JP4603452B2 - Pre-coated aluminum alloy plate and method for producing press-formed product - Google Patents

Description

  The present invention relates to a precoated aluminum alloy plate excellent in press formability and film removal property.

From the viewpoints of downsizing, weight reduction, high designability, and the like, the materials of electronic device housings are changing from steel to aluminum alloys. In particular, most digital camera housings are made of aluminum alloy. Such an electronic device casing is manufactured by first applying lubricating oil to an aluminum alloy plate, press-molding, then solvent cleaning, alkali cleaning, or acid cleaning, and then alumite treatment.
Recently, due to miniaturization, weight reduction, high designability, and complicated shape of electronic devices, high formability that enables complex processing while using high-strength aluminum alloys in the manufacture of electronic device casings. In addition, cost reduction and environmental improvement are strongly desired.

As for high formability, there is a limit to improvement from material properties by reviewing aluminum alloy components and process conditions.
Therefore, there are methods of improving the viscosity of the lubricating oil used for press molding, increasing the oiliness, or increasing the amount of lubricating oil. However, when the viscosity of the lubricating oil is improved or the oiliness is increased, it becomes difficult to remove the oil after molding, and as a result, it is necessary to increase the cleaning in the next process, resulting in an increase in manufacturing cost and a longer cleaning time. Deteriorate production efficiency.

  In addition, there is a demand for cost reduction by improving the production yield and reducing the amount of lubricating oil and cleaning liquid used. Since the lubricity during press molding affects the yield, stable high lubricity is strongly desired during press molding. Furthermore, from the viewpoint of environmental improvement, there is a demand for a direction in which the currently used lubricating oil and cleaning are minimized. In addition, as an aluminum alloy board which improved lubricity, there exists a thing which apply | coated the solid lubricant, for example (patent document 1).

Japanese Patent Laid-Open No. 06-099225

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a precoated aluminum alloy plate that is excellent in press formability and easy to process after press forming.

A first invention is a pre-coated aluminum alloy plate for press molding comprising a substrate made of an aluminum alloy plate and an organic resin film formed by baking coating covering at least one surface of the substrate.
The organic resin constituting the organic resin film has a glass transition point of 70 ° C. or higher, an acid value of 50 KOH / g or higher, a molecular weight of 20,000 to 100,000, and sodium hydroxide or potassium hydroxide, ammonia or amine as a neutralizing agent. Including a water-soluble acrylic resin containing one or more selected,
The organic resin film contains carnauba, and the carnauba content is 0.1 wt% to 30 wt%,
The thickness of the organic resin film is 0.1 μm to 30 μm,
And the said organic resin film exists in the precoat aluminum alloy board characterized by being removable from the said board | substrate by making it contact with alkaline aqueous solution of pH8 or more (Claim 1).

The pre-coated aluminum alloy plate includes a substrate made of an aluminum alloy plate and an organic resin film. The organic resin constituting the organic resin film includes the specific water-soluble acrylic resin, so that the organic resin film can be removed from the substrate when brought into contact with an alkaline aqueous solution having a pH of 8 or more. It is.
Therefore, the precoated aluminum alloy plate is excellent in press formability and can be easily processed after press forming.

  That is, the water-soluble acrylic resin contained in the organic resin film has a glass transition point of 70 ° C. or higher. Thereby, the moldability excellent at the time of shaping | molding, such as press work, is obtained. When the glass transition point is less than 70 ° C., there is a problem that sufficient formability cannot be obtained due to an increase in tool temperature during actual pressing.

  The acid value of the water-soluble acrylic resin, that is, the acid value indicating the amount of carboxyl groups contained in the water-soluble acrylic resin is 50 mgKOH / g or more, and contains the neutralizing agent. Thereby, the organic resin film containing the water-soluble acrylic resin can be easily removed from the substrate by contacting with an alkaline aqueous solution having a pH of 8 or higher. When the acid value of the water-soluble acrylic resin is less than 50 mgKOH / g or does not contain the neutralizing agent, the removal of the organic resin film from the substrate (film removal) by contact with an alkaline aqueous solution having a pH of 8 or more , There is a problem that you can not do enough.

