JP5192733B2 - Can processing for cans - Google Patents

Description

  The present invention relates to a ground treatment method for a metal can such as iron, zinc, and aluminum, and more particularly to a ground surface treatment method for an aluminum can.

  Conventionally, chromate chemical conversion treatment agents are known as chemical conversion treatment agents used for surface treatment of aluminum-based metals. The chromate conversion coating formed by the chromate conversion treatment agent has excellent corrosion resistance and adhesion after application of various paints, so its application covers a wide range of building materials, home appliances, fin materials, car evaporators, beverage cans, etc. Patent Document 1). However, since the chromate chemical conversion treatment agent uses harmful chromium metal, it is difficult to treat the waste liquid. For this reason, environment-friendly non-chromium metal surface treatment compositions are being developed in recent years.

For example, Patent Document 2 discloses a metal including at least one vanadium compound (A) and at least one metal selected from the group consisting of cobalt, nickel, zinc, magnesium, aluminum, calcium, strontium, barium, and lithium. Sheet coil and molding using metal as a raw material by treating the surface of the metal material with a metal surface treatment agent containing the compound (B) and further containing a water-soluble polymer and / or an aqueous emulsion resin Metal surface treatment method that gives excellent corrosion resistance and alkali resistance to the surface of the product, and further has excellent interlaminar adhesion with a resin layer and metal material formed by painting or laminating and forming a film containing no chromium It is disclosed.
JP-A-5-125555 JP 2004-183015 A

  However, the non-chromium metal surface treatment composition disclosed in Patent Document 2 cannot be said to have sufficient corrosion resistance after laminating, and there is a problem that aluminum sludge generation when applied to aluminum cannot be suppressed. It was.

  The present invention has been made in view of the above problems, and its purpose is to provide high adhesion to a laminate film and the like as compared with conventional chemical conversion treatment methods, and to generate aluminum sludge. An object of the present invention is to provide a non-chromium base treatment method for cans that can be suppressed.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, by treating the surface of the metal with a metal surface treatment composition containing a predetermined amount of fluorine ions, zirconium ions, aluminum ions, and polyitaconic acid, an adhesive layer is formed on the treated surface, The present inventors have found that the above problems can be solved and have completed the present invention. More specifically, the present invention provides the following.

  (1) A can surface treatment method comprising a step of forming a chemical conversion film by treating a metal surface with a metal surface treatment composition and then forming an adhesive layer on the chemical conversion film, the metal surface treatment A metal surface treatment having a pH of 2 or more and 5 or less, comprising effective fluorine ions of 1 ppm to 1000 ppm, zirconium ions of 10 ppm to 10,000 ppm, aluminum ions of 10 ppm to 2000 ppm, and polyitaconic acid of 50 ppm to 10,000 ppm. A method for treating a base for a can as a composition.

  (2) The base treatment method for a can according to (1), wherein the adhesive layer is formed by treating with a post-treatment agent containing a cationic group-containing resin and an aqueous resin.

  (3) The base treatment method for a can according to (2), wherein the cationic group-containing resin has 5.0 meq / g or more of a cationic group in a resin solid content.

  The “cationic group” in the present invention specifically means at least one selected from the group consisting of an amino group, an imino group, a guanidine group, and a biguanide group.

  (4) The can base treatment method according to (2) or (3), wherein the cationic group-containing resin is polyallylamine and / or polylysine.

  (5) The can according to any one of (2) to (4), wherein the aqueous resin is a resin including at least one selected from the group consisting of an acrylic resin, a urethane resin, a polyester resin, a phenol resin, and an epoxy resin. Ground surface treatment method.

  (6) The base treatment method for a can according to (5), wherein the acrylic resin is an oxazoline group-containing acrylic resin containing at least two oxazoline groups in one molecule.

  (7) The can base treatment method according to any one of (1) to (6), wherein the metal is an aluminum-based metal.

