JP2003001759A - Resin-coated seamless can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin-coated seamless can excellent in corrosion resistance and impact resistance. SOLUTION: In the resin-coated seamless can comprising a resin-coated metal sheet wherein the surface of a metal substrate is coated with a polyester resin layer containing polyethylene terephthalate, the residual strain δ of the polyester resin layer on the inner surface of a can body part represented by the formula (1), δ(%)=(ΔV/V0)×100 (wherein V0 is the initial length in the height direction of the free film wherein the polyester resin layer of the can body part is peeled from the metal substrate and ΔV is change quantity at the time of heating of the part corresponding to V0 from a glass transition point to low crystallizing temperature) is not more than 10%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-coated seamless can, and more particularly to a resin-coated seamless can having excellent corrosion resistance and impact resistance.

[0002]

2. Description of the Related Art Conventionally, as a side seamless can (seamless can), a metal material such as an aluminum plate, a tin plate or a tin-free steel plate is subjected to at least one step of drawing between a drawing die and a punch. To form a cylindrical cup consisting of a side-seamless body and a bottom integrally connected to the body seamlessly, and then, if desired, squeezing between the ironing punch and the die on the body. A can body is known in which the body is thinned by processing (drawing /
Ironing process). Further, it is already known that, instead of the ironing, thinning of the side wall portion is performed by bending and stretching at the curvature corner of the redrawing die (drawing / thinning drawing). Further, thinning draw forming and ironing work in which ironing is applied at the time of the thinning drawing work to thin the side wall portion are already known (drawing / thinning draw forming and ironing work).

As the organic resin coating method for side-surface seamless cans, in addition to the generally widely used method of applying an organic paint to a can after molding, a resin film is preliminarily laminated on a metal material before molding. It is also known to use a coated metal plate of polyester, vinyl organosol, epoxy, phenol, acrylic or the like in the production of a can body by thin-drawing.

Regarding the coating method of a thermoplastic resin film represented by thermoplastic polyester on a metal substrate,
A great number of proposals have been made, for example, a method in which a biaxially stretched film is bonded directly or via a bonding primer layer to a metal substrate by thermal bonding (see, for example, Japanese Unexamined Patent Application Publication No. Hei 3
No. 101930, JP-A-5-4229, and JP-A-6-172556), a method of extrusion coating a molten resin onto a metal substrate (JP-A-10-86308), and the like are employed.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Drawing / ironing, drawing / thinning drawing, or drawing /
Thinning draw forming and ironing (hereinafter these processing methods are called drawing / thinning draw forming and / or ironing)
For seamless cans formed by, the degree of processing is becoming stricter year by year in order to reduce costs, and for cans in which a biaxially stretched film that has been commonly used in the past is laminated on a metal substrate by heat bonding. With resin-coated metal sheets, it has become difficult to follow the severe and severe processing. On the other hand, a resin coated metal plate for a can in which a molten resin is directly extrusion-coated on a metal substrate or a cast film is laminated, the resin is maintained in an unoriented state, so that the above-described severe processing against Extrusion-coated resin-coated metal sheets have recently been used because of their high degree of followability.

These extrusion-coated or cast film-laminated thermoplastic resin-coated metal plates are
It is formed into a cylindrical cup by drawing, and then formed into a seamless can having a high height and a thin side wall by drawing forming and / or ironing. In this seamless can, the state of the adhesive interface between the coating resin layer and the metal substrate greatly differs between the can bottom and the can body. That is, at the bottom of the can, the degree of processing is not so severe that the adhesive interface is substantially preserved in the form of the resin-coated metal plate before processing, while at the body of the can, the degree of processing is severe.
Since processing strains are accumulated in the coating resin layer at the adhesive interface, the occurrence of peeling or cracking at the adhesive interface may be recognized, and when a seamless can is formed regardless of the presence or absence of the surface treatment layer on the surface of the metal substrate. The corrosion resistance and impact resistance were reduced.