  The water-soluble acrylic resin has a molecular weight of 20,000 to 100,000. When the molecular weight is less than 20,000, the adhesion may be improved, but there is a problem that the moldability is inferior. On the other hand, when it exceeds 100,000, the moldability may be improved, but the adhesion is improved. There is a problem that the film is inferior and the film removal becomes difficult.

  In the present invention, since the lubricity at the time of pressing can be ensured by the organic resin film that can be easily removed as described above, there is almost no need to separately prepare a lubricant or clean it. Excellent in terms of cost and environmental improvement.

The second invention is a method for producing a press-formed product of an aluminum alloy plate,
Using a die having a processed hole and a punch that can be inserted into the processed hole, the surface on which the organic resin film is formed of the precoated aluminum alloy plate of the first invention is positioned on the die side and pressed. Pressing process for forming a press-molded product,
A method for producing a press-molded product, comprising: removing the organic resin film from the substrate by bringing the press-molded product into contact with an alkaline aqueous solution having a pH of 8 or more ( Claim 9 ).

This manufacturing method implements at least the pressing step and the film removal step after using the excellent precoated aluminum alloy plate of the first invention. Thereby, the press-molded product excellent in the designability can be obtained.
That is, in the pressing step, as described above, the surface of the precoated aluminum alloy plate on which the organic resin film is formed is positioned on the die side and pressed. In this case, the above-mentioned organic resin film having excellent lubricity is disposed on the side where the die and the precoated aluminum alloy plate are in contact with each other. Therefore, even if molding with a high degree of processing is performed, there is no defect such as galling. Press formability is obtained. Therefore, the yield at the time of press molding can be improved.

Further, after the pressing step, the film removal step is performed. In this film removal step, the press-formed product is brought into contact with an alkaline aqueous solution having a pH of 8 or higher. Here, the pre-coated aluminum alloy plate as the material positively employs the organic resin film that includes the water-soluble acrylic resin and can be removed from the substrate by contacting with an alkaline aqueous solution having a pH of 8 or more. is doing. Therefore, by carrying out this film removal step, it is possible to remove the organic resin film from the substrate and remove the film. This makes it possible to easily obtain a press-molded product from which the organic resin film is removed and the substrate is exposed, and the surface is protected by the organic resin film. It will be excellent. Therefore, even if alumite treatment or the like is performed thereafter, the design property is high.
In addition, as described above, after performing a pressing process using a material having a special organic resin film, it can be removed very easily by the above-described film removal process, so a lubricant can be separately prepared, There is no need to perform cleaning, and costs can be reduced and the environment can be improved.

In the precoated aluminum alloy sheet of the present invention, the organic resin film contains carnauba, the content of the carnauba is 0.1 wt% to 30 wt%, and the thickness of the organic resin film is 0.1 μm to 30 μm .

That is, it is preferable to contain 0.1% to 30% by weight of the carnauba with respect to the organic resin film. In this case, extremely excellent lubricity is exhibited during press molding.
When the content of carnauba is less than 0.1% by weight, there is a problem that the effect of improving lubricity by carnauba cannot be obtained sufficiently. Moreover, when it exceeds 30 weight%, there exists a problem that there exists a possibility that an organic film may not fully be removed by a film removal process.

  The thickness of the organic resin film is preferably 0.1 μm to 30 μm. When the film thickness is less than 0.1 μm, it cannot be uniformly coated due to the roughness of the surface of the aluminum alloy plate. On the other hand, when the thickness exceeds 30 μm, there is a problem that film formation becomes difficult and film removal properties are inferior.

Further, it is preferable that the alkali aqueous solution is sodium hydroxide (claim 2).
In this case, it is easy to obtain as an industrial product, and the effect of relatively reducing the cost of the film removal step can be obtained.
The alkaline aqueous solution is more preferably pH 9-12.
If the alkaline aqueous solution is less than pH 9, the time required to remove the organic resin film may be long. On the other hand, if the pH exceeds 12, the aluminum alloy plate surface after the organic resin film is removed May dissolve more than necessary.

