JP3207781B2 - How to recycle aluminum scrap - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling aluminum scrap by removing a coating applied to the surface of aluminum scrap typified by a used aluminum beverage can (hereinafter abbreviated as aluminum can). Things.

[0002]

2. Description of the Related Art Aluminum or aluminum alloys are excellent in light weight, corrosion resistance, heat conductivity, etc.
It is widely used in various products such as aluminum building materials (such as aluminum sashes) and aluminum vehicle parts (such as panel materials and body materials). For example, JIS 3004 series aluminum alloys are used as body materials for aluminum cans. These aluminum materials have generally been discarded after use until recently, but recently, effective use of resources and preservation of the environment have been considered. From a viewpoint, aluminum cans have been actively collected and reused, and there are reports that the collection rate has reached 60% or more at present.

[0003] However, generally, the outer surface of the aluminum can is printed with a paint on a polyester resin material, and the inner surface is also coated with an epoxy resin film. Recycling of aluminum cans was not always efficient. That is, when the aluminum can is melted while the above-mentioned coating is formed, the coating in the coating generates heat and promotes the oxidation of the molten metal to lower the melting yield, or the titanium compound contained as a pigment in the coating. Is mixed in the aluminum (alloy) molten metal, thereby increasing the amount of impurity elements. Furthermore, the resin material in the coating generates harmful components such as gas in the dissolving step, which is not preferable in terms of working environment.

[0004] Since various problems are caused by the coating on the surface of the aluminum can as described above, methods for removing the coating as described below have been proposed. Thermal removal method by combustion (roasting method) This is a method in which a film on the surface of an aluminum can is burned by previously heating the aluminum can at a temperature not higher than the melting temperature of aluminum. According to this method, the film is burned in the molten metal. Since there is no dissolution, the dissolution yield is improved. However, harmful components are generated by burning the coating film in another place prior to the melting step, and TiO ₂ and combustion residues contained as a pigment in the paint remain on the aluminum can surface as they are. .

[0005] A method of mechanically removing a film from an aluminum can by, for example, performing shot blasting using an iron ball or the like (Japanese Patent Publication No. 7-61611) is known. According to this method, most of the coating can be removed, and the generation of harmful components can be prevented because the coating does not burn.
On the other hand, it has been pointed out that when the iron ball collides with the aluminum can with high energy by shot blasting, the iron ball is worn and iron powder as a powder is mixed into the aluminum can as an impurity element. It was also difficult to remove the coating applied to the inner surface of the can.

Combination of roasting method and mechanical removal method After the coating is burned by the roasting method, the combustion residue and TiO ₂ of the coating are mechanically removed from the aluminum can by a device utilizing a shear force or the like. Methods have also been proposed. However, since the principle of film removal is mainly combustion, the point that harmful components are generated at the time of film combustion has not been solved, and the combined use of the roasting method and the mechanical removal method is too costly. Was not introduced.

As described above, the techniques proposed so far do not always efficiently recycle aluminum, and there has been a demand for a method capable of efficiently removing a film from aluminum scrap such as an aluminum can.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to efficiently remove the above-mentioned film of aluminum scrap having a film such as a paint or a coating material formed on a surface thereof. It is an object of the present invention to provide a method of recycling aluminum scrap that can be performed.

[0009]

According to the present invention, there is provided a method of recycling aluminum scrap having a coating film formed on the surface thereof. The aluminum scrap is cut into aluminum pieces. Cutting process, while immersing the aluminum piece in the stripping solution,
The aluminum piece was placed in a rotatable cylindrical mesh cage, and the mesh cage immersed in a stripping solution such that the immersion rate of the mesh cage was in the range of 10 to 40%. The shaft of the mesh cage was rotated. The gist of the invention is to provide a film peeling step of removing the film from the aluminum piece by applying a mechanical peeling force to the aluminum piece by rotating the aluminum piece in a horizontal state as a center, and prior to the film peeling step. Therefore, it is recommended to provide a drying or washing / drying step for removing the liquid adhering to the aluminum pieces.

In carrying out the above-mentioned film peeling step,
The aluminum piece is placed in a rotatable cylindrical mesh cage, and a part of the mesh cage is immersed in a stripping solution, and the mesh cage is rotated to separate the coating.
It is recommended that removal be performed.

