JP2003025500A - Resin coated seamless can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin coated seamless can which is excellent in anticorrosive property and shock resistance. SOLUTION: This resin coated seamless can comprises a resin coated metal plate wherein a polyester resin layer containing polyethylene terephthalate is coated on the surface of a metal base body. In such a resin coated seamless can, the dynamic hardness DH of the polyester resin layer on the internal surface side of the can body section, which is represented by an equation DH=37.838×P/D<2> (1), is set to be not more than 20. In this case, P represents a load, and D represents an insertion depth when the load P is applied to 1 g at a speed of 29 mgf/sec to the polyester resin layer of the can body section by a 115 deg. triangular pyramid-shape indentator.

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 is greatly different between the can bottom and the can body.
That is, since the degree of processing is not severe at the bottom of the can, the adhesive interface is substantially preserved in the form of the resin-coated metal plate before processing, while the degree of processing is severe at the body of the can. Since internal stress due to processing in the coating resin layer at the adhesive interface becomes large, peeling or cracking may be observed at the adhesive interface, and a seamless can was obtained regardless of the presence or absence of the surface treatment layer on the surface of the metal substrate. The corrosion resistance and impact resistance at that time 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 dynamic hardness DH of the polyester resin layer on the inner surface side of the can is 20 or less at the upper part of the can body. DH = 37.838 × P / D ² (1) P: load, D: when a load P is applied to the polyester resin layer of the can body part with a 115 ° triangular pyramid indenter at a speed of 29 mgf / sec up to 1 g For this reason, it is desirable that the resin-coated metal plate has a non-oriented polyester resin layer provided on a metal substrate. Further, the resin-coated seamless can of the present invention is thinned by drawing / thinning draw forming and / or ironing forming so that the thickness of the can body portion becomes 20 to 85% of the thickness of the can bottom portion. preferable. The resin-coated seamless can of the present invention comprises two polyester resin layers,
It is preferable that 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 composed of polyethylene terephthalate / isophthalate having an isophthalic acid content of 8 to 25 mol%. Further, the resin-coated seamless can of the present invention,
The polyester resin preferably has an intrinsic viscosity of 0.6 dl / g or more. Further, in the resin-coated seamless can of the present invention, the crystallinity of the polyester resin layer on the upper part of the can body is preferably in the range of 20 to 55% by the density method.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION [Resin-coated seamless can] The resin-coated seamless can of the present invention is formed by drawing / thinning a resin-coated metal plate in which a surface of a metal substrate is coated with a polyester resin layer containing polyethylene terephthalate. as well as/
Alternatively, it is formed by ironing.

The resin-coated seamless can of the present invention comprises the above polyester resin-coated metal plate between the punch and the die,
It is formed by drawing into a cup with a bottom, followed by thinning by bending and stretching and / or ironing. The side wall of the cup is thinned by the thinning and / or ironing, and the resin coating layer of the formed can body of the seamless can is at least uniaxially molecularly oriented.

FIG. 1 is a schematic view showing an embodiment of the resin-coated seamless can of the present invention. 1, a resin-coated seamless can 10 is formed by drawing, thinning, and / or ironing a resin-coated metal plate 1, and includes a can bottom portion 11 and a can body portion 12. In the can body 12, the upper half of the straight portion divided into the upper and lower parts is the can body 15, and the lower half is the lower part 16 of the can body. Can body 1
2, a neck portion 13 formed as desired,
A flange portion 14 formed via the neck portion 13 is formed. In the resin-coated seamless can 10 formed as described above, the polyester resin layer 3 in the can body portion 12 is molecularly oriented in at least one axial direction, while the polyester resin layer 3 in the can bottom portion 11 is maintained in a non-oriented state. It is characterized by the fact that Further, in the resin-coated seamless can 10 of the present invention formed as described above,
It is considered that the upper part 15 of the can body has a relatively higher degree of processing when forming a can than