JP5060460B2 - Resin-coated aluminum plate with excellent resin adhesion - Google Patents

Description

 The present invention relates to an aluminum plate provided with a resin, and more particularly to an aluminum plate excellent in resin adhesion after a forming process for forming a bottomed cylindrical structure by drawing.

Aluminum plates or aluminum alloy plates (hereinafter referred to as “aluminum plates”) are lightweight, have appropriate mechanical properties, and have excellent characteristics such as aesthetics, moldability, and corrosion resistance. Widely used in structural materials and machine parts.
In order to further improve the corrosion resistance and elution resistance, to improve the appearance, to prevent scratches, and the like, the aluminum plate for the above uses is often subjected to coating with a resin paint and laminating of a resin film. At this time, in order to improve the resin adhesion and the corrosion resistance, the aluminum plate is subjected to a base treatment based on existing technology (for example, a chemical-molding base treatment such as phosphate chromate, chromate chromate and zirconium phosphate). It is common. In the case of an aluminum cap, a pre-coating material is often used which is subjected to a base treatment and resin coating on an aluminum plate as a material and then molded.
Pre-coated aluminum alloy plates for cap molding are required to have resin adhesion that prevents the resin from peeling even after molding, corrosion resistance that is not affected by corrosive atmospheres, and workability that can withstand advanced molding. The In response to such demands, various proposals have been made in a wide range of fields, particularly from the standpoint of improving coating film adhesion. In particular, in the ground treatment method, in addition to chemical molding ground treatment based on the prior art, a method is proposed in which an organic material for improving adhesion is provided thereon, and then a resin is provided thereon.

For example, in Patent Document 1, after an aluminum plate is subjected to phosphoric acid chromate treatment, the aluminum plate is treated in a solution containing a specific phenol polymer, or the aluminum plate is subjected to phosphoric acid chromate treatment and then subjected to silane treatment. A method has been proposed in which a treated aluminum plate is prepared and coated with a thermoplastic resin to form a resin-coated aluminum plate, which is then drawn and ironed to form a capacitor exterior container.
Further, Patent Document 2 is a phosphoric acid chromate in which the chemical-molding ground treatment film has a Cr adhesion amount of 1 mg / m ² or more and 30 mg / m ² or less and a surface C amount of 50 mg / m ² or less. A polymer of an acrylic acid compound containing one or more carboxyl groups per average molecular weight of 500 and having a weight average molecular weight of 1,000 or more and 1,000,000 or less is provided at an adhesion amount of 5 mg / m ² or more and 5000 mg / m ² or less. An aluminum plate for cap molding provided with a coating film containing 5 mass% or more of pigment on the dry weight is provided.
Further, in Patent Document 3, the average interval Sm of the surface irregularities is in the range of 5 to 200 μm, the average inclination angle θa of the uneven slopes is in the range of 3 to 30 °, and the ten-point average roughness Rz. Is in the range of 0.5 to 5 μm, and an aluminum alloy plate for coating excellent in adhesion of the coating layer is proposed.

JP 2001-303273 A JP 2008-126515 A Japanese Patent No. 3680206

However, the conventional techniques as described above have the following problems. In other words, aluminum caps used in re-sealable containers such as bottle cans are capacitor cases that are the subject of Patent Document 1 such as deep drawing molding, screw molding, and perforation processing with pilfer proofing. Compared with, it undergoes very severe processing. In addition, since bottle cans have been adopted for hot beverages, the cap resin is also required to have retort resistance. Furthermore, in recent years, the demand for thinner aluminum has been increasing from the viewpoint of cost reduction, and attempts have been made to reduce the thickness and strength of aluminum materials. However, when such high-strength materials are processed into caps, the mold clearance is more Since the molding load is severely increased, the stress applied to the material surface is higher than before.
Under such conditions, the techniques such as Patent Documents 1, 2, and 3 have problems such as peeling of the coating film after retorting because the resin adhesion after being subjected to severe processing is insufficient.