It is preferable to provide a washing step of rotating the mesh basket in a state where a part of the mesh basket is immersed in a washing solution to wash the aluminum pieces after the coating stripping step. When the washing step is provided after the peeling step, in either the film peeling step or the washing step, the mesh cage may be simply immersed in the peeling liquid or the cleaning liquid without rotating the mesh basket.

[0012] It is also possible to use a filter to separate the coating pieces generated in the coating stripping step and / or the washing step, and to circulate the stripping liquid and / or the cleaning liquid. Further, after the coating stripping step and / or the cleaning step, a steam cleaning step of cleaning the aluminum pieces with the steam of the cleaning liquid is provided, and after the cleaning step and / or the steam cleaning step, a drying step of the aluminum pieces is provided. Is also good.

After the step of drying the aluminum pieces, a step of removing the film by wind force or a washing and drying step of washing and drying the aluminum pieces may be provided. If cast in the atmosphere, an aluminum ingot can be obtained.

The stripping solution is a solution containing a halogen-based solvent, a lower alcohol and an acid as main components, wherein the content of the halogen-based solvent is 70 to 85 vol% and the content of the lower alcohol is 10 to 20 vol. It is recommended to use which is%. The stripping solution may further contain a surfactant and / or an evaporation inhibitor. As the halogen-based solvent, one or more selected from the group consisting of methylene chloride, tricrene, and perchrene is used, methanol is used as the lower alcohol, and formic acid is used as the acid component, or formic acid or Halogenated acetic acid may be used. As the cleaning liquid, the stripping liquid may be used, or the halogen-based solvent may be used.

As a typical example of the aluminum scrap used in the recycling method of the present invention, an aluminum can is cited. In addition to the aluminum can, an aluminum laminate having a printed layer formed on an aluminum foil may be used. Alternatively, a coated aluminum building material or aluminum vehicle component may be used.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention merged the prior art by combining the chemical stripping effect of the stripping solution described later with the mechanical stripping effect of the friction between aluminum pieces cut to an appropriate size. We have developed a technique to remove the coating from the aluminum pieces much more effectively.

FIG. 1 is an explanatory diagram showing a typical process flow when the recycling method of the present invention is adopted. First, a series of schematic processes will be described with reference to FIG. 1, and then each process will be described in detail. .

[I] Cutting step: The used aluminum can is cut into an appropriate size by a shredder 1 to form an aluminum piece. [II] Coating peeling step: The aluminum piece is placed in a rotatable cylindrical mesh basket 2 and rotated by a method shown in FIG. 2 while a part of the mesh basket 2 is immersed in a stripping liquid 2a. You. The rotation of the mesh basket is controlled at an appropriate speed so that the aluminum pieces in the mesh basket do not rotate while always adhering to the inner surface of the basket. Rubbing provides a mechanical peeling force. Therefore, after being immersed in the stripping solution 2a and applying a chemical peeling force to the film, the film is further peeled off from the aluminum piece by further applying a mechanical peeling force.

[III] Cleaning step: Next, the aluminum piece is immersed in the cleaning liquid 3a to separate the coating piece peeled from the aluminum piece. At this time, the mesh basket may be rotated in the same manner as in the film peeling step.

[IV] Vapor cleaning step: The cleaning liquid is evaporated by the heating means 4a, whereby the surface of the aluminum piece is subjected to steam cleaning, and the separation and removal of the coating piece is promoted. The vapor is cooled by the cooling means 4b provided at the upper part, becomes a liquid, and falls downward to be collected. [V] Drying step: The aluminum piece is heated and dried, and the cleaning liquid is carried out of the processing apparatus while adhering to the aluminum piece, and is prevented from being lost.

The above-mentioned steps [II] to [V] are desirably performed inside the processing apparatus 6 having a double door and taking into consideration the airtightness with the outside. The aluminum pieces are conveyed while being loaded in the mesh basket, and are subjected to respective processes until a drying step. Thereafter, if necessary, the aluminum pieces are pressed and melted, and if necessary, the components of the aluminum alloy are adjusted and cast to obtain various aluminum materials.

