser light absorber or by irradiating the laser with a pulse, the magnesium alloy is directly irradiated with the laser. However, it has little effect on the mandrel. In this way, the film can be removed with a low-power laser, so that the core metal for the steering wheel is left with a thermal history even when it is reused by covering it with a crosslinked polyurethane resin composition during factory recycling. The cored bar can be reused.

  Since the film component liquefied by laser irradiation has a low molecular weight, it can be easily removed by immersing it in an organic solvent. The organic solvent at this time is not particularly limited, and examples thereof include acetone, ethanol, 2-propanol, methanol, xylene and the like. Further, the coating component can be easily removed from the cored bar by wiping the liquefied coating component using tissue paper or a cloth scrape soaked in an organic solvent.

  It is a preferred embodiment of the present invention that the steering wheel core bar cleaned by the cleaning method of the present invention is used for manufacturing an ingot made of a magnesium alloy. By completely removing the film from the metal core by laser irradiation, generation of impurities that affect the quality when melted is suppressed. Therefore, it is possible to reproduce the ingot with good quality. In addition, according to the examination result of the inventors of the present invention, when the film was peeled off from the cored bar only by a mechanical method, about 3 g of the film remained with respect to 600 g of the cored bar. Even when 11 kg of such a core metal was mixed with 1400 kg of clean scrap and melted, precipitates were found on the entire surface of the melt, and could not be regenerated into a high-purity ingot. This also shows that it is important to completely remove the coating from the core metal surface in order to regenerate the core metal.

It is also a preferred embodiment of the present invention that the steering wheel core bar cleaned by the cleaning method of the present invention is used for manufacturing a steering wheel. Defective products that occur during the manufacture of a steering wheel are usually separated for each material and then the magnesium alloy is remelted. However, if the cleaning method of the present invention is used, a heat history is left on the steering wheel core metal. The film can be removed and reused as it is. Further, according to the method of the present invention, a defective product as compared with the case of reproducing by melting, less CO ₂ emissions, since the excellent energy efficiency, low environmental impact.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these. The test method in this example was performed according to the following method.

(1) Observation of the cross-sectional shape of the steering wheel After physically peeling off the film of the crosslinked polyurethane resin composition, the rim portion was cut to a thickness of 10 mm, embedded in an epoxy resin, and then the cut surface was polished to a mirror surface Got. An electron micrograph was taken from the cross-sectional direction of the sample using an X-ray microanalyzer “JXA-8500FS” manufactured by JEOL Ltd.

Example 1
ASTM No. A steering wheel in which the surface of a metal core for a steering wheel made of a magnesium alloy having AM60 (magnesium content of 94% by weight and aluminum content of 6% by weight) was covered with a film made of a crosslinked polyurethane resin composition was used for the test. The film was a foam of a crosslinked polyurethane resin composition containing a black pigment. The steering wheel was immersed in hot water at 100 ° C. for 10 minutes, and then the film was roughly peeled manually. Further, the remaining film was scraped off with a blade while the steering wheel was attached to a lathe and rotated. The shape of the core metal was an ellipse having a diameter of about 380 mm and a cross-sectional shape of the rim portion having a major axis of about 20 mm and a minor axis of about 15 mm. The core metal was cut into a size of about 10 to 15 cm for the convenience of carrying out the test. An appearance photograph of the steering wheel core at this time is shown in FIG. As can be seen from the photograph, the film remained on the most part of the surface of the metal core after the above process. At this time, about 10 g of film remained on 600 g of the core metal. Further, FIG. 2 shows a cross-sectional photograph of the adhesion interface between the film remaining after the film is mechanically peeled off and the core metal for the steering wheel. From the photograph, it can be seen that the foamed film is firmly adhered to the cored bar.

