JPH01145137A - Composite steel plate having excellent di workability and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a continuous DI moldability and at the same time improve a corrosion resistance by forming two layers over the steel surface of the inner face of a can; i.e. a polyester having a melting pint lower than that of Sn and thereon a polyester having a melting point higher than that of Sn, and hot-pressing to bond them together at a temperature lower than the melting point of Sn. CONSTITUTION:A polyester film is composed of two layers; a polyester resin having a melting point lower than that of Sn as lower layer (which is the side contacting with a steel plate) and a polyester resin having a melting point higher than that of Sn as upper layer. By hot pressing to bond the lower layer of the two-layer film on the steel plate having a Sn-film, an excellent composite steel plate is obtained, minimizing the generation of Sn-Fe alloy layer and making the most of the good DI moldability of the upper layer. The thickness of the polyester film having a melting point lower than that of Sn is to be 1-20mum, that having a melting point higher than that of Sn is to be 8-45mum and the total thickness of the polyester film is to be 10-60mum. The polyester film used for the upper and lower layers is a saturated polyester resin containing no double bond in its molecular chain; that is, a polymer of saturated multivalent carboxylic acid and saturated multivalent alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to materials for can containers, particularly DI cans.More specifically, the present invention relates to materials for can containers, particularly DI cans. The present invention relates to a composite steel plate with excellent properties and a method for manufacturing the same.

[Conventional technology]

Can containers can be classified from the perspective of can bodies: canopies, bottom lids,
Cans are broadly classified into 3-piece cans consisting of a body, 2-piece cans consisting of a canopy, and 2-piece cans consisting of a canopy.

The 2-piece can is currently Draw and
Redraw) can and D I (Draw and I
ronning) cans are mainly widely used.

In particular, DI cans are closely connected to our daily lives as cans for beer and carbonated drinks, and the number of DI cans manufactured is increasing year by year.

The material used for DI cans is aluminum or tin plated with Sn, and the former is DI-A.
The latter are commonly referred to as DI-3 cans, and aluminum is used in larger quantities.

There are various reasons for this, but the main reason is that aluminum is easier to DI-process than tin, and the material itself has good corrosion resistance, so the inner surface of the can after DI processing only needs to be painted once (single coat). . On the other hand, in the case of tinplate, two coats are required for corrosion resistance.

This double coating increases the number of steps, reduces productivity, and increases can costs.Therefore, the emergence of a material for DI-3 cans that can maintain high corrosion resistance with a single coating is eagerly awaited.

In order to meet these demands, for example, JP-A-54-945
85 and Japanese Unexamined Patent Publication No. 54-132683, a method of applying DI processing after painting the steel plate has been proposed, but the practical performance, especially the corrosion resistance, is not sufficient and it has not been put into practical use. not present.

Regarding corrosion resistance, it goes without saying that it is a well-known fact that a laminate material in which resin films are laminated can provide better corrosion resistance than the above-mentioned proposal by appropriately selecting the film thickness.

However, there is no proposal to use a laminated steel plate laminated with a resin film as a material for DI cans.

[Problem that the invention seeks to solve]

As mentioned above, furiki, which is currently used as a material for DI-3 cans, requires double coating for corrosion resistance.
The emergence of a material for DI-3 cans that has corrosion resistance equivalent to that of A cans is desired.

The present invention was developed in view of the above-mentioned circumstances, and therefore, it is an object of the present invention to provide a material for D[-3 cans that has excellent DI processability, a single coat, and good corrosion resistance, and a method for manufacturing the same.

[Means and effects for solving the problems] In order to achieve the above object, the present invention provides a tin film layer on one side of the steel plate (the surface that will become the outside surface of the can) and a tin film layer on the other side (the surface that will become the inside surface of the can). ) is characterized by a composite steel plate laminated with polyester films having different melting points and the lamination method, and consists of the following structure.

(1) A steel plate has an Sn coating layer on one side, a chemical conversion coating on the other side, a polyester film with a melting point lower than the melting point of Sn on the upper layer, and a polyester film with a melting point higher than the melting point of Sn on the upper layer. A composite steel sheet with excellent DI processability, which is laminated with a polyester film.

