JP4146455B2 - Coating film recycling method and coating film recycling system from coated magnesium alloy material - Google Patents

Description

  The present invention relates to a technique for recycling a coating film from a coated magnesium alloy material.

  Cases of mobile electronic devices such as notebook computers, mobile phones, and PDAs are required to have high strength, to efficiently dissipate heat generated by built-in electronic components, and to have excellent recyclability. In order to cope with these demands, metal casings have been adopted instead of conventional resin casings as mobile electronic device casings.

  As a material constituting a metal casing for an electronic device, a light alloy mainly composed of a light metal such as magnesium (Mg) or aluminum (Al) has attracted attention from the viewpoint of weight reduction of the device. In particular, Mg has the largest specific strength among single metals that can be used as a structural material, and has a feature that heat dissipation is as high as that of Al, and specific gravity is about 70% smaller than that of Al. Therefore, an Mg alloy containing Mg as a main component is useful as a constituent material of an electronic device casing.

  As an injection molding method for parts and products made of Mg alloy, a die casting method is generally employed. Alternatively, the thixo molding method may be employed. When, for example, a notebook personal computer casing is injection-molded by using a molten Mg alloy by die casting or thixo-molding, the volume occupied by the molding target portion is about 30 to 50% with respect to one molten metal injection amount. . The remaining 50 to 70% is occupied by a portion that is cut and removed after molding, that is, an Mg alloy solidified by a sprue or runner in a mold. According to the die casting method or thixo molding method, the material loss rate in one injection molding is thus large. Therefore, in the field of Mg alloy material injection molding, from the viewpoint of effective use of earth resources and cost reduction, the parts that are cut and removed after injection molding and the Mg alloy material obtained by product recovery are again used for injection molding. Establishment of recycling technology for use as a material to be provided is desired.

  A method for producing an Mg alloy recycled material from a portion cut and removed after injection molding of the Mg alloy material is disclosed in Patent Document 1 below. According to the method, the portion to be cut and removed after injection molding of the Mg alloy material is melted again together with a predetermined flux, and after being adjusted in the molten state, it is cooled and solidified to form an Mg alloy having a predetermined composition. Played.

  On the other hand, parts and products made of Mg alloy that are shipped to the market are generally subjected to a coating treatment, and a coating film is formed on the surface thereof. When the Mg alloy material on which the coating film is formed is melted without removing the coating film in the above-described method, a large amount of organic gas is produced by burning the resin material such as acrylic resin or urethane resin contained in the coating material. Is not preferable. In addition, the molten metal may be excessively contaminated by titanium or the like contained in the paint, which is not preferable. Therefore, when manufacturing the Mg alloy recycled material from the Mg alloy material obtained by product recovery, it is necessary to remove the coating film formed on the surface of the Mg alloy material before melting the Mg alloy material.

  Techniques for removing the coating film formed on the surface of the Mg alloy material are disclosed in, for example, Patent Document 2 and Patent Document 3 below. Patent Document 2 discloses a wet blast method. The wet blasting method is a method for physically removing a coating film by spraying water as a fluid onto an Mg alloy material to be coated together with inorganic particles such as alumina. However, in such a wet blast method, it is difficult to properly remove the coating film when the coated surface of the Mg alloy material has an uneven shape. Specifically, since the inorganic particles tend not to collide in the recesses, the coating film may not be sufficiently removed. Moreover, in the convex part, since the collision frequency of inorganic particles tends to be excessive, the Mg alloy on the member surface may be scraped off together with the coating film.

  Patent Document 3 discloses a technique for performing heat treatment of a Mg alloy material to be coated at a temperature at which the paint decomposes and volatilizes in a non-oxidizing atmosphere. However, according to this technique, a chamber for performing heat treatment under special conditions is required. In addition, according to the technique, a large amount of organic gas is generated after the paint is decomposed, and thus an apparatus for appropriately treating the generated gas is further required.

  As another technique for removing the coating film formed on the surface of the Mg alloy material, a technique using an alkaline solution is known. This method is a method for removing the coating film by washing or the like after the coated Mg alloy material is immersed in an alkaline solution to swell the coating film by the action of the alkaline solution. However, in the conventional method of dipping in an alkaline solution, one dipping treatment is performed until the entire coating film swells. Specifically, the Mg alloy material to be coated is kept immersed in the alkaline solution until both layers of the coating composed of the undercoat layer and the topcoat layer are swollen. In such immersion treatment, the immersion time may require a long time of about 2 hours. In addition, when the coating film swells, the alkaline solution is contaminated by dissolving or diffusing the metal powder contained in the coating film, so that it is used for the immersion treatment for swelling the entire coating film. The alkaline solution tends to deteriorate early in the process of being repeatedly used for the immersion treatment.

  The following Patent Document 4 and Patent Document 5 also disclose coating film removal methods. However, the methods disclosed in these are techniques for removing a coating film from a resin molded body to which coating is applied, and a coating film formed on the surface of an Mg alloy material that is a metal member. It is not a technique for removing.

  Moreover, in the conventional technique, the coating film peeled off from the Mg alloy material in the immersion treatment and the subsequent water washing is discarded as industrial waste. Such handling of the coating film is not preferable from the viewpoint of effective use of earth resources and environmental protection.