Further, the organic resin film is preferably in less than 4 seconds contact time with the alkali aqueous solution can be removed from the substrate (claim 3).
In this case, the film removal step can be carried out efficiently, and more preferably within 2 seconds. If the contact time exceeds 4 seconds, it is difficult to increase the efficiency of the film removal process.

Moreover, it is preferable that the film thickness of the said organic resin film is 10 micrometers or less ( Claim 4 ).
In this case, the effect of suppressing the accumulation of resin powder and wax component on the mold during continuous press molding can be obtained.

The organic resin constituting the organic resin film preferably contains, in addition to the water-soluble acrylic resin, a polyalkylene glycol having a molecular weight of 800 to 35000 or a urethane resin as an additive resin ( claim). Item 5 ).
Also in this case, the organic resin film can be easily removed with an alkaline aqueous solution. Moreover, the effect that it is easy to oil-impregnate carnauba as an inner wax is also acquired.

When the polyalkylene glycol is added as the additive resin in addition to the water-soluble acrylic resin as the organic resin, the molecular weight is limited to 800-35000. When the molecular weight is less than 800, it is difficult to form a solid film in a normal state, and when it exceeds 35,000, it is difficult to paint or remove the film.
When the additive resin is a urethane resin, any molecular weight may be used.

Moreover, it is preferable that the surface of the said organic resin film is apply | coated with the lubricant containing 1 or more types chosen from an oil-based agent, an extreme pressure agent, and a solid lubricant ( Claim 6 ).
Even if such a lubricant is not applied, high lubricity is obtained by the organic resin film, but the oily agent, extreme pressure agent, or solid lubricant is further applied to the surface of the organic resin film. In this case, the lubricity of the organic resin film can be further improved, and it can be applied to extremely severe molding.

Examples of the oily agent include polyol esters, fats and oils, fatty acid esters, higher alcohols, higher fatty acids, and α-olefins.
Examples of extreme pressure agents include chlorine, sulfur, and phosphorus. From the viewpoint of the environment, sulfur and phosphorus are more preferable.
Examples of the solid lubricant include metal soap and grease.
Further, any oil may be used as long as it affects metal according to the use environment.

Further, the organic resin film has resin beads having a particle diameter of 1 to 120 μm and a particle diameter of 1 to 3 times the thickness of the organic resin film. It is preferable that a part is contained (claim 8).
In this case, scratch resistance at the time of molding is improved, handling scratches until press molding is suppressed, and the yield is improved.

When the particle size of the resin beads is 1 part by weight or less, the effect of adding the resin beads is not recognized, and when it exceeds 100 parts by weight, the effect is not changed and the cost increases. To do.
When the particle size of the resin beads is less than 1 times the organic resin film, the resin beads do not protrude from the organic resin film, and the effect is reduced. In addition, when it exceeds 3 times, the organic resin film is difficult to trap the resin beads, and there is a problem that the resin beads are easily dropped.

Moreover, it is preferable that a base treatment layer for improving the adhesion between the organic resin film and the substrate is formed on the surface of the substrate.
In this case, the adhesion between the organic resin film and the substrate is improved, the moldability of the organic resin film is further improved, and the scratch preventing effect can be further enhanced.

As the above-mentioned base treatment layer, chromate treatment such as phosphate chromate, chromate chromate, etc., and chemical film treatment such as non-chromate treatment with titanium phosphate, zirconium phosphate, molybdenum phosphate, zinc phosphate other than chromium compounds, etc. There is a film obtained by (chemical conversion treatment).
The chemical conversion film treatment method includes a reaction type and a coating type, and any method may be employed in the present invention.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited only to these examples.
In this example, a plurality of types of samples (pre-coated aluminum alloy plates) were prepared as examples and comparative examples of the present invention, and their characteristics were evaluated.