(2) One side of the steel plate has an Sn film layer, and the other side has an S
n coating layer, a chemical conversion coating on the upper layer, and an S coating on the upper layer.
a polyester film having a melting point less than or equal to the melting point of n;
A composite steel sheet with excellent DI processability, in which a polyester film having a melting point higher than the melting point of Sn is laminated on the upper layer.

(3) The thickness of the polyester film having a melting point below the melting point of Sn of the steel plate in (1) or (2) above is 1 to 20 cm, and the thickness of the polyester film having a melting point above the melting point of Sn is 8 to 45) rm, polyester A composite steel plate with excellent DI workability, in which the total thickness of the film is on the 10-60 side.

(4) Using a steel plate having a Sn film layer on one side and a chemical conversion film layer or a Sn film layer and a chemical conversion film layer on the other side, Sn is applied on the chemical conversion film layer of the steel plate. A method for producing a temporary composite steel having excellent DI workability, in which a polyester film having a melting point of not more than the melting point and a polyester film having a melting point of 871 points or more on the upper layer are thermocompression bonded at a temperature not more than the melting point of Sn.

As mentioned above, the structure of the present invention is a steel plate in which a two-layer polyester film is formed on the surface of the steel plate, which becomes the inner surface of the can, with a lower layer of polyester having a melting point lower than the melting point of Sn and a polyester resin layer having a melting point higher than the melting point of Sn. , and the above-mentioned two-layer polyester film are thermocompression bonded at a temperature below the melting point of Sn.

First, the polyester film used in the present invention will be described.

The polyester film in the present invention consists of two layers: the lower layer (the side in contact with the steel plate) is a polyester resin whose melting point is lower than the melting point of Sn, and the upper layer is a polyester resin whose melting point is higher than the melting point of Sn.

This difference in melting point between the upper layer and the lower layer, with the melting point of Sn as the boundary, is related to the steel plate with the Sn-based coating.
This is an important requirement in the present invention.

That is, in terms of DI moldability only, the S used for the upper layer
This is possible only with stell film having a melting point higher than n.

However, at present, tin plated with Sn is the most suitable steel product for 01 cans, and the lubricating effect of pure Sn is particularly important for the outer surface of the can, which is subjected to ironing. In this case, the amount of pure Sn must be at least Ig/rrr. On the other hand, it is also known that the 5n-Fe alloy layer conversely inhibits Dr formability.

When thermocompression laminating is performed on an m-plate having a Sn-based film (Sn film or a film obtained by chemical conversion treatment on the Sn film) and used in a 01 can, consideration must be given to the formation of a Sn-Fe alloy layer.

For this reason, it is not preferable to thermocompress a resin film having a melting point higher than that of Sn. For example, the melting point of a polyester film called PET is 265°C, but an even higher temperature is required to provide sufficient adhesive strength, and it is difficult to simply perform Sn plating at such a high temperature. When thermocompression bonded to matte tin plate, the 5n-Fe alloy layer is formed in an amount of about 0.6 g/rd or more.

The amount of the 5n-Fe alloy layer produced naturally varies depending on the thermocompression bonding temperature and the heat cycle such as cooling, but there is no doubt that it will be produced to a greater or lesser extent.

In recent years, with the trend toward lower Sn weights in tinplates for DI cans, it is expected that the alloy layer will inevitably become a problem.

Therefore, the use of a thermocompression bonded laminate material for DI cans using a resin film having a melting point higher than the melting point of Sn is very effective when considering the use of a steel plate whose outer surface is at least Sn-plated.

On the other hand, in the case of a polyester film having a melting point lower than that of Sn, although it has the advantage that the amount of Sn alloy layer formed during thermocompression bonding is small, it has a drawback in DI formability, especially continuous formability. The reason for this is not clear at present, but it is probably a problem with the hardness of the film itself, especially the surface hardness.

For example, when looking at how a film gets scratched during DI processing, ester resins with a high melting point are much less likely to get scratches than ester resins with a low melting point.

As a result of research based on the above knowledge, the lower layer is a polyester film with a melting point lower than the melting point of Sn and 180°C or higher, preferably 200°C or higher, and the upper layer is a two-layer polyester film with a melting point higher than the melting point of Sn. By thermo-compression bonding the lower layer of the two-layer film to a steel plate with a Sn-based film, each function works effectively.
It has been found that an excellent composite steel sheet can be obtained by suppressing the formation of the -Fe alloy layer as much as possible and taking advantage of the good DI formability of the upper layer.

