JP2017213884A - Thermoplastic polyester resin coated metal sheet, can made of thermoplastic polyester resin coated metal sheet and manufacturing method of thermoplastic polyester resin coated metal sheet - Google Patents

Abstract

Disclosed is a resin-coated metal plate that is excellent in formability, corrosion resistance, and general-purpose material properties, and has excellent retort resistance when formed into a can.
SOLUTION: At least one surface of a metal material has a resin coating layer made of an unstretched thermoplastic polyester resin, and the resin coating layer emits linearly polarized laser light on the interface side with the metal material. The resin coating layer has a region where the half-value width of the Raman shift peak of the thermoplastic polyester resin caused by C═O stretching vibration in the vicinity of 1730 cm ⁻¹ in the laser Raman spectroscopy used is 20 to 24 cm ^−1. A thermoplastic polyester resin-coated metal sheet having a region in which the half-value width of the Raman shift peak is 14 to 18 cm ⁻¹ on the surface side. A coated metal plate, wherein the thermoplastic polyester resin layer is a single layer or a multilayer, and the layer constituting the surface of the resin layer is composed of a polyethylene plate containing 5 mol% or less of isophthalic acid as a copolymerization component.
[Selection figure] None

Description

  The present invention relates to a thermoplastic polyester resin-coated metal plate. More specifically, the present invention relates to a thermoplastic polyester resin-coated metal plate excellent in moldability, corrosion resistance, and general-purpose material properties, a can having excellent retort resistance comprising a thermoplastic polyester resin metal plate, and a method for producing a thermoplastic polyester resin-coated metal plate. .

  From the viewpoint of simplifying the manufacturing process of metal cans, hygiene and environmental conservation, resin films were coated on tin, tin-free steel, aluminum and other metal plates instead of organic solvent-based coatings on the inner and outer surfaces of the cans. Later, a technique for producing a can by drawing or the like has been studied. In such examination, many proposals have conventionally been made regarding a metal plate coated with a resin film.

  As conventional proposals, for example, a method of coating a metal plate with a polyester resin film by thermal bonding is disclosed in Patent Document 1 and Patent Document 2 below.

Japanese Patent Publication No. 60-47103 JP-A-3-212433

  The polyester resin-coated metal plate obtained by the method disclosed in Patent Document 1 has many applications that can be applied as a can material due to its excellent formability, corrosion resistance, and economy. However, in applications where it is necessary to perform retorting for sterilization after filling the contents of the can, the metal under the polyester resin layer is discolored or corroded, and the commercial value is significantly reduced.

  This phenomenon is caused by the presence of an amorphous polyester layer (amorphous polyester resin layer) formed near the metal plate when the polyester resin layer is laminated on a metal plate heated to a temperature equal to or higher than the melting point of the polyester resin. It is considered that the barrier property of the entire layer is lowered and water vapor and corrosive components permeate through this layer.

  On the other hand, the polyester resin-coated metal plate disclosed in Patent Document 2 is not higher than the melting point of the polyester resin in order to improve retort resistance, which is a defect of the polyester resin-coated metal plate obtained by the method of Patent Document 1. The polyester resin layer is laminated on the metal plate at a temperature of, and the amorphous polyester resin layer formed at the time of lamination is made as thin as possible to prevent a decrease in retort resistance due to the amorphous polyester resin layer.

  However, although the retort resistance as a polyester resin-coated metal plate is excellent, the following problems also occur because the amorphous polyester resin layer is made as thin as possible. That is, since the polyester resin layer is laminated on a metal plate heated to a temperature below the melting point of the polyester resin, the melt viscosity of the polyester resin in contact with the metal plate at the time of lamination is high, and the metal plate surface is uniformly and sufficiently wet. In addition, since the melted layer is extremely thin, the adhesiveness between the laminated polyester resin layer and the metal plate is unstable.

  The problem to be solved by the present invention is excellent in moldability, work adhesion, corrosion resistance, general-purpose material properties, etc. required for can materials, and after filling the molded can body with the contents, the retort treatment is performed. The purpose is to develop a can material that does not discolor or corrode the metal under the film coating on the inner surface of the can. More specifically, for example, deep-drawn cans, thin-walled deep-drawn cans, etc., the can body is subjected to printing before or after the molding process, and the outer surface of the can is subjected to printing, and heating is performed to cure the printing ink, It is an object of the present invention to provide a thermoplastic polyester resin-coated metal plate that can be applied to applications in which the contents are subsequently filled and retorted, and a method for producing the same. Further, for example, cans, deep-drawn cans, drawn redrawn cans (DRD cans), etc., the can body is filled with the contents as it is without being subjected to printing before or after the molding process, and subjected to retort processing. Another object of the present invention is to provide a thermoplastic polyester resin-coated metal plate that can be applied to various uses and a method for producing the same.

  An object of the present invention is to provide a thermoplastic polyester resin-coated metal plate excellent in moldability, corrosion resistance and general-purpose material properties, and excellent in retort resistance when molded into a can, and a method for producing the same.

  In order to solve the above problems, the present inventor has conducted various studies, and as a result, the polyester resin film is thermally fused to a metal plate having a chromium hydrated oxide film having excellent adhesion to the polyester resin film, such as TFS. By controlling the polyester resin layer before retorting, the crystal state of the polyester resin layer on the interface side with the metal plate and the crystal state of the polyester resin layer on the surface side are appropriately adjusted. It has been found that a polyester resin-coated metal sheet having excellent moldability, corrosion resistance and general-purpose material properties and excellent retort resistance can be obtained by controlling the content within the range.