In producing each sample, first, an A1050 aluminum alloy plate having a tempering of H24 and a thickness of 0.8 mm was used as a substrate.
In addition, the substrate was degreased using acetone.

In the coating treatment, a predetermined paint was applied to the substrate after the degreasing treatment by a bar coating method, baked at a temperature of 250 ° C. for 2 minutes, and cured to form each coating film.
Moreover, in producing each coating film, acrylic resin (AC), polyalkylene glycol (AG), and urethane resin (UR) are used as the organic resin (base resin or additive resin), and the acrylic resin is neutralized. , Sodium hydroxide (SH), ammonia (AM), and oleic acid (OA), methyl oleate (OAM), tricresyl phosphate (TCP), and calcium stearate (STCa) as lubricants, Polytetrafluoroethylene was used as the resin beads.
These resins, lubricants, resin beads, and carnauba were mixed at a blending ratio shown in Table 1 to form a coating film. In addition, the formed coating film is shown in Table 1, Table 2, and Table 4.

In this example, each sample was evaluated for formability, scratch resistance, film removal, and handleability.
<Moldability>
Molded using a cylindrical punch hydraulic deep drawing machine. The maximum height that can be formed without breaking the sample was evaluated, and ◎ and ○ were accepted.
(Processing conditions)
Blank diameter: φ110 mm, punch diameter: φ50 mm, punch corner: 5R, wrinkle holding load: 10 kN, molding speed: 100 mm / min.
(Evaluation criteria)
A: 7 mm or more, B: 5 mm or more and less than 7 mm, X: less than 5 mm

<Scratch resistance>
In a Bowden friction test, a hard sphere with a load of 100 g and a diameter of 0.25 inch was slid back and forth on the surface of the sample, and the number of sliding times until the coating film was broken was evaluated. did.
(Evaluation criteria)
◎: 100 times or more, ○: 50 times or more and less than 100 times, ×: less than 50 times

<Film removal>
A specimen of 100 mm × 50 mm was bent at 90 ° in the center in the width direction, immersed in an alkaline aqueous solution (sodium hydroxide aqueous solution, liquid temperature 60 ° C.) stirred with a magnetic stirrer, washed with water, and dried. The presence or absence of remaining organic resin film was visually confirmed, and the immersion time was evaluated. ◎ and ○ were accepted.
(Evaluation criteria)
◎: Less than 2 seconds, ○: 2 seconds or more and less than 4 seconds, ×: 4 seconds or more

<Handability>
After stacking 10 pieces of 100 mm × 50 mm specimens, placing a 5 kg weight, leaving it for one week at 30 ° C. and 100% humidity, removing the weights, and using a suction cup to peel one by one from above. The handleability was evaluated. ○ was accepted.
(Evaluation criteria)
○: When all sheets were peeled one by one, ×: When two or more sheets were peeled, the results of evaluation are as shown in Table 3 and Table 5.

As is known from Tables 1 to 3, Samples E1 to E22 all showed good results in all evaluation items such as moldability, scratch resistance, film removal property, and handleability.
As known from Table 4 and Table 5, since the film thickness of Sample C1 was below the lower limit of the preferred range of the present invention, the substrate could not be uniformly coated, and the moldability and scratch resistance were reduced. Moreover, since the film thickness exceeded the upper limit of the preferable range of this invention for the sample C2, the film removal property fell.

In sample C3, the molecular weight of the organic resin was below the lower limit of the present invention, so that the lubricity could not be satisfied and the moldability was lowered. In addition, since the molecular weight of the organic resin exceeded the upper limit of the present invention, the sample C4 was deteriorated in film removal because the alkaline aqueous solution hardly penetrated into the organic resin film.
In sample C5, since the molecular weight of the organic resin was below the lower limit of the preferred range of the present invention, it was difficult to form a solid film, and the moldability and scratch resistance were reduced. Moreover, since the molecular weight of the organic resin exceeded the upper limit of the preferable range of the present invention, the film removal property of the sample C6 was lowered because the alkaline aqueous solution was difficult to penetrate into the organic resin film.