Corrosion resistance is liable to progress undercoat corrosion generally called under film corrosion (UFC) in a seamless can made of a thermoplastic resin-coated metal plate. This corrosion is a phenomenon in which the metal substrate below the film layer is corroded even though the coverage by the film is apparently safe, but it is required to prevent this.

Impact resistance has what is called dent resistance when it is made into an actual canned product. This is because when the canned products are dropped or when the canned products collide with each other, the canned products are hit. Even if a dent called a mark is formed, it is required that the adhesion and coverage of the coating be completely maintained.

Therefore, an object of the present invention is to provide a resin-coated seamless can which is excellent in corrosion resistance and impact resistance in a resin-coated seamless can made of a resin-coated metal plate having a surface of a metal substrate coated with a thermoplastic resin. Is.

[0010]

The resin-coated seamless can of the present invention is a resin-coated seamless can comprising a resin-coated metal plate in which a surface of a metal substrate is coated with a polyester resin layer containing polyethylene terephthalate. The residual strain δ of the polyester resin layer on the inner surface side of the can body represented by the formula is 10% or less. δ (%) = (ΔV / V0) × 100 (1) where V0 is the initial length in the height direction of the free film obtained by peeling the polyester resin layer of the can body part from the metal substrate, and ΔV is the part corresponding to V0. Is the amount of change when is heated from the glass transition point to the low temperature crystallization temperature.

With the above structure, even if the surface-treated layer on the surface of the metal substrate is cracked, the adhesion with the resin layer can be enhanced, and corrosion (UFC) under the film of the seamless can can be suppressed.
Further, there is an effect that an effect of enhancing the impact resistance (dent resistance) of the film can be obtained.

In the resin-coated seamless can of the present invention, it is preferable that the resin-coated metal plate has a non-oriented polyester resin layer provided on the metal substrate.

The resin-coated seamless can of the present invention is
It is preferable that the thickness of the can body is reduced by drawing / bending and / or ironing so that the thickness of the can body is 20 to 85% of the thickness of the can bottom.

The polyester resin forming the resin-coated seamless can of the present invention preferably has an intrinsic viscosity of 0.6 (dl / g) or more.

The polyester resin layer forming the resin-coated seamless can is composed of two layers, the surface layer (A) is composed of polyethylene terephthalate / isophthalate having an isophthalic acid content of 15 mol% or less, and the lower layer (B) is isophthalic acid. It is preferably composed of polyethylene terephthalate / isophthalate having a content of 8 to 25 mol% and higher than the isophthalic acid content of the surface layer (A).

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Resin-coated seamless can] FIG.
FIG. 1 is a schematic view showing an embodiment of a resin-coated seamless can of the present invention. FIG. 2 is a reference sectional view of a resin-coated metal plate used in the present invention. FIG. 3 is a reference sectional view of another resin-coated metal plate used in the present invention. 1 to 3,
The resin-coated seamless can 10 is formed by drawing and thinning the resin-coated metal plate 1 and / or ironing it, and is composed of a can bottom 11 and a can body 12. The resin-coated seamless can 10 of the present invention includes a metal base 2
Squeeze the resin-coated metal plate 1 whose surface is coated with a polyester resin layer 3 containing polyethylene terephthalate
It is formed by thinning and forming and / or ironing.

Further, the resin-coated seamless can 10 of the present invention.
Is formed by drawing the above-mentioned polyester resin-coated metal plate 1 between a punch and a die into a cup shape having a bottom, followed by thinning drawing by bending and stretching and / or ironing. The cup side wall is thinned by the thinning draw forming and / or ironing process, and the thermoplastic resin layer 3 of the formed can body 12 of the resin-coated seamless can 10 is molecularly oriented in at least one axial direction. There is.