JP 2001-316739 A JP 2000-263443 A Japanese Patent Laid-Open No. 2001-20018 JP-A-5-84746 JP-A-6-114842

  The present invention has been conceived under such circumstances, and in a short time, the coating film formed on the surface of the magnesium alloy material can be achieved while achieving a long life of the treatment liquid to be used. It is an object of the present invention to provide a coating film recycling method including a method for appropriately removing the coating film, and a coating film recycling system from a coated magnesium alloy material.

  According to a first aspect of the present invention, a coating film recycling method is provided. The coating film recycling method includes a first treatment in which a first alkaline solution is allowed to act on a magnesium alloy material to which coating is applied, and the first alkaline solution on a magnesium alloy material that has undergone the first treatment. A coating film removing step including a second treatment in which a second alkaline solution or an acid solution is applied, a step of collecting the coating film separated from the magnesium alloy material in the first treatment and the second treatment, and a recovery And a step of producing a coating film regenerating material by pulverizing the coated film.

  According to the coating film removing step (coating film removing method) in the first aspect of the present invention, the coating film formed on the surface of the magnesium alloy material can be appropriately removed in a short time. The coating film in the magnesium alloy material to be coated generally comprises an overcoat layer for achieving a desired color tone and an undercoat layer for achieving a good coating state of the overcoat layer on the surface of the magnesium alloy. The topcoat layer contains a relatively large amount of factors that degrade the treatment liquid, such as resin components for paint, color pigments, and dyes, and tends to swell relatively quickly due to the action of an alkaline solution. On the other hand, the undercoat layer contains, for example, an epoxy resin or an acrylic resin as a main component, and tends to swell relatively slowly by the action of an alkaline solution. In the conventional coating film removing method using an alkaline solution, the magnesium alloy material to be coated is continuously immersed in the same alkaline solution until the undercoat layer swells after the overcoat layer. In such immersion treatment, first, the topcoat layer swells due to the action of the alkali solution, and accordingly, a relatively large amount of deterioration factors derived from the topcoat layer dissolve or diffuse in the alkali solution. Therefore, the alkaline solution deteriorates to a considerable extent by swelling the topcoat layer. It takes a long time for the alkali solution thus deteriorated to swell the undercoat layer that is inherently difficult to swell. As a result, according to the conventional method, the net time required to swell and remove the entire coating film becomes redundant.

  In contrast, in the coating film removing step in the first aspect, the coating film is exposed to at least two solution treatments. The first treatment with the first alkaline solution is terminated, for example, when the topcoat layer is swollen, and after the swollen topcoat layer is removed, subsequently, a second alkaline solution different from the first alkaline solution, or A second treatment with an acid solution is performed. Here, the second alkaline solution different from the first alkaline solution refers to an alkaline solution that is not used as the first alkaline solution in the first treatment, and has the same composition as the first alkaline solution. It may also have a different composition. When the second alkaline solution is used in the second treatment, the second alkaline solution acts on the undercoat layer immediately because the overcoat layer has already been removed. Since this second alkaline solution is not deteriorated due to swelling of the overcoat layer, even if it is an undercoat layer that is inherently difficult to swell, the undercoat layer exhibits its ability as a treatment liquid sufficiently. Is swollen and peeled from the substrate. As a result, the net time required to swell and remove the entire coating film is reduced compared to the conventional method. When an acid solution is used in the second treatment, the acid solution immediately acts on the undercoat layer since the overcoat layer has already been removed. This acid solution decomposes or dissolves the undercoat layer by chemical action. Alternatively, the acid solution causes the undercoat layer to swell and peel from the substrate. As a result, the net time required to remove the entire coating is shorter than in the conventional method.

  Moreover, according to the coating-film removal process in a 1st side surface, the lifetime improvement of the processing liquid to be used can be achieved. In the above-described conventional coating film removing method, the magnesium alloy material to be coated is continuously immersed in the same alkaline solution until all of the undercoat layer following the topcoat layer swells. Therefore, according to the conventional method, the deterioration factor derived from the undercoat layer dissolves or diffuses in the treatment liquid in addition to the deterioration factor derived from the overcoat layer by one immersion treatment. Thus, when the alkaline solution containing a relatively large amount of deterioration factors is used again for the immersion treatment of a new magnesium alloy material to be coated, its ability as a treatment liquid is considerably reduced. That is, the lifetime of the treatment liquid in the conventional method is relatively short.

  On the other hand, in the coating film removing step in the first aspect, the coating film is exposed to at least two solution treatments (first treatment and second treatment), and the first alkaline solution used in the first treatment, In the second alkaline solution or acid solution used in the two treatments, all deterioration factors derived from the entire coating film are not mixed. Therefore, deterioration of each processing liquid is suppressed. Thus, when the treatment liquid containing a relatively small amount of deterioration factor is used again for the immersion treatment of a new magnesium alloy material to be coated, the decrease in the ability as the treatment liquid is small. That is, the life of the treatment liquid is relatively long.

  As described above, in the coating film removing step in the first aspect, the coating film formed on the surface of the magnesium alloy material can be appropriately removed in a short time while achieving a long life of the treatment liquid to be used. It can be done.