(8) zirconium containing 2 mg / ^{m 2} or more 100 mg / ^{m 2} or less in terms of metal element, and containing 0.5 mg / ^{m 2} or more 20 mg / ^{m 2} or less in the organic carbon content in terms derived from the polyitaconic acid polyitaconic Obtained by the base treatment method for cans according to any one of (1) to (7), having a chemical conversion film and an adhesive layer having a dry film amount in terms of total organic carbon amount of 2 mg / m ² or more and 200 mg / m ² or less. Can base.

  ADVANTAGE OF THE INVENTION According to this invention, compared with the conventional chemical conversion treatment method, the non-chromium base treatment method for cans which can give high adhesiveness with respect to a laminate film etc. can be provided.

  Hereinafter, embodiments of the present invention will be described.

<Metal surface treatment composition>
The base treatment method for a can according to the present embodiment includes a step of forming an adhesive layer on the treated surface after surface-treating the metal with the metal surface treatment composition. The metal surface treatment composition used in the present embodiment contains a predetermined amount of effective fluorine ions, zirconium ions, aluminum ions, and polyitaconic acid.

  When the surface of an aluminum material is treated by the can base treatment method according to the present embodiment, aluminum is dissolved by fluorine ions, and as a result, the pH rises, so that a zirconium compound is precipitated. At this time, it is considered that both the aluminum compound and polyitaconic acid are deposited to form a film.

  Thus, since the chemical conversion film formed with a zirconium compound, an aluminum compound, and polyitaconic acid has the carboxyl group based on polyitaconic acid, it can express the outstanding adhesiveness. In addition, when polyitaconic acid interacts with aluminum ions, generation of sludge can be significantly suppressed.

  The method for producing the metal surface treatment composition is not particularly limited, and can be obtained by adjusting pH after blending effective fluorine ions, zirconium ions, aluminum ions, and polyitaconic acid as described later.

[Effective fluorine ion]
The effective fluorine ion in the metal surface treatment composition is 1 ppm or more and 1000 ppm or less, preferably 5 ppm or more and 100 ppm or less. Here, “effective fluorine ion” means fluorine ion in a free state in the treatment bath, and the effective fluorine ion concentration is determined by measuring the treatment bath with an apparatus having a fluorine ion electrode. When the effective fluorine ion concentration is less than 1 ppm, etching is insufficient and a sufficient amount of zirconium film cannot be obtained, so that adhesion and corrosion resistance are lowered. When the amount is more than 1000 ppm, the etching is excessive and the zirconium film is not deposited, and the adhesion and corrosion resistance are lowered. Examples of the fluorine ion source include hydrofluoric acid, ammonium fluoride, ammonium hydrofluoride, sodium fluoride, sodium hydrofluoride and the like in addition to the fluorinated zirconate compound. The effective fluorine ion concentration can be adjusted.

[Zirconium ion]
The content of zirconium ions in the metal surface treatment composition is 10 ppm to 10000 ppm, preferably 50 ppm to 1000 ppm. When the zirconium ion content is less than 10 ppm, the zirconium ion content in the chemical conversion film is small, so that the adhesion and corrosion resistance are lowered. If it exceeds 10000 ppm, an increase in performance cannot be expected, which is disadvantageous in terms of cost. Examples of the zirconium ion source include fluorozirconic acid or its lithium, sodium, potassium, ammonium salt, zirconium fluoride, and the like. It can also be obtained by dissolving a zirconium compound such as zirconium oxide in an aqueous fluoride solution such as hydrofluoric acid.

[Aluminum ion]
The content of aluminum ions in the metal surface treatment composition is 10 ppm or more and 2000 ppm or less, preferably 50 ppm or more and 1000 ppm or less. When the content of aluminum ions is less than 10 ppm, the amount of polyitaconic acid deposited decreases and sufficient adhesion cannot be obtained. When it is more than 2000 ppm, the chemical conversion reaction is inhibited and sludge is generated in the chemical conversion bath. Examples of the aluminum ion source include aluminum hydroxide, aluminum fluoride, aluminum oxide, aluminum sulfate, aluminum nitrate, aluminum silicate, aluminate such as sodium aluminate, and fluoroaluminum such as sodium fluoroaluminate.