At the upper end of the can body portion 12, a neck portion 13 formed as desired and a flange portion 14 formed via the neck portion 13 are formed. In the resin-coated seamless can 10 formed as described above, the polyester resin layer 3 in the can body portion 12 is maintained in a state of being molecularly oriented in at least one axial direction, while the can bottom portion 11
The polyester resin layer 3 is characterized by being maintained in a non-oriented state. The resin-coated seamless can 10 of the present invention may be one in which both surfaces of the metal substrate 2 are coated with the polyester resin layer 3. In this case, a resin-coated metal plate 1 in which a polyester resin layer 3 is coated on both surfaces of a metal substrate 2 having a sectional structure as shown in FIG.
Is formed by drawing, thinning, and / or ironing. Further, the inner surface layer 5 may be further formed on the inner surface polyester resin layer 3 having the cross-sectional structure as shown in FIG. Such an inner surface layer 5 is provided on the inner surface side of the resin-coated seamless can 10, and for example, a resin having a low adsorptivity for the flavor component in the content is preferably used.

[Polyester Resin Layer] The resin-coated seamless can 10 of the present invention is characterized in that the residual strain (δ) of the polyester resin layer 3 on the inner surface side of the can body portion 12 is 10% or less. The residual strain (δ) defines an adhesion inhibiting factor. When the residual strain (δ) is larger than 10%, peeling or cracking occurs at the adhesive interface between the coating resin layer and the metal substrate, and corrosion resistance However, the impact resistance is lowered, which is not preferable. That is, to explain this point, the residual strain (δ) of the polyester resin layer on the inner surface side of the can body portion, which is defined by the above formula (1), is higher than that of the free film obtained by separating the can body polyester resin layer from the metal substrate. The ratio between the initial length in the depth direction (V0) and the amount of change (ΔV) when the portion corresponding to V0 is heated from the glass transition point to the low temperature crystallization temperature is shown.

In the resin-coated seamless can of the present invention, the polyester resin layer containing polyethylene terephthalate on the inner surface of the can body has the initial length in the height direction of the free film obtained by peeling the polyester resin layer on the inner surface of the can body from the metal substrate. Ratio (δ) between the temperature (V0) and the amount of change (ΔV) when the V0 corresponding part is heated from the glass transition point to the low temperature crystallization temperature
Is maintained below 10%. As a result, even if the polyester resin is molecularly oriented in a uniaxial direction by drawing / thinning drawing and / or ironing, the factors inhibiting adhesion at the adhesive interface between the metal substrate surface and the polyester resin layer are removed, and corrosion resistance is improved. The remarkable feature is that the impact resistance and the like can be improved. That is, enhancing the adhesion at the adhesive interface between the coating resin layer and the surface of the metal substrate,
Prevents undercoat corrosion (UFC) of seamless cans, and
The impact resistance (dent resistance) of the coating can be enhanced.

The property of residual strain (δ) of the resin-coated seamless can can be imparted by the orientation state of the coated polyester resin before processing, seamless can molding conditions, heat treatment after seamless can molding, and the like. In order to control the strain (δ), a substantially unoriented polyester resin-coated metal plate laminated with an extrusion coat or cast film is used, and after forming a seamless cup by thinning drawing and / or ironing, the can barrel It is necessary to alleviate the strain (residual stress) due to the processing of the coating resin layer of the part and to perform heat treatment for thermally fixing the molecular chain orientation.

This heat treatment is preferably carried out in the temperature range of generally Tg + 50 ° C. or higher, especially Tg + 100 to melting point (Tm) −5 ° C., based on the glass transition point (Tg) of the resin coating layer. On the low temperature side, the strain of the coated polyester resin layer is insufficiently relaxed, and the post-processability tends to decrease, while on the high temperature side above the temperature range, the molecular orientation formed during can molding is relaxed. This is because the tendency tends to increase and the corrosion resistance and impact resistance of the can body part deteriorate. When the resin coating layer is a multilayer having two or more layers, it is preferable to perform heat treatment so that the lowermost resin coating layer falls within the above temperature range. By this heat treatment, the heat resistance of the coated polyester resin layer is improved, the adhesion to the metal substrate is also improved, and the workability for post-processing such as neck-in processing and flange processing, or the flavor resistance is also improved.

