JPH0413144B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin-coated steel sheet for containers. More specifically, the present invention relates to a resin-coated steel sheet for containers that is excellent in aesthetic appearance and processing corrosion resistance.

[Conventional technology]

Conventionally, in the can manufacturing industry, surface-treated steel sheets such as tinplate and electrolytic chromic acid treated steel sheets have been coated once or multiple times. Sometimes, tinplate is
Because of its glittering properties, it has been widely used in applications where appearance is important. Applying multiple coats in this manner not only complicates the baking process but also requires a long baking time. Also,
It has the disadvantage that a large amount of solvent components are discharged during the formation of a coating film, and must be led to a special incinerator and incinerated. In addition, the paint used for painting is
Since thermosetting resins mainly composed of epoxy resins were used, severe processing could cause cracks in the coating film, and as a result, depending on the contents, the surface-treated steel sheets could be corroded. There were times when I had to do it. In order to solve these drawbacks, attempts have been made to laminate a thermoplastic resin film to a metal plate. As an example, a polyolefin film laminated on a metal plate (Japanese Unexamined Patent Application Publication No. 1989-1999)
141786), one in which a copolymerized polyester resin film is laminated on a metal plate (Japanese Patent Publication No. 57-23584), and one in which a polyester film is laminated on a metal plate using an adhesive (Japanese Patent Publication No. 58-39448).

[Problem that the invention seeks to solve]

However, polyolefin film laminated steel sheets are not satisfactory in terms of corrosion resistance and heat resistance, and copolymer polyester laminated steel sheets have the disadvantage of being high in cost and lacking in practicality. In addition, polyester film-laminated steel sheets, which have an adhesive layer containing metal powder, etc. at the interface between the polyester film and the metal sheet, can maintain initial adhesion, but when subjected to high-temperature hot water treatment such as retort sterilization, the adhesive strength increases. However, since it contains metal powder and the like, it has disadvantages such as a lack of adhesive thin film coating properties. Also,
Although it is possible to use tinplate, which has excellent aesthetics, as the steel plate used for the plastic film laminated steel plate, it is not practical because it is expensive.

[Means for solving problems]

As a result of various studies to solve the above problems, the present invention has developed a resin-coated steel sheet in which a biaxially oriented polyethylene terephthalate resin film with a specific Al vapor deposition layer is laminated on one or both sides of the steel sheet. This is a revolutionary resin-coated steel sheet for containers that not only has excellent adhesion and processing corrosion resistance, but also has excellent aesthetics.

Hereinafter, the content of the present invention will be explained in detail.
First, the biaxially oriented polyethylene terephthalate resin film is a polycondensate of polyethylene glycol and terephthalic acid, which is extruded from a known extruder, formed into a film, and then stretched biaxially and horizontally. And,
Although the film thickness is not particularly limited, it is preferably 5 to 50 μm. If the thickness is less than 5 μm, the lamination workability to steel plates will be significantly reduced, and sufficient processing corrosion resistance will not be obtained. On the other hand, 50μ
m or more, it is not economical when compared with epoxy resin paints widely used in the field of can manufacturing.

As a pre-treatment step for depositing Al on the film, in order to improve the adhesion between the deposited Al and the film, the film is coated with an epoxy resin and its curing agent such as phenol, urea, amide, etc.
One or more types of ester-based, acrylic-based, and urethane-based compositions are applied at a dry coating weight of 0.05 to 5.0 g/m ²
It is preferable to apply it.

The epoxy resin used here is preferably an epoxy resin having an epoxy equivalent of 400 to 4,000.
When using an epoxy resin with an epoxy equivalent of 400 or less, it is continuously applied to the film in a solution state,
Even after the solvent is evaporated in a dryer oven, the epoxy resin remains sticky, so although it is possible to wind the film, it is completely impossible to unwind it, making it impractical.
On the other hand, when an epoxy resin having an epoxy equivalent of 4000 or more is used, it is not preferable because the adhesiveness to the film after the curing reaction with the curing agent tends to decrease.

The blending ratio of epoxy resin and curing agent varies depending on the type of curing agent and cannot be determined uniquely, but it is generally 5 parts by weight per 100 parts by weight of the epoxy resin solid content.
It is sufficient to add up to 100 parts by weight.