  The coating film recycling method according to the first aspect of the present invention includes the coating film removing step or the coating film removing method as described above from the magnesium alloy material to be coated. Therefore, according to the coating film recycling method of the first aspect, it is possible to extend the life of the treatment liquid used in removing the coating film from the coated magnesium alloy material, and to remove the coating film appropriately in a short time. Therefore, it is possible to efficiently recover the coating film from the treatment liquid and efficiently prepare a coating film reclaimed material. The coating film reclaimed material thus obtained can be effectively used as an extender or a modifying filler, for example, by adding it to a resin composition for forming a resin molded body by mold molding. . As such a resin composition, for example, a resin composition containing a thermoplastic resin selected from the group consisting of ABS resin, polycarbonate resin, polypropylene resin, polystyrene resin, polyamide resin, and polyphenylene sulfide resin is preferable. Furthermore, the coating film recycled material can also be used by adding it to asphalt as an extender.

  In the first aspect of the present invention, preferably, the first alkaline solution and / or the second alkaline solution contains potassium hydroxide as an alkali main component. The acid solution used in the second treatment preferably contains an organic acid as the acid main component.

  The first treatment and / or the second treatment using the second alkaline solution is preferably performed at a temperature of 60 to 90 ° C, more preferably 70 to 80 ° C. If the temperature of the alkaline solution is lower than 60 ° C., the coating film tends not to swell sufficiently, which is not preferable. In addition, when the temperature is higher than 90 ° C., the alkali solution excessively acts on the metal powder contained in the coating film, and a relatively large amount of metal hydroxide is generated, and the deterioration of the alkali solution tends to proceed. It is not preferable.

  When an acid solution is used in the second treatment, the second treatment is preferably performed at a temperature of 20 to 70 ° C, more preferably 30 to 60 ° C. If the temperature of the acid solution is lower than 20 ° C., the coating film tends not to swell or dissolve sufficiently, which is not preferable. Moreover, when it is higher than 70 degreeC, there exists a tendency for an acid solution to act too much and to melt | dissolve to the magnesium alloy under a coating film, and is unpreferable.

  The first aspect of the present invention preferably includes a step of washing the magnesium alloy material with water after the first treatment and / or the second treatment. By appropriately washing the magnesium alloy material that has undergone the first treatment and the second treatment with water at a predetermined water pressure, the coating film that has been swollen and has reduced the coating power on the surface of the magnesium alloy material is appropriately removed from the surface of the magnesium alloy material. Is possible. Preferably, the method further includes a step of recovering the coating film separated from the magnesium alloy material in the water washing step or the water washing operation.

  According to the 2nd side surface of this invention, the coating-film recycling system from a to-be-coated magnesium alloy material is provided. The coating film recycling system includes: a first treatment that causes a first alkaline solution to act on a magnesium alloy material that has been coated; and the first alkaline solution that is applied to the magnesium alloy material that has undergone the first treatment. A coating film removing step including a second treatment in which a second alkaline solution or an acid solution is applied, and a step of collecting the coating film peeled off from the magnesium alloy material in the first treatment and the second treatment; And a step of producing a coating film regenerating material by pulverizing the recovered coating film.

  The coating film recycling system according to the second aspect of the present invention is configured to include execution of the coating film recycling method according to the first aspect. Therefore, according to the coating film recycling system of the 2nd side, the same technical effect as mentioned above about the 1st side can be enjoyed.

  FIG. 1 is a flowchart of a paint film removal process included in a paint film recycling method or work performed by a paint film recycling system according to the present invention. By this coating film removal process, for example, the coating film formed on the surface of the magnesium (Mg) alloy material as shown in FIG. 2 is removed. The Mg alloy material shown in FIG. 2 is a notebook PC case, and a predetermined portion of the surface thereof is coated. For example, the coating film has an undercoat layer containing an epoxy resin as a main component and an acrylic resin as a main component. And an overcoat layer.

  In this coating film removal process, first, in the first treatment S11, the Mg alloy material to be coated is immersed in the first alkaline solution. The first alkaline solution used for the dipping treatment is 10 to 20 times the volume of the Mg alloy material. The temperature of the first alkaline solution is 60 to 90 ° C., and the immersion time is 20 to 60 minutes. The first alkaline solution preferably contains an alkali metal or alkaline earth metal hydroxide as an alkali component. As the alkali component, potassium hydroxide is particularly preferable. The concentration of potassium hydroxide in the first alkaline solution is preferably 2 to 40 wt%. By such first treatment S11, the overcoat layer swells and the coating force with respect to the undercoat layer decreases, and a part thereof peels off. In addition, a part of the undercoat layer where the overcoat layer has peeled off also swells, and the coating force on the Mg alloy material decreases.

Next, the Mg alloy material is pulled up from the first alkaline solution and washed with water in the washing step S12. In this step, water is sprayed on the Mg alloy material using a shower device. The water pressure at this time is 0.5 to ² kgf / cm ² . Or in this process, you may wash with water by immersing Mg alloy material in the washing water stored in the predetermined bathtub. By such water washing step S12, mainly the top coat layer swollen on the surface of the Mg alloy material or the main coat layer piece adhering to the surface of the Mg alloy material is physically removed from the Mg alloy material. The By the first process S11 and this step described above, the overcoat layer is mainly removed from the Mg alloy material.