[Polyitaconic acid]
The content of polyitaconic acid in the metal surface treatment composition is 50 ppm to 10000 ppm, preferably 100 ppm to 1000 ppm. When the content of polyitaconic acid is less than 50 ppm, the adhesiveness is lowered because the content of polyitaconic acid in the chemical conversion film is small. When the amount is more than 10,000 ppm, the improvement in performance cannot be expected, which is disadvantageous in terms of cost.

  Specific examples of preferable polyitaconic acid include polyitaconic acid, alkali metal salt and / or ammonium salt of polyitaconic acid. Furthermore, if necessary, a polyitaconic acid-polymaleic acid copolymer having an itaconic acid segment, a polyitaconic acid copolymer such as a polyitaconic acid- (meth) acrylic acid copolymer, a polyitaconic acid-sulfonic acid copolymer, and the like, and These alkali metal salts and / or ammonium salts can also be used. The molecular weight of the polyitaconic acid is, for example, 260 to 1000000, and preferably 1000 to 70000.

  When the polyitaconic acid is a copolymer, the content of the itaconic acid segment in the copolymer is regarded as an active ingredient. For example, when 200 ppm of polyitaconic acid-polymaleic acid copolymer is contained and the mass ratio of itaconic acid to maleic acid in this copolymer is 1/1, the amount of polyitaconic acid is 200 ppm × 1/2. = 100 ppm.

  When the polyitaconic acid is a copolymer, the content of the itaconic acid segment in the copolymer is preferably 10% by mass or more, and more preferably 50% by mass or more.

[PH]
The pH of the metal surface treatment composition is 2 or more and 5 or less, preferably 3 or more and 4.5 or less. When the pH is less than 2, the etching is excessive, and when the pH is more than 5, the etching is insufficient. Adjustment of pH is performed by adding nitric acid when pH is high, and adding ammonia, sodium hydroxide, or potassium hydroxide when pH is low.

[Additive]
The metal surface treatment composition may be obtained by adding a predetermined amount of various additives within a range not impairing the effects of the present invention. For example, metal ions such as manganese, zinc, calcium, iron, magnesium, molybdenum, vanadium, titanium, silicon; surfactants such as anionic surfactant and nonionic surfactant; citric acid, gluconic acid, malonic acid, succinic acid Other chelating agents such as tartaric acid and phosphonic acid may be added.

[Processing method]
In the can base treatment method according to the present embodiment, the target can material preferably contains an aluminum-based metal from the viewpoint of easily obtaining the effects of the present invention. The aluminum metal means aluminum, an aluminum alloy, and a mixture thereof. It does not specifically limit as a method to apply a metal surface treatment composition, For example, the method by spraying treatment, immersion treatment, etc. is mentioned. You may apply a metal surface treatment composition, after performing a degreasing process and an etching process as needed.

[Chemical conversion film]
The above chemical conversion coating formed by the metal surface treatment composition, it is preferable that the zirconium containing terms of metal elements 2 mg / m ² or more 100 mg / m ² or less. More preferably, it is 10 mg / m ² or more and 25 mg / m ² or less. If it is less than 2 mg / m ² , appropriate corrosion resistance cannot be obtained, and even if it exceeds 100 mg / m ² , adhesion and corrosion resistance are not improved accordingly, resulting in high costs. The amount of polyitaconic acid contained in the chemical conversion film is preferably an organic carbon content in terms derived from the polyitaconic or less 0.5 mg / ^{m 2} or more 20 mg / ^{m 2.} More preferably, it is 1 mg / m ² or more and 10 mg / m ² or less. If it is less than 0.5 mg / m ² , appropriate adhesion cannot be obtained, and if it exceeds 20 mg / m ² , adhesion and corrosion resistance are not improved accordingly, resulting in high costs.