As a result of repeated studies to solve the above problems, the inventor of the present invention has reduced the overall “convex” in the surface roughness of the aluminum plate, while making only the “concave” deep, and B) An acrylic resin containing one or more carboxyl groups per weight average molecular weight of 500 and having a weight average molecular weight of 1,000 or more and 1,000,000 or less may be provided at an adhesion amount of 5 mg / m ² or more and 5000 mg / m ² or less. I found it effective.

That is, on the surface of an aluminum material having an arithmetic average height Ra of 0.1 μm or more and 0.5 μm or less and a load length ratio Rmr (1.5 μm) of 50% or more, at least one carboxyl group per 500 weight average molecular weights. An aluminum plate comprising an acrylic resin having a weight average molecular weight of 1,000 to 1,000,000 and a resin coating film having a dry weight of 5 mg / m ^{2 to} 5000 mg / m ² .

Moreover, it is an aluminum plate manufactured by hot rolling or cold rolling, the surface shape is subjected to final rolling with a roll having a maximum height Rz of 1.0 μm or more and 5.0 μm or less, and then the surface shape After the straightening process is performed with a roll having an arithmetic average height Ra of 0.01 μm or more and 0.5 μm or less, the weight average molecular weight of 500 contains one or more carboxyl groups and the weight average molecular weight of 1,000 to 1,000,000. The water-based or solvent-based acrylic resin paint is applied so that the dry weight is 5 mg / m ² or more and 5000 mg / m ² or less, and is dried in an atmosphere of 30 ° C. or more and 300 ° C. or less for 1 second or more and 600 seconds or less. It is a manufacturing method of the aluminum plate excellent in the resin adhesiveness after the shaping | molding process of Claim 1 characterized by the above-mentioned.

  As described above, the aluminum plate made according to the claims of the present invention exhibits an anchor effect due to the configuration of an appropriate surface roughness, and the adhesion between the aluminum surface and the resin is further increased by the presence of an appropriate acrylic resin. As a result, the resin adhesion after molding is extremely excellent.

Hereinafter, details of the present invention will be described in order.
The present invention is roughly composed of two elements. That is, “to form a smooth surface exceeding 50% on the surface of the aluminum material and a surface having a recess having an appropriate depth” and “resin coating made of acrylic resin on the surface having the above surface roughness”. “To form a film”.

First, the effect of surface roughness will be described.
First, the aluminum plate surface must have an arithmetic average height Ra of 0.1 μm to 0.5 μm. The arithmetic average height is the average of the absolute values of the roughness curve at the reference length, and the measuring method follows JIS B 0601-2001. This is most frequently used as an index for intuitively expressing the degree of unevenness, and the lower the value, the smoother the surface. When Ra is less than 0.1 μm, since the surface is too smooth, when the resin is formed and processed by means such as coating and laminating, the adhesion improving effect due to the resin flowing into the recess, the so-called anchor effect Does not occur, and the adhesiveness of the resin decreases. On the other hand, when Ra exceeds 0.5 μm, since the overall unevenness is severe, it is possible to expect a certain degree of improvement in adhesion due to the anchor effect described above. However, on the other hand, the resin coating is locally thinned at the convex portion, and that portion is easily cracked during processing and tends to be a starting point of peeling.

  In addition, the aluminum plate surface needs to have a load length ratio Rmr (1.5 μm) of 50% or more. This is an indispensable item for utilizing the anchor effect to the maximum while preventing the resin coating from being locally thinned. The load length ratio is a ratio of the load length Mr of the contour curve element to the evaluation length at a certain cutting level c (1.5 μm in the present invention), and its measuring method is JIS B 0601- Follow 2001. Rmr (1.5 μm) = 50% means that when the surface is cut horizontally from the highest convex portion at a depth of 1.5 μm, 50% of the surface is cut off. According to the present invention, 50% or more of the entire region is included within 1.5 μm from the highest convex portion. In other words, a very smooth region with a height difference of 1.5 μm or less occupied 50% or more of the whole.