Next, the reason why the coating weight of the composition consisting of an epoxy resin and its curing agent is preferably within the range of 0.05 to 5.0 g/m ² is that if it is 0.05 g/m ² or less, uniform coating on the film is required. This makes it difficult to adhere to the Al vapor deposited layer, and the adhesion to the Al deposited layer tends to partially decrease. On the other hand, if the coating weight is 5.0g/ ^m2 or more,
Although the adhesion between the film and the Al vapor-deposited layer is ensured, after application to the film, the ability to remove the solvent in a dryer oven decreases, resulting in a significant decrease in workability.

Next, the step of coating the film with a composition comprising an epoxy resin and its curing agent in a solution state and then drying it in a dryer oven is also important, and the drying temperature is preferably within 60 to 150°C. If the drying temperature is below 60°C, the solvent removal property will be significantly reduced and the workability will be significantly reduced. On the other hand, if the drying temperature is 150° C. or higher, the reaction between the epoxy resin and its curing agent will proceed significantly, resulting in a decrease in the adhesion between the film and the Al deposited layer.

Next, Al is preferably deposited to a thickness of 50 to 3000 Å on the epoxy resin composition-coated surface of the biaxially oriented polyethylene terephthalate resin film coated with the epoxy resin composition, using a vacuum evaporation method or the like. Here, the Al vapor deposition method may be any known vacuum vapor deposition method and is not particularly limited. If the deposition thickness is less than 50 Å, the aesthetics will not improve and the
If it exceeds Å, although aesthetics can be ensured, the deposition rate must be reduced, resulting in a significant drop in productivity.

Examples of copolymerized polyester resins include the following polymers of saturated polycarboxylic acids and saturated polyhydric alcohols.

Saturated multivalent carboxylic acids: phthalic acid, isophthalic acid, terephthalic acid, succinic acid, azelaic acid, adipic acid, sebacic acid, dodecanedioic acid, diphenylcarboxylic acid, 2,6 naphthalene dicarboxylic acid, 1,4 cyclohexane dicarboxylic acid, One or more types of trimethic anhydride.

Saturated polyhydric alcohol: ethylene glycol,
1,4 butanediol, 1,5 pentanediol, 1,6 hexanediol, propylene glycol, polytetramethylene glycol, trimethylene glycol, polyethylene glycol, triethylene glycol, neopentyl glycol,
One or more of 1,4 cyclohexanedimethanol, trimethylolpropane, and pentaerythritol.

The polymer may be in the form of a solution or a film, and there are no particular restrictions.

For example, in the case of a solution-type polymer composition, the polymer composition is continuously applied to a metal plate using a roller coater, the solvent component is evaporated in a drying oven, and then the aforementioned biaxially oriented polyethylene terephthalate film is coated with the polymer composition. Can be laminated on top of things. Alternatively, the polymer composition may be applied in advance onto a biaxially oriented polyethylene terephthalate film using a roller coater and dried in a drying oven.

Next, in the case of a film, when making a biaxially oriented polyethylene terephthalate film, the polyethylene terephthalate film and the polymer composition are coextruded using a coextruder, and then biaxially and horizontally stretched and heated. It may also be a two-layer resin film that has undergone a fixing process.

The coating amount of the polymer composition is 0.5 to 0.5 by dry weight.
30 g/m ² is preferred. If the coating amount is less than 0.5 g/ ^m2 , the adhesion between the metal plate and the above-mentioned biaxially oriented polyethylene terephthalate film will decrease significantly, and if it is subjected to severe processing as a material for containers, the biaxially oriented polyethylene terephthalate film will deteriorate. , it becomes easy to peel off from the steel plate described below. On the other hand, 30g/ ^m2
If it becomes more than that, the cost will increase and it will not be economical.

Although the polymer composition is basically a thermoplastic resin, it may be made into a thermosetting resin by adding a curing agent such as melamine resin, urethane resin, or urea resin.