  Next, in 2nd process S13, Mg alloy material is immersed in a 2nd alkaline solution. The second alkaline solution used for the dipping treatment is 10 to 20 times the volume of the Mg alloy material. The temperature of the second alkaline solution is 60 to 90 ° C., and the immersion time is, for example, 30 to 70 minutes in a range where the total with the immersion time in the first treatment S11 does not exceed 90 minutes. The 2nd alkali solution can use the thing of the same composition as a 1st alkali solution. Alternatively, the second alkaline solution may have a composition different from that of the first alkaline solution depending on the component composition of the undercoat layer. By such 2nd process S13, an undercoat layer swells and the coating force with respect to Mg alloy material falls. A part of the undercoat layer is peeled off from the Mg alloy material.

  In 2nd process S13, it can replace with the above-mentioned 2nd alkaline solution, and can also use an acid solution. When an acid solution is used as the treatment liquid for immersing the Mg alloy material after the water washing step S12, the acid solution has a volume 10 to 20 times the volume of the Mg alloy material. The temperature of the acid solution is 20 to 70 ° C., and the immersion time is 5 to 30 minutes. The acid solution preferably contains an organic acid as an acid component. Examples of the organic acid include formic acid, acetic acid, and benzoic acid. When formic acid is employed as the organic acid, the concentration of formic acid in the acid solution is preferably 2 to 40 wt%. According to such second treatment S13, the undercoat layer is peeled off from the Mg alloy material under the action of decomposition and dissolution.

Next, the Mg alloy material is pulled up from the second alkaline solution or acid solution, and this is washed with water in the washing step S14. Also in this process, a shower apparatus is used, and the water pressure sprayed on the Mg alloy material is set to 0.5 to ² kgf / cm ² . Or in this process, you may wash with water by immersing Mg alloy material in the washing water stored in the predetermined bathtub. By such washing step S14, the undercoat layer swollen on the surface of the Mg alloy material or the undercoat layer piece adhering to the surface of the Mg alloy material is physically removed from the Mg alloy material.

  Next, in the drying step S15, the Mg alloy material that has undergone the water washing step S14 is dried. For example, the Mg alloy material is dried by leaving it in a dryer at a temperature of 50 to 80 ° C. for 30 minutes to 1 hour.

  Through the above steps, for example, the coating film can be satisfactorily removed not only on the flat surface portion 1 of the notebook computer housing shown in FIG. 2, but also on the housing side wall 2, the retracting portion 3, and the fine uneven portions 4. it can. The total of the immersion times in the first treatment 11 and the second treatment 13 of this embodiment may be shorter than the single immersion time in the conventional method. This is because, in the second treatment 13, a second alkaline solution or an acid solution whose ability as a treatment solution is not excessively lowered is used. Further, the life of each processing solution is longer than that of the conventional method. That is, the treatment liquid according to the present invention can be used more effectively in a larger number of immersion treatments than the treatment liquid of the conventional method. This is because not all deterioration factors derived from the coating film are mixed into the first alkaline solution and the second alkaline solution or the acid solution.

  FIG. 3 is a flowchart of the Mg alloy recycled material manufacturing method according to the related art of the present invention. It is known that when an Mg alloy undergoes a recycling process, Fe contained in the alloy tends to increase and Mn tends to decrease. Therefore, in the embodiment of the related art, by adjusting the contents of both the Fe component and the Mn component contained in the Mg alloy, a forging Mg alloy corresponding to JIS MD1D or AZ91D is manufactured as a recycled material. explain.

  In the recycled material manufacturing method of the present embodiment, first, the coating film of the Mg alloy material to be coated is removed by performing the first process S11 to the drying step S15 in the same manner as described above with reference to FIG. Mg alloy material is obtained.

Next, in melting step S21, the Mg alloy material from which the coating film has been removed is melted together with the first flux in a melting furnace. Specifically, the Mg alloy material that has been crushed or once ingot and the first flux in powder form are put into a melting furnace heated to about 680 ° C. in advance, and then heated to about 720 ° C. Dissolve them. At this time, in order to ensure the homogeneity of the molten Mg alloy, that is, the molten metal, the molten metal in the melting furnace is agitated by rotating a mechanical impeller. The first flux is added mainly for the purpose of reducing oxides generated during melting and precipitating impurities such as oil in the molten metal as sludge in a later step. And alkaline earth metal halides are used. More specifically, a powder mixture containing 40-60 wt% MgCl ₂ , 15-35 wt% KCl, 1-10 wt% CaF ₂ and 10-30 wt% BaCl ₂ is used as the first flux. it can. Moreover, when ignition occurs on the surface of the molten metal, the first flux is appropriately added according to the ignition state.

Next, in the sludge separation step S22, impurities in the molten metal are separated as sludge by continuing to stir the molten metal. In this step, when separation of sludge is confirmed in the molten metal, the separation of sludge is promoted by adding a powdery second flux to the molten metal. The second flux is substantially the same as the first flux, but the proportion of each component is different from the first flux, and it is preferable to reduce the proportion of BaCl ₂ having a large specific gravity. More specifically, as the second flux, for example, a powder mixture containing 60 to 75 wt% MgCl ₂ , 20 to 35 wt% KCl, 0.1 to 5 wt% CaF _2, and ₁ to 10 wt% BaCl ₂ is used. Can be used. Moreover, when ignition occurs on the surface of the molten metal, the second flux is appropriately added according to the ignition state.

