JPH09240672A - Surface-treated tab material excellent in resistance to hot-water treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify chemical treatment process of a surface-treated tab material to be attached on the end of a can, by a method wherein a chromate coat containing chromium (III) compound and organic polymer compound is formed on a side or both sides of an Al or Al alloy plate and a coat of water-base paint is formed on the chromate coat. SOLUTION: A surface-treated tab material to be attached on the end of a beer can, etc., is made of Al or Al alloy plate, and a chromate coat containing chromium (III) compound and organic polymer compound is formed on a side or both side of the Al plate and a water-base paint coat is formed on the chromate coat. The coating weight of the chromate coat is designated within a range of 5-100mg/m<2> . Acrylic denatured epoxy is used as water-base coating and the coating weight of the water-base paint is designated within a range of 5-50mg/dm<2> . When such surface-treated tab material is produced, the Al plate is degreased, dried, applied with a chromate treatment liquid, dried, applied with a water-base paint and baked to form a water-base paint coat on the chromate coat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated tab material, and more particularly to the technical field of a surface-treated tab material attached to the end of a can such as a beverage can or a can.

[0002]

2. Description of the Related Art In general, Al (aluminum) or Al alloy is widely used in fields such as daily necessities and building materials because it has an oxide film with strong protective power on the surface and exhibits excellent corrosion resistance in practical use. There is. Further, Al or Al alloy is excellent in corrosion resistance, is lightweight, and is also excellent in moldability and can openability, and soft drinks such as beer and carbonated drinks, fruit juice drinks and coffee drinks, and easy canned products. The usefulness as an open end or full open end can material is recognized, and the usage amount tends to increase year by year. Furthermore,
The tab material attached to the end of the can also tends to increase with the increase in the end material.

Such tab materials are usually JIS 5082, 51
Al alloy plate such as 82 is used. In general, these Al alloy plates are subjected to chemical conversion treatment on their surfaces in order to have corrosion resistance, and after being coated with a solvent-based paint, processed into tab shapes. By the way, after filling the container (can) with contents (beverage, etc.) and tightening the ends, some beverages are subjected to retort sterilization (hot water treatment), but the conditions of the above chemical conversion treatment and / or coating If it is inappropriate, discoloration such as blackening due to contact with hot water or whitening due to steam exposure may occur during hot water treatment. Therefore, it is required that the tab material does not cause a defective appearance due to hot water treatment, that is, has excellent hot water treatment property.

At present, phosphoric acid chromate treatment is generally used for chemical conversion treatment of Al or Al alloy plate of tab material. The phosphoric acid chromate film obtained by this phosphoric acid chromate treatment plays a role as a base for improving the corrosion resistance of Al or Al alloy and improving the coating film adhesion, and has excellent properties as a base for tab materials. Have

On the surface after the chemical conversion treatment, an epoxy urea-based or vinyl chloride-based solvent-based paint is applied. This solvent-based paint is easy to control the painting work,
Further, it is possible to obtain a high degree of finishability and coating film performance at the same time, and it has excellent properties as a coating material for tab materials.

The phosphoric acid chromate treatment and the application of the solvent-based paint give a tab material having a phosphoric acid chromate film on the surface of the Al or Al alloy plate and a film of the solvent-based paint on the film. That is, the conventional tab material is Al or
A surface-treated tab material having a chromate phosphate coating on the surface of an Al alloy plate and a coating made of a solvent-based paint on the coating. This conventional surface-treated tab material has excellent corrosion resistance due to the excellent characteristics of the phosphoric acid chromate film and the film composed of the solvent-based paint, and is retort sterilized (hot water treatment).
In this case, discoloration such as black discoloration or white discoloration is unlikely to occur, and heat resistance to hot water treatment (that is, discoloration such as black discoloration or white discoloration due to hot water treatment) is excellent.

[0007]

However, in the conventional surface-treated tab material described above, its production (ie, Al or Al
Chromate phosphate treatment of alloy plate and coating with solvent-based paint)
At that time, there are the following problems or requests to be solved.

