JPH03212433A - Production of metal plate coated with polyester resin having excellent heat resistance - Google Patents

Abstract

PURPOSE:To obtain the subject metal plate having excellent working corrosion resistance, etc., by heating a metal plate containing hydrated chromium oxide at a specific temperature and applying a specific biaxially oriented polyester film to a surface of the metal plate using a laminated rubber roll heated at a specific temperature. CONSTITUTION:The object metal plate can be produced by heating (A) a polyester film having a thickness of 5-50mum, a crystal melting temperature of 200-250 deg.C, a density of 1.3500-1.4100 and a plane orientation coefficient of 0.050-0.1600 and containing ethylene terephthalate unit accounting for 75-99% of the ester recurring units at a temperature between Tm-50 deg.C and Tm (Tm is crystal melting temperature) and laminating the film A to (B) one or both surfaces of a metal plate (e.g. steel plate) surface-treated preferably with 10-150mg/m<2> of metallic chromium as the lower layer and 5-30mg/m<2> of hydrated chromium oxide, etc., as the upper layer using (C) a lamination roll heated at a temperature between Tm-150 deg.C and Tm-10 deg.C.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a polyester resin-coated metal plate with excellent heat resistance, and more specifically, relates to a method for manufacturing a metal plate coated with a polyester resin having excellent heat resistance. This invention relates to a method for producing a polyester resin-coated metal plate with excellent heat resistance, which comprises laminating a specific polyester film on one or both sides of the plate at a temperature below the crystal melting temperature of the polyester film.

[Conventional technology]

Conventionally, in the can manufacturing industry, metal plates such as furiki, electrolytic chromic acid treated steel plates, and aluminum plates have been coated once or multiple times. Applying multiple coats in this way not only complicates the baking process (and requires a large amount of baking time). Attempts have been made to do so. - For example, polyester film is laminated onto a metal plate without using an adhesive (Japanese Patent Publication No. 60-47103, Japanese Patent Application Laid-open No. 61-14934).
0), a polyester film laminated to a metal plate using a specific adhesive (Special Publication No. 63-13829,
JP-A No. 61-149341) and the like are disclosed.

In addition to the field of can manufacturing, a method (Japanese Patent Publication No. 59-46786) has been disclosed in which a polyester film is bonded under heat and pressure to a metal article without using an adhesive.

[Problem to be solved by the invention]

However, Japanese Patent Publication No. 60-47103 and Japanese Patent Publication No. 1493
The method of laminating a polyester film to a metal plate without using an adhesive disclosed in No. 40 requires lamination to a metal plate heated above the melting point of the polyester film. , is characterized in that an amorphous polyester layer is formed, and the polyester layer improves adhesion to the metal plate.

Such polyester resin-coated metal sheets exhibit excellent processing adhesion and processing corrosion resistance, but when used in applications requiring sterilization under high-temperature retort conditions of 100 to 135°C, the amorphous polyester layer formed crystallizes. It tends to become milky white.

In particular, this opalescence phenomenon tends to occur during retort processing (if water vapor does not uniformly hit the polyester-coated metal plate, a spotty whitening phenomenon will occur (hereinafter referred to as retort brushing phenomenon), which will significantly impair the appearance. It had some drawbacks.

Furthermore, a laminate in which an oriented polyester film is adhered to a metal article in a temperature range from (glass transition temperature +80)°C to less than the melting point disclosed in Japanese Patent Publication No. 59-46786,
Although it exhibits a slight adhesive strength using the T-beer method, it cannot be put to practical use as a material for the cans of the present invention, which requires strict processing characteristics.

The method disclosed in JP-A No. 61-20736 and JP-A No. 61-149341 in which a polyester film is laminated onto a metal plate using a specific adhesive is such that lamination is performed at a temperature below the melting point of the polyester film, so that the area near the metal plate is Polyester does not easily form an amorphous polyester layer. Therefore, although the retort brushing phenomenon does not occur even if the retort treatment is performed, the process of applying a specific adhesive onto the polyester film in advance is not only complicated but also costly.

[Means to solve the problem]

The present invention aims to solve the above problems (as a result of various studies, it was found that a specific polyester film is laminated continuously at high speed on one or both sides of a metal plate with a specific surface treatment layer). The polyester resin-coated metal sheet obtained by the method of the present invention not only has excellent processing adhesion and processing corrosion resistance (but also can be used as lid material and body of food or beverage cans that require sterilization under high-temperature steam). Widely used as a material (applicable).

Hereinafter, the content of the present invention will be explained in detail.