Qualitatively expressing the condition satisfying the above conditions of Ra and Rmr (1.5 μm), “As a whole, the anchor effect is rough enough to be expected, and more than 50% is a very smooth plateau. The rest is in the shape of a recess. Since there are no protruding convex portions, thin portions of the coating film do not occur, and the concave portions are scattered, so that the coating film exhibits an anchor effect. By combining this effect, excellent workability is exhibited.
In addition, as long as the said conditions satisfy | fill the said aluminum plate, a manufacturing method and a material will not ask | require. Specifically, any of a rolled material, an extruded material, a cast material, a forged material, etc. can be applied, and any of aluminum alloys used industrially, such as 1000 series, 3000 series, 5000 series, and 7000 series, can be used. Also effective.

Second, the action of the acrylic resin will be described.
In the present invention, an acrylic resin having one or more carboxyl groups per weight average molecular weight of 500 and having a weight average molecular weight of 1,000 to 1,000,000 is most suitable as a material to be provided on the aluminum plate surface. This is because the carboxyl group contained in the acrylic resin is strongly bonded to the Al—O portion present on the aluminum surface and the polar group on the film surface in the chemical conversion coating, and the resin skeleton is the resin component of the coating film. This is because it exerts a strong effect on both the aluminum surface and the coating film in order to exert the effect of forming the molten adhesive layer. In addition, acrylic resins generally have high refractive index and are colorless, and do not contain bisphenol A, which is pointed out to be an endocrine disrupting substance (so-called environmental hormone). It has. As long as the above requirements are satisfied, an acrylic resin known in the prior art can be applied as it is in the present invention. Specifically, polyacrylic acid, polyacrylic acid ester, polymethacrylic acid, polymethacrylic acid ester, polyhydroxyacrylic acid, polyhydroxyacrylic acid ester and copolymers thereof are suitable. In addition, resins whose pH is adjusted with ammonia, amines, alkali metal hydroxides, or the like can also be suitably used. Furthermore, a resin in which a melamine compound and a urea compound are added as a cross-linking agent can also be suitably used.
Moreover, the molecular weight of the acrylic resin used for this invention must be a thing of 1000-1 million in terms of a weight average molecular weight. This is because when the weight average molecular weight is less than 1000, the water solubility of the resin coating film increases, and elution of the acrylic resin layer in retort treatment or the like is concerned. When the weight average molecular weight exceeds 1,000,000, the flexibility of the resin coating film is increased. This is because cracks in the resin film itself are easily generated and uneven coating due to an increase in viscosity is likely to occur.

In the present invention, it is essential that the resin coating film made of the acrylic resin has a dry weight of 5 mg / m ² or more and 5000 mg / m ² or less. If the resin coating is applied so that the dry weight is less than 5 mg / m ² , it is industrially difficult to uniformly apply to the surface of the aluminum plate, and there is a risk that partial application omission occurs. Further, if it exceeds 5000 mg / m ² , the residual stress of the acrylic resin layer becomes large, which causes cohesive failure of the resin layer when strong processing is performed. Furthermore, the dry weight of the resin coating film is more preferably 10 mg / m ² or more and 500 mg / m ² or less. This is because the risk of coating omission can be almost avoided at 10 mg / m ² or more, and the effect of the present invention is almost saturated at 500 mg / m ² . Both of them are industrial disadvantages.

  The aluminum plate thus obtained can be suitably used particularly as a cap molding material by providing a resin on its surface by means such as painting and laminating. About resin used for a resin coating film, what is necessary is just based on a prior art. For example, in the case of a paint, commonly used resins such as polyester resins, epoxy resins, and vinyl chloride resins can be used as they are. The paint may be water-soluble or solvent-based, and may contain a pigment such as titanium oxide. For example, in the case of a laminate, a film such as polyethylene terephthalate (PET) resin or polybutylene terephthalate resin (PBT) manufactured based on the conventional technology may be thermocompression bonded at a temperature equal to or higher than the film melting point. Furthermore, on these resins, various ink layers for the purpose of imparting color may be provided, and various finishing clear coating films may be provided as a top coat.