Hereinafter, the present invention will be described in detail for each step. [I] Cutting Step First, it is necessary to cut an aluminum can into aluminum pieces of an appropriate size. By cutting the aluminum can, the peeling liquid can easily come into contact with the coating surface on the inner surface of the aluminum can, and the coating on both surfaces can be easily removed. Further, the stripping solution that has entered the inside of the can cannot be easily recovered using the aluminum can as it is, but cutting the stripping solution is advantageous in collecting the stripping solution.

Further, the apparent specific gravity can be increased by finely cutting the aluminum can. Therefore, it is desirable to cut the aluminum can into about half or less. According to actual measurements, for example, the apparent specific gravity of the aluminum piece without cutting the aluminum piece is about 0.04 kg / l, whereas the apparent specific gravity of the aluminum piece divided into 20 equal parts is about 0.14 kg / l. Therefore, the size of the apparatus can be reduced by increasing the apparent specific gravity by making the aluminum piece as small as possible within a range that does not protrude from the mesh of the mesh basket, and the apparatus and the recycling line can be made compact. be able to.

When the aluminum can is cut to about 1/50, the size of the cut aluminum piece is about 20 mm.
It is about the angle. However, when the aluminum pieces are cut into smaller pieces, the effect of rubbing between the aluminum pieces is reduced, and the mechanical peeling effect is reduced. Also,
Since it is necessary to reduce the mesh width of the mesh basket into which the aluminum pieces are put (for example, about 10 mm or less),
The coating pieces peeled off from the aluminum pieces are more likely to adhere to the mesh basket mesh, and the circulation of the peeling liquid is deteriorated, thereby lowering the peeling efficiency. For the above reasons, aluminum cans are 1 / 2-
It is desirable to cut to a size of about 1/50,
It is more desirable to cut to a size of about 10 to 1/20.

In cutting the aluminum can into aluminum pieces, a known shredder may be used, and a shredder such as a biaxial shearing type, a uniaxial shearing type, or a hammer type may be used.
What is necessary is just to select suitably according to the size of a piece of aluminum, a processing amount, etc. The collected aluminum cans may be so-called loose cans, each of which is independently present, or so-called press cans, in which a plurality of aluminum cans are compressed into briquettes. In the case of a press can, it may be cut using a large shredder, but it may be cut back by returning to a loose can state by applying an impact.

The cut aluminum pieces generally have a liquid content of the contents of the aluminum can attached thereto. When the aluminum pieces are directly taken to the next film peeling step, they are mixed into the peeling liquid,
Since the service life of the stripping solution is shortened, it is desirable to provide a drying step to evaporate the water, or to provide a washing and drying step to remove the liquid. The aluminum piece may be dried using a heating furnace or the like, but care must be taken because if the heating temperature is too high, the coating is denatured and peeling in the coating peeling step becomes difficult. As the coating, usually, a polyester resin is used on the outer surface of the aluminum can and an epoxy resin is used on the inner surface, so that these materials are heated at a temperature at which the material does not thermally deteriorate to remove moisture. It is desirable. The heating temperature needs to be 250 ° C. or lower, preferably 180 ° C. or lower, and 150 ° C.
The following is more preferable.

[II] Coating stripping step Next, the coating applied to the aluminum piece is chemically stripped by dipping in a stripping solution, and the coating is removed by applying a mechanical stripping force. As a method of applying a mechanical peeling force to the aluminum piece, the aluminum piece is charged into a rotatable cylindrical mesh cage, and the mesh cage is rotated while a part of the mesh cage is immersed in a peeling liquid. Is recommended as a very effective method.

The amount of the aluminum pieces to be charged into the mesh basket is preferably in the range of 10 to 60% in terms of the volume ratio (hereinafter, referred to as occupancy) of the aluminum pieces occupying the mesh basket. When the occupancy is less than 10%, the mechanical peeling effect due to the rubbing between the aluminum pieces becomes insufficient. In addition, the mesh basket must be made larger than necessary or the throughput of the aluminum pieces must be reduced, resulting in lower production efficiency. On the other hand, when the occupancy of the aluminum piece exceeds 60%, the movement of the aluminum piece in the mesh basket is restricted, and the aluminum piece rotating while being pressed against the outer wall is easily generated,
The mechanical peeling effect due to the rubbing between the aluminum pieces becomes insufficient. In addition, the peeled coating pieces are likely to adhere to the aluminum pieces and remain. FIG. 3 is a graph (solid line) showing the relationship between the occupancy of aluminum pieces and the film removal rate described below. It can be seen that if the aluminum piece is loaded into the mesh basket so that the occupancy is in the range of 10 to 60%, the film removal rate is 70% or more, which is preferable.