Next, examples of the steel plate used in the present invention include sheet-shaped and coil-shaped steel plates, steel foils, iron foils, and surface-treated steel plates. especially,
Electrolytic chromic acid treated steel sheet with a two-layer structure of chromium hydrated oxide on the top layer and metallic chromium on the bottom layer, nickel-plated steel sheet, galvanized steel sheet, chromium hydrated oxide-coated steel sheet, polar groups such as carboxyl groups or chelates. Examples include organic matter-treated steel sheets having a structure, or phosphate-treated or chromate-treated steel sheets.

Next, an example of a method for laminating the biaxially oriented polyethylene terephthalate resin film on the above-mentioned steel plate is to apply the above-mentioned copolymerized polyester resin to one side of the steel plate by a normal roll cord method, heat it, After drying, a biaxially oriented polyethylene terephthalate film, on which Al has been vapor-deposited in advance by the above-mentioned treatment method, is laminated so that the non-vapor-deposited surface is in contact with the copolymerized polyester surface.
After lamination, either rapid cooling or slow cooling may be performed.

One of the features of the present invention is that adhesion appears instantaneously during lamination, and there is no need for heat activation treatment, such as reheating, which is generally practiced after lamination. Of course, it goes without saying that there is no problem in performing reheating treatment after lamination.

The Al vapor-deposited biaxially oriented polyethylene terephthalate resin film laminated steel sheets thus obtained have excellent appearance, processing corrosion resistance, and processing adhesion, and can be widely used as resin-coated steel sheets for containers, but they require retort sterilization treatment. For products, Al
It is preferable to overcoat the vapor-deposited layer as a top coat with a conventionally used epoxy/phenol paint, epoxy/urethane paint, vinyl paint, organosol paint, or the like.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 A cold-rolled steel plate with a thickness of 0.21 mm was electrolytically degreased in a 70 g sodium hydroxide solution, pickled with a 100 g sulfuric acid solution, washed with water, and then treated with chromic anhydride 60 g/
, in a solution containing 3 g of sodium fluoride at a current density of 20 A/dm ² and an electrolyte temperature of 50° C., and immediately washed with hot water at 80° C. and dried. The amount of metallic chromium in the obtained electrolytically chromic acid-treated steel sheet was 120 mg/m ² , and the amount of hydrated chromium oxide was 10 mg/m ² as chromium.

A biaxially oriented polyethylene terephthalate film treated under the following conditions was continuously laminated on one side of the electrolytic chromic acid treated steel sheet thus treated.

Al deposited layer thickness 550Å Dry weight of epoxy resin composition below Al deposited layer 0.06 g/m ² (Epoxy resin (epoxy equivalent: 3000) 80 parts para-cresol resol 20 parts) Biaxially oriented polyethylene terephthalate film (product name Lumirror) Toray Industries, Inc.) Copolymerized polyester resin composition (trade name) for the lower layer of a 12 μm biaxially oriented polyethylene terephthalate film
Byron 20S (Toyobo Co., Ltd.) dry weight 8g/m ² How to apply copolymerized polyester resin to the steel plate
Roll coating method Copolymerized polyester resin heating and drying conditions Gas oven at 220℃ for 60 seconds Steel plate temperature just before lamination 220℃ Reheating conditions after lamination 210℃ for 30 seconds Cooling method after lamination Rapid cooling Obtained Al vapor deposition Apply epoxy/phenol paint to one side (non-laminated side) of a resin-coated steel plate to a dry weight of 60 mg/dm ² and heat it at 200℃ for 10 minutes.
After being heated and cured for a minute, it was slowly cooled.

A 202-type can lid and a drawn can with a drawing ratio of 2.14 were obtained by using the Al vapor-deposited resin-coated steel plate so that the Al vapor-deposited surface was the outer surface. The molded can lid and squeezed can were double-sealed using a known can manufacturing method, but there was no peeling of Al from the biaxially oriented polyethylene terephthalate film, and the film had a shiny appearance. In addition, double-sealed and integrated containers are heated to 37℃ and 90%
After aging for 10 days at a relative humidity of 100 mL, no external rust was observed, and no peeling of Al was observed at all.