As a manufacturing method for obtaining an aluminum plate having excellent resin adhesion after molding as in the present invention, the surface shape is subjected to final rolling with a roll having a maximum height Rz of 1.0 μm to 5.0 μm, Next, after performing a straightening process with a roll having a surface shape with an arithmetic average height Ra of 0.1 μm or more and 0.5 μm or less, the weight average molecular weight of 500 contains one or more carboxyl groups and a weight average molecular weight of 1000 An aqueous or solvent-based acrylic resin paint having a viscosity of 1 million or less is applied to a dry weight of 5 mg / m ² or more and 5000 mg / m ² or less. The method of drying for less than a second can be mentioned.

  Although the method of forming the aluminum material includes casting such as die casting, rolling with a roll, extrusion or drawing with a mold, almost all methods for producing an aluminum plate include hot or cold rolling with a roll. Used. In particular, in order to obtain appropriate mechanical properties, a method of performing cold rolling after rolling to a certain thickness by hot rolling is often used. Here, in the final stage of rolling, that is, in the final pass when the material comes into contact with the rolling roll, the surface roughness of the rolling roll is transferred to the material by setting the maximum height Rz to 1.0 μm or more and 5.0 μm or less. Is done. The purpose of this step is to moderately roughen the aluminum plate surface, and if the roll surface Rz is less than 1.0 μm, sufficient concaves are not formed on the plate surface, and Ra becomes smaller after the correction step described below. Too much. On the other hand, when the thickness exceeds 5.0 μm, the surface becomes rough enough to prevent the convexity from being crushed in the correction process, and Ra after the correction process becomes too large.

Subsequently, for the aluminum plate whose surface is moderately roughened in the rolling step, by performing a correction step with a roll having an arithmetic average height Ra of 0.01 μm or more and 0.5 μm or less on the roll surface, An aluminum plate having a surface roughness conforming to the requirement of item 1 is obtained. The straightening process is also referred to as a leveling process, a leveler process, or the like, and is mainly performed to remove distortion of the aluminum plate after cold rolling, and equipment called a roller leveler is often used. In this roller leveler, unevenness on the surface of the material is moderately crushed by using a smooth roll having an arithmetic average height Ra of 0.01 μm or more and 0.5 μm or less.
Specifically, the aluminum surface at the end of the rolling process has approximately the same amount of concave portions and convex portions, but the concave portions are preserved as they are when subjected to a correction process using a smooth roll. On the other hand, only the convex part is crushed and smoothed. As a result, an aluminum plate having an Rmr (1.5 μm) of 50% or more can be obtained while keeping Ra at 0.1 to 0.5 μm on the surface of the aluminum plate. When Ra on the roll surface of the roller leveler is less than 0.01 μm, the roll is too smooth and may idle and the correction process may not be performed sufficiently. On the other hand, if it exceeds 0.5 μm, the action of crushing the convexity of the aluminum plate does not work sufficiently and Ra on the plate surface becomes too large.

  In addition, after the surface roughness shape of the aluminum plate is adjusted in this way, the degreasing process and chemical conversion based on the prior art are aimed at improving the wettability of the subsequent acrylic resin paint or further improving the corrosion resistance of the material. Processing steps can be added. Specifically, an aqueous solution of a commercially available alkaline degreasing agent having a pH of about 9 to 13 is heated to around 60 degrees and sprayed onto the surface of the aluminum plate with a spray, or chromium phosphate and hydrogen fluoride after the degreasing step. Examples thereof include a chemical conversion treatment step such as a phosphoric acid chromate treatment in which an acid is allowed to act. In recent years, a so-called non-chromium chemical conversion treatment using a zirconium compound, a titanium compound, or the like has come to be used as an environmentally-friendly chemical conversion treatment, which is naturally applicable to the present invention.