<Post-treatment agent>
In the base treatment method for cans according to this embodiment, after the treatment with the metal surface treatment composition is performed, an adhesive layer is formed using a post-treatment agent. The post-treatment agent includes a cationic group-containing resin and an aqueous resin, and the adhesive layer formed using the post-treatment agent has high adhesion with the chemical conversion film obtained by the treatment with the metal surface treatment composition.

[Cationic group-containing resin]
The cationic group-containing resin contained in the post-treatment agent has a cationic group in the resin solid content of 5.0 meq / g or more, preferably 7.0 meq / g or more. When the cationic group is less than 5.0 meq / g, the adhesion effect is weak and the adhesion is lowered. The preferable content of the cationic group-containing resin is 50 ppm or more and 8000 ppm or less. When the content of the cationic group-containing resin is less than 50 ppm, the adhesiveness is lowered because the content of the cationic group-containing resin is not sufficient. When it is more than 8000 ppm, the film thickness becomes thick and the adhesiveness decreases. Specific examples of the cationic group-containing resin include polyallylamine, polylysine, polyvinylamine, and polyethyleneimine. Among these, polyallylamine and / or polylysine having a primary amino group are preferably used.

[Aqueous resin]
The aqueous resin contained in the post-treatment agent is a resin including at least one selected from the group consisting of an acrylic resin, a urethane resin, a polyester resin, a phenol resin, and an epoxy resin. Among these, the acrylic resin is preferably an oxazoline group-containing acrylic resin containing at least two oxazoline groups in one resin molecule. The oxazoline group contained in the oxazoline group-containing acrylic resin can react with an acidic group such as a carboxyl group or a phenolic hydroxyl group to form a crosslinked structure. As the oxazoline group-containing acrylic resin, commercially available products can be used. For example, “Epocross WS500” (trade name, manufactured by Nippon Shokubai Co., Ltd.), “Epocross WS700” (trade name, manufactured by Nippon Shokubai Co., Ltd.), and “NK” Linker FX "(trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.) can be used. The oxazoline value of the oxazoline group-containing resin is preferably 100 to 240. Outside these ranges, the intended effect may not be obtained. A preferable content of the aqueous resin is 30 ppm or more and 4000 ppm or less. When the preferable content of the aqueous resin is less than 30 ppm, the adhesiveness is lowered because the content of the aqueous resin is not sufficient. When the content is more than 4000 ppm, the film thickness is increased and the adhesion is lowered.

[Dry film amount]
Dry film weight of the total organic carbon in terms of the adhesive layer formed by the post-treatment agent including the above-mentioned cationic-group containing resin and aqueous resin is preferably 2 mg / m ² or more 200 mg / m ² or less. When the dry film amount in terms of the total organic carbon amount is less than 2 mg / m ² , the amount of resin (functional group amount) is small, so that the adhesion is lowered. When it is more than 200 mg / m ² , the film thickness becomes thick and the adhesiveness decreases. Here, the “dry film amount in terms of the total organic carbon amount” means the total organic carbon amount contained in the dry film. The total organic carbon amount can be measured using a commercially available total organic carbon automatic analyzer or the like.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited only to these Examples.

[Metal surface treatment]
An aluminum alloy (5182 material) was prepared as an aluminum-based metal, and degreasing was performed by immersing in a 2% aqueous solution (65 ° C.) of a degreasing agent “SCL420N-2” (trade name) manufactured by Nippon Paint Co., Ltd. for 7 seconds. . After degreasing, it was washed with water and then immersed in a 2% aqueous sulfuric acid solution (50 ° C.) for 3 seconds for acid cleaning. After the acid cleaning and water washing, each metal surface treatment composition shown in Examples and Comparative Examples was sprayed. Then, after washing with water and dehydrating with a roll squeeze, it was dried under conditions of 80 ° C. × 60 seconds.