Comparative Example 1 Using the same electrolytic chromic acid treated steel sheet as in Example 1, a biaxially oriented steel sheet was treated under the same conditions as in Example 1, except that only the epoxy resin composition below the Al vapor deposited layer was removed. Polyethylene terephthalate films were laminated in the same manner as in Example 1, and the other side was coated with epoxy/phenol paint with a dry weight of 60%.
It was coated at a concentration of mg/dm ² , cured by heating at 200°C for 10 minutes, and then slowly cooled.

A 202-type can lid and a drawn can with a drawing ratio of 2.14 were obtained by using the Al vapor-deposited resin-coated steel plate so that the Al vapor-deposited surface was the outer surface. When the molded can lid and squeeze can were double-sealed using a known can-making method, the vapor-deposited Al layer was partially peeled off from the biaxially oriented polyethylene terephthalate film near the double seam. Furthermore, when a double-sealed and integrated container was aged for 10 days at 37°C and 90% relative humidity, no rust was observed on the outside, but near the double-sealed draw can. Some of the vapor-deposited Al was missing.

Example 2 A cold rolled steel plate with a thickness of 0.21 mm was electrolytically degreased in a 70 g sodium hydroxide solution, pickled with a 100 g sulfuric acid solution, washed with water, and then treated with 80 g/80 g of chromic anhydride.
, sulfuric acid 0.8g/, sodium silicate 1g/
current density 20A/dm ² , electrolyte temperature 50
Cathode electrolysis treatment under the conditions of 80°C immediately.
Washed with hot water and dried. The amount of metallic chromium in the obtained electrolytic chromic acid treated steel sheet was 160mg/
^m2 , the hydrated chromium oxide is 22mg/ ^m2 as chromium.
It was hot.

A biaxially oriented polyethylene terephthalate film treated under the following conditions was continuously laminated on both sides of the electrolytic chromic acid treated steel sheet thus treated.

Al deposited layer thickness 1400Å Dry weight of epoxy resin composition below Al deposited layer 1.0 g/m ² (Epoxy resin (epoxy equivalent: 2500) 75 parts para-cresol resol 25 parts) Biaxially oriented polyethylene terephthalate film (product name Lumirror) Toray Industries, Inc.) 12μm Dry weight of the copolymerized polyester resin composition of the lower layer of the biaxially oriented polyethylene terephthalate film
25g/m ² (Coat the film with a polycondensate of terephthalic acid/isophthalic acid = 8/2 and polyethylene glycol by coextrusion method) Heating method of steel plate Heater roll method Steel plate temperature immediately before lamination 245℃ Cooling method after lamination Rapid cooling A vinyl organosol paint was applied to both sides of the obtained Al-deposited resin-coated steel sheet to a dry weight of 65 mg/ ^m2 , and after curing by heating at 190℃ for 10 minutes,
It was slowly cooled.

A 202-type can and a drawn can with a drawing ratio of 2.14 were obtained from the Al vapor-deposited resin-coated steel plate by a known can-making method. The molded squeeze can was filled with commercially available tomato juice, deaerated, double-sealed, and heat sterilized at 115°C for 60 minutes, followed by a 6-month storage test at 50°C. After the actual can test, the can was opened and the corrosion state of the inner surface of the can and the adhesion of the biaxially oriented polyethylene terephthalate film were investigated, but no abnormalities were observed, and the can had a bright and beautiful appearance.

In addition, we conducted a storage test for 14 days in an atmosphere of 50℃ and 90% relative humidity, and investigated for filamentous rust or spot rust near the double-sealed can lid, but no abnormalities were observed, and the beautiful Al color was maintained. had.

Comparative Example 2 Using the same electrolytic chromic acid treated steel plate as in Example 2, vinyl organosol paint was applied to both sides of the plate to a dry weight of 65 mg/m ² and then heated at 190°C.
After heating and curing for 10 minutes, it was slowly cooled.

The painted steel plate was processed in the same manner as in Example 2 to obtain a can lid and a squeeze can, filled with tomato juice in the same manner as in Example 2, and subjected to a real can storage test at 50°C for 6 months. I went.

After the actual can test, the can was opened and the corrosion state of the inside of the can was investigated. Several black dots of rust were observed near the double seam of the drawn can and near the compound insertion part of the can lid.