  In Sample C7, the content of carnauba was below the lower limit of the preferred range of the present invention, so that the lubricity was insufficient and the moldability was lowered. In Sample C8, since the content of carnauba exceeds the upper limit of the preferred range of the present invention, most of the organic resin film was covered with carnauba, and the alkaline aqueous solution became difficult to react, and the film removal property and handleability were reduced.

In Sample C9, since the particle size of the resin beads was below the lower limit of the preferred range of the present invention, most of the organic resin film was covered with the resin beads, the alkaline aqueous solution became difficult to react, and the film removal property decreased. In Sample C10, since the resin beads had a particle diameter exceeding the upper limit of the preferred range of the present invention, the resin beads were easily dropped and the scratch resistance was reduced.
In sample C11, since the content of the resin beads exceeded the upper limit of the preferable range, most of the organic resin film was covered with the resin beads, the alkaline aqueous solution became difficult to react, and the film removal property was lowered.

In Sample C12, since the acid value was below the lower limit of the present invention, the organic resin film was not sufficiently removed in the film removal step, and the film removal property was lowered.
Since sample C13 did not contain a neutralizing agent, the organic resin film was not sufficiently removed in the film removal step, and the film removal performance was reduced.
In Sample C14, the glass transition point was lower than the lower limit of the present invention, so that the tool temperature increased during actual pressing, and the formability decreased.

Claims (9)

In a pre-coated aluminum alloy plate for press molding comprising a substrate made of an aluminum alloy plate and an organic resin film formed by baking coating covering at least one surface of the substrate,
The organic resin constituting the organic resin film has a glass transition point of 70 ° C. or higher, an acid value of 50 KOH / g or higher, a molecular weight of 20,000 to 100,000, and sodium hydroxide, or potassium hydroxide, ammonia or amine as a neutralizing agent. Including a water-soluble acrylic resin containing one or more selected,
The organic resin film contains carnauba, and the carnauba content is 0.1 wt% to 30 wt%,
The thickness of the organic resin film is 0.1 μm to 30 μm,
And the said organic resin film is removable from the said board | substrate by making it contact with alkaline aqueous solution of pH8 or more, The precoat aluminum alloy plate characterized by the above-mentioned.   2. The precoated aluminum alloy sheet according to claim 1, wherein the alkaline aqueous solution is sodium hydroxide.   3. The precoated aluminum alloy plate according to claim 1, wherein the organic resin film can be removed from the substrate within a contact time of 4 seconds with the alkaline aqueous solution.   4. The precoated aluminum alloy sheet according to claim 1, wherein the organic resin film has a thickness of 10 μm or less.   5. The organic resin constituting the organic resin film according to claim 1 further contains a polyalkylene glycol having a molecular weight of 800 to 35000 or a urethane resin in addition to the water-soluble acrylic resin. A precoated aluminum alloy plate characterized by the above.   6. The lubricant according to claim 1, wherein the surface of the organic resin film is coated with a lubricant containing at least one selected from an oily agent, an extreme pressure agent, and a solid lubricant. Pre-coated aluminum alloy plate.   7. The organic resin film according to claim 1, wherein the organic resin film includes resin beads having a particle diameter of 1 to 120 μm and a particle diameter of 1 to 3 times the thickness of the organic resin film. A pre-coated aluminum alloy plate, which is contained in an amount of 1 to 100 parts by weight with respect to 100 parts by weight.   The precoated aluminum alloy sheet according to any one of claims 1 to 7, wherein a surface treatment layer for improving adhesion between the organic resin film and the substrate is formed on a surface of the substrate. .   In the method of manufacturing a press-formed product of an aluminum alloy plate,
  The surface on which the organic resin film is formed of the precoated aluminum alloy plate according to any one of claims 1 to 8, wherein a die having a processed hole and a punch that can be inserted into the processed hole are formed on the die side. A press process for forming a press-molded product by being pressed at a position;
  A method for producing a press-molded product, comprising: removing the organic resin film from the substrate by bringing the press-molded product into contact with an alkaline aqueous solution having a pH of 8 or more.