<Example 1>
Fluorozirconic acid, aluminum hydroxide, hydrofluoric acid, and polyitaconic acid (“PIA-728”, trade name, molecular weight of about 3000) manufactured by Iwata Chemical Industries, Ltd. as an aluminum ion scavenger, A metal surface treatment composition was obtained by blending aluminum ions at 10 ppm, effective fluorine ions at 1 ppm, and polyitaconic acid at 200 ppm, and adjusting the pH to 3.5 by adding ammonia.

<Examples 2 to 17>
In the same manner as in Example 1, Examples 2 to 17 were obtained by changing the blending amounts of the respective components as shown in Table 1.

<Comparative Example 1>
Comparative Example 1 was prepared by mixing and preparing in the same manner as in Example 1 except that none of zirconium ions, aluminum ions, and effective fluorine ions was added.

<Comparative example 2>
Comparative Example 2 was prepared and prepared in the same manner as in Example 1 except that no polyitaconic acid was added.

<Comparative Example 3>
A comparative example 3 was prepared by mixing and preparing in the same manner as in Example 1 except that aluminum ions were not blended.

<Comparative example 4>
A comparative example 4 was prepared and prepared in the same manner as in Example 1 except that 200 ppm of phenol resin (manufactured by Showa Polymer Co., Ltd., “Shonol BRL-141B”, trade name) was blended in place of polyitaconic acid.

<Comparative Example 5>
Comparative Example 5 was prepared and prepared in the same manner as in Example 1 except that 200 ppm of polyacrylic acid (manufactured by Nippon Pure Chemical Co., Ltd., “Julimer AC10L”, trade name) was used instead of polyitaconic acid.

<Comparative Example 6>
Comparative Example 6 was prepared and prepared in the same manner as in Example 1 except that 200 ppm of polymethacrylic acid (manufactured by Nippon Pure Chemical Co., Ltd., “AC30H”, trade name) was used instead of polyitaconic acid.

<Comparative Example 7>
Comparative Example 7 was prepared and prepared in the same manner as in Example 1 except that 200 ppm of tannic acid (manufactured by Sumitomo Dainippon Pharma Co., Ltd., “N tannic acid”, trade name) was used instead of polyitaconic acid.

<Comparative Example 8>
The chromium-based surface treatment composition phosphoric acid chromate (manufactured by Nippon Paint Co., Ltd., “Alsurf 407/47”, trade name) was used as Comparative Example 8.

<Sludge property>
After treating 0.1 m ² of aluminum alloy (5182 material) per liter of the metal surface treatment composition, the turbidity in the metal surface treatment composition was visually observed. The evaluation criteria were as follows. The results are shown in Tables 1 and 2.
○: No turbidity.
X: There is turbidity.

[Evaluation]
<Measurement of content in chemical conversion film>
The amount of zirconium deposited on the prepared chemical conversion film was measured using a fluorescent X-ray analyzer (manufactured by Shimadzu Corporation, “XRF1700”, trade name). The amount of aluminum ion scavenger adhering was measured as the amount of organic carbon derived from the aluminum ion scavenger using a total organic carbon measuring device ("RC-412", trade name, manufactured by LECO). The respective measured amounts are shown in Tables 1 and 2.

[Post-processing]
<Example 18>
As shown in Table 3, for the metal treated with the metal surface treatment composition prepared in Example 1, polyallylamine (manufactured by Nitto Boseki Co., “PAA-10C”, trade name, cationic group content 17.5 meq / g). ) And a post-treatment agent containing 300 ppm of a phenol resin (manufactured by Showa Polymer Co., Ltd., “BRL141B”, trade name) with a bar coater so that the dry film amount is 20 mg / m ^2, and then 80 ° C. × Dry for 60 seconds to obtain a can base. The amount of dry film in terms of total organic carbon was measured using a total organic carbon measuring device (LECO, “RC-412”, trade name).

