JPH03268938A - Aluminum material for can excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To form an org. film having excellent corrosion resistance by making constant the content and glass transition temp. of the phenol resin in paint applied to aluminum. CONSTITUTION:A phenol resin is contained in a water-solouble epoxy resin being a matrix resin in an amount of 2wt.% or more to make it possible to impart hydrophobicity to the film of the water-soluble epoxy resin in a degree exceeding the hydrophilicity of the film originally possessed by the water-soluble epoxy resin being the matrix resin and the water resistance such as moisture content or water-permeability of the film is markedly enhanced. The content of the phenol resin in the water-soluble epoxy resin being the matrix resin is set to 2-25wt.%. Further, by setting the glass transition temp. of the film to 90 deg.C or higher, excessive corrosion resistance is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aluminum material for cans having excellent corrosion resistance, and more specifically, to an aluminum material for cans having an excellent corrosion resistance. This invention relates to an aluminum material for cans that has excellent corrosion resistance.

C. Prior Art Conventionally, organic solvent-based paints have been used by means such as roll coating to coat aluminum cans, which are coated with organic coatings with excellent corrosion resistance. Because of this, there are problems such as environmental pollution in handling and baking, and production efficiency in response to the ever-increasing demand for plate materials.

Nowadays, instead of organic solvent-based resins, organic coatings are being applied using water-soluble resins, mainly self-emulsifying evoquino resins. However, since the coating film of water-soluble resin contains many hydrophilic functional groups such as carpoyl groups and hydroxyl groups that water-soluble resin originally has, the water content and water resistance such as water permeability of the coating film is It is inferior to solvent-based resins, and it is difficult to achieve high corrosion resistance.

Therefore, in order for the aluminum material for cans coated with water-soluble resin to have high corrosion resistance, it is necessary to increase the degree of curing of the matrix resin by increasing the curing temperature and prolonging the curing time, and to Efforts have been made to make the film thicker and the coating film denser, but this is still not sufficient.

Furthermore, among aluminum materials for cans, pre-coated materials for can ends are particularly required to have good adhesion in order to be processed into ends. This pre-coating is a method of coating before the coil is formed to the same size at the rolling manufacturer, rather than after the can is formed.There is an increasing demand for this from rolling manufacturers rather than can manufacturers, and since the can is formed after coating. This requires even greater adhesion of the paint.

However, the adhesion of water-soluble resin coatings is generally inferior to that of organic solvent-based resin coatings, so surface treatments such as chromate treatment are performed to improve adhesion. Disposal of waste liquid becomes a major problem.

[Problems to be Solved by the Invention] In view of the various problems of conventional aluminum materials for cans with good corrosion resistance as described above, the present inventor has conducted intensive research, and as a result, the surface of aluminum materials for cans has been improved. By carefully selecting the type of coating to coat the cans, they developed an aluminum material for cans that has excellent coating adhesion and corrosion resistance.

[Means for Solving the Problems] The features of the aluminum material for cans having excellent corrosion resistance according to the present invention are as follows:
The coating film contains ~25% by volume of phenolic resin and has a glass transition temperature of at least 90°C.

The aluminum material for cans having excellent corrosion resistance according to the present invention will be described in detail below.

First, the materials used in the aluminum material for cans having excellent corrosion resistance according to the present invention will be explained.

As the water-soluble epoxy resin, it is preferable to use an epoxy resin grafted with a compound containing a carboxylic acid monomer, which is dispersed in water containing a basic solvent and a water-soluble organic solvent. It is preferable to use a water-dispersible anionic epoxy resin. In this case, the basic solvent used is preferably amines, and the water-soluble organic solvent includes alcohols, ethers, ketones, esters, and the like.

The phenol resins are those synthesized from a 1.4-functional phenol compound (1), a 3-functional phenol compound (II), a 2-functional phenol compound, etc., and formaldehyde under an alkali catalyst. In particular, an initial condensate using a tetra- or tri-functional phenol compound is good. In this case, the alkali catalyst can be a strong base catalyst such as sodium hydroxide or potassium hydroxide, or a weak base catalyst such as sodium carbonate or aqueous ammonia, and these catalysts can be used alone or in combination. .

And, as a method of adjusting the glass transition temperature, ■Curing conditions: Adjustment of curing temperature and curing time.

■Resin composition - For example, as a compound containing a carboxylic acid monomer to be grafted onto Epoquine resin, a component such as styrene which originally has a high glass transition temperature is used.

■Molecular weight: For example, lower the molecular weight without changing the molecular structure and increase the functional series (crosslinking points) per molecular weight.

Specific examples include.

Next, the content and glass transition temperature of the phenol resin relative to the water-soluble epoxy resin of the matrix resin used in the aluminum material for cans having excellent corrosion resistance according to the present invention will be explained.

With a coating film made only of water-soluble epoxy resin as a matrix resin, even if the glass transition temperature is adjusted to a range of 90°C or higher, there is no improvement in the corrosion resistance of the aluminum material for cans provided with the organic coating. If the content of phenolic resin was less than 2vt%, no improvement in corrosion resistance could be expected;
When the phenol resin was contained in an amount of 2 wt % or more, the corrosion resistance of the aluminum material for cans provided with the organic coating was significantly improved.