First, as a polyester film, at least 75 to 99% of the ester repeating units consist of ethylene terephthalate units, and the remaining 1 to 25% of the ester repeating units are
One of phthalic acid, isophthalic acid, terephthalic acid, succinic acid, azelaic acid, adipic acid, cepatic acid, dodecanedioic acid, diphenylcarboxylic acid, 2.6 naphthalene dicarboxylic acid, 1.4 cyclohexane dicarboxylic acid, trimethic anhydride, or Two or more acid components, ethylene glycol, 1.4 butanediol, 1.5 bentanediol, 1.6 hexanediol, propylene glycol, polylatramethylene glycol, trimethylene glycol, trimethylene glycol, neopentyl glycol, 1 .4 One or more saturated polyhydric alcohols selected from cyclohexane dimetatool, trimethylolpropane, and pentaerythritol are used.

Such a polyester resin is formed into a film using a known extruder, and after being formed into a film, it is stretched in both the vertical and horizontal directions, and then subjected to a heat setting process to obtain a polyester film with excellent barrier properties.

Although the thickness of the polyester film is not particularly limited, it is preferably within the range of 5 to 50 μm.

If the thickness is less than 5 μm, the laminating workability will be significantly reduced and sufficient processing corrosion resistance will not be obtained. On the other hand, if the thickness is more than 50 μm, it is less economical than epoxy paints widely used in the can manufacturing field. Not.

The crystal melting temperature of such polyester film is 200~
The temperature is preferably within the range of 250°C.

The crystal melting temperature here refers to the differential scanning calorimeter (881
0, manufactured by Seiko Electronics Co., Ltd.), 10 °C/mi
n.

An endothermic peak is observed when the temperature is raised at a heating rate of
The temperature that indicates the maximum depth of the endothermic peak.

When the crystal melting temperature of the polyester film is 250'C or higher, when laminating it onto a metal plate, it is necessary to laminate it at a temperature considerably higher than the crystal melting temperature when considering process adhesion and process corrosion resistance, and as a result, the metal plate A large amount of amorphous polyester layer is formed in the vicinity, and the above-mentioned retort brushing properties are significantly reduced.

On the other hand, when the crystal melting temperature is 200° C. or less, the lamination properties of the polyester film itself are significantly reduced, and it becomes extremely difficult to laminate a thin polyester film of 10 μm or less at high speed.

Next, the density of the polyester film is also an important factor in completing the present invention, and the density is 1.3500 to 1.
．． It is preferably within the range of 4100.

If the density is less than 1.3500, the polyester film will have a large amount of amorphous parts, and if it is laminated to a metal plate and then subjected to various dry heat processes in the can manufacturing process, or if it is When subjected to wet heat treatment, the amorphous portion turns into coarse spherulites, resulting in poor appearance such as whitening, or a significant decline in processing adhesion, processing corrosion resistance, etc.

On the other hand, in the case of high-density polyester with a density of 1.4100, there are extremely few amorphous parts in the film.
It is practically difficult to laminate the polyester film onto a metal plate at a temperature below the crystal melting temperature of the polyester film.

Next, the orientation of the polyester film is also an important factor when considering the processing adhesion, processing corrosion resistance, and retort brushing properties of the polyester film. That is,
It is important that the plane orientation coefficient is within the range of 0.050 to 0.1600.

The planar orientation coefficient here is determined by a refractometer and is defined as (longitudinal refractive index+lateral refractive index)÷2−thickness direction refractive index.

When the plane orientation coefficient is 0.1600 or more, the polyester film becomes rigid and the processability decreases (and it becomes very difficult to laminate the polyester film at a temperature below the crystal melting temperature. 0
When it is less than 50, the degree of orientation between molecules decreases (because
When post-heat treatment or hot water treatment is performed, spherulites tend to be easily formed and both appearance and workability tend to deteriorate significantly.

Moreover, if the plane orientation coefficient is 0.050 or less, the polyester film tends to become brittle over time, and the properties become unstable, which is not preferable.

Such a polyester film may be blended with a coloring agent such as a pigment or dye to improve its aesthetics, an inorganic lubricant to impart slipperiness, or an antistatic agent.

Next, examples of metal plates used in the present invention include surface-treated metal plates such as sheet-shaped and coil-shaped steel plates, steel foils, and aluminum plates. The quality and quantity of the surface treatment film on the metal plate are very important.

In particular, the lower layer is metallic chromium and the upper layer is chromium hydrated oxide.
Electrolytic chromic acid treated steel sheet with a layered structure, tin-plated steel sheet, nickel-plated steel sheet, or aluminum sheet with chromium hydrated oxide or an upper layer of chromium hydrated oxide,
A surface-treated material whose lower layer is a metallic chromium layer has excellent adhesion to the above-mentioned polyester film. The amount of metallic chromium is 10 to 150 ■/m2, the amount of hydrated chromium oxide is 5 to 30 ■/m2, the amount of Sn is 0.1 to 5.6 g/m", and the amount of Ni is 0.05
The surface treatment film in the range of ~3.0 g/m" has particularly excellent adhesion to the polyester film mentioned above, and has sufficient processing adhesion even when subjected to the severe deep drawing processing required for can materials. have power.

Next, the temperature of the laminating rubber roll and the temperature of the metal plate when laminating such a polyester film on a metal plate are important, and the temperature of the laminating rubber roll and the temperature of the metal plate during lamination must be within a predetermined temperature range. For the first time, the present invention can be achieved.

The temperature of the laminated rubber roll is preferably within the range of (crystal melting temperature -150)C to (crystal melting temperature -10)C. If the temperature of the laminating rubber roll is below (crystal melting temperature - 150'C), the polyester film cannot be stably laminated in the temperature range of the metal plate described below, and air bubbles etc. will easily enter the polyester film after lamination. It has little adhesive strength and is of little practical use. Also, the temperature of the laminated rubber roll is (crystal melting temperature - 1
If the temperature of the metal plate is set to a temperature higher than the crystal melting temperature of the polyester film, even if the temperature is below 50)°C, lamination is possible and the adhesive strength of the polyester film is strong. The more the polyester film layer near the metal plate becomes amorphous, as a result,
When post-heat treatment and post-hot water treatment are performed, processing adhesion and appearance are significantly reduced due to crystallization of the amorphous polyester layer.

On the other hand, the temperature of the laminated rubber roll is (crystal melting temperature +
10) When the temperature exceeds 0C, it approaches the crystal melting temperature range of the polyester film (therefore, the polyester film tends to soften and adhere to the laminated rubber roll, significantly reducing workability. There are particular restrictions on the material of the rubber for the laminated rubber roll. However, silicone rubber rolls, fluororubber rolls, etc., which have excellent thermal conductivity and heat resistance, are preferable.

Next, the temperature of the metal plate just before it is laminated is:
(Crystal melting temperature -50) C. to crystal melting temperature is preferable.

When the temperature of the metal plate is below (crystal melting temperature -50°C), the polyester film cannot be firmly adhered to the metal plate no matter how the temperature of the surface of the laminated rubber roll is adjusted. On the other hand, when the temperature of the metal plate exceeds the crystal melting temperature, as mentioned above, a part of the polyester film layer near the surface of the metal plate becomes an amorphous polyester layer, and after going through various post-heating steps in the can manufacturing process. Alternatively, when subjected to a hot water treatment process such as retort treatment, processing adhesion and processing corrosion resistance may decrease, and the amorphous polyester layer may become cloudy due to heat-induced crystallization, resulting in poor appearance.

Cooling after lamination may be performed through either a rapid cooling process or a slow cooling process.

In the process of producing a large amount of amorphous polyester layer by high-temperature lamination as seen in JP-A-61-149340, a process of rapid cooling after lamination is necessary to prevent thermal crystallization of the amorphous polyester layer. When the formation of an amorphous polyester layer is very small as in the invention, a rapid cooling process to prevent thermal crystallization is not necessarily required after lamination.

Next, methods for heating the metal plate include known hot air circulation heat transfer methods, resistance heating methods, induction heating methods, heat roll heat transfer methods, etc., and are not particularly limited; In consideration of simplicity, the heat roll heat transfer method is preferable.

〔Example〕

This will be explained in detail in Examples below.

Example 1 A cold-rolled steel plate with a thickness of 0.21 mm was electrolytically degreased in a 70 g/l sodium hydroxide solution, and the degreasing of 100 g/I! After pickling with sulfuric acid solution and washing with water, chromic anhydride 60g/
n.

Current density 20A in a solution of sodium fluoride 3g/l
/dm2 and an electrolyte temperature of 50° C., and immediately washed with hot water of 80° C. and dried.

The following polyester films were continuously laminated on both sides of the strip-shaped electrolytically chromic acid treated steel sheet having a width of 300 mm thus treated under the following conditions.

Biaxially oriented polyester film 12μm (polycondensate of ethylene glycol and terephthalic acid/isophthalic acid) Crystal melting temperature 229℃ Density
1.3869 plane orientation coefficient
0.1011 Temperature of steel plate just before lamination
225°C laminating roll surface temperature is 17
Example 2 of Silicon Mouth Controlled at 0 DEG C. Both sides of the same electrolytic chromic acid treated steel sheet as in Example 1 were laminated continuously under the following conditions.

Biaxially oriented polyester film 15 μm (polycondensate of ethylene glycol and terephthalic acid/azelaic acid) Crystal melting temperature 240°C Density
1.3991 plane orientation coefficient
0.1510 Temperature of steel plate just before lamination: 210°C Laminating roll surface temperature: 17
Silicon roll controlled at 0°C Example 3 A cold-rolled steel sheet similar to that in Example 1 was subjected to the same pretreatment as in Example 1, and then treated with 80 g/l of tin sulfate and 60 g of phenolsulfonic acid (60% aqueous solution). /j2, using an electrolyte containing 5 g/l of ethoxylated α-naphtholsulfonic acid, tin plating was performed under the conditions of a current density of 15 A/dm2 and an electrolyte temperature of 40°C, followed by reflow treatment, washing with water, and grinding. Continued Chromic anhydride 30g/jl', sulfuric acid 0.3g/l'! Chromic acid treatment was performed using an electrolytic solution at a current density of 40 A/d m2 and an electrolytic solution temperature of 50° C., followed by washing with water and drying.

Both sides of the obtained strip-shaped tin-plated steel plate with a width of 300 mm were
The following polyester films were laminated continuously under the following conditions.

Biaxially oriented polyester film 16μm (polycondensate of ethylene glycol and terephthalic acid/cepatic acid) Crystal melting temperature 220°C Density
1.3854 plane orientation coefficient
0.1008 Temperature of steel plate just before lamination: 195°C Laminating roll surface temperature: 15
Silicon roll controlled at 0°C Example 4 A cold-rolled steel sheet similar to that in Example 1 was pretreated in the same manner as in Example 1, and then 40 g/] of nickel chloride (hexahydrate) and nickel sulfate (6 water salt) 250g/J, boric acid 40g/Jl
Current density 10A/dm2 using a Watts bath consisting of '
Nickel plating of 0.6 g/m2 was applied at a bath temperature of 45°C, and after washing with water, 30 g/m of sodium dichromate was applied.
Chromate treatment was performed in a solution of
Dry.

The polyester film shown below was continuously laminated on both sides of the obtained strip-shaped nickel-plated steel plate having a width of 300 mm under the conditions shown below.

Biaxially oriented polyester film 16μm (polycondensate of ethylene glycol and terephthalic acid/isophthalic acid) Crystal melting temperature 211℃ Density
1.3721 plane orientation coefficient
0.0668 Temperature of steel plate just before lamination
178°C laminating roll surface temperature is 105
Comparative example 1 of silicone roll controlled at ℃ Using the same steel plate as in Example 1 which had only been degreased and pickled, it was continuously heated under the same conditions as in Example 1 except for the polyester film. Laminated.

Biaxially oriented polyester film 12μm (polycondensate of ethylene glycol and terephthalic acid) Crystal melting temperature 258℃ Density
1.4041 plane orientation coefficient
0.1670 Comparative Example 2 Using the same steel plate and polyester film as in Example 1, polyester films were laminated on both sides of the steel plate under the lamination conditions shown below.

Temperature of steel plate immediately before lamination: 242°C Laminating roll Silicone roll with surface temperature controlled at 180°C Comparative Example 3 Using the same steel plate and polyester film as in Example 4, laminating both sides of the steel plate under the conditions shown below. laminated with polyester film.

Temperature of steel sheet immediately before lamination: 260°C Laminating roll Silicone roll whose surface temperature was controlled at 55°C The obtained polyester resin-coated metal sheet was evaluated using the following test method, and the results are shown in Table 1. .

(1) Measurement of plating amount on metal plate The plating amount and film amount were measured by fluorescent X-ray method.

(2) Processing adhesion of polyester resin-coated metal plate After punching a polyester resin-coated metal plate into a disc with a diameter of 96 mm and drawing a cylindrical cup at a drawing ratio of 2.36,
Peeling of the polyester film from the inner and outer surfaces of the cup was expressed as the length of peeling from the end surface of the cup.

(3) Hot water resistance of the polyester resin-coated metal plate The polyester resin-coated metal plate was subjected to hot water treatment for 1 hour under retort conditions at 120°C, and changes in the appearance of the polyester resin-coated metal plate were visually evaluated.

(4) Heat resistance of polyester resin-coated metal plate After baking the polyester resin-coated metal plate in an atmosphere of 200° C. for 10 minutes, changes in the appearance of the polyester resin-coated metal plate were visually evaluated.

〔Effect of the invention〕

The thus obtained metal plate laminated with polyester film on one or both sides has excellent processing corrosion resistance, heat resistance,
Because it has excellent hot water resistance, it can be widely used as a material for melting vessels, such as drawn or drawn cans that are painted or printed, easy-open lids or can bottom lids, crowns, and caps.

Claims (1)

[Claims] Crystal melting temperature is 200-250℃, density is 1.3500
~1.4100, plane orientation coefficient 0.050~0.160
0 biaxially oriented polyester film is heated within the range of (crystal melting temperature -50) °C to crystal melting temperature,
At least one or both sides of a metal plate containing hydrated chromium oxide should be laminated using a laminating rubber roll heated within the range of (crystal melting temperature -150) °C to (crystal melting temperature -10) °C. A method for manufacturing a polyester resin-coated metal plate with excellent heat resistance.