<Examples 19 to 34>
Can base, in the same manner as in Example 18, except that the metal treated with the metal surface treatment composition was changed to those obtained by treating with the metal surface treatment composition prepared in Examples 2 to 17, respectively. Got.

<Examples 35 and 36>
By using the metal surface treatment composition prepared in Example 3 in place of the metal surface treatment composition prepared in Example 1, and adding partially concentrated hydrochloric acid to polyallylamine to partially block the cationic groups contained therein. A can base was obtained in the same manner as in Example 18 except that the cationic group contents were 5.0 meq / g and 4.0 meq / g, respectively.

<Example 37>
Instead of the metal surface treatment composition prepared in Example 1, the metal surface treatment composition prepared in Example 3 was used, and instead of phenol resin, polyacrylic acid (Johnson Polymer Co., Ltd., “John Crill 70”, trade name) Example 37 was treated in the same manner as in Example 18 except that the above was used.

<Example 38>
Instead of the metal surface treatment composition prepared in Example 1, the metal surface treatment composition prepared in Example 3 was used, and polyurethane (“SF820”, trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used instead of the phenol resin. Example 38 was carried out in the same manner as Example 18 except that it was used.

<Example 39>
In place of the metal surface treatment composition prepared in Example 1, the metal surface treatment composition prepared in Example 3 was used, and polyester (Toyobo Co., Ltd., “Vainal MD-1480”, trade name) was used instead of the phenol resin. Example 39 was carried out in the same manner as in Example 18 except that was used.

<Example 40>
The metal surface treatment composition prepared in Example 3 was used instead of the metal surface treatment composition prepared in Example 1, and an epoxy resin (“Hitaroid 7800-J21” manufactured by Hitachi Chemical Co., Ltd. ) Was used in the same manner as in Example 18 except that was used as Example 40.

<Example 41>
In place of the metal surface treatment composition prepared in Example 1, the metal surface treatment composition prepared in Example 3 was used. Instead of polyallylamine, polylysine (“polylysine” manufactured by Chisso Corporation, trade name, cationic group content) Example 41 was treated in the same manner as in Example 18 except that 7.8 meq / g) was used.

<Example 42>
In place of the metal surface treatment composition prepared in Example 1, the metal surface treatment composition prepared in Example 3 was used. Instead of polyallylamine, polylysine (“polylysine” manufactured by Chisso Corporation, trade name, cationic group content) 7.8 meq / g) was treated in the same manner as in Example 18 except that polyacrylic acid (manufactured by Johnson Polymer Co., Ltd., “John Crill 70”, trade name) was used instead of phenol resin. .

<Example 43>
The metal surface treatment composition prepared in Example 3 was used instead of the metal surface treatment composition prepared in Example 1, and an oxazoline group-containing acrylic resin (“Epocross WS700” manufactured by Nippon Shokubai Co., Ltd. Example 43 was treated in the same manner as in Example 18 except that the name was used.

<Example 44>
Using the metal surface treatment composition prepared in Example 3 instead of the metal surface treatment composition prepared in Example 1, the amount of polyallylamine and the amount of phenol resin were changed to 300 ppm, and an oxazoline group-containing acrylic resin (Japan) Example 44 was prepared by treating the catalyst in the same manner as in Example 18 except that 400 ppm of “Epocross WS700” (trade name) manufactured by Catalyst Co., Ltd. was added.

<Examples 45 to 48>
The composition and composition ratio of the post-treatment agent in Example 18 were the same, only the concentration was changed, and the dry film amount in terms of the total organic carbon amount of the adhesive layer was 2 mg / m ² , 50 mg / m ² , 100 mg / m ^2. , And 200 mg / m ² were changed to Examples 43 to 48, respectively.

<Comparative Example 9>
The metal treated with the metal surface treatment composition prepared in Example 3 was used as Comparative Example 9 without any post-treatment process.

<Comparative Example 10>
Comparative Example 10 was treated in the same manner as in Example 18 except that the metal was degreased and washed, and the metal was treated without being treated with the metal surface treatment composition and changed to a dried metal.