The crystallization of the polyester resin is roughly classified into thermal crystallization and oriented crystallization, and the polyester resin layer of the resin-coated seamless can of the present invention mainly has the latter crystallization characteristics described above. Is a feature. That is, the polyester resin layer on the upper part of the can body is highly oriented and crystallized at the time of seamless can molding, and the subsequent heat treatment does not cause coarse lamella-type crystals, resulting in heat resistance, impact resistance and corrosion resistance. It is possible to impart excellent properties. The heat treatment operation is performed before or after the trimming for cutting the can ear portion generated during seamless can molding.

The required heat treatment time differs depending on the degree of molecular orientation formed on the coated polyester resin layer of the can body during can forming, but a short time is generally sufficient, and specifically 1 to It is preferable to perform it for 10 minutes. In the present invention, the seamless can after heat treatment may be gradually cooled or rapidly cooled. In the can body portion 12 on the inner surface side of the can of the resin-coated seamless can of the present invention, molecular orientation occurs due to processing, while in the can bottom portion 11, since the degree of processing is not severe, the coating resin layer at the bottom of the can is unoriented. In this state, the bonding interface between the surface of the metal substrate 2 and the coating resin layer 3 is preserved in the form of the resin-coated metal plate. As a result, the adhesiveness of the adhesive interface between the coating resin layer and the metal substrate is maintained, the undercoat corrosion (UFC) of the seamless can is suppressed, and the impact resistance (dent resistance) of the coating is enhanced. Is obtained.

The resin-coated seamless can 10 of the present invention is formed by drawing, followed by bending and stretching to reduce the thickness and / or draw forming.
Or, by ironing, the thickness of the can body 12 becomes the bottom 11 of the can.
The thickness is preferably 20 to 85%, more preferably 40 to 80%. Two
This is because when the thickness is less than 0%, it is considered that sufficient molecular orientation cannot be imparted to the polyester resin layer on the inner surface of the can body portion 12, and when the thickness is more than 85%, it is substantially thin. This is because the realization cannot be achieved.

Two types of molecular orientations are formed in the polyester resin layer 3 of the can body portion 12 of the resin-coated seamless can 10 formed by the drawing / thinning draw forming and / or ironing process of the present invention. The first one is that polyester resin molecules are oriented in the can axis (can height) direction due to plastic flow during drawing / thinning draw forming and / or ironing, which is close to fiber orientation. . The second one is peculiar to the ironing process, and is patent 2970.
As described in Japanese Patent No. 459, the benzene ring surface of the polyester molecule is oriented in a state of being substantially parallel to the film surface. All of these molecular orientations contribute to the improvement of various properties of the resin-coated seamless can, particularly dent property and corrosion resistance.

In the present invention, the heat treatment is performed so that the residual strain (δ) of the polyester resin layer containing polyethylene terephthalate in the can body portion on the inner surface side of the can is 10% or less. It is also preferable to carry out in terms of the effect of suppressing internal strain remaining due to processing.

Next, the polyester resin used for the resin-coated seamless can of the present invention should have a molecular weight sufficient to form a thin film layer on a metal substrate, and its intrinsic viscosity (IV) is 0.6 dl / g or more, especially 0.65
It is preferably in the range of 1.4 to 1.4 dl / g. When the intrinsic viscosity (IV) is less than 0.6 dl / g, it does not have heat resistance to withstand various heat treatments, processability for forming seamless cans, and processability for subsequent post-processing. This is because the polyester resin out of the above numerical range does not have sufficient mechanical properties and lacks barrier properties against corrosive components and content resistance. Since the polyester resin in the above range has a large molecular weight, the half-crystallization time (τ)
Is long and is also useful in terms of preventing thermal crystallization described later.

In the present invention, in order to maintain the polyester resin layer in the body of the can in a state of being oriented in at least a uniaxial direction, a resin capable of molecular orientation is used as the polyester resin, and processing into a seamless can is also performed in the body of the can. It is preferable to carry out so that the orientation in the uniaxial direction remains in the resin layer.