Next, in the cleaning step S23, the molten metal is cleaned. Specifically, after the stirring of the molten metal is stopped, the molten metal is sedated for 10 to 30 minutes, thereby allowing sludge to settle at the bottom of the melting furnace. At this time, an antioxidant gas layer covering the surface of the molten metal is formed. Specifically, a powdery third flux is added to the molten metal. The third flux generates a gas that is decomposed by the heat of the molten metal to prevent oxidation of the molten metal, and when the gas is filled in the melting furnace, an antioxidant gas layer that covers the surface of the molten metal is formed. It is formed. As the third flux, for example, a powder mixture containing 60 to 90 wt% of sulfur (S) and 10 to 40 wt% of MgF ₂ can be used.

  Next, in the component analysis step S24, the components contained in the cleaned molten metal are analyzed. Specifically, first, a part of the molten metal is extracted from the melting furnace, and a cylindrical sample having a diameter of 5 cm and a length of 5 cm is cast from the molten metal. And the content rate of Fe component and Mn component in a molten metal is specified by performing a component analysis about this sample. As an analysis method, for example, arc-type emission spectroscopic analysis can be employed.

  Next, in component adjustment process S25, based on the measurement result obtained by the previous process, the content rate of Fe component and Mn component is adjusted in a desired range. For example, when producing a forging Mg alloy corresponding to AZ91D, the desired range of the Fe component is 40 ppm (0.004 wt%) or less, and the desired range of the Mn component is 0.17 to 0.4 wt%.

  It is known that when an Mg alloy undergoes a recycling process, Fe contained in the alloy increases. Therefore, in order to adjust the Fe component, an appropriate amount of Fe precipitant according to the excess amount is required. Add to molten metal. As the Fe precipitating agent, for example, an Al—Mn intermetallic compound can be used. On the other hand, when the Mg alloy undergoes a recycling process, it is known that Mn contained in the alloy decreases. Therefore, in order to adjust the Mn component, an appropriate amount of Mn is supplied according to the shortage amount. Add the agent to the melt. As the Mn supply agent, simple Mn or a compound containing Mn can be used. For example, an Al—Mn intermetallic compound can also be used as a Mn supplier. If the Fe and Mn component content is already in the desired range, no Fe precipitant and Mn feed are added.

  After appropriately determining the type and amount, the Fe precipitation agent and the Mn supply agent are added to the molten metal, and after the molten metal is stirred and subsequently cleaned, the component analysis step S24 is performed again. Such component adjustment step S25 and subsequent component analysis step S24 are repeated until the contents of the Fe component and the Mn component fall within the desired ranges.

  Next, in a casting step S26, an ingot of a predetermined size is cast as a casting material from a molten metal having a desired component composition. In this way, the Mg alloy recycled material according to this embodiment is manufactured.

  According to the Mg alloy recycled material manufacturing method as described above, the coating film can be efficiently removed from the Mg alloy material to be coated in the water washing step S14 from the first processing S11. Therefore, the Mg alloy recycled material is efficiently manufactured. be able to. In addition, as the Mg alloy material melted in the melting step S21, a material obtained by sufficiently removing the coating film from the Mg alloy material to be coated is used. Therefore, it is possible to avoid the generation of organic gas due to the burning of the resin material derived from the paint in the dissolving step S21. At the same time, it is possible to prevent the molten metal from being excessively contaminated by a metal such as Ti, which is not preferable for the Mg alloy, derived from the paint. In addition, the content of the Fe component and the Mn component in the Mg alloy material varies depending on the number of times of recycling and other factors, but according to this method, the content of the Fe component and the Mn component can be individually and flexibly handled. is there. Thus, according to this Mg alloy recycled material manufacturing method, an Mg alloy recycled material having a target composition, that is, a composition corresponding to the composition of a virgin Mg alloy, can be manufactured efficiently and appropriately.

  FIG. 4 is a flowchart of the work performed by the paint film recycling method or the paint film recycling system according to the present invention. In the present embodiment, first, the coating film is removed from the Mg alloy material to be coated by performing the first process S11 to the water washing step S14 in the same manner as described above with reference to FIG.

  Next, in the collecting step S31, the coating film pieces peeled from the magnesium alloy material in the first process S11 to the water washing step S14 are collected. Specifically, the first alkaline solution used in the first treatment S11, the second alkaline solution or acid solution used in the second treatment S13, and the flowing water or Mg sprayed on the Mg alloy material in the washing steps S12 and S14 The washing water in which the alloy material is immersed is filtered, and the coating film piece peeled off from the magnesium alloy material is isolated from the treatment liquid.

  Next, in water washing process S32, the coating film piece collect | recovered as mentioned above is washed with water, and the process liquid adhering to the coating film piece is fully removed. Next, in the drying step S33, the coating film piece is dried. For example, the coating film piece is dried by being left at 80 ° C. for 2 hours in a dryer. Next, in the pulverization step S34, the dried coating film pieces are pulverized to a desired particle size. For example, the coating film piece is put into a mortar, and the coating film piece is pulverized until the diameter becomes 1 mm or less.