In addition, when we conducted a storage test for 14 days in an atmosphere at 50℃ and 90% relative humidity, many filamentous rusts with a length of 3 to 15 mm appeared near the double seam of the can lid, which significantly damaged the appearance of the container. was.

Example 3 A cold-rolled steel plate with a thickness of 0.21 mm was electrolytically degreased in a 70 g sodium hydroxide solution, pickled with a 100 g sulfuric acid solution, washed with water, and then dried with a dryer.

Biaxially oriented polyethylene terephthalate films treated under the following conditions were continuously laminated on both sides of the thus cleaned black plate.

Al deposited layer thickness 2000Å Dry weight of epoxy resin composition below Al deposited layer 4.5 g/m ² (Epoxy resin (epoxy equivalent: 550) 70 parts urea resin 30 parts) Biaxially oriented polyethylene terephthalate film (product name Lumirror Toray Co., Ltd.) Copolymerized polyester resin composition (trade name) for the lower layer of a 16 μm biaxially oriented polyethylene terephthalate film
How to apply Byron 103S (Toyobo Co., Ltd.) dry weight 12g/ ^m2 copolymerized polyester resin to the steel plate...
Roll coating method Heating and drying of copolyester resin The dry weight of the paint is 40mg/dm ²
It was coated so as to have the following properties, cured by heating at 205°C for 10 minutes, and then slowly cooled.

A 202-type can lid and a drawn can with a drawing ratio of 2.14 were obtained from the Al vapor-deposited resin-coated steel plate by a known can-making method. Fill a molded squeeze can with 0.5% salt solution,
After double-sealing, a real can storage test was conducted at 37°C for 20 days.

After the actual can test, the can was opened and the corrosion state on the inside of the can and the adhesion of the biaxially oriented polyethylene terephthalate film were investigated, but no abnormalities were found.
The shiny appearance of Al remained intact.

In addition, the amount of iron eluted in 0.5% saline solution after the actual can test was measured by atomic absorption spectrometry, and it was below the detection limit.

In addition, we conducted a storage test for 14 days in an atmosphere at 37℃ and 90% relative humidity, and investigated thread-like rust or spot rust near the double-sealed can lid. Although 5mm has appeared, Al
Since it appeared in the lower layer of the vapor deposited layer, it had the brightness of Al, which was quite beautiful in appearance.

Comparative Example 3 On both sides of the same black plate as in Example 3,
After drying the epoxy/phenol paint using the same treatment method as in Example 3, can lids and squeeze cans were made using the same can-making method as in Example 3, filled with 0.5% saline solution, and After applying heavy wrapping, a real can storage test was conducted at 37℃ for 20 days.

After the actual can test, the can was opened and the state of corrosion on the inside of the can was investigated. Red rust had developed over the entire inside of the can, and most of the thin film had peeled off from the base steel plate. In addition, a storage test was carried out for 14 days at 37°C and a relative humidity of 90%, and filamentous rust or spot rust was investigated, and filamentous rust with a length of 6 to 19 mm appeared on the can lid and steel can part. The appearance was noticeably poor.
In addition, cracks had occurred in the paint film near the double seaming area, and blackish brown rust had appeared on the entire surface.

〔Effect of the invention〕

The Al vapor-deposited resin-coated steel sheet thus obtained has glitter, so it not only has an excellent appearance, but also has excellent processing corrosion resistance and processing adhesion, so it can be widely applied as a material for containers.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views of the resin-coated steel sheet of the present invention. FIGS. 3 and 4 are cross-sectional views of a container formed using the resin-coated steel sheet of the present invention. 1... Steel plate, 2... Copolymerized polyester resin,
3... Biaxially oriented polyethylene terephthalate resin layer, 4... Epoxy resin and curing agent, 5...
Al vapor deposition layer, 6... Epoxy phenol paint, 7
...Vinyl organosol paint.

Claims (1)

[Claims] 1 A composition having an Al vapor deposited layer of 50 to 3000 Å as the outermost layer, and an epoxy resin and one or more of its curing agents such as phenol, urea, amide, ester, acrylic, and urethane in the inner layer. 1. A resin-coated steel sheet for containers, which has a biaxially oriented polyethylene terephthalate resin layer as the inner layer, and a copolymerized polyester resin layer as the bottom layer.