The volume ratio (hereinafter referred to as the immersion ratio) of immersing the mesh cage loaded with the aluminum pieces is 10 to 4%.
A range of 0% is preferred. When the immersion ratio exceeds 40%, the mesh cage becomes resistant to the rotational force, and the mechanical peeling effect due to the rubbing of the aluminum pieces decreases. On the other hand, when the immersion rate is less than 10%, the stripping solution does not spread over the entire aluminum piece, and the chemical stripping effect is reduced. The graph of FIG. 3 also shows the relationship between the immersion rate and the film removal rate (dotted line). Immersion rate is 10-4
When it is in the range of 0%, the film removal rate is 70% or more, which is preferable.

As the stripping solution used in the stripping step, it is recommended to use a solution containing a halogen-based solvent, a lower alcohol and an acid as main components. As the halogen-based solvent, one or more selected from the group consisting of methylene chloride, tricrene, and perchrene may be used, and methanol is used as the lower alcohol, and formic acid is used as the acid component, or Preferably, formic acid and halogenated acetic acid are used.

The stripper having the above composition has the ability to allow the halogen-based solvent to penetrate into the resin, which is the main component of the film formed on the surface of the aluminum piece, to expand and swell the resin.
The above film absorbs the stripping liquid up to 7 times its own weight and swells.
Softens. Therefore, it is considered that the film peels from the aluminum piece when the expansion force of the film swelled by the action of the above-mentioned stripping liquid exceeds the adhesion force between the aluminum piece and the film.

As the main solvent of the stripping solution, a solvent having a higher vapor pressure at room temperature, in other words, a solvent having a lower molecular weight has a larger stripping effect, and the above-mentioned halogen-based solvent is preferable. Among the above-mentioned halogen-based solvents, methylene chloride is most preferable, but instead of methylene chloride, trichlene or perchrene may be used, and although the peeling effect is slightly lower than that of methylene chloride, the vapor pressure at room temperature is low. Solvent loss due to evaporation can be reduced.

When the content of the halogen-based solvent, which is the main solvent, is too small, a sufficient peeling effect cannot be expected. On the other hand, when the content is too large, the other components become relatively small, and the overall content of the stripping solution is reduced. Since the chemical stripping effect is impaired, the content is desirably 70 vol% or more and 85 vol% or less.

The lower alcohol added to the stripping solution does not directly affect the swelling / softening action on the film.
Rather, the stripping ability is reduced, but since it has a function of dissolving the acid component as the accelerator in the halogen-based solvent of the main solvent, a stripping solution containing a lower alcohol has a larger stripping effect. However, if the content of the lower alcohol is too small, a sufficient effect is not expected, and if the content is too large, the effect is saturated. Methanol may be used as the lower alcohol.

Acid components (formic acid, halogenated acetic acid, etc.)
Has an effect of accelerating the action of the halogen-based solvent as the main solvent, so it is desirable to contain 3 to 15%. Further, as other components, a surfactant and an evaporation inhibitor may be contained.

The surfactant lowers the surface tension of the main solvent, the accelerator and the like, makes them easily penetrate into the coating layer on the surface of the aluminum piece, reduces the interfacial tension of the coating layer, and swells and peels off. It has the function of separating and removing the coating layer from the surface of the aluminum piece. As the surfactant, a combination of a nonionic surfactant and a fluorine-based surfactant is preferable. As the content of the above surfactant, the effect is not exhibited if it is too small, and the effect is saturated even if it is too large,
It is desirable that the content be 0.1 vol% or more and 5 vol% or less.

However, care must be taken because if the dissolution is carried out with the surfactant attached, the dissolution yield may decrease. This is because the surfactant burns during melting and generates heat, which promotes the oxidation of the molten aluminum alloy and increases oxidation loss. , The melting yield is lowered. Therefore, in order to obtain a high dissolution yield, it is desirable to provide a washing and drying step before dissolving. If such a washing and drying step is not provided, it is recommended not to use a high molecular weight surfactant which easily burns.