  Next, in the resin molding step S35, a resin molded body is produced by using the pellet-shaped coating film recycled material obtained as described above as an extender. Specifically, first, for example, using a twin-screw kneading extruder, the thermoplastic resin material and the coating film recycled material pellet are melt-kneaded at a predetermined mixing ratio. The addition rate of the coating film recycled material pellet is 10 to 60 wt%. Examples of the thermoplastic resin material include ABS resin, polycarbonate resin, polypropylene resin, polystyrene resin, polyamide resin, and polyphenylene sulfide resin. Next, a resin molded body having a desired shape is molded from the resin composition thus prepared using an injection molding machine. In addition to such use, the coating film recycled material pellet can be used as an asphalt extender by adding to the asphalt.

  Next, examples according to the present invention will be described together with comparative examples.

[Example 1]
<Manufacture of Mg alloy recycled materials>
A notebook personal computer casing as shown in FIG. 2 made of Mg alloy and coated with surface as an Mg alloy material to be coated was first immersed in 2 L of a first alkaline solution. The coating film formed on the surface of the notebook personal computer casing is composed of an undercoat layer mainly composed of an epoxy resin and an overcoat layer mainly composed of an acrylic resin. The first alkaline solution contains 3.5 wt% potassium hydroxide, 2.5 wt% sodium hydroxide, 20 wt% anionic surfactant, and 40 wt% diethylene glycol monoethyl ether. The temperature of the first alkaline solution was maintained at 70 ° C., and the immersion time was 10 minutes. By such dipping treatment, the top coat layer was mainly swollen. Next, after the Mg alloy casing was pulled up from the first alkaline solution, the Mg alloy casing was washed with running water having a water pressure of 1 kgf / cm ² . As a result, the overcoat layer was mainly removed.

Next, the Mg alloy casing was immersed in 2 L of the second alkaline solution. The second alkaline solution has the same component composition as the first alkaline solution. The temperature of the second alkaline solution was maintained at 70 ° C., and the immersion time was 40 minutes. By such immersion treatment, the undercoat layer of the coating film was swollen. Next, after the Mg alloy casing was pulled up from the second alkaline solution, the Mg alloy casing was washed with running water having a water pressure of 1 kgf / cm ² . As a result, the undercoat layer was removed. Next, the Mg alloy casing was dried by leaving it in a dryer. In this way, in the Mg alloy notebook personal computer case, the coating film formed on the flat surface portion 1, the housing side wall 2, the retracting portion 3, and the fine uneven portions 4 shown in FIG. It could be removed properly by treatment.

Next, to the melting furnace (60 L) preheated to about 680 ° C., 30 kg of the Mg alloy casing from which the coating film has been removed as described above and 1 kg of the first flux are charged, and then the melting furnace is set to 720. These were dissolved by raising the temperature to 0 ° C. The first flux, the MgCl ₂ 50wt%, 25wt% of KCl, the CaF ₂ 5 wt%, a powder mixture containing BaCl ₂ 20 wt%. In order to obtain the homogeneity of the molten Mg alloy, that is, the molten metal, the molten metal was stirred with a mechanical impeller. The rotation speed of the impeller was 100 rpm.

Stirring was continued, and when the sludge began to separate from the molten metal, 0.2 kg of the second flux was charged into the molten metal. The second flux, the MgCl ₂ 67.5wt%, 27.5wt% of KCl, the CaF ₂ 1 wt%, a powder mixture containing BaCl ₂ 4.5 wt%. And according to the ignition state of the molten metal surface, the 2nd flux was added 0.1 kg suitably. By adding such a second flux, the separation of sludge from the molten metal was promoted.

Next, stirring was stopped and the molten metal was allowed to calm for 20 minutes, so that sludge was settled in the molten metal to clean the molten metal. At that time, immediately after the stirring was stopped, 0.2 kg of the third flux was charged into the molten metal. The third flux is a powder mixture containing 80 wt% S and 20 wt% MgF ₂ . SF ₆ was generated by charging the third flux and filled in the melting furnace, and an antioxidant gas layer covering the molten metal surface was formed by SF ₆ . In this way, the sludge was sufficiently settled in a state where the oxidation of the molten metal was suppressed.

  Next, 0.2 kg was extracted as a sample from the cleaned molten metal, and a cylindrical sample (diameter 5 cm, length 5 cm) was cast from the molten metal. Next, component analysis was performed on this sample using an arc emission spectroscopic analyzer (PDA-5500II, manufactured by Shimadzu Corporation). As a result, the Fe content was 0.0058 wt%, and the Mn content was 0.120 wt%.

  Next, in order to decrease the Fe content and increase the Mn content, an Al—Mn intermetallic compound having both functions of an Fe precipitant and a Mn supply agent was charged into the melting furnace. In order to obtain a forging Mg alloy (Fe: 0.004 wt% or less, Mn: 0.17 to 0.4 wt%) corresponding to AZ91D, the input amount of the Al—Mn intermetallic compound was 4 kg. Next, after stirring the molten metal whose components were adjusted in this way, the molten metal was purified by being calmed for 10 minutes.

  Next, 0.2 kg was extracted as a sample from the cleaned molten metal, and a cylindrical sample (diameter 5 cm, length 5 cm) was cast from the molten metal. Next, when component analysis was performed on this sample using an arc type emission spectroscopic analyzer (PDA-5500II, manufactured by Shimadzu Corporation), the Fe content decreased to 0.0015 wt%, and the Mn content was 0. It was increased to 210 wt%. Next, five ingots (5 kg) were cast from the molten metal whose components were adjusted to the desired composition in this way. In this way, an Mg alloy recycled material could be manufactured from the coated Mg alloy notebook computer casing.