That is, the phosphoric acid chromate treatment of an Al or Al alloy plate is performed through a number of steps.
(A) Degreasing of Al or Al alloy plate, (B) Washing with water, (C) Alkaline etching, (D) Washing with water, (E) Chromate phosphoric acid treatment (immersing in phosphoric acid chromate treatment liquid or spray coating of the treatment liquid) ), (F) Washing with water, and (G) Drying are sequentially performed, so that the treatment process as a whole is very complicated. Further, it is necessary to remove the sludge generated during the alkali etching in (C) above and the waste water treatment for the washing water used in (F) above. These are problems to be solved or solved, especially in the era of mass production of tab materials as in the present, the number of treatment steps is as small as possible, and sludge removal treatment and waste liquid treatment are unnecessary,
Therefore, it is desired to develop a chemical conversion treatment for tab materials that can reduce the treatment cost.

Further, in the process of coating the solvent-based paint after the phosphoric acid chromate treatment, the solvent-based paint basically has a bad influence on the working environment, and therefore improvement thereof is desired. or,
When solvent-based paint is applied and baked after drying, the organic solvent volatilizes, and if it is directly discharged into the atmosphere, it may cause pollution such as foul odors or natural destruction such as air pollution.
Although the exhaust gas is exhausted after the exhaust gas treatment, it is desired to reduce the exhaust gas treatment amount. Especially in the future,
Regarding the volatiles (gas) of organic solvents in solvent-based paints such as those mentioned above, emission control of VOC (volatile organic compounds), which is one of the causative substances, has become stricter in Europe and the United States as part of measures to prevent air pollution. In Japan, emission regulations tend to become stricter, and it is strongly desired to reduce the amount of volatile organic compounds that require exhaust gas treatment, which in turn reduces the exhaust gas treatment amount. Becomes

The present invention has been made in view of such circumstances, and its purpose is to solve the above-mentioned problems and to compare the case of the conventional surface-treated tab material with the chemical conversion treatment step in the production. Is simple and has a small number of steps, does not require sludge removal treatment and waste liquid treatment, and can improve the working environment in the painting process, and the amount of volatile organic compounds that require exhaust gas treatment is small, which in turn exhaust gas treatment. An object of the present invention is to provide a surface-treated tab material whose amount can be reduced and which is equivalent to or more than the conventional surface-treated tab material and which is excellent in hot water resistance.

[0011]

In order to achieve the above object, the surface-treated tab material according to the present invention is the surface-treated tab material according to claims 1 to 3, which has the following constitution. It is a thing. That is, the surface-treated tab material according to claim 1 is provided with a chromate film containing a chromium trivalent compound and an organic polymer compound on one surface or both surfaces of an Al plate or an Al alloy plate, and a water-based paint film on the film. It is a surface-treated tab material having excellent heat-resistant water treatment property, characterized by being provided (first invention).

The surface-treated tab material according to claim ² is a surface-treated tab material having excellent heat-resistant water treatment properties according to claim 1, wherein the amount of chromium deposited on the chromate film is 5 to 100 mg / m ² . 2 invention). In the surface-treated tab material according to claim 3, the film of the water-based paint is made of acrylic modified epoxy, and the film amount is 5 to 50 mg / dm ^2.
Alternatively, it is a surface-treated tab material excellent in heat-resistant water treatment property according to 2 (third invention).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is implemented, for example, as follows. An Al plate or an Al alloy plate for tab material is first degreased and washed with water as a pretreatment, and then coated chromate treatment containing a water-soluble chromium trivalent compound and a water-soluble organic polymer compound on one or both surfaces thereof. After applying the liquid and drying, apply the water-based paint and bake. Then, on one or both sides of the Al plate or Al alloy plate, a chromate film containing a chromium trivalent compound and an organic polymer compound is provided, and a water-based coating film is provided on the film.
That is, the surface-treated tab material according to the present invention (first invention) can be obtained.

As can be seen from the embodiments of the present invention, the surface-treated tab material according to the present invention is a coating type that contains pretreatments such as degreasing and washing, a water-soluble chromium trivalent compound and a water-soluble organic polymer compound. Application of chromate treatment liquid, drying,
Since it can be obtained by sequentially performing the steps of coating and baking of water-based paint, compared to the case of the conventional surface-treated tab material, the chemical conversion treatment step is simple and the number of steps is small in manufacturing, and the sludge removal treatment is also performed. And waste liquid treatment is unnecessary, and further, the working environment in the coating process can be improved, and the amount of volatile organic compounds requiring exhaust gas treatment is small,
As a result, the exhaust gas treatment amount can be reduced.

That is, the steps of coating and drying the above-mentioned coating type chromate treatment liquid correspond to the chemical conversion treatment step, and this step is the chemical conversion treatment step in the case of manufacturing the conventional surface-treated tab material "(A)". Degreasing, (B) water washing, (C) alkali etching, (D) water washing, (E) phosphoric acid chromate treatment, (F) water washing,
(G) Drying ”is extremely simple and has a small number of steps.