The anti-evaporation agent is effective in coating the surface of the stripping solution to prevent the halogen-based solvent from evaporating.
Using hydrocarbons such as water, paraffin or fatty acids, etc.
It is desirable to add in the range of 0.1 vol% or more and 2 vol% or less.

[III] Cleaning Step For the purpose of removing the film pieces peeled from the aluminum pieces, it is desirable to wash the aluminum pieces by immersing them in a cleaning solution. At this time, not only can the aluminum pieces in the mesh basket be immersed in the cleaning liquid, but also if the mesh basket is rotated in the same manner as in the film peeling step, the aluminum pieces can be rubbed against each other to provide a mechanical peeling force, It is desirable because it can be washed in a short time. As the cleaning liquid, the stripping liquid or the halogen-based solvent may be used.
If the cleaning treatment time is too short, a sufficient removal effect cannot be obtained, and if the cleaning treatment time is too long, the effect is saturated. Therefore, the time may be about 5 to 10 minutes.

[IV] Vapor Cleaning Step Vapor cleaning the aluminum pieces using the above-mentioned stripping liquid or halogen-based solvent vapor even after the above-mentioned film peeling step or after the immersion cleaning in the above-mentioned cleaning step. It is desirable to provide a washing step.

By providing such a steam cleaning step, the overall cleaning time can be shortened, and since the aluminum pieces are heated by the steam, drying in the subsequent step is also easy. . Further, the vapor of the cleaning liquid is preferably collected by installing a cooling pipe in the upper part of the vapor cleaning chamber to cool and condense the vapor so that the cleaning liquid can be recovered.

[V] Drying Step In the case of performing steam cleaning, it is possible to dry with the residual heat. However, if a drying step is provided and heating is performed positively, the processing time can be shortened. In addition, the coating (particularly the coating on the inner surface side) peeled off from the aluminum piece may not be removed due to the deformation of the aluminum piece depending on its shape (for example, if there is a bent portion). . Therefore, it is desirable to provide a film removing step of separating the film by wind force after the drying step. Such film removal can be performed, for example, by blowing air when the aluminum piece after the drying step is charged from a belt conveyor into a transport container or the like.

After the drying step and the film removing step provided after the above-mentioned washing step, an aluminum alloy can be obtained by casting as it is or as a briquette and then melted in air. In addition, as described above, when a polymer-based surfactant or the like is contained in the stripping solution, it is recommended that the aluminum pieces be washed with water before the dissolving step, and a washing and drying step of drying after that be performed. . However, if dissolution is carried out in this step with insufficient drying and moisture attached during washing, steam explosion may occur. Therefore, it is necessary to thoroughly dry after washing.

In the present invention, the coating pieces separated from the aluminum pieces are contained in the stripping solution or the washing solution as fine pieces or powdery solids, and float or precipitate. In order to separate the stripping solution or the cleaning liquid from the coating piece, it may be filtered using a filter having a multi-hole body (see 5 in FIG. 1). It is recommended to recirculate to use. The filter may be selected in consideration of the processing efficiency and the filtering ability, but it is appropriate that the filter has a mesh size of about 30 to 200 μm.

Separated coating pieces may also contain up to about seven times the weight of the coating itself of stripper or cleaning liquid. Therefore, from the viewpoint of recovering as much of the stripping solution or cleaning solution as possible and improving the recycling rate, the coating film swollen with the stripping solution or cleaning solution is pressurized at 2 atm or more, or 0.5 atm. It is desirable to recover the stripping solution or the cleaning solution contained in the coating pieces by reducing the pressure below. If the pressure is too high or too low, the effect is saturated. Therefore, when pressurizing, the upper limit is set to 20 atm, and when reducing the pressure, the lower limit is set to 0.15 atm.