Therefore, it is preferable to use a homopolyester such as polyethylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate for the polyester resin layer laminated on the inner surface side of the can of the metal substrate. However, it is desirable to reduce the maximum crystallinity that the polyester resin layer can reach from the viewpoint of thermal crystallization prevention, impact resistance and workability. Therefore, it is preferable to introduce a copolymerization ester unit other than ethylene terephthalate into the raw material polyester. This copolymerized ester unit can be introduced by copolymerization. Further, in the case of a polymer blend or a copolyester which can be made into a multi-layer, the uniaxial orientation generated during molding into a seamless can tends to be relaxed as compared with the homopolyester.

The polyester resin layer used in the present invention may be composed of a plurality of resin layers, the surface layer is made of polyethylene terephthalate / isophthalate having an isophthalic acid content of 15 mol% or less, and the lower layer is made to have an isophthalic acid content of 8 to 25. It is desirable to use polyethylene terephthalate / isophthalate in mol% and more than that in the surface layer. Adhesion to a metal substrate, high workability, corrosion resistance, impact resistance, flavor adsorption resistance, and the like are imparted by using such two layers.

The resin-coated seamless can of the present invention is
It is preferable that the crystallinity of the polyester resin layer on the upper part of the can body is in the range of 20 to 55% by the density method. If the crystallinity is less than 20%, the adhesion to the metal substrate, the corrosion resistance, and the impact resistance are poor, and the amount of flavor components adsorbed in the content tends to increase, which is not preferable as a seamless can. On the other hand, if it exceeds 55%, the adhesion to the metal substrate is poor, and there is a high possibility that the polyester resin layer will crack during processing. Crystallinity (X
c) is generally represented by the following formula (2). Xc = [dc (d-da)] / [d (dc-da)] × 100 (2) In the formula (2), dc is the density of the perfect crystal layer = 1.455 g /
cm ³ , and da is the density of the completely amorphous layer = 1.335 g
/ Cm ³ and d is the density of the sample (g / cm ³ ).

In the polyester resin layer, compounding agents known per se, for example, antioxidants such as sterically hindered phenols, antiblocking agents such as amorphous silica, pigments such as titanium dioxide (titanium white), Various antistatic agents, lubricants and the like can be added according to a known formulation.

[Resin-Coated Metal Plate] Next, the resin-coated metal plate used in the resin-coated seamless can of the present invention will be described with reference to FIGS. The resin-coated metal plate 1 used for the resin-coated seamless can 10 of the present invention is one in which a non-oriented polyester resin layer 3 is laminated on a metal substrate 2. The reason for using the non-oriented polyester resin layer is the extrusion coating method of molten resin and unstretched film (cast film).
This is because the resin-coated metal plate can be manufactured with a small number of steps and at a low cost by using the laminating method. Further, since the polyester resin layer 3 formed on the resin-coated metal plate 1 is in an unoriented state, it is excellent in drawability / thinning draw forming and / or ironing workability, and the can body part 1
This is because the thickness of the seamless can 10 can be made thin and the height of the seamless can 10 can be easily increased. In addition, the reason why the biaxially stretched film that has been conventionally used for cans is not used is that it is difficult to process and leads to cost increase.

The resin-coated metal plate 1 used in the present invention is manufactured by thermally bonding the polyester resin layer 3 capable of molecular orientation to the metal substrate 2 in an unstretched state. That is, in order to reduce the residual strain δ of the polyester resin layer 3 on the inner surface side of the seamless can 10 to 10% or less, it is important to laminate the polyester resin layer 3 in a substantially unoriented state. The metal base 2 and the polyester resin layer 3 forming the resin-coated metal plate 1 will be described below.