In this way, by applying an aqueous or solvent-based carboxyl group-containing acrylic resin paint prepared at an appropriate concentration to the aluminum surface from which an ideal surface roughness shape was obtained, and drying it, An aluminum plate can be obtained. At this time, if the drying temperature is lower than 30 ° C, the volatilization rate of water or solvent is slow, which adversely affects the productivity. If the drying temperature exceeds 300 ° C, energy for maintaining the temperature is wasted. In particular, when a water-soluble acrylic resin is used, it is easy to generate a bumpy liquid film. From the viewpoint of productivity, energy, and bumping prevention, the drying temperature is more preferably 60 ° C. or higher and 200 ° C. or lower. When the drying time is less than 1 second, the water or solvent is not sufficiently volatilized, and when it exceeds 600 seconds, the productivity is adversely affected. From the viewpoint of solvent volatilization and productivity, the drying time is more preferably 10 seconds or more and 60 seconds or less. In addition, there is no restriction | limiting in particular about the application | coating method of an acrylic resin coating material, The method of squeezing with a roll after immersing a board in a solution, the method of apply | coating to a board with a coater roll, the method of spraying on a board with a spray, etc. can be used. Among them, a method using a coater roll is particularly preferable in order to control the adhesion amount of the acrylic resin to be 5 mg / m ² or more and 5000 mg / m ² or less. In order to measure the adhesion amount of the acrylic resin, a reflection infrared absorption spectrum measurement method can be used when the target value of the adhesion amount is about 500 mg / m ² or less, and a gravimetric method can be used when the target value is more.

Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.
As the aluminum material, a JIS5151-H39 alloy plate having a thickness of 0.23 mm was used. The details of the plate manufacturing process and the measurement results of the surface roughness of the plate are as described in Table 1. These plates were subjected to degreasing treatment or phosphoric acid chromate treatment based on the prior art as pretreatment. That is, the surface of the plate was degreased with a commercially available alkaline degreasing agent “Surf Cleaner EC370” (Nihon Paint, concentration 1.0%, temperature 60 ° C.), and commercially available phosphoric acid chromate treatment for some examples. A phosphate chromate film was formed with the agent “Alsurf 408/48” (manufactured by Nippon Paint, concentration 2.0% / 0.4%, temperature 45 ° C.). The amount of the film was adjusted to Cr adhesion amount = 10 mg / m ² .

As the acrylic resin paint for application to the above aluminum material surface, an acrylic resin having the properties shown in Table 2 dissolved in water or an organic solvent (2-butanone) was used. For the acrylic resins in Table 2, A: polyacrylic acid, B: polyacrylic acid, C: polymethacrylic acid ester, D: polyacrylic acid ester, E: polyacrylic acid, F: polyacrylic acid ester were used. The concentration of the acrylic resin paint was 100 g / liter. These solutions were applied with a stainless bar coater so as to have a dry weight shown in Table 3, and dried for 30 seconds in an oven having an atmosphere of 120 ° C. and a wind speed of 15 m / second.
The following evaluation was performed on the samples thus obtained.

[Applying paint]
The sample was painted according to the following procedure.
・ External surface (surface corresponding to the external surface in cap molding described later): Commercially available solvent coating for cap “White Coaching” (containing titanium oxide pigment, polyester resin, coating amount 13g / m ² , baking temperature = 190 After applying ℃, baking time = 600 seconds, commercially available solvent-type paint for cap “Topcoat” (Polyester resin, coating amount 5g / m ² aiming, baking temperature = 180 ° C, baking time = 600 seconds ) Was applied.
・ Inner surface (surface corresponding to inner surface in cap molding described later): Commercially available solvent coating for cap “Topcoat” (Polyester resin, coating amount 5g / m ² aiming, baking temperature = 180 ° C, baking time = 600 seconds).