The recycling method of the present invention is not limited to the recycling of used aluminum cans, but may be applied to any aluminum scrap having a coating such as a paint formed on its surface. Alternatively, an aluminum laminated material having a printed layer formed on an aluminum foil, an aluminum building material (an aluminum sash or the like) coated with a polymer material, an aluminum automobile part having a coating film formed by painting or the like ( Panel material, body material, etc.). Regardless of the aluminum scrap, it is cut into an appropriate size according to the mesh width of the mesh basket to be used to form an aluminum piece,
If a mechanical peeling force is applied while being immersed in the stripping solution, it is possible to efficiently recycle aluminum scrap. The aluminum laminate may be immersed in a treatment liquid in a roll state without cutting, and continuously separated into an aluminum foil and a printed layer.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention, and any design changes based on the gist of the preceding and following aspects will be described. It is included in the technical range of.

[0048]

EXAMPLE 1 For the purpose of examining the relationship between the composition of the stripping solution and the degree of film removal, the content of methanol and formic acid was adjusted, and the following stripping test was performed. First, a used aluminum can is cut into aluminum pieces having a size of about 1/10 to 1/20 using a biaxial shear type shredder, and the aluminum pieces are loaded into a rotatable cylindrical mesh basket at an occupancy of 50%. Then, the coating was stripped by immersing the strip in a stripping solution at 30% and rotating the mesh basket for 10 minutes. Next, rotary cleaning for 10 minutes and steam cleaning for 10 minutes were performed using methylene chloride as a cleaning liquid, and a drying treatment was performed at room temperature for 10 minutes.

The degree of film removal was visually evaluated and evaluated as follows. The results are shown in Table 1 together with the dissolution yield measured after dissolution. ：: Almost peeled △: Approximately 50% peeled ×: Almost no peeling

[0050]

[Table 1]

No. In all of the samples 1 to 3, most of the films were peeled off. The dissolution yield is caused by the degree of film removal of the recycled material, and is desirably 90% or more.
o. The dissolution yields of 1 to 3 all indicate 90% or more. No. Nos. 4 to 8 indicate that the methanol or acid component (formic acid + halogenated acetic acid) in the stripping solution is too small, or
This is an example of a case where there are too many. It can be seen that the dissolution yield is lower than in Examples 1-3.

Example 2 In order to investigate the relationship between the state of adhesion of the coating pieces, the cleaning time and the cleaning method, No. 1 of Example 1 was used. After peeling off the coating in the same manner as in 1, the substrate was washed under the conditions shown in Table 2.
The results are shown in Table 2.

[0053]

[Table 2]

It can be seen that the cleaning time is preferably 5 minutes or more in the case of rotary cleaning, and 10 minutes or more in the case of immersion cleaning.

Example 3 For the purpose of investigating the relationship between the state of adhesion of the coating pieces and the steam cleaning time when the steam cleaning method was employed as the cleaning method, No. 1 of Example 1 was used. After the coating was peeled off and washed in the same manner as in Example 1, steam cleaning was performed under the conditions shown in Table 3. Table 3 shows the results
It is described together.

[0056]

[Table 3]

It can be seen that even when steam cleaning is used as the cleaning method, the coating pieces can be removed in a cleaning time of 5 minutes or more.

Example 4 For the purpose of examining desirable conditions in the drying step after the cleaning step, the presence or absence of steam cleaning and heating (atmospheric temperature 4
0 ° C.) and the drying time were varied while rotating the mesh basket to examine the wetness after drying. The results were evaluated as described below and are shown in Table 4. ○: No wetting △: Slightly wet ×: Wet

[0059]

[Table 4]

To dry in a short time, perform steam cleaning,
And it can be confirmed that it is desirable to heat.

Example 5 The effects of the use of a recycled material from which the coating of a used aluminum can was removed on the dissolution yield of aluminum and the content of Ti as an impurity were examined as follows. .

As the melting furnace, a refractory furnace (20 t) equipped with a forehearth was used. As the aluminum material to be recycled (hereinafter referred to as “recycled material”), a briquette (1 mx 1 m) obtained by pressing a used aluminum can by removing the coating by about 70% or more by the recycling method of the present invention.
× 1 m). In dissolving the above recycled material, first, 79.7% pure aluminum
The molten metal was melted in the air at 20 ° C. to make a molten metal. The briquette was charged into the molten metal at a mixing ratio of 0 to 100%, and the briquette was pressed into the molten metal to be dissolved. After the briquette is completely dissolved, a flux for removing slag (JDR1183 manufactured by Foseco Japan) is added to the surface of the slag floating on the surface of the molten metal at 0.02% by weight of the molten metal, and the flux and the slag are sufficiently stirred. After the exothermic reaction was caused, the slag on the surface of the molten metal was discharged out of the furnace by a rake to remove the slag.