In FIG. 2 showing an example of the sectional structure of the resin-coated metal plate 1 used in the present invention, the resin-coated metal plate 1 comprises a metal base 2 and a polyester resin layer 3 located at least on the inner surface side of the can. . Further, it is also preferable that the resin-coated metal plate 1 is provided with an outer surface coating 4, and the outer surface coating 4 may be the same as the polyester resin layer 3, or may be an ordinary can paint or resin. It may be a film.

In FIG. 3 showing another example of the sectional structure of the resin-coated metal plate, the polyester resin layer 3 on the inner surface of the can is shown.
It is also preferable to provide the inner surface layer 5 on the above. For example, the inner surface layer is a polyester or copolyester derived from a terephthalic acid component or an isophthalic acid component, which has low adsorptivity to the flavor component in the content, and the lower layer is an isophthalic compound excellent in adhesiveness to a metal substrate. A copolyester having a large copolymerization amount of an acid or the like is preferable.

The resin-coated metal plate 1 used in the present invention can be produced by extrusion-coating the polyester resin layer 3 on the metal substrate 2 in a molten state and thermally adhering it. Further, as another manufacturing method, it can also be manufactured by thermally adhering an unstretched film (cast film) of a polyester resin formed in advance onto the metal substrate 2. The total thickness of the polyester resin layer 3 used in the present invention is preferably in the range of 2 to 60 μm, particularly 3 to 40 μm from the viewpoint of metal protection effect and workability. Moreover, you may use an adhesive agent and an adhesion primer as needed.

[Metallic Substrate] As the metallic substrate, various surface-treated steel plates and light metal plates such as aluminum can be used. As the surface-treated steel sheet, one or more kinds of surface treatment such as zinc-plated, tin-plated, nickel-plated, nickel-tin-plated, electrolytic chromic acid treatment, chromic acid treatment, etc. are obtained by annealing a cold-rolled steel sheet and then secondary cold rolling. What has been done can be used. An example of a suitable surface-treated steel sheet is an electrolytic chromic acid-treated steel sheet, particularly 10 to 200 mg / m ²
Metal chrome layer of 1 to 50 mg / m ² (metal conversion)
Chrome oxide layer, which has excellent adhesion to resin coatings and coatings, and excellent corrosion resistance. Other examples of the surface-treated steel sheet are 0.5 to 1
A hard tin plate having a tin plating amount of 1.2 g / m ² . It is desirable that the upper layer of this tin plate be treated with chromic acid or chromic acid / phosphoric acid so that the amount of chromium becomes 1 to 30 mg / m ^{2 in} terms of metallic chromium. Furthermore, as another example, an aluminum-coated steel sheet plated with aluminum, pressure-welded with aluminum, or the like can be used.

As the light metal plate, an aluminum plate or an aluminum alloy plate can be used. An aluminum alloy plate having excellent corrosion resistance and workability has a Mn: 0.2.
To 1.5% by weight, Mg: 0.8 to 5% by weight, Zn:
It is preferable that the composition is 0.25 to 0.3% by weight, Cu: 0.15 to 0.25% by weight, and the balance is AL. The upper layer of these light metal plates is also preferably subjected to chromic acid treatment or chromic acid / phosphoric acid treatment so that the chromium amount becomes 20 to 300 mg / m ^{2 in} terms of metal chromium. The surface treatment of the light metal plate can also be performed by using a water-soluble phenol resin in combination.

The thickness of the base metal plate of the metal substrate varies depending on the type of metal, the use or size of the seamless can, but it is generally preferable to use a thickness of 0.10 to 0.50 mm. Above all, in the case of the surface-treated steel sheet, 0.
A thickness of 10 to 0.30 mm is preferable, and
In the case of a light metal plate, one having a thickness of 0.15 to 0.40 mm is preferable.

[0042]

The present invention will be described in more detail with reference to the following examples. [Production of Polyester Resin-Coated Seamless Can] A resin-coated seamless can was prepared as shown below. The resin composition and the like are shown in Table 1.