In this way, by making the content of phenol resin 2vt% or more with respect to the water-soluble epoxy resin that is the matrix resin, hydrophilic functionalities such as carboquinol groups that the water-soluble epoxy resin that is the matrix resin originally has It is possible to impart hydrophobicity to the coating film that exceeds the hydrophilicity caused by the large amount of groups contained in the coating film, and improves water resistance such as water content and water permeability of the coating film. This is because the results are significantly improved. At the same time, adhesion is also improved. Therefore, it can be sufficiently used for cans, especially for can ends, and even if corrosion occurs, it can suppress the progression from pitting corrosion to corrosion on the paint film.

Furthermore, if the phenolic resin is contained in an amount exceeding 25 vt% with respect to the water-soluble Evoquin resin, the water-soluble epoxy resin and the phenol resin will separate, and the water-soluble epoxy resin will coagulate, making it impossible to implement the method. Therefore, the amount of phenol resin contained in the water-soluble epochene resin, which is the matrix resin, is 2 to 25 wt%.

Furthermore, the glass transition temperature needs to be 90°C or higher; if it is lower than 90°C, sufficient water resistance cannot be obtained even if the phenolic resin content is in the range of 2 to 25 vt%, or Adhesion cannot be obtained, and therefore sufficient corrosion resistance cannot be obtained. The upper limit of the dislocation temperature is preferably set at 150° C. Above this temperature, the coating film tends to oxidize and deteriorate. Therefore, the glass transition temperature is set to 90°C or higher.

The coating film described above is preferably applied by an electrodeposition coating method.

The coating film coated on the surface of the highly corrosion-resistant aluminum material for cans according to the present invention by electrodeposition coating includes colorants, paint additives, erasing agents, brightening agents, rubber elastic agents, etc. other than corrosion-resistant agents. By mixing aniono-type compositions having the following characteristics, any coating film can be produced.

Materials that can be used for the aluminum material for cans having excellent corrosion resistance according to the present invention include aluminum materials that are not pretreated, and aluminum materials that have been subjected to phosphate treatment, chromate treatment, and alumite treatment.

[Example] An example of the aluminum material for cans having excellent corrosion resistance according to the present invention will be described.

Example 2) Method for preparing paint A dispersion of water-soluble evoquino resin was distilled under reduced pressure to reduce the water-soluble solvent to 2vi% or less, and ion-exchanged water was added dropwise with stirring to dilute the solid content to 10*t%.

Next, a phenol resin (ammoniaresol resin) was dissolved in 100 parts of butylcarpitol, and the solution was slowly added dropwise into the stirred dispersion of water-soluble epoxy resin over 2 hours, and then the pH was adjusted with trimethylethanolamine.
was adjusted to 8 and used as a paint for aluminum materials for organic coated cans.

2) Sample Preparation Method An aluminum material of f20.5+1111, which had been subjected to normal alkali degreasing, was coated with the paint of 1) above to a thickness of 5 μm lead by electrodeposition. In this case, the paint temperature is 30℃
The curing conditions for the coating film are as shown in Table 1.

3) Corrosion test conditions The samples were immersed in a 1% NaCl, pH 3, 40°C aqueous solution for two weeks to determine whether corrosion occurred.

-1) Method for measuring glass transition temperature Similar to the sample preparation method described above, a 25 μm aluminum foil was coated with a 10 μm thick VI. This was immersed in dilute hydrochloric acid to dissolve the aluminum foil and form a thin film for measurement. For this measurement, viscoelasticity was measured using DMS (tensile mode, 2 Hz) manufactured by Seiko Electronics Industries, Ltd.

Table 1 shows the amount of phenolic resin, curing conditions, glass transition temperature and corrosion resistance.

For example, after being immersed in boiling water for 1 hour, a 1 mm pattern is made on the substrate, processed with Erichsen (usually 6 questions on a steel plate), and a tape peeling test is performed on L pieces. In the secondary adhesion test,
No peeling is observed.

As a result of testing Examples 1 to 10 of aluminum materials for cans with excellent corrosion resistance according to the present invention shown in Table 1 under these conditions,
No peeling was observed, and the adhesion of the coating film was good.

As is clear from Table 1, it can be seen that the aluminum material for cans having excellent corrosion resistance according to the present invention exhibits better corrosion resistance than the comparative example.

"Effects of the Invention" As explained above, the aluminum material for cans having excellent corrosion resistance according to the present invention can be obtained by keeping the content of phenolic resin and glass transition temperature constant in the paint coated on aluminum. , resulting in an organic coating with excellent corrosion resistance,
It is an extremely useful aluminum material for cans.

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Claims (1)

[Claims] 2 to 2 for the water-soluble epoxy resin of the matrix resin.
An aluminum material for cans having excellent corrosion resistance, characterized in that it contains 25 wt% of phenolic resin and is coated with a coating film having a glass transition temperature of at least 90°C or higher.