The amount of the obtained molten aluminum was measured, and the melting yield (the ratio of the amount of aluminum obtained after melting to the total amount of the recycled material and the aluminum base metal charged) was calculated.

Using a rotary blade type ash press, the aluminum content was recovered from the removed slag by the ash squeezing method, the amount thereof was measured, and the recovery rate was calculated based on the total amount of the recycled material and the aluminum ingot. did.

The results are shown in Table 5 together with the case where the recycled material from which the coating was not removed was used. In addition, the dissolution yield in the table is converted to a ratio when 100% of the recycled material is used. Next, the Ti content in the aluminum melt obtained by adding the aluminum melt obtained by ash drawing to the aluminum melt after removing the slag was measured. The results are shown in Table 5.

[0066]

[Table 5]

It can be seen that the use of the recycled material from which the coating has been peeled off by the recycling method of the present invention significantly improves the dissolution yield. In addition, when the recycled material from which the coating is not removed is used, the Ti content in the aluminum melt obtained by ash drawing is high, and when added to the aluminum melt after the slag removal, the Ti content exceeds 0.03%. , Could not be recycled into aluminum can body material. It can be seen that the Ti content can be controlled to 0.03% or less by using the recycled material from which the coating has been peeled off by the recycling method of the present invention.

Example 6 The dissolution yield was measured in the same manner as in Example 1 for the purpose of examining the relationship between the surfactant in the stripping solution and the presence or absence of a washing / drying step and the dissolution yield. The results are shown in Table 6.
A nonionic surfactant was used as the surfactant, and 1 vol% was contained in the stripping solution. Washing was carried out by immersion in running water for about 5 minutes, followed by drying in a rotary kiln.

[0069]

[Table 6]

When water washing and drying were not carried out using a surfactant in the stripping solution (No. 32), the dissolution yield was higher than that in the case where the film stripping according to the present invention was not carried out (No. 31). Although the effect of improvement is small, when washing and drying are performed (No.
33) High dissolution yield of over 90% was obtained. In addition, when washing and drying are not performed (No. 34), it can be seen that a high dissolution yield can be obtained by not including a surfactant in the stripping solution.

Example 7 In order to examine the effect of the heating temperature in the drying step performed between the cutting step and the film peeling step on the film formed on the inner surface of the aluminum can, the heating temperature in the air heating furnace was changed. Various changes were made in the range of 100 ° C. to 300 ° C., and changes in the coating were examined. The evaluation was made by visual judgment as follows. The results are shown in Table 7. ：: No change Δ: Part or whole discoloration ×: Burning

[0072]

[Table 7]

In any of the aluminum can coatings, water could be removed without burning at a temperature of 150 ° C. or lower.

[0074]

As described above, according to the present invention, it is possible to provide a method of recycling aluminum scrap which can efficiently remove the coating of the aluminum scrap having the coating formed on the surface.

Further, according to the recycling method of the present invention, it is possible to greatly improve the melting yield by using the recycled material from which the film has been peeled off. The content of Ti can be suppressed to 0.03% or less even by adding, so that it becomes possible to recycle the aluminum can body material.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a typical process flow when a recycling method according to the present invention is adopted.

FIG. 2 is a schematic explanatory view showing an example of a peeling step.