[Example 1] The melting point was measured using an extrusion / film forming apparatus.
An unstretched film of isophthalic acid copolymerized polyethylene terephthalate (PET / IA) resin having a (Tm) of 220 ° C was prepared and heated to 250 ° C.
m, A3004 material, chromic acid / phosphoric acid surface treatment) were attached to both surfaces to produce a resin-coated metal plate. A disc-shaped blank is punched out from this resin-coated metal plate by a conventional method to form a shallow-drawn cup, and the resin-coated seamless can with a can body thinning rate of 60% by redrawing and ironing processing according to a conventional method. Of 200 or less, which is lower than the melting point (Tm) of the resin.
Heat treatment was performed at ℃.

Example 2 In Example 1, melting point (Tm)
Was 220 ° C., and a resin-coated seamless can was prepared and heat-treated under the same conditions, except that an unstretched film prepared by blending PBT with an isophthalic acid copolymerized polyethylene terephthalate (PET / IA) resin as a base was prepared.

Comparative Example 1 A resin-coated seamless can was prepared under the same conditions as in Example 1 and heat-treated at 240 ° C. above the resin melting point (Tm).

[Comparative Example 2] A resin-coated seamless can was prepared under the same conditions as in Example 2 and heat-treated at 240 ° C above the resin melting point (Tm).

[Comparative Example 3] In Example 1, the melting point (Tm)
Is a biaxially stretched film of isophthalic acid copolymerized polyethylene terephthalate (PET / IA) resin having a temperature of 220 ° C.,
A resin-coated seamless can was produced under the same conditions. However, delamination was found to occur in the can body during processing, and the polyester resin layer adhesion, dent resistance, and corrosion resistance of the can body could not be evaluated.

[Comparative Example 4] In Example 2, the melting point (Tm)
A 220- ° C. isophthalic acid copolymerized polyethylene terephthalate (PET / IA) resin was used as a base, and a resin-coated seamless can was produced under the same conditions using a biaxially stretched film blended with PBT. However, delamination was found to occur in the can body during processing, and the polyester resin layer adhesion, dent resistance, and corrosion resistance of the can body could not be evaluated.

The resin-coated seamless cans produced in the above Examples and Comparative Examples were evaluated by the following methods.

[Measurement of Amount of Change in Heating] As shown in FIG. 4, in the resin-coated seamless can of the present invention, a can body was formed at 0 ° direction (21) and 90 ° direction (22) with respect to the rolled metal base material. 5m wide from the area with the highest reduction rate
A sample 23 of m × 15 mm in length was cut out. If a film or printing ink is placed on the outer surface of the can of each sample, remove it with sulfuric acid and then 10w
Only the substrate was dissolved in t% concentration hydrochloric acid water. When the substrate was completely melted, the isolated film on the inner surface of the can was gently washed with water and dried. Then, the measurement was performed using a thermomechanical analyzer (Thermo MechanicaL AnaLyzer: TMA) manufactured by Rigaku Co., Ltd. The measurement conditions and the like are as follows. Gauge distance (V0): 10 mm Pre-load on sample: Approximately 1000 g / mm ² Measurement temperature range: 35 ° C to 250 ° C Temperature rising rate: 10 ° C / min The heating change amount of the film at this time is ΔV, and Point-to-point distance
The residual strain (δ) was expressed as a ratio with (V0). The results are shown in Table 1.

[Evaluation of Scratch Retort] As shown in FIG. 5, a flaw 26 is put around the midpoint 24 of the straight length (TwL) of the can body and the entire circumference of the neck 25 of the can, and the retort treatment is performed at 125 ° C. for 30 minutes. did. As an evaluation method, the occurrence of delamination in the scratched portion was visually observed. The evaluation results are shown in Table 1.

[Evaluation of can barrel model dent] A steel ball having a diameter of 16 mm was placed at the midpoint of the straight length (TwL) of the can barrel.
The dent ERV when a 1 kg cylindrical weight was dropped from a height of 20 mm was measured. As a result, the dent ERV showed a favorable value at 1.0 mA or less. The results are shown in Table 1.