Furthermore, the film thickness of the lower layer and the upper layer is set to 1 to 1, respectively.
The reasons for limiting the range to 201 rm, 8 to 45 chambers, and the total film thickness to 10 to 60 mm will be explained.

As can be seen from the above explanation of the functions of the lower layer and upper layer films, the lower layer film basically plays the role of a binder between the upper layer film and the steel plate.

However, since the lower layer film is melted during thermocompression bonding with the steel plate, it becomes integrated with the upper layer film, and the boundary between them becomes unclear. If the thickness of the lower layer film is too thin, the lower layer film will be completely integrated with the upper layer film, so that it will not be able to sufficiently adhere to the steel plate.

Therefore, the lower limit of the thickness of the lower layer film is 1 um, which is the minimum thickness that allows it to be integrated with the upper layer film and maintain adhesive strength with the steel plate.

Further, the upper limit of the thickness of the lower layer film is limited to 20-.

The above is the reason why the thickness of the lower layer film is limited to 1 to 20 mm.
~6- is good.

On the other hand, in the case of the upper layer film, the film thickness is 8 to 45-
It is. The lower limit of 8 bars is the minimum thickness that provides good formability even after thermocompression bonding of the lower film. The upper limit of 45 has a relationship with the thickness of the underlying film when it exceeds 45-, but the effect on DI formability not only becomes saturated, but also
Sometimes it can be inferior. Moreover, the can cost increases and it is not economically advantageous.

Furthermore, the total thickness by adding the film thickness of the lower layer and the upper layer,
I will explain the reason why I limited it to 10-60#lI.

If the lower limit is less than 10, many film defects will easily occur in the film after DI molding, and even if a top coat is applied,
In the case of a chemically treated steel plate without a Sn film on its inner surface, the corrosion resistance may not be sufficient. Therefore, 10- or more is required.

Moreover, even if it exceeds the upper limit of 604, it is not so effective for corrosion resistance and the performance becomes saturated. Therefore 6
0 feet is sufficient.

Naturally, the lower layer, upper layer, and their total film thickness must be set in a balance between DI formability and corrosion resistance.

In this sense, the lower layer film thickness is 2~6p, the upper layer film thickness is 8~40p, and the total film thickness is 10~45n.
is preferred.

Next, the polyester fill used for the upper and lower layers is a saturated polyester resin that does not contain double bonds, and as is well known, it is a polymer of saturated polyhydric carboxylic acid and saturated polyhydric alcohol.

The polyester film used for the lower layer has a temperature of 232° C. or lower, which is the melting point of Sn, and the polyester film used for the upper layer has a temperature of 232° C. or higher, which is the melting point of Sn.

The saturated polyester resin used for the lower layer includes terephthalic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, etc. as saturated polyhydric carboxylic acids, and ethylene glycol, diethylene glycol, triethylene glycol, 1. as saturated polyhydric alcohols. There are 4-butadiol and the like, and the melting point is adjusted to 180 to 230°C depending on the content ratio.

Further, as the saturated polyester resin used for the upper layer, polyethylene terephthalate, which is a polymer of 0 terephthalic acid and ethylene glycol, and polybutylene terephthalate, which is a polymer of terephthalic acid and 1.4-butylene diol, can be used.

Next, the composite steel plate of the present invention will be described.

The present invention relates to a material for DI cans, but as mentioned above, currently the material for DI cans made from steel plates is Sn.
Plated tin is used.

In particular, since the outer surface of a DI can undergoes extreme processing called ironing, a Sn film, which is a good solid lubricant, is currently indispensable.

This point remains the same in the present invention, and the Sn coating is required on the surface that contacts the outer surface of the can, and in this case, the coating structure is from the inner surface of the can during can manufacturing: polyester film/chemical conversion coating/
It consists of Sn film/steel plate/Sn film, or preferably polyester film/chemical conversion film/Sn film/steel plate/Sn film/chemical conversion film.

Furthermore, in the present invention, unlike tinplate, which is a conventional DI can material made of steel plate, the surface that corresponds to the inner surface of the can, that is, the surface to which the polyester film is thermocompression bonded, has no Sn film.
Good formability and corrosion resistance can be obtained even if the steel plate is simply subjected to chemical conversion treatment.