FIG. 3 is a graph showing the relationship between the occupation ratio of aluminum pieces and the film removal ratio, and the relationship between the immersion ratio and the film removal ratio.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shredder 2 Mesh basket 2a Stripping liquid 3a Cleaning liquid 4a Heating means 4b Cooling means 5 Filter 6 Processing device

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshimitsu Takahashi 2-3-1, Shinhama, Araimachi, Takasago City, Hyogo Prefecture Inside Kobe Steel, Ltd. Takasago Works (72) Inventor Koichi Nagata 2-3-3 Shinhama, Araimachi, Takasago City, Hyogo Prefecture No. 1 Inside Kobe Steel, Ltd. Takasago Works (72) Inventor Kenji Osumi 1-5-5 Takatsukadai, Nishi-ku, Kobe City Inside Kobe Research Institute, Kobe Steel Co., Ltd. (72) Inventor Tomoji Takahashi Nishi-ku, Kobe City 1-5-5 Takatsukadai Kobe Steel Research Institute Kobe Research Institute (72) Inventor Kazuhisa Fujisawa 1-5-5 Takatsukadai Nishi-ku Kobe City Kobe Steel Research Institute Kobe Research Institute (72) Invention Person Minoru Fukuda 1800 Fukuoka Aluminum Industry Co., Ltd., 2800 Hisahara, Hisayama-cho, Kasuya-gun, Fukuoka Prefecture (56) References 23063 (JP, A) JP-A-1-287231 (JP, A) JP-A-8-49023 (JP, A) JP-A-7-265820 (JP, A) JP-A-7-265817 (JP, A) JP-A-6-91516 (JP, A) JP-B-1-52480 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22B 1/00-61/00 B08B 3/14 C09D 9/00

Claims (18)

(57) [Claims] 1. A method for recycling aluminum scrap having a coating film or the like formed on a surface thereof, wherein the aluminum scrap is cut into aluminum pieces, and the aluminum scrap is immersed in a stripping liquid. The aluminum piece was placed in a rotatable cylindrical mesh cage, and the mesh cage was immersed in a stripping solution so that the immersion rate of the mesh cage was in the range of 10 to 40%. rotation
A method for recycling aluminum scrap, comprising a film peeling step of removing a film from an aluminum piece by applying a mechanical peeling force to the aluminum piece by rotating the aluminum piece in a horizontal state as a center . 2. The recycling method according to claim 1, further comprising a drying step or a washing / drying step of removing a liquid adhering to the aluminum pieces prior to the film peeling step. 3. The mesh basket is a cylindrical mesh basket.
The method according to claim 1 or 2 that. 4. The cleaning method according to claim 3, further comprising, after the film peeling step, a washing step of washing the aluminum piece by rotating the mesh basket while a part of the mesh basket is immersed in a washing liquid. Recycling method. 5. The recycling method according to claim 1, wherein the coating strip generated in the coating stripping step and / or the cleaning step is separated by a filter, and the stripping liquid and / or the cleaning liquid are circulated. . 6. The recycling method according to claim 4, further comprising a steam washing step of washing the aluminum pieces with steam of a washing liquid after the coating stripping step and / or the washing step. 7. The recycling method according to claim 4, further comprising a step of drying an aluminum piece after the cleaning step and / or the steam cleaning step. 8. The recycling method according to claim 7, further comprising a coating removing step of separating the coating by wind power after the drying of the aluminum pieces. 9. The recycling method according to claim 7, further comprising a washing and drying step of washing and drying the aluminum pieces after the drying step of the aluminum pieces and / or the film removing step. 10. After any of the drying step of claim 7, the film removing step of claim 8, or the washing / drying step of claim 9, the mixture is cast as it is or in the form of briquettes, and then melted in the air. The recycling method according to claim 7. 11. A halogen-based solvent,
The recycling method according to claim 1, wherein a solution containing a lower alcohol and an acid as main components is used. 12. The recycling method according to claim 11, wherein the stripping solution further contains a surfactant . 13. The method according to claim 1, wherein the halogen-based solvent is selected from the group consisting of methylene chloride, trichlene, and perchrene.
The recycling method according to claim 11 or 12, wherein the recycling method is a kind or two or more kinds. 14. The recycling method according to claim 11, wherein the lower alcohol is methanol, and the acid component is formic acid, or formic acid and halogenated acetic acid. 15. The recycling method according to claim 11, wherein the stripping solution or the halogen-based solvent is used as the cleaning solution. 16. The recycling method according to claim 1, wherein an aluminum laminate in which a printing layer is formed on an aluminum foil is used as the aluminum scrap . 17. A coated aluminum building material as an aluminum scrap.
The recycling method according to any of the above. 18. A coated aluminum vehicle part is used as the aluminum scrap .
16. The recycling method according to any one of 15 above.