[Evaluation of Cross-cut Corrosion] As shown in FIG. 6, about the midpoint 24 of the straight length (TwL) of the can body, the 0 ° direction (21), 90 ° with respect to the rolled metal base material.
Cross-cut 2 with a length of 30 mm in direction (22)
7 was put in with a commercially available cutter. Then, citric acid 0.
002mol / l, trisodium citrate 0.002m
It was dipped in a model corrosive solution of ol / l and 0.02 mol / l of sodium chloride at 50 ° C. for 2 weeks for aging. The evaluation method is
The corrosion state was visually confirmed. The evaluation results are shown in Table 1.

[0054]

[Table 1]

[0055]

According to the resin-coated seamless can of the present invention, the residual strain δ of the polyester resin layer on the inner surface side of the can body is controlled to be 10% or less, which is excellent.
A resin-coated seamless can having corrosion resistance, impact resistance, etc. can be obtained.

[Brief description of drawings]

FIG. 1 is a reference view of a resin-coated seamless can of the present invention.

FIG. 2 is a reference sectional view of a resin-coated metal plate used in the present invention.

FIG. 3 is a reference cross-sectional view of another resin-coated metal plate used in the present invention.

FIG. 4 is a reference diagram showing an evaluation method in an example of the present invention.

FIG. 5 is a reference diagram showing an evaluation method in an example of the present invention.

FIG. 6 is a reference diagram showing an evaluation method in an example of the present invention.

[Explanation of symbols]

1: Resin coated metal plate 2: Metal substrate 3: Thermoplastic resin layer (polyester resin layer) 4: Outer coating 5: Inner surface layer 10: Seamless can 11: Can bottom 12: Can body 13: Neck 14: Flange part 21: 0 ° direction with respect to the rolled metal plate 22: 90 ° direction to the rolled metal plate 23: Sample 24: Midpoint 26: Scratch 27: Cross cut

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Kurisu             179 Oguchinakamachi, Kanagawa-ku, Yokohama-shi, Kanagawa F term (reference) 3E061 AA16 AB13 AC09 AD02 AD04                       AD06 BA01 BB14 DA02                 3E062 AA04 AB14 AC09 JA07 JB11                       JC02 JD03                 4F100 AB01A AK41B AK41C AK41J                       AK41K AK42B AK42C AK42J                       BA02 BA03 BA10A BA10B                       BA10C BA13 DA01 GB16                       JA06B JB02 JK10 JK20B                       YY00B YY00C

Claims (5)

[Claims] 1. A resin-coated seamless can comprising a resin-coated metal plate in which the surface of a metal substrate is coated with a polyester resin layer containing polyethylene terephthalate, wherein a polyester resin layer on the inner surface side of the can body is represented by the following formula (1). The residual can δ of 10% or less is a resin-coated seamless can. δ (%) = (ΔV / V0) × 100 (1) V0: Initial length in height direction of free film obtained by peeling can body polyester resin layer from metal substrate, ΔV: Glass transition point of V0 corresponding part Change from high temperature to low temperature crystallization temperature 2. The resin-coated seamless can according to claim 1, wherein the resin-coated metal plate is a metal substrate provided with a non-oriented polyester resin layer. 3. The resin-coated seamless can is characterized in that the thickness of the can body is reduced to 20 to 85% of the thickness of the can bottom by drawing / bending / stretching and / or ironing. Item 1. A resin-coated seamless can according to Item 1 or 2. 4. The resin-coated seamless can according to claim 1, wherein the polyester resin forming the polyester resin layer has an intrinsic viscosity of 0.6 (dl / g) or more. 5. The polyester resin layer comprises two layers,
The surface layer (A) is composed of polyethylene terephthalate / isophthalate having an isophthalic acid content of 15 mol% or less, the lower layer (B) has an isophthalic acid content of 8 to 25 mol%, and more than the isophthalic acid content of the surface layer (A). The resin-coated seamless can according to any one of claims 1 to 4, which is composed of a large amount of polyethylene terephthalate / isophthalate.