[Evaluation of adhesion after cap processing]
Apply 50 mg / m ^{2 of} commercially available silicon lubricant on both sides of the above painted sample, and after drawing with cap molding machine (cap diameter = 38 mm, cap height = 18 mm), then perforation・ Screw processing was performed in this order. With respect to the obtained cap, the coating film peeling state of the perforation part, the lower end of the cap and the bead part was visually observed immediately after molding / after retorting (125 ° C. × 30 minutes). The length of the part where the peeling occurred relative to the total length of the perforation part, the lower end of the cap, and the bead part was recorded in% units, and the average value was determined according to the following criteria.
Occurrence of peeling 0% or more and less than 5% Judgment = ◎
Peeling 5% or more and less than 10% Judgment = ○
Peeling 10% or more and less than 25% Judgment = △
Peeling occurrence 25% or more and less than 50% Judgment = ×
Peeling 50% or more Judgment = ××

  As is apparent from Table 3, Examples 1 to 14 satisfy the conditions of the surface roughness and the acrylic resin, which are the requirements of the present invention, and in the cap molding test, showed good results immediately after molding / after retorting. On the other hand, since Comparative Examples 1-11 did not satisfy the requirements of the present invention, the coating film peeled off. Specifically, in Comparative Examples 1 and 2, since Ra is too low, the anchor effect is insufficient and coating film peeling occurs. In Comparative Example 3, since the surface Ra is too high, the coating film is locally thinned, the coating film cannot withstand the processing, and is peeled off. In Comparative Example 4, although Ra is appropriate, Rmr (1.5 μm) is too low. Therefore, the coating film is also locally thinned, and it is not able to withstand processing, resulting in peeling. In Comparative Example 5, Ra is too high and Rmr (1.5 μm) is too low, so that the workability is remarkably lowered despite the effect of the acrylic resin, and the coating film is peeled off. In Comparative Example 6, the acrylic resin is not provided, and the adhesion of the coating film to the aluminum plate is insufficient, and thus the coating film is peeled off. Comparative Example 7 has insufficient adhesion because the carboxyl group of the acrylic resin is insufficient, and Comparative Example 8 has an effect on molding itself because the molecular weight of the acrylic resin is too low, but peeling after retorting Is remarkable. In Comparative Example 9, since the molecular weight of the acrylic resin is too high, the resin is cracked during molding, and the coating film is peeled off. Since the comparative example 10 has too few application amounts of an acrylic resin, peeling of a coating film cannot be suppressed. Since Comparative Example 11 has too much acrylic resin, stress is accumulated in the resin layer at the time of molding, which induces peeling of the coating film.

Claims (2)

Contains one or more carboxyl groups per weight average molecular weight of 500 on the surface of an aluminum material having an arithmetic average height Ra of 0.1 μm or more and 0.5 μm or less and a load length ratio Rmr (1.5 μm) of 50% or more The resin adhesion after molding processing is characterized in that it is made of an acrylic resin having a weight average molecular weight of 1,000 to 1,000,000 and a resin coating film having a dry weight of 5 mg / m ^{2 to} 5000 mg / m ² is formed. Resin-coated aluminum plate with excellent properties. It is an aluminum plate manufactured by hot rolling or cold rolling, and the surface shape is subjected to final rolling with a roll having a maximum height Rz of 1.0 μm or more and 5.0 μm or less, and then the surface shape is arithmetic After performing the straightening step with a roll having an average height Ra of 0.01 μm or more and 0.5 μm or less, the weight average molecular weight of 500 contains one or more carboxyl groups and the weight average molecular weight of 1,000 to 1,000,000. Applying an aqueous or solvent-based acrylic resin coating to a dry weight of 5 mg / m ^{2 to} 5000 mg / m ² and drying in an atmosphere of 30 ° C. to 300 ° C. for 1 second to 600 seconds. The method for producing a resin-coated aluminum plate according to claim 1, which is excellent in resin adhesion after molding.