In the above chemical conversion treatment step, since there is no alkali etching step, no sludge is generated and the sludge removal treatment is unnecessary. Further, since it is not necessary to wash with water after the application of the chemical conversion treatment liquid (chromate treatment liquid), the waste liquid treatment is unnecessary.

In the coating process of coating and baking the water-based paint after the above chemical conversion treatment process, unlike the solvent-based paint, the water-based paint hardly emits the solvent at room temperature and the amount of the solvent released even at a relatively high temperature. Due to the fact that it has less properties, the working environment is clean and the hygiene safety is high, and the amount of exhaust gas generated is small even during baking.

Therefore, in the case of the surface-treated tab material according to the present invention, as compared with the case of the conventional surface-treated tab material, the chemical conversion treatment step is simple and the number of steps is small in the manufacturing process, and the sludge removal treatment and the waste liquid are processed. No treatment is required, the working environment in the painting process can be improved, and the amount of volatile organic compounds requiring exhaust gas treatment is small, and thus the exhaust gas treatment amount can be reduced. In addition, since water-based paint is used as the paint in the painting process, there is no risk of fire due to the paint, there is no need to install new painting equipment, and the paint that adheres to the painting equipment can be washed with water. Is also unnecessary, which leads to cost reduction.

As described above, the surface-treated tab material according to the present invention is provided with a chromate film containing a chromium trivalent compound and an organic polymer compound on one or both surfaces of an Al plate or an Al alloy plate, and the chromate film is provided on the film. It is provided with a film of water-based paint. An Al plate or Al alloy plate having such a chromate film and a water-based paint film is unlikely to undergo discoloration such as blackening or whitening during hot water treatment, and is treated with a heat-resistant water treatment equal to or more than the conventional surface treatment tab material. It has excellent properties. This is a finding obtained as a result of the inventors' earnest studies. Therefore, the surface-treated tab material according to the present invention is as excellent in hot water resistance as the conventional surface-treated tab material or more.

The reason why the surface-treated tab material according to the present invention is excellent in heat-resistant water treatment is that contaminant ions in hot water are difficult to be adsorbed. That is, Al or Al by hot water treatment
The cause of discoloration such as blackening or whitening of the alloy is that the contact between Al or Al alloy and hot water forms a boehmite layer on the surface of Al or Al alloy, and Si, Ca contained in the hot water in that layer. This is because various impurities such as Fe and Fe are adsorbed, but the adsorption of such impurities is less likely to occur due to the chromate film containing the chromium trivalent compound and the organic polymer compound and the film of the water-based paint.

The chromate film containing the chromium trivalent compound and the organic polymer compound is coated with the coating type chromate treatment liquid containing the water-soluble chromium trivalent compound and the water-soluble organic polymer compound and dried. However, such treatment corresponds to so-called coating type chromate treatment. By the way, generally, in the coating-type chromate treatment, in order to crosslink the water-soluble organic polymer, a treatment liquid containing a water-soluble chromium trivalent compound is applied to the metal surface,
A material that forms an organic-inorganic composite film on the surface by drying, that is, a coating type chromate treatment liquid containing a water-soluble chromium trivalent compound and a water-soluble organic polymer compound is applied to the metal surface and dried. , An organic-inorganic composite film formed by crosslinking a water-soluble organic polymer. Therefore, it can be said that the chromate film containing the chromium trivalent compound and the organic polymer compound is an organic-inorganic composite film containing the crosslinked organic polymer and the chromium trivalent compound.

As the water-soluble chromium trivalent compound contained in the coating type chromate treatment liquid, chromium nitrate, chromium phosphate, chromium sulfate, chromium hydroxide and the like can be used, and as the water-soluble organic polymer compound, , Polyacrylic acid, polymethacrylic acid, polyvinyl alcohol, polyacrylamide, phenol resin and the like can be used. The content of the water-soluble chromium trivalent compound in this coating type chromate treatment liquid is not particularly limited, but 0.01% or less in terms of the corrosion resistance of the coating film, the coating appearance after clear coating, and the adhesion.
The content of the water-soluble organic polymer compound is not particularly limited, but is preferably 0.1 to 10% from the viewpoint of corrosion resistance and adhesion.