The reason for this is that when a steel plate is simply chemically treated, the corrosion resistance of the material itself is inferior to when it has an Sn film, but on the other hand, the adhesive strength with the film is higher, so a healthy film is more likely to be maintained. It works in a positive direction in terms of DI formability and corrosion resistance.

Of course, it goes without saying that the adhesive strength is further improved by chemical conversion treatment applied to the surface, whether or not the Sn film is present.

In this case, the coating structure is Polm/chemical conversion coating/steel plate/Sn coating/chemical conversion coating from the inner surface of the can during can manufacturing.

Note that the chemical conversion treatment referred to here refers to chromate treatment, which is usually called chemical treatment applied to tinplate, and T F
It refers to chromium chromate treatment, which is a coating on steel sheets called S (Tin Free 5teel).

As for the chemical conversion treatment, as shown in the example of the film structure above, the surface that corresponds to the outer surface of the can is not an essential requirement in the present invention, but it is preferable from the viewpoint of primary rust prevention of the material.

Next, a method for laminating a polyester film onto a steel plate will be described.

In the present invention, as a method for laminating a film on a steel plate,
A method called thermocompression bonding is used. Bonding films by thermocompression bonding requires heating the steel plate to a predetermined temperature. this,
As a method of heating the steel plate, a method of passing the steel plate through a heated furnace, energization heating in which the steel plate is heated by passing electricity through it, induction heating, etc. can be used.

Furthermore, when adhering a film to a steel plate, if a method is adopted in which two layers of film are adhered from the beginning or a method in which the lower layer and upper layer are adhered at the same time, the material for single coat DI-3 cans of the present invention can be obtained. You can achieve the purpose you set out to achieve.

Of course, it is also possible to first adhere the lower layer film and then adhere the upper layer film.

In any case, the method for adhering the film to the steel plate may be selected according to the equipment used.

The structure and operation of the present invention have been explained above, but by using the composite steel sheet of the present invention, good continuous DI formability can be obtained, and at the same time, the internal coating can be easily simplified due to the dramatic improvement in corrosion resistance. It is.

In addition, the composite steel sheet obtained by the present invention can be used not only for DI cans but also for D
It is also used as rD can body material and can lid material including EOE.

〔Example〕

Hereinafter, the effects of the present invention will be specifically shown in Examples.

Example 1 Sn adhesion amount was 2.8 g/rd on the outer surface of the can, and 0 on the inner surface of the can.
．． A polyethylene isophthalate film (melting point approximately 195°C ) 8 side, the upper layer is made of polyethylene terephthalate film (melting point 265°C) 16 tones M, 25-140/#I+, each with a total film thickness of 24//l1l (A film), 33 tones (B film), 48 tones ( The lower layer of the two-layer film of C film) was thermocompression bonded at a plate temperature of 220°C to obtain composite steel plates A, B, and C, respectively.

The continuous DI formability of the composite steel sheets A, B, and C thus obtained was examined using a can diameter of 211t and a C350d beer can size. The results are composite steel plates A and B.

For both cases, continuous DI bottom molding of 100 cans or more was possible.

Furthermore, in order to examine the film integrity of the DI molded can, a solution containing 1% NaCl and 0.2 of a surfactant was placed in the can, and an overvoltage of +6y was applied with the can body as the anode and platinum as the cathode. The current value was measured to examine the soundness of the film after DI processing (hereinafter this test will be referred to as QTV test).

Further, the inner surface of the DI molded can was coated with an epoxyphenol can paint to a dry coating thickness of 8 μm, and baked at 205° C. for 10 minutes.

QTV tests were also conducted on DI cans that had been top coated.

For comparison, a QTV test was also conducted on a commercially available DI-3 can.

The results are shown in Table 1.

Table 1: The composite steel sheet obtained by the present invention can be subjected to continuous DI forming, and as can be seen from Table 1, the QTV test value after topcoating is equivalent to that of commercially available DI-S cans.