After the film covering the steering wheel core bar was mechanically peeled as described above, the surface of the core bar was irradiated with a pulse of laser light. As the laser device, YVO ₄ laser marker (wavelength 1064 nm) manufactured by Miyachi Technos Co., Ltd. was used. The laser beam spot diameter was set to 50 to 60 μm, and the distance to the top of the core metal was set to 130 mm. The output was 25 A, the frequency was 50 kHz, and irradiation was performed at a scanning speed of 100 mm / sec. During laser irradiation, scanning was performed in a straight line, and the entire surface of a portion of about 4 cm in the longitudinal direction of the cut core metal was irradiated once while moving by 50 μm in a direction perpendicular to the scanning direction. The appearance photograph of the cored bar at this time is shown in FIG. As can be seen from the photograph, the film was completely removed from many portions of the core metal surface. In this part, it is presumed that the crosslinked polyurethane was instantaneously thermally decomposed by laser irradiation, resulting in low molecular weight and vaporization. Moreover, the liquefied resin component was observed in part. This was liquefied as a result of the low molecular weight of the crosslinked polyurethane. The liquefied film component remaining on the surface was wiped off using a tissue paper soaked with acetone. Thereafter, in order to reliably remove the film to the details, the same region as the first laser irradiation was irradiated with a laser once at a frequency of 1 kHz. The appearance photograph of the cored bar at this time is shown in FIG. As can be seen from the photograph, the coating on the surface of the metal core that could not be completely removed by mechanical peeling was completely removed by the laser beam.

Comparative Example 1
This is an example in which the mandrel for the steering wheel was cleaned by firing in an atmospheric furnace. The mandrel for the steering wheel from which the film was mechanically peeled by the same method as in Example 1 was fired in an atmospheric furnace for 1 hour. The calcination temperatures were 300, 400 and 500 ° C. As an example of the result of firing in an atmospheric furnace, a photograph of the appearance of a steering wheel core bar when fired at 500 ° C. is shown in FIG. As can be seen from the photograph, the carbonized film component remained on the surface of the steering wheel core bar after firing. Moreover, the surface state of the cored bar after firing did not show a large difference depending on the firing temperature. Immediately after the start of the treatment, the surface of the coating is carbonized to form a barrier layer, and the inside of the coating is sealed. Since the film is a foam containing air and has low thermal conductivity, the temperature inside the film is lower than that of the surface, and the decomposition of the crosslinked polyurethane does not proceed. As a result, it is presumed that the film was carbonized and burned.

Comparative Example 2
This is an example in which the mandrel for the steering wheel was cleaned by a method of removing the crosslinked polyurethane resin composition using a solvent or the like. In the test, acetone, xylene, sodium hydroxide and hydrochloric acid were used. The steering wheel core bar having the film mechanically peeled off in the same manner as in Example 1 was immersed in each of the above liquids for 72 hours, washed with water as necessary, and dried. When immersed in acetone and xylene, the film was not dissolved at all. Even when immersed in sodium hydroxide, the film was not dissolved at all. When immersed in hydrochloric acid, the test was stopped because foaming from the surface of the magnesium alloy generated heat.

Claims (7)

A method for cleaning a mandrel for a steering wheel, wherein the surface of the mandrel made of a magnesium alloy is removed from the steering wheel formed by covering the surface of the mandrel with a crosslinked polyurethane resin composition film containing a laser light absorber. ,
Mechanically peeling the film from the steering wheel in advance, and irradiating the crosslinked polyurethane resin composition remaining on and attached to the surface of the core metal with laser light to decompose the crosslinked polyurethane. A method for cleaning a mandrel for a steering wheel.   The method for cleaning a metal core for a steering wheel according to claim 1, wherein the crosslinked polyurethane resin composition is a foam.   The method for cleaning a mandrel for a steering wheel according to claim 1 or 2, wherein the laser beam has a wavelength of 350 to 11000 nm.   The method for cleaning a metal core for a steering wheel according to any one of claims 1 to 3, wherein the laser beam is a pulse wave.   The method for cleaning a mandrel for a steering wheel according to any one of claims 1 to 4, further comprising a step of washing or wiping off the polyurethane that has been decomposed and liquefied, following the step of decomposing the crosslinked polyurethane.   The manufacturing method of the ingot which consists of magnesium alloys which cools, after heating and fuse | melting the metal core for steering wheels cleaned by the method in any one of Claims 1-5.   A method for manufacturing a steering wheel, wherein the core for a steering wheel cleaned by the method according to any one of claims 1 to 5 is covered with a crosslinked polyurethane resin composition.