<Comparative Examples 11-16>
As shown in Table 4, for each metal treated with various metal surface treatment compositions prepared in Comparative Examples 1-3, 5, 6, and 8, various post-treatment agents were applied and dried in the same manner as in Example 18. To Comparative Examples 11-16.

<Comparative Examples 17-21>
As shown in Table 4, for each metal treated with the various metal surface treatment compositions prepared in Example 3, various post-treatment agents consisting only of an aqueous resin were applied and dried in the same manner as in Example 18 as a comparative example. 17-21.

<Adhesion: T peel test>
A PET film was sandwiched between two test pieces (5 mm × 15 mm) of each metal obtained in Examples and Comparative Examples, and thermocompression bonded with a hot press (240 ° C. × 5 seconds, 10 kgf / cm ² ). Next, each test piece was cut to a width of 5 mm and subjected to a high-temperature and high-humidity test at 125 ° C. for 30 minutes, and then peel strength was measured with a Tensilon tester “UTM-II-20R” manufactured by Orientec (peeling speed) : 40 mm / min). The laminate adhesion was evaluated based on the tensile strength (kgf / 5 mm) obtained by the measurement. The evaluation criteria were as follows. The results are shown in Tables 3 and 4.
A: Tensile strength of 1.5 or more.
○: Tensile strength of 1.0 or more and less than 1.5.
Δ: Tensile strength of 0.5 or more and less than 1.0.
X: Tensile strength is less than 0.5.

  As shown in the table, there was no problem with the sludge property of this example. Moreover, it was confirmed that the adhesiveness of the laminate film is better than Comparative Examples 9 to 15 and Comparative Examples 17 to 21 and superior to Comparative Example 16 using phosphoric acid chromate.

Claims (6)

A can base treatment method comprising the steps of: treating a surface of an aluminum-based metal with a metal surface treatment composition to form a chemical conversion film; washing the chemical conversion film with water; and then forming an adhesive layer on the chemical conversion film. There,
The metal surface treatment composition has an effective fluorine ion of 1 ppm or more and 1000 ppm or less, a zirconium ion of 10 ppm or more and 10000 ppm or less, an aluminum ion of 10 ppm or more and 2000 ppm or less, and a pH of 2 or more and 5 or less containing 50 ppm or more and 10,000 ppm or less of polyitaconic acid. A metal surface treatment composition of
The conversion coating, zirconium containing 2 mg / ^{m 2} or more 100 mg / ^{m 2} or less in terms of metal element, and an organic carbon content in terms derived from the polyitaconic acid polyitaconic 0.5 mg / ^{m 2} or more 20 mg / ^{m 2} Containing
A base treatment method for a can, which is formed by treating the adhesive layer with a post-treatment agent containing a cationic group-containing resin and an aqueous resin.   The can base treatment method according to claim 1, wherein the cationic group-containing resin has a cationic group of 5.0 meq / g or more in a resin solid content.   3. The can surface treatment method according to claim 1, wherein the cationic group-containing resin is polyallylamine and / or polylysine.   The method for treating a ground for cans according to any one of claims 1 to 3, wherein the aqueous resin is a resin containing at least one selected from the group consisting of an acrylic resin, a urethane resin, a polyester resin, a phenol resin, and an epoxy resin.   The method for ground treatment of a can according to claim 4, wherein the acrylic resin is an oxazoline group-containing acrylic resin containing at least two oxazoline groups in one molecule. Zirconium containing 2 mg / ^{m 2} or more 100 mg / ^{m 2} or less in terms of metal elements, and contains 0.5 mg / ^{m 2} or more 20 mg / ^{m 2} or less in the organic carbon content in terms derived from the polyitaconic acid polyitaconic conversion coating The can base obtained by the can ground treatment method according to any one of claims 1 to 5 , comprising an adhesive layer having a dry film amount in terms of total organic carbon amount of 2 mg / m ² or more and 200 mg / m ² or less.