Example 2 The amount of Sn deposited on the outer surface of the can was 2.8 g/g,
The surface that corresponds to the inner surface of the can is a single-sided chromium/chromate treated surface that does not contain Sn and is simply a TFS type chromium/chromate treated steel plate, and the lower layer is polyethylene terephthalate/isophthalate film (melting point approximately 210°C) 3
-1 The upper layer is a polyethylene terephthalate film (melting point 265°C).The lower layer is a two-layer film consisting of 12 layers and 50 layers, each with a total film thickness of 15 layers (D film) and 53 layers (E film), at a plate temperature of 230 degrees Celsius. Thermocompression bonding was performed to obtain composite steel plates E.

In addition, the lower layer film thickness is 12 feet and the upper layer film thickness is 25 feet, and the total thickness is 37 feet (F film), 4O-
The lower layer of the two-layer film (G film) was heat-compressed onto the surface without the Sn film at a plate temperature of 230°C following the procedure of Example 1.
Formability, QTV test of DI molded cans, QT after topcoating
A V test was conducted.

As a result, regarding continuous DI formability, composite steel sheet, E,
Continuous DI moldability of 100 cans or more was possible for both F and G.

The results of the QTV test are shown in Table 2.

Table 2 The composite steel plate obtained by the present invention has excellent DI formability,
Furthermore, as can be seen from Table 2, even in the QTV test after topcoating, the can shows the same performance as the commercially available DI-3 can.

Example 3 One side of the steel plate used in Example 2 was plated, the other side was treated with chromium and chromate, and the lower layer was a polyethylene terephthalate sebacate film (melting point about 195°C) 10 m For the upper layer, polybutylene terephthalate film (melting point 235°C) 15 and 25 tones were simultaneously thermocompressed at a plate temperature of 230°C to obtain a composite steel plate H with a total film thickness of 25 tones and a composite steel plate I with a total film thickness of 35tnn, respectively. .

Continuous DI formability, QTV test for formed cans, and QTV test after topcoating were conducted on these composite steel plates H and I according to the procedure of Example 1.

As a result, continuous DI forming on one side was possible for both composite steel plates H and I.

The results of the QTV test are shown in Table 3.

Table 3 The composite steel sheet obtained by the present invention not only shows excellent continuous DI formability, but also has properties equivalent to commercially available DI-3 cans in the QTV test after topcoating, as shown in Table 3. shows.

〔Effect of the invention〕

The composite steel sheet obtained by the present invention not only has excellent DI formability, but also has a DI-3 of the current level of DI-4 when painted after forming.
It exhibits properties equivalent to or better than cans, and has good corrosion resistance.

Therefore, since it becomes possible to omit the process at the can manufacturer, it is possible to reduce costs.

In addition, the composite steel sheet obtained by the present invention can be used not only as a material for DI cans, but also as a material for deep drawn cans such as DrD cans, and as a material for EO cans.
It can also be effectively used as a material for can lids containing E.
The effects on industry are significant.

Claims (1)

[Scope of Claims] 1) A steel plate has an Sn coating layer on one side, a chemical conversion coating on the other side, a polyester film having a melting point lower than the melting point of Sn on the upper layer, and a Sn coating layer on the upper layer. A composite steel sheet with excellent DI processability, characterized by laminating polyester films having a melting point higher than the melting point. 2) One side of the steel plate has a Sn film layer, and the other side has a Sn film layer.
A film layer, a chemical conversion film on the top layer, and a Sn film on the top layer.
A composite steel sheet with excellent DI processability, characterized in that a polyester film having a melting point of Sn or lower and a polyester film having a melting point of Sn or higher layered thereon is laminated thereon. 3) The thickness of the polyester film having a melting point lower than or equal to the melting point of Sn is 1 to 20 μm, the thickness of the polyester film having a melting point higher than or equal to the melting point of Sn is 8 to 45 μm, and the total thickness of the polyester film is 10 to 60 μm. The composite steel plate with excellent DI workability according to either the first term or the second term. 4) Using a steel plate having a Sn coating layer on one side and a chemical conversion coating layer or a Sn coating layer and a chemical conversion coating layer on the other side, Sn on the chemical conversion coating layer of the steel plate is used.
A method for producing a composite steel sheet with excellent DI workability, characterized by thermocompression bonding a polyester film having a melting point below the melting point of Sn and a polyester film having a melting point above the melting point of Sn on the upper layer at a temperature below the melting point of Sn. .