<Measurement of bending strength>
Five JIS Z 2204 No. 1 test pieces (10 mm × 50 mm × 3.2 mm) were prepared from the recycled Mg alloy material obtained as described above by die casting, and the bending strength of these test pieces was measured. Specifically, a universal testing machine (trade name: INSTRONON 5581, manufactured by Instron Japan) was used, and a three-point bending test was performed on each test piece in accordance with JIS K 7055. The test conditions were such that the distance (span) between the two support points was 40 mm, and the load speed of the load with respect to the approximate center between the two support points was 2 mm / min. On the other hand, five JIS Z 2204 No. 1 test pieces were similarly prepared from the virgin material (AZ91D), and a three-point bending test was performed on these test pieces under the same conditions. As a result, the test piece made from the Mg alloy recycled material of the present example has almost the same strength as the test piece made from the virgin material, showing an average bending strength of about 400 MPa, and its maximum and minimum values. The difference was about 13%.

<Corrosion resistance test>
Five JIS Z 2204 No. 1 test pieces (10 mm × 50 mm × 3.2 mm) were prepared from the recycled Mg alloy material obtained as described above by die casting, and these test pieces were compliant with JIS Z 2371. Corrosion resistance was evaluated by a salt spray test. On the other hand, five JIS Z 2204 No. 1 test pieces were similarly prepared from virgin materials, and the corrosion resistance of these test pieces was evaluated under the same conditions. As a result, the corrosion amount of the test piece of this example was almost the same as the corrosion amount of the test piece prepared from the virgin material.

<Evaluation of formability>
From the Mg alloy recycled material obtained as described above, 50 notebook computer cases (320 mm × 240 mm × 1.2 mm) having a shape as shown in FIG. 2 were formed by die casting. On the other hand, 50 notebook personal computer cases were similarly molded from virgin materials. As a result, the recycled Mg alloy material of this example showed the same formability as the virgin material. For example, the non-defective rate of the product was about 80% as in the case where the virgin material was used. Here, the non-defective product ratio refers to a ratio of a molded product that satisfies the appearance standard as a product without causing short shots of molten metal, sink marks and chipping in the molded product.

[Example 2]
As for the Mg alloy material to be coated, the notebook PC case as shown in FIG. 2 which is the same as that in Example 1, is the same as in Example 1 until the immersion treatment with the first alkaline solution and the subsequent cleaning. The overcoat layer was removed. Next, the Mg alloy casing was immersed in a 2 L acid solution. This acid solution contains 5 wt% of organic acid, formic acid, 15 wt% of benzyl alcohol, and 40 wt% of ethylene glycol monobutyl ether. The temperature of the acid solution was maintained at 40 ° C., and the immersion time was 5 minutes. By such immersion treatment, the undercoat layer of the coating film was swollen or dissolved. Next, after the Mg alloy casing was pulled up from the acid solution, the Mg alloy casing was washed with running water having a water pressure of 1 kgf / cm ² . As a result, the undercoat layer was removed. Next, the Mg alloy casing was dried by leaving it in a dryer. In this way, in the notebook computer case made of Mg alloy, the coating film formed on the flat surface portion 1, the housing side wall 2, the retracting portion 3, and the fine uneven portion 4 shown in FIG. It could be removed properly by treatment.

  Using the Mg alloy casing from which the coating film has been removed in this manner, from the melting in the melting furnace to the casting of the 5 kg ingot through the component analysis and the component adjustment, the Mg alloy recycled material is obtained in the same manner as in Example 1. Manufactured. When this Mg alloy recycled material was subjected to bending strength measurement, corrosion resistance test, and formability evaluation in the same manner as in Example 1, the Mg alloy recycled material of this example also exhibited the same characteristics or physical properties as the virgin material. It was.

[Comparative Example 1]
A notebook personal computer casing as shown in FIG. 2 as the Mg alloy material to be coated as shown in FIG. 2 was first immersed in 2 L of a first alkaline solution. The same first alkaline solution as in Example 1 was used. At this time, the temperature of the first alkaline solution was maintained at 70 ° C. In order to sufficiently remove the coating film by subsequent washing with flowing water having a water pressure of 1 kgf / cm ² , the immersion time in the first alkaline solution had to be 90 minutes or more. For example, in the case where the immersion treatment is stopped in about 50 minutes and the Mg alloy recycled material is manufactured through the same process as in Example 1 using the Mg alloy material with the coating film remaining, the organic harmful gas in the molten metal. If a large amount of precipitates are generated, or if the alloy composition greatly deviates from the desired range, the productivity of the Mg alloy recycled material is significantly reduced.

Example 3
In a state where 200 notebook PC cases as shown in FIG. 2 made of Mg alloy and coated with surface as Mg alloy material to be coated are housed in a jig, first, a stainless steel processing bath (1 m ³ ) Was immersed in the 800 L first alkaline solution prepared. The coating film formed on the surface of the notebook personal computer casing is composed of an undercoat layer mainly composed of epoxy resin and an overcoat layer mainly composed of urethane resin. The first alkaline solution contains 3.5 wt% potassium hydroxide, 2.5 wt% sodium hydroxide, 20 wt% anionic surfactant, and 40 wt% diethylene glycol monoethyl ether. The temperature of the first alkaline solution was maintained at 70 ° C., and the immersion time was 10 minutes. By such immersion treatment, the topcoat layer of the coating film was mainly swollen and a part thereof was peeled off. Next, after lifting the casing from the first alkaline solution, the casing was immersed in 800 L of first cleaning water prepared in the treatment bath (1 m ³ ). Thereby, about 90% of the coating film was peeled off from the casing.