Regarding the chromate film containing the chromium trivalent compound and the organic polymer compound, the amount of chromium contained in the film (the amount of chromium deposited on the chromate film) is 5 mg /
When it is less than m ² , the heat-resistant water treatment property is deteriorated and discoloration may occur during hot water treatment. When it is 5 mg / m ² or more, the heat-resistant water treatment property is excellent and the hot water treatment is excellent. When it exceeds 100 mg / m ² , the hot water treatability is saturated and the improvement in hot water treatability is small relative to the increase in the amount of chromium deposited. The efficiency of addition of the valent compound tends to be poor, and the economic efficiency tends to be lowered. From this point of view, it is desirable that the amount of chromium deposited on the chromate film is 5 to 100 mg / m ² (second invention). Furthermore, if it is set to 20 to 100 mg / m ² , discoloration will surely not occur during hot water treatment, so that it is more desirable.

It is desirable that the film of the water-based paint is made of an acrylic modified epoxy resin and the amount of the film is 5 to 50 mg / dm ² (third invention). That is, there are various types of water-based paints, and polyester, amino resin, epoxy resin and the like can be used. Among them, the water-based paint containing acrylic modified epoxy is a coating film obtained by coating and baking (acrylic). Corrosion resistance (coating made of modified epoxy) (base material anti-corrosion effect) is excellent, adhesion to the substrate is excellent, monomer types are plentiful, and synthetic work such as emulsion polymerization is easy. It is desirable to form a coating film by using an aqueous paint containing such an acrylic modified epoxy because of its advantages such as. In this case, if the thickness of the film is less than 5 mg / dm ^2, the hot water resistance may deteriorate and discoloration may occur during hot water treatment. If the thickness is 5 mg / dm ² or more, Highly resistant to hot water, it is extremely unlikely that discoloration will occur during hot water treatment, but if it exceeds 50 mg / dm ² ,
The degree of improvement in hot water treatment is small relative to the increase in the amount of coating film due to saturation of hot water treatment, resulting in a decrease in economic efficiency. From this point of view, the thickness of the film is preferably 5 to 50 mg / dm ² in terms of film amount. Furthermore,
When the amount is 10 to 50 mg / dm ² , discoloration does not occur reliably during hot water treatment, so it is more desirable to do so.

Here, as the epoxy resin portion of the acrylic modified epoxy, bisphenol A type epoxy resin, orthocresol novolac type epoxy resin, phenol resin modified epoxy resin or the like can be used, and the acrylic portion is polyacrylic acid. And polymethacrylic acid can be used.

In the present invention, the type of the Al plate or Al alloy plate of the base material is not particularly limited, and Al plate or various Al alloy plates can be used. For example, Al alloy plate of JIS 5082, 5182 etc. Can be used. The chromate film and the water-based paint film may be provided on one side or both sides of the Al plate or Al alloy plate, and which one is selected is determined according to the necessity (tab press workability, etc.). Good.

[0027]

【Example】

(Example) An Al alloy plate corresponding to JIS 5182 and having a thickness of 0.285 mm was prepared as an Al alloy plate for tab material. this
The Al alloy plate was first degreased by immersing it in a 75 ° C. sulfuric acid-phosphoric acid aqueous solution for 30 seconds as a pretreatment, and then washed with tap water for 15 seconds. Next, this Al alloy plate was dissolved in water with 0.5% of chromium nitrate as a water-soluble chromium trivalent compound and 1.0% of polyacrylic acid as a water-soluble organic polymer compound contained in a coating type chromate treatment liquid (chemical agent). ), Squeeze with a roll, then 150
It was dried by exposing it to air at 0 ° C for 10 seconds. Next, a commercially available acrylic modified epoxy aqueous paint (solid content 30%) was applied to one surface of this Al alloy plate using a roll coater, and then baked by heating for 30 seconds in an atmosphere of 250 ° C. . In this way, chromium 3 is deposited on one side of the Al alloy plate.
A surface-treated tab material (a surface-treated tab material according to an example of the present invention) having a chromate film containing a valent compound and an organic polymer compound and having a film of an aqueous paint on the film was obtained. The amount of chromium (Cr) adhered to the chromate film and the amount of water-based paint adhered (film amount) were changed as shown in Table 1 below.