That is, according to the present invention, an unstretched thermoplastic polyester resin layer is provided on at least one surface of a metal material, and the thermoplastic polyester resin layer is a linearly polarized laser on the interface side with the metal material. The half-value width of the Raman shift peak of the thermoplastic polyester resin due to C = O stretching vibration in the vicinity of 1730 cm ⁻¹ in laser Raman spectroscopy using light (meaning shifted peak in Raman spectroscopy) is 20 cm. ^-1 or more and 24 cm ^-1 or less, and on the surface side opposite to the metal material, the half width of the Raman shift peak is 14 cm ^-1 or more and 18 cm ^-1. A thermoplastic polyester resin-coated metal plate having a second region which is the following is provided.

  Furthermore, according to this invention, the can which consists of the said thermoplastic polyester resin coating metal plate is provided.

  Furthermore, according to this invention, the manufacturing method of the said thermoplastic polyester resin coating metal plate is provided.

The thermoplastic polyester resin-coated metal plate of the present invention has an unstretched thermoplastic polyester resin layer on at least one surface of the metal material, and the thermoplastic polyester resin layer is on the interface side with the metal material. The half width of the Raman shift peak of the thermoplastic polyester resin due to C = O stretching vibration in the vicinity of 1730 cm ⁻¹ in laser Raman spectroscopy using linearly polarized laser light is 20 cm ⁻¹ or more and 24 cm ⁻¹ or less. It is important to have a first region and a second region having a half-value width of the Raman shift peak of 14 cm ⁻¹ or more and 18 cm ⁻¹ or less on the surface side of the thermoplastic polyester resin layer. It is a feature.

  Discoloration or corrosion at the interface between the thermoplastic polyester resin layer and the metal plate during retort treatment is caused by poor barrier properties due to the low crystalline state of the thermoplastic polyester resin layer. In order to suppress it, it is necessary to increase the crystal state of the thermoplastic polyester resin layer. On the other hand, in order to maintain or improve the formability of the thermoplastic polyester resin-coated metal plate, it is desirable that the thermoplastic polyester resin layer has a low crystal state and a large elongation. Thus, retort resistance and formability are mutually contradictory characteristics.

  In the present invention, the thermoplastic polyester resin layer has a large elongation and excellent moldability, but even if there is a region with poor retort resistance, this region and the region with excellent retort resistance are thermoplastic polyester. By making the structure coexisting in the thermoplastic polyester resin layer in the resin-coated metal plate, it has been found that the occurrence of discoloration and corrosion is effectively suppressed during retort processing, and both of these conflicting characteristics are at a high level. It is now possible to have both.

  According to the present invention, it has excellent moldability, corrosion resistance and general-purpose material properties, and is excellent in retort resistance when molded into a can.

FIG. 1 is a diagram showing a thickness direction distribution of a Raman shift peak half-value width in a resin layer cross section of a thermoplastic polyester resin-coated metal plate of Examples and Comparative Examples. FIG. 2 is a diagram showing a thickness direction distribution of a Raman shift peak half-value width in a resin layer cross section of a thermoplastic polyester resin-coated metal plate of other examples and other comparative examples. FIG. 3 is a diagram showing a thickness direction distribution of a Raman shift peak half-value width in a resin layer cross section of a thermoplastic polyester resin-coated metal plate of still another example and a comparative example.

  Since the moldability and retort resistance strongly depend on the crystalline state of the thermoplastic polyester resin layer, the crystalline state in the thickness direction of the thermoplastic polyester resin layer in the two regions (first region and second region), that is, the crystalline state Formability and retort resistance can be organized by profile (analysis result of crystal state in the thickness direction).

In the present embodiment, in a crystalline polymer such as polyethylene terephthalate among thermoplastic polyester resins, the half-width of the Raman band near 1730 cm ⁻¹ derived from the stretching vibration of the carbonyl group (C═O) is an index of the crystalline state. In addition, since the sample can be measured as it is without the need for sampling, and the sample can be irradiated with laser light focused to about 1 μm, the local state can be measured, so the crystal state profile by laser Raman spectroscopy can be obtained. Adopted.

  In addition, when the above half-value width is reduced, the density of the thermoplastic polyester resin is increased and the crystallinity is increased. On the contrary, when the half-value width is increased, the density of the thermoplastic polyester resin is decreased and the crystallinity is decreased.

FIG. 1 is a diagram showing the thickness direction distribution of Raman shift peak half-value widths for several examples of thermoplastic polyester resin-coated metal plates in Examples and Comparative Examples described later. The outline of this embodiment will be described with reference to this figure. The horizontal axis in the figure is the distance (thickness) from the surface of the thermoplastic polyester resin layer, and the vertical axis is the heat caused by C = O stretching vibration in the vicinity of 1730 cm ⁻¹ in the laser Raman spectroscopy of the cross section of the thermoplastic polyester resin layer. This is the half width of the Raman shift peak of the plastic polyester resin, and shows the above-mentioned crystal state profile.
In light of the evaluation results of Examples and Comparative Examples described later, the following can be said.

(1) Comparative Example 11 is a thermoplastic polyester resin-coated metal plate that is not subjected to post-heat treatment after laminating an unstretched thermoplastic polyester resin film in a heated environment. The crystal state profile shows that the half-value width of the Raman shift peak of the thermoplastic polyester resin caused by C = O stretching vibration in the vicinity of 1730 cm ⁻¹ in laser Raman spectroscopy depends on the position in the thickness direction of the thermoplastic polyester resin layer. not a substantially constant above a 24cm ^-1, not present thermoplastic polyesters half width on the surface side of the resin layer is not less 14cm ^-1 or more 18cm ^-1 or less is the area (second area of above).

The can made of the thermoplastic polyester resin-coated metal plate represented by (1) has good moldability but poor retort resistance, and the poor retort resistance is a region where these crystalline states are high ( It is understood that the (second region) does not exist.
Although the resin composition or the layer structure is different from that of Comparative Example 11, Comparative Example 1, Comparative Example 7, Comparative Example 9, and Comparative Example 10 are obtained by laminating an unstretched thermoplastic polyester resin film in a heating environment, and then post-heating. It is the same as Comparative Example 11 in that it is a thermoplastic polyester resin-coated metal plate that is not treated. The crystal state profile of laser Raman spectroscopy is the same as that of Comparative Example 11, and the moldability is good but the retort resistance is poor. I'm doing it.

(2) Comparative Example 12 is obtained by subjecting the same thermoplastic polyester resin-coated metal plate as Comparative Example 11 to post-heating treatment. The crystal state profile of this example has a region at which the half-value width of the Raman shift peak is about 20 cm ⁻¹ on the surface side of the thermoplastic polyester resin layer and has a higher crystal state than Comparative Example 11, but the half-value width is 14 cm. ^-1 or more and not reaching an area of 18 cm ^-1 or less (the above-described second region).

  And in the can made of the thermoplastic polyester resin-coated metal plate shown in (2), the retort resistance is still inferior, and it is recognized that the crystal state in the vicinity of the surface layer is increased by the post-heating treatment, but the retort resistance It is understood that it is insufficient to contribute to sex.

(3) Comparative Example 13 is a thermoplastic polyester resin-coated metal plate that is not subjected to post-heating treatment after laminating a stretched thermoplastic polyester resin film in a heating environment. The crystalline state profile of this example shows that the half-value width of the Raman shift peak is about 16 cm ⁻¹ on the surface side of the thermoplastic polyester resin layer (a second region having a half-value width of 14 cm ⁻¹ or more and 18 cm ⁻¹ or less. However, there is a region where the crystal state with a half-width of the Raman shift peak of about 18 cm ⁻¹ remains considerably on the interface side with the metal material, and a half of the crystal state is present on the interface side with the metal material. There is no first region having a value width of 20 cm ⁻¹ or more and 24 cm ⁻¹ or less.

  And in the can made of the thermoplastic polyester resin-coated metal plate shown in (3), the retort resistance is good, but the moldability is inferior, and it has such a crystalline state on the interface side with the metal material. Resin coating results in poor moldability.

(4) In Comparative Example 14, the same thermoplastic polyester resin-coated metal plate as in Comparative Example 13 is subjected to post-heating treatment. Crystalline state profile of this example, the half-width of the Raman shift peaks in the thermoplastic polyester resin layer, remained from 13cm ^-1 at 15cm ^-1, and overall half-value width becomes smaller relative to Comparative Example 13 The first region having a half width of 20 cm ⁻¹ or more and 24 cm ⁻¹ or less does not exist on the interface side with the metal material.

And in the can which consists of a thermoplastic polyester resin coating metal plate shown by this (4), although retort resistance improves, it will worsen about a moldability.
In addition, in order to improve moldability when the stretched thermoplastic polyester resin film is applied, a first region having a half width of 20 cm ⁻¹ or more and 24 cm ⁻¹ or less is formed on the interface side with the metal material. It is necessary to lower the crystal state as is done. In order to achieve this by post-heating treatment, it is conceivable to increase the post-heating temperature to a level at which the thermoplastic polyester resin layer in the vicinity of the interface with the metal material melts. In this case, the surface of the thermoplastic polyester resin layer It is presumed that the side also melts and the retort resistance decreases.

(5) Example 2 is a thermoplastic polyester resin-coated metal plate obtained by laminating an unstretched thermoplastic polyester resin film in a heating environment and then post-heating treatment. The crystal state profile in this example has a first region having a half-value width of 20 cm ⁻¹ or more and 24 cm ⁻¹ or less on the interface side with the metal material, and a half-value width on the surface side of the thermoplastic polyester resin layer. A second region having a value width of 14 cm ⁻¹ or more and 18 cm ⁻¹ or less exists.

  And the can which consists of a thermoplastic polyester resin-coated metal plate shown in (5) has a remarkably improved retort resistance while maintaining a good formability, and has a profile in this example. Thus, it can be seen that both formability and retort resistance can be achieved.

  On the other hand, Comparative Example 12 is also a thermoplastic polyester resin-coated metal plate that has been subjected to post-heating treatment after laminating an unstretched thermoplastic polyester resin film in a heating environment. As a result, the crystalline state profile of laser Raman is different.

  In addition to Example 2, Examples 7 and 8 are examples of thermoplastic polyester resin-coated metal plates that have the same crystal state profile as Example 2 and are excellent in both formability and retort resistance. In consideration of these, (a) it is preferable to employ a resin having a low copolymerization ratio and high crystallinity as the resin constituting the surface of the thermoplastic polyester resin layer, (b) It is preferable that the thermoplastic polyester resin film has a multilayer structure, and a resin having a lower melting point than the resin of the layer (surface layer) on the surface side is selected as the resin on the layer (lower layer) side in contact with the metal material, or ( c) In the case of a multilayer structure, it can be read that the surface layer is preferably thicker than the lower layer.

  From the above, the crystalline state in a certain range in the vicinity of the surface of the thermoplastic polyester resin and the interface between the metal plates of the thermoplastic polyester resin-coated metal plate is an index of retort resistance and formability, respectively. As a result of detailed investigations on this point, it has been found that there is a close relationship between this index and the thermal behavior of the thermoplastic polyester resin of the thermoplastic polyester resin-coated metal plate. In other words, by controlling the resin component and the manufacturing conditions, the half-value width of the Raman shift peak in the thickness direction is controlled to a specific range, so that the can made of a thermoplastic polyester resin-coated metal plate has excellent retort resistance and formability. It was found that this balance can be achieved. The present invention is based on this new finding.

  In the present embodiment, it is possible to improve the retort resistance under a specific resin component and a specific lamination condition without causing a decrease in moldability despite post-heating treatment. In other words, the significance of the laminating process is to adhere the thermoplastic polyester resin to the metal plate by melting the thermoplastic polyester resin layer having a specific resin component and then rapidly cooling to ensure moldability with the metal plate. And obtaining a specific crystallization ready state by subsequent post-heating. The significance of the post-heating process is to suppress the crystallization of the thermoplastic polyester resin layer at the metal plate interface, while promoting the crystallization of the thermoplastic polyester resin layer in the vicinity of the surface opposite to the metal plate. The structure of a thermoplastic polyester resin layer having excellent properties and moldability.

In the present embodiment, (a) the thermoplastic polyester resin layer has a C = O stretching vibration in the vicinity of 1730 cm ⁻¹ in laser Raman spectroscopy using linearly polarized laser light on the interface side with the metal plate. A region (first region) in which the half width of the Raman shift peak of the thermoplastic polyester resin is 20 cm ⁻¹ or more and 24 cm ⁻¹ or less, and (b) a surface opposite to the interface side in the thermoplastic polyester resin layer It is necessary that a region (second region) in which the half width of the Raman shift peak is 14 cm ⁻¹ or more and 18 cm ⁻¹ or less is present on the same thermoplastic polyester resin-coated metal plate. It is. As described above, when only one of the regions exists, the moldability and the retort resistance cannot be achieved at the same time. As described above, the region where the half width of the Raman shift peak is within the predetermined range (first Area and second area) must exist.

  Here, “there is a region where the half-value width of the Raman shift peak is within a predetermined range” means that laser Raman spectroscopy measurement is performed at a plurality of points (at least 4 points, preferably 8 points or more) in the thickness direction of the resin coating layer. This means that there is at least one measurement point where the half-value width of the Raman shift peak is within a predetermined range.

The first region where the half-value width of the Raman shift peak on the interface side with the metal plate is 20 cm ⁻¹ or more and 24 cm ⁻¹ or less exists over a predetermined thickness range (thickness direction). preferable. It is preferable that the half width region of the predetermined thickness range can be confirmed to exist at least in a range from the interface with the metal plate to 5 μm, for example. The first region preferably exists over a thickness range of 1 μm to 7 μm, although it depends on the thickness of the thermoplastic polyester resin layer. In this regard, when expressed as a ratio to the total thickness of the thermoplastic polyester resin layer, the first region preferably exists over a thickness range of 5 to 40%.

On the other hand, on the surface side of the thermoplastic polyester resin layer, in the second region where the half-value width of the Raman shift peak is 14 cm ⁻¹ or more and 18 cm ⁻¹ or less, the half-value width of the Raman shift peak on the interface side is 20 cm ^−1. It is sufficient if it is present on the surface side of the thermoplastic polyester resin layer with respect to the first region, which is 24 cm ⁻¹ or less, and preferably exists at least in the range from the surface of the thermoplastic polyester resin layer to 5 μm. Preferably it can.

The second region half-width is is 18cm ^-1 or less 14cm ^-1 or more Raman shift peak of the surface side of the thermoplastic polyester resin layer is also be present over a predetermined thickness range (thickness direction) Preferably, although it depends on the thickness of the resin coating layer, it preferably exists in a thickness range of 1 μm to 13 μm. When expressed as a ratio to the total thickness of the thermoplastic polyester resin layer, the second region is preferably present over a thickness range of 5 to 80%, more preferably 10 to 75%. According to the examples shown later, the thickness of the thermoplastic polyester resin layer is 8 μm and 12 μm, the thickness is 1 to 5 μm, and the thickness of the thermoplastic polyester resin layer is 17 μm, and the thickness is 4 to 13 μm. A second region is preferably present.

(Metal material used for thermoplastic polyester resin coated metal plate)
As the metal material of the present embodiment, coiled or sheet-like steel plates, copper foils, iron foils and aluminum plates, aluminum foils, and other metal plates widely used as container materials can be used. What gave the surface treatment which forms an oxide film is suitable.
In particular, a surface-treated steel sheet having a two-layer structure in which the lower layer is metallic chromium and the upper layer is chromium hydrated oxide, so-called tin-free steel (hereinafter referred to as TFS), is particularly excellent in adhesion to the film. Suitable as metal material used in form.

From the viewpoint of corrosion resistance, the amount of metallic chromium in TFS is preferably in the range of 70 to 200 mg / m ^{2 in} terms of chromium. From the viewpoint of adhesiveness, the amount of chromium hydrated oxide of TFS is preferably in the range of 10 to 30 mg / m ^{2 in} terms of chromium.

In addition, a tin plate having a tin plating layer on the steel plate surface and a chromium hydrated oxide film on the surface is also suitable.
Furthermore, as the surface treatment, a so-called chromium-free treatment that forms an oxide film made of a metal oxide such as Zr, Ti, or Al, or an organic oxide such as phosphoric acid may be performed.

(Thermoplastic polyester resin used for thermoplastic polyester resin coated metal sheet)
The thermoplastic polyester resin of the present embodiment is polyethylene terephthalate itself or polyester in which a copolymer component other than ethylene terephthalate is introduced into the polyester. Terephthalic acid as an acid component is necessary from the viewpoint of mechanical strength, heat resistance, corrosion resistance, and the like. Furthermore, the crystallinity of the polyester resin can be controlled by copolymerizing an acid component other than terephthalic acid.

  In the thermoplastic polyester resin-coated metal plate of the present embodiment, it is particularly preferable that the thermoplastic polyester resin contains 1 to 15 mol% of isophthalic acid as a copolymerization component. In this embodiment, since the crystalline state of the thermoplastic polyester resin layer is limited to a narrow range, the crystallinity of the polyester resin must be strictly adjusted. Therefore, it is preferable to use isophthalic acid in the above range. . If the amount of isophthalic acid is large, the crystallinity of the polyester resin layer is low, so the crystalline state of the thermoplastic polyester resin layer tends to be low, and as a result, discoloration and corrosion of the metal plate as the base material are likely to occur after retorting. . On the other hand, if the amount of isophthalic acid is less than the above range, the crystallinity of the polyester resin is high, so the crystalline state of the thermoplastic polyester resin layer tends to be high, the thermoplastic polyester resin layer is not given flexibility, and can molding In severe molding such as a drawing process, a part of the resin is torn and the metal surface is easily exposed.

In addition, the thermoplastic polyester resin of the present embodiment preferably has an intrinsic viscosity (IV) measured using a phenol / tetrac mouth ethane mixed solvent as a solvent in a range of 0.5 to 1.0 dL / g, In particular, it is preferably in the range of 0.6 to 0.9 dL / g.
When this intrinsic viscosity is larger than the above range, the adhesion between the thermoplastic polyester resin layer and the metal plate is deteriorated. Moreover, when this intrinsic viscosity is smaller than the said range, the moldability of a thermoplastic polyester resin-coated metal plate cannot be ensured.

In the present embodiment, as long as the above characteristics and composition are satisfied, other copolymer components may be contained in a small amount.
For example, dibasic acids other than terephthalic acid and isophthalic acid include aromatic dicarboxylic acids such as phthalic acid and naphthalenedicarboxylic acid: aliphatic dicarboxylic acids such as succinic acid, adipic acid, and sebacic acid: An alicyclic dicarboxylic acid is mentioned.
Examples of glycol components other than ethylene glycol include aliphatic glycols such as butylene glycol, diethylene glycol, and propylene glycol, alicyclic glycols such as hexhexethanol, and aromatic glycols such as bisphenol A. Two or more of these dibasic acids and glycol components may be used in combination.

  Further, for the thermoplastic polyester resin of the present embodiment, known additives for resin such as anti-blocking agents such as silica, inorganic fillers such as titanium dioxide, lubricants such as wax and silicone compounds, and the like are known. It can be added according to the recipe.

  In the present embodiment, it is desirable to use a film made of an unstretched thermoplastic polyester resin. Even if the thermoplastic polyester resin film is laminated on the metal plate, the resin is cut or the resin is scraped even if the metal plate on which the thermoplastic polyester resin film is laminated is subjected to severe molding such as drawing and / or drawing ironing. This is because it is necessary to increase the intrinsic viscosity of the resin finger and strengthen the resin so that the resin does not stick or become wrinkled, and cracks are not generated, cracked or further peeled off.

  In the present embodiment, the thickness of the thermoplastic resin film is preferably 8 to 60 μm and more preferably 12 to 40 μm in the case of a single layer film. When the thickness is less than 8 μm, the operation of laminating the thermoplastic resin film on the metal plate becomes extremely difficult, and the resin layer after drawing or the like is likely to be defective, and the contents are formed by molding into a can. When filled, the barrier properties against corrosive components are not sufficient. On the other hand, when the thickness is increased, the barrier property is sufficient, but it is economically disadvantageous to have a thickness exceeding 60 μm.

In the case of a multilayer film, the thickness of the thermoplastic resin film varies in terms of the ratio of the thickness of each layer from the viewpoints of formability, barrier properties, and influence on the flavor of the contents, but the total thickness is 8 to The thickness of each layer may be adjusted so as to be 60 μm.
When the thermoplastic resin film has a multi-layer structure, the melting point of the thermoplastic polyester resin of the layer in contact with the metal plate (lower layer) is the thermoplasticity of the surface side layer (the upper layer above the lower layer, for example, the surface layer). When the temperature is lower than the melting point of the polyester resin, it is preferable because the crystal state of the surface side layer can be maintained and the adhesion to the metal plate can be improved.

(Production method used for thermoplastic polyester resin coated metal sheet)
In this embodiment,
(A) Heating and press-bonding an unstretched thermoplastic polyester resin film to the metal material by heating the metal material (metal plate),
(B) After thermocompression bonding, the thermoplastic polyester resin film is rapidly cooled to form a thermoplastic polyester resin layer on the metal material,
(C) After the above rapid cooling, the thermoplastic polyester resin layer is post-heat treated at a temperature of 180 to 220 ° C.
Hereinafter, the detailed contents in the steps (A) to (C) will be described.

  The method of heating the metal material in the step (A) includes a method of directly contacting the surface of the metal plate such as a method using a heated roll in addition to resistance heating and high frequency induction heating generally used for manufacturing tinplate and the like. Can be used. Among these, the metal plate before coating the thermoplastic polyester resin film is a non-contact heating method such as high-frequency induction heating, infrared radiation heating, or laser beam heating that can be heated to that temperature in a short time. It is preferable to ensure the cleanliness of There is no need to regulate the atmosphere when heating, but an inert gas atmosphere is more preferable because it suppresses oxidation of the metal plate.

For the pressure lamination and cooling of the thermoplastic resin film in the steps (A) and (B), a pair of rolls (referred to as “laminate rolls”) made of silicon rubber or fluororubber is used. The average pressure during the pressure lamination and cooling of the thermoplastic resin film by this roll is preferably in the range of 100 to 400 N / cm ² , more preferably in the range of 150 to 250 N / cm ² . It is because the contact with the thermoplastic polyester resin film laminated | stacked with a metal plate is inadequate that it is less than 100 N / cm < ² >, and the outstanding adhesiveness cannot be obtained.

On the other hand, this average pressure is sufficient as long as the laminated thermoplastic polyester resin film does not cause plastic deformation, and does not need to exceed 400 N / cm ² . In general, when a film is laminated on a metal plate using a roll, a part of the roll in the circumferential direction is deformed by pressure and is in contact with the metal plate within a certain length. The contact length is called the nip length, but the average pressure mentioned above is the value obtained by dividing the total pressure applied to this roll by this nip length x metal plate width (contact area). It is.

  And the cooling time at the time of the pressure lamination by a roll is determined by this nip length and the lamination speed of a thermoplastic polyester resin film. The cooling time during pressure lamination is desirably in the range of 10 to 45 milliseconds, more preferably in the range of 15 to 25 milliseconds. When this time is 10 milliseconds or less, cooling by this roll is insufficient, and excellent adhesion of the laminated thermoplastic polyester resin film is not ensured. Even if the cooling time at the time of pressure lamination is 45 milliseconds or more, there is no problem particularly from the viewpoint of adhesion of the thermoplastic polyester resin film, but it is preferable from the viewpoint of high-speed continuous productivity of the thermoplastic polyester resin-coated metal plate of this embodiment. Absent.

The surface temperature of the laminate roll needs to be, for example, in the range of 30 ° C. to the glass transition temperature (Tg) of the thermoplastic polyester resin plus 20 ° C., more preferably in the range of 50 ° C. to the glass transition temperature Tg. When Tg plus 20 ° C. of the thermoplastic polyester resin is exceeded, wrinkles are generated during lamination, which is not preferable. Moreover, if it is less than 30 degreeC, a big cooling device will be needed and it is unpreferable.
In addition, the glass transition temperature (Tg) of a thermoplastic polyester resin can be measured using a differential scanning calorimeter (DSC).

The heating temperature in the laminate is to obtain adhesion between the thermoplastic polyester resin layer and the metal plate and to prepare for the specific crystallization by the subsequent post-heating, and is an important point of this embodiment. One.
The heating temperature is desirably in the range of the melting point of the thermoplastic polyester resin described above (the production method used for the polyester resin-coated metal plate of the present invention) to the melting point plus 50 ° C. By setting the temperature of the metal plate to a temperature range equal to or higher than the melting point with respect to the melting point of the thermoplastic polyester resin, the resin softens or melts, the wetting at the interface with the metal plate becomes good, and excellent adhesion is achieved. Can be obtained. The reason why the temperature is 50 ° C. or lower is that if it exceeds 50 ° C., the effect of crystallization by post-heating does not occur.

  In step (B), after coating the thermoplastic polyester resin film on a metal material (metal plate), in order to control the crystalline state of the thermoplastic polyester resin layer of this embodiment, it is rapidly cooled (quenched) to a temperature below the glass transition point. ) It is desirable that the quenching is performed at a temperature equal to or lower than the glass transition temperature Tg of the thermoplastic polyester resin, for example, within 1.0 to 5.0 seconds, more preferably within 1.0 to 2.5 seconds after lamination.

  The cooling method may be water cooling, liquid nitrogen cooling, or other methods, but is preferably performed in a water bath below the glass transition point of the resin. If it is kept at a temperature exceeding the glass transition point of the resin for a long time without quenching, the amorphous polyester layer formed at the metal plate interface becomes spherulite and coarse, and the work adhesion and work corrosion resistance are greatly reduced. .

In the step (C), in order to appropriately control the heat treatment by post-heating, the thermoplastic polyester resin layer immediately after lamination (before post-heating) is in an amorphous state throughout the thickness direction, that is, half of the Raman shift peak. The value width is 20 cm ⁻¹ or more over the entire thickness direction, preferably 24 cm ⁻¹ or more and preferably 28 cm ⁻¹ or less.

This post-heat treatment is performed in order to obtain a specific crystallization preparation state while maintaining the adhesion of the thermoplastic polyester resin layer achieved by the lamination, and is one of the important points of this embodiment. .
The temperature and time of the post-heating treatment can be arbitrarily selected as long as the half-width range of the Raman shift peak specified in the present embodiment can be achieved, but the temperature range from the crystallization temperature to the melting point of the thermoplastic polyester resin. Among these, it is desirable to carry out at a temperature of 180 to 220 ° C. within 5 seconds.
Regarding the heat treatment in post-heating, when the thermoplastic polyester resin film is a multilayer film, when laminating the multilayer thermoplastic polyester resin film, the above-mentioned “melting point of the resin” is the layer on the side in contact with the metal plate. It is the melting point of the resin.

Even if this heat treatment temperature is higher than the crystallization temperature of the thermoplastic polyester resin, if it is less than 180 ° C., the crystallization does not proceed sufficiently, and the half-value width of the Raman shift peak is 14 cm ⁻¹ or more and 18 cm ^−1. This is because the following predetermined region (second region) is not formed.
On the other hand, even if this heat treatment temperature is below the melting point of the thermoplastic polyester resin, if it exceeds 220 ° C., crystallization reaches the interface with the metal plate, so the interface side with the metal plate specified in this embodiment This is because a predetermined region (first region) of 20 cm ⁻¹ or more and 24 cm ⁻¹ or less is not formed.

In addition, when the heat treatment temperature in this post-heating is a temperature range from the crystallization temperature of the polyester resin layer to the melting point or less, the second region where the half-value width is 14 cm ⁻¹ or more and 18 cm ⁻¹ or less as the heat treatment time increases is Although increased, the half width of the interface with the metal plate is decreased first region is is 24cm ^-1 or less at 20 cm ^-1 or more. Accordingly, the heat treatment time by post-heating is such that the half width is 20 cm ⁻¹ or more and 24 cm ⁻¹ or less on the interface side with the metal plate, and the half width 14 cm ⁻¹ on the surface side of the thermoplastic polyester resin layer. It is necessary to set so that the second region of 18 cm ⁻¹ or less is formed together.
Moreover, when the area | region whose half value width is less than 14 cm < ^-1 > is formed in the surface side of a thermoplastic polyester resin layer, there exists a possibility that the moldability of a thermoplastic polyester resin coating metal plate may fall.

  The invention is illustrated in the following examples. These examples are illustrative and are not limited in any way to the following examples.

(Evaluation method)
The following evaluation was performed with respect to the thermoplastic polyester resin-coated metal plates of Examples and Comparative Examples described later. The evaluation results are shown in Table 1 together with the production conditions of each example.
Note that FIG. 2 shows the influence of the temperature of post-heating treatment on the same film. FIG. 3 shows the effect of the post-heating treatment time on the same film as FIG.
Evaluation in each example was performed as follows.

(Raman spectroscopy)
Using a NRS-5100 laser Raman spectrophotometer manufactured by JASCO Corporation, the resin coating layer was measured at 12 points in depth (thickness) direction at equal intervals from the surface under the following measurement conditions, and C = near 1730 cm ^−1. The carbonyl peak half-width profile resulting from O stretching vibration was calculated.
Read the half-width profile, and if there is a region with a half-width of 20 cm ⁻¹ or more on the interface side with the metal plate as the base material, “○” in the column of “interface side with metal plate 20 ≦ half-value width”, heat If there is a region with a half-value width of 18 cm ⁻¹ or less on the surface side of the plastic polyester resin layer (the side opposite to the above interface), mark “○” in the column of “Surface side half-value width ≦ 18 of the resin layer”. When there was no area | region, "x" was described in each column.

Also for those above regions are present, the thickness range of the region of the half-width ≦ 18cm ^-1, and 20 cm ^-1 ≦ the thickness range of the half-value width of the region were also shown in μm units. Further, if the half-value width of the region on the interface side with the metal plate satisfies the requirement of 24 cm ⁻¹ or less, “○” in the column of “half-value width ≦ 24 with the metal plate”, the surface side of the thermoplastic polyester resin layer If the half-value width of the region of 14 satisfies the requirement of 14 cm ⁻¹ or more, “○” is written in the column of “resin layer surface 14 ≦ half-value width”, and if these requirements are not satisfied, “ × ”was marked.

Measurement condition:
Excitation wavelength 532nm
Objective lens × 100
Grating 1800L / mm

(Container performance evaluation)
A DRD can was molded from the obtained thermoplastic polyester resin-coated metal plate. The contents were filled with 3% acetic acid and subjected to a retort treatment at 125 ° C. for 45 minutes. After the treatment, the can was disassembled and the inside was observed.
If the metal plate turns black, the “Contents” column in Table 1 indicates “x”, and if the metal plate has a streak discoloration along the shock line formed in the circumferential direction during molding, “X” was written in the column, and “△” was marked in each column when these discolorations were mild, and “◯” was marked in each column.

[Comparative Example 1]
The surface layer is polyethylene terephthalate (IA2) containing 2 mol% of isophthalic acid as a copolymerization component, and the lower layer is polyethylene terephthalate (IA15) containing 15 mol% of isophthalic acid as a copolymerization component. An unstretched multilayer polyester resin film consisting of two layers was formed.
This film was laminated with TFS having a plate thickness of 0.18 mm to a laminating temperature of 225 ° C., with the lower layer on the TFS side, and laminated under the following laminating conditions to obtain a thermoplastic polyester resin-coated metal plate.

<Lamination conditions>
Time to quench: 1.33 sec
Laminating roll temperature: 68 ° C
Crimping time: 22.5msec
Laminate roll pressure: 250 N / cm ²

[Comparative Example 2]
After a non-stretched thermoplastic polyester resin film was laminated on TFS in the same manner as in Comparative Example 1, it was heated to 125 ° C. as a post-heating treatment, and immediately after reaching the post-heating temperature, it was air-cooled (the retention time of the post-heating temperature was About 1 second), a thermoplastic polyester resin-coated metal plate was obtained.

[Comparative Example 3]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 160 ° C.

[Example 1]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 180 ° C.

[Example 2]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 200 ° C.

[Example 3]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 220 ° C.

[Comparative Example 4]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 240 ° C.

[Comparative Example 5]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 160 ° C. and the post-heating time was 10 minutes.

[Comparative Example 6]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 180 ° C. and the post-heating time was 10 minutes.

[Example 4]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 200 ° C. and the post-heating time was 10 minutes.

[Example 5]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 220 ° C. and the post-heating time was 5 seconds.

[Example 6]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 2 except that the post-heating temperature was 220 ° C. and the post-heating time was 30 seconds.

[Example 7]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Example 2 except that the surface layer was homopolyethylene terephthalate (Homo-PET).

[Example 8]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Example 2 except that the surface layer was a copolymer component and polyethylene terephthalate (IA5) containing 5 mol% of isophthalic acid was used.

[Example 9]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Example 2, except that the thickness of the surface layer was 6 μm, the thickness of the lower layer was 2 μm, and the total thickness of the multilayer film was 8 μm.

[Comparative Example 7]
As a film to be coated, an unstretched thermoplastic polyester resin film of IA2 single layer was formed with a thickness of 8 μm, and the laminating temperature was 245 ° C. Others were carried out similarly to the comparative example 1, and obtained the thermoplastic polyester resin-coated metal plate.

[Comparative Example 8]
In the same manner as in Comparative Example 7, an unstretched thermoplastic polyester resin film was laminated on TFS, heated to 200 ° C. as a post-heating treatment, and immediately cooled to air after reaching the post-heating temperature (retention time of the post-heating temperature was About 1 second), a thermoplastic polyester resin-coated metal plate was obtained.

[Comparative Example 9]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 7, except that the thickness of the thermoplastic polyester resin film was 12 μm.

[Example 10]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 8, except that the thickness of the thermoplastic polyester resin film was 12 μm.

[Comparative Example 10]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 7, except that the thickness of the thermoplastic polyester resin film was 17 μm.

[Example 11]
A thermoplastic polyester resin-coated metal plate was obtained in the same manner as in Comparative Example 8, except that the thickness of the thermoplastic polyester resin film was 17 μm.

[Comparative Example 11]
As a thermoplastic polyester resin film to be coated, a non-stretched multilayer polyester resin film consisting of two layers of a surface layer of IA5 thickness of 5 μm, a lower layer of IA15 thickness of 12 μm, and a total of 17 μm was formed. Similarly, a thermoplastic polyester resin-coated metal plate was obtained.

[Comparative Example 12]
In the same manner as in Comparative Example 11, an unstretched thermoplastic polyester resin film was laminated on TFS, then heated to 200 ° C. as a post-heating treatment, and immediately cooled to air after reaching the post-heating temperature (retention time of the post-heating temperature was About 1 second), a thermoplastic polyester resin-coated metal plate was obtained.

[Comparative Example 13]
The thermoplastic polyester resin-coated metal was the same as Comparative Example 1 except that a stretched polyester resin film composed of a single layer of polyethylene terephthalate (IA11) containing 11 mol% of isophthalic acid as a copolymerization component was used as the thermoplastic polyester resin film to be coated. I got a plate.

[Comparative Example 14]
After the stretched polyester resin film was laminated on TFS in the same manner as in Comparative Example 13, it was heated to 200 ° C. as a post-heating treatment and immediately cooled after reaching the post-heating temperature (the post-heating temperature was maintained for about 1 second). Thus, a thermoplastic polyester resin-coated metal plate was obtained.

[Example 12]
Thermoplastic polyester resin-coated metal plate as in Example 2, except that tin plate (# 311) having a tin plating amount of 2.8 g / m 2 was used instead of TFS as a base material (metal plate as a metal material) Got.

  The thermoplastic polyester resin-coated metal plate of the present invention and its production method can be widely applied in a wide range of can manufacturing fields.

Claims (9)

At least one surface of the metal material has an unstretched thermoplastic polyester resin layer,
The thermoplastic polyester resin layer is
On the interface side with the metal material, the half width of the Raman shift peak of the thermoplastic polyester resin due to C = O stretching vibration in the vicinity of 1730 cm ⁻¹ in laser Raman spectroscopy using linearly polarized laser light is 20 cm ^−. It has a first region and is 24cm ^-1 or less than ^1, and,
On the surface side to the metal material on the side opposite, the thermoplastic polyester resin coated metal plate and having a second region half-width is is 18cm ^-1 or less 14cm ^-1 or more of the Raman shift peak .   2. The heat according to claim 1, wherein the thermoplastic polyester resin layer is a single layer or a multilayer, and the layer constituting the surface of the thermoplastic polyester resin layer is made of polyethylene terephthalate having 5 mol% or less of isophthalic acid as a copolymerization component. Plastic polyester resin coated metal plate.   The thermoplastic polyester resin-coated metal plate according to claim 1 or 2, wherein the thermoplastic polyester resin layer is a multilayer, and a melting point of a lower layer in contact with the metal material is lower than a melting point of an upper layer forming the surface of the resin layer.   The thermoplastic polyester resin-coated metal plate according to any one of claims 1 to 3, wherein a thickness of the thermoplastic polyester resin layer is 8 µm or more and 60 µm or less.   The thermoplastic polyester resin-coated metal plate according to any one of claims 1 to 4, wherein the metal material is a metal plate having an oxide film.   A can comprising the thermoplastic polyester resin-coated metal plate according to any one of claims 1 to 5. A method for producing a thermoplastic polyester resin-coated metal plate according to any one of claims 1 to 5,
(1) Heating and press-bonding an unstretched thermoplastic polyester resin film to the metal material by heating the metal material,
(2) After the thermocompression bonding, the thermoplastic polyester resin film is rapidly cooled to form a thermoplastic polyester resin layer on the metal material,
(3) A method for producing a thermoplastic polyester resin-coated metal sheet, wherein the thermoplastic polyester resin layer is post-heat treated at a temperature of 180 to 220 ° C. after the rapid cooling.   8. The method for producing a thermoplastic polyester resin-coated metal plate according to claim 7, wherein the thermoplastic polyester resin layer formed in the step (2) is in an amorphous state over the entire thickness direction.   The method for producing a thermoplastic polyester resin-coated metal sheet according to claim 7 or 8, wherein, in the step (3), the thermoplastic polyester resin layer is cooled immediately after reaching the temperature of the post-heating treatment. .