Next, 200 housings were immersed in an 800 L acid solution prepared in a treatment bath (1 m ³ ). This acid solution contains 5 wt% of organic acid, formic acid, 15 wt% of benzyl alcohol, and 40 wt% of diethylene glycol monobutyl ether. The temperature of the acid solution was maintained at 40 ° C., and the immersion time was 5 minutes. By such immersion treatment, the undercoat layer was mainly swollen and a part thereof was peeled off. Next, after pulling up the casing from the acid solution, the casing was immersed in 800 L of second cleaning water prepared in the treatment bath (1 m ³ ). Thereby, all of the coating film was removed. Next, the Mg alloy casing was dried by leaving it in a dryer. In this way, in the notebook computer case made of Mg alloy, the coating film formed on the flat surface portion 1, the housing side wall 2, the retracting portion 3, and the fine uneven portion 4 shown in FIG. It could be removed properly by treatment. Using the Mg alloy casing from which the coating film has been removed in this way, a Mg alloy recycled material is manufactured in the same manner as in Example 1 from melting in the melting furnace to component casting and ingot casting. We were able to.

  From the first alkaline solution, the first washing water, the acid solution, and the second washing water used in the series of steps for removing the coating film, a coating film piece mainly composed of an epoxy resin or a urethane resin was collected. Specifically, each treatment liquid in which the coating film pieces were precipitated or suspended was filtered, and the coating film pieces separated from the Mg alloy material were isolated from the treatment liquid. Next, the collected coating film piece was washed with water, and the treatment liquid adhering to the coating film piece was sufficiently removed. Next, the coating film piece was dried by leaving it in a dryer at 80 ° C. for 2 hours. Next, the coating film piece was put into a mortar, and the coating film piece was pulverized until the diameter became 1 mm or less. In this way, about 4 kg of a pellet-shaped coating film regenerated material could be produced from 200 coated Mg alloy casings.

  Next, using a twin-screw kneading extruder (trade name: KZW 15-30MG, manufactured by Technobel), 50 wt% of the recycled film pellet obtained as described above and 50 wt% of the polypropylene resin were melt-kneaded. . It knead | mixed on the conditions of the temperature of 220 degreeC, and the rotational speed of a mixing part of 100 rpm. Next, from the resin composition thus prepared, a flower pot (height 300 mm, opening diameter 300 mm, wall thickness 2) as shown in FIG. 5 using an injection molding machine (trade name: AUTOSHOT, manufactured by FANUC). 5 mm). This flower pot had a good appearance and a practical strength. In this way, the coating film of the Mg alloy material to be coated could be appropriately recycled.

It is a flowchart of the coating-film removal method (coating-film removal process) in this invention. An example of the magnesium alloy housing | casing for notebook computers is represented. It is a flowchart of the magnesium alloy recycled material manufacturing method which concerns on the related technique of this invention. It is a flowchart of the coating-film recycling method which concerns on this invention (or the operation | work performed by a coating-film recycling system). The flower pot obtained by the coating-film recycling method (or operation | work performed by a coating-film recycling system) based on this invention is represented.

Explanation of symbols

S11 First treatment S12 Water washing step S13 Second treatment S14 Water washing step S15 Drying step S21 Dissolution step S22 Sludge separation step S23 Cleaning step S24 Component analysis step S25 Component adjustment step S26 Casting step S31 Recovery step S32 Water washing step S33 Drying step S34 Grinding Process S35 Resin molding

Claims (5)

A first treatment that causes a first alkaline solution to act on a magnesium alloy material that has been coated, and a second alkali that is different from the first alkaline solution on the magnesium alloy material that has undergone the first treatment. A coating film removing step including a second treatment in which a solution or an acid solution is allowed to act;
Recovering the coating film peeled off from the magnesium alloy material in the first treatment and the second treatment;
And a step of producing a coating film recycled material by pulverizing the collected coating film.   2. The method according to claim 1, comprising: a step for washing the magnesium alloy material with water after the first treatment and / or the second treatment; and a step for collecting a coating film peeled off from the magnesium alloy material in the washing step. Coating recycling method.   The coating-film recycling method of Claim 1 or 2 which produces a resin molding from the resin composition which added the said coating-film reproduction | regeneration material.   The coating film recycling method according to claim 1 or 2, wherein the coating film regenerating material is added to asphalt. In coating film recycling system from coated magnesium alloy material,
A first treatment that causes a first alkaline solution to act on a magnesium alloy material that has been coated, and a second alkali that is different from the first alkaline solution on the magnesium alloy material that has undergone the first treatment. A film removal step including a second treatment in which a solution or an acid solution is allowed to act;
Recovering the coating film peeled off from the magnesium alloy material in the first treatment and the second treatment;
A coating film recycling system configured to perform a step of producing a coating film recycling material by pulverizing the collected coating film.

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