On the other hand, instead of the coating type chromate treatment liquid, a phosphoric acid chromate treatment liquid is used for phosphoric acid chromate treatment, and a commercially available epoxy urea-based solvent-based paint is used in place of the water-based paint containing the acrylic modified epoxy. Using
A surface-treated tab material according to Comparative Example 1 was obtained by the same method as in the above-described example of the present invention except for these points. or,
Without performing such chemical conversion treatment and coating, only the same alkaline degreasing as described above was performed, and an Al alloy plate (tab material) according to Comparative Example 2
I got

The surface-treated tab material according to the example of the present invention thus obtained, the surface-treated tab material according to the comparative example 1,
Then, with respect to the Al alloy plate (tab material) according to Comparative Example 2, a boiling water test was conducted in which these were immersed in boiling tap water for 30 minutes. In addition, a retort test was conducted in which distilled water at 125 ° C was treated under pressure for 30 minutes using an autoclave. Then, the surface of the surface-treated tab material after these tests was visually observed to evaluate the degree of discoloration. Here, the boiling water test is a kind of hot water treatment test for evaluating the heat resistant water treatment property. The retort test is a hot water treatment test under conditions corresponding to the retort sterilization treatment (hot water treatment).

The results of the above tests are shown in Table 1. Further, Table 1 also shows whether or not there is a problem in manufacturing the tab material, that is, whether waste liquid treatment or exhaust gas treatment is necessary or not. It should be noted that the degree of discoloration is evaluated on a scale of 5, and in the column of degree of discoloration in Table 1, 1 indicates a large degree of discoloration, and 2, 3, 4 indicates a slight degree of discoloration, and 5 indicates a discoloration. It means that it did not occur, and when it is 3 or more, there is no problem related to discoloration, and it indicates that it can be put to practical use without any trouble.

As can be seen from Table 1, since the Al alloy plate (tab material) according to Comparative Example 2 was not subjected to chemical conversion treatment and coating, there were no problems in manufacturing the tab material, and there was no waste liquid treatment. Exhaust gas treatment is unnecessary, but the degree of discoloration is 1 and extremely large in both the boiling water test and the retort test, and the hot water resistance is extremely poor.

The surface-treated tab material according to Comparative Example 1 has an extremely small discoloration degree of 4 both in the boiling water test and in the retort test, and is excellent in heat-resistant water treatment. Treatment and exhaust gas treatment are required.

The surface-treated tab material according to the embodiment of the present invention is
The degree of discoloration in the boiling water test and retort test is 3 to
4, which is extremely small, and is as excellent in hot water resistance as the case of the surface-treated tab material according to Comparative Example 1.
Further, there is no problem in manufacturing the tab material, and waste liquid treatment and exhaust gas treatment are unnecessary.

In the surface-treated tab materials according to the examples of the present invention, the boiling water test and the retort test are performed when the amount of chromium (Cr) deposited on the chromate film and the amount of water-based coating (the amount of coating) are greater than when the amount is small. In this case, the degree of discoloration is small and the heat-resistant water treatment is excellent. Of these, the amount of chromium deposited on the chromate film and the amount of water-based paint deposited were each 3 mg /
Even when the least a m ^2, 3mg / dm ^2, has a sufficient heat water treatment resistance degree of discoloration if the retort test a 3 in the case of boiling water test, discoloration on hindrance It can be used without any practical use.

[0035]

[Table 1]

[0036]

As described above, the surface-treated tab material according to the present invention has a simple chemical conversion treatment step and a small number of steps in the manufacturing process, as compared with the conventional surface-treated tab material. No waste liquid treatment is required, the working environment in the painting process can be improved, the amount of volatile organic compounds requiring exhaust gas treatment is small, and the exhaust gas treatment amount can be reduced. Excellent in hot water treatment, equivalent to or better than treated tab material,
The effect that discoloration such as black discoloration or white discoloration hardly occurs during hot water treatment is exerted. Furthermore, there is no danger of fire due to paint in the painting process during manufacturing, and because the paint adhering to the painting equipment can be washed with water, there is no need for exhaust gas treatment, which in turn leads to cost reduction. .

Claims (3)

[Claims] 1. A chromate film containing a chromium trivalent compound and an organic polymer compound is provided on one surface or both surfaces of an Al plate or an Al alloy plate, and a water-based paint film is provided on the film. A surface-treated tab material with excellent hot water resistance. 2. The amount of chromium deposited on the chromate film is 5
The surface-treated tab material according to claim 1, which has a resistance to hot water treatment of up to 100 mg / m ² . 3. The surface-treated tab material excellent in hot water treatment property according to claim 1, wherein the film of the water-based paint is made of acrylic modified epoxy and the film amount is 5 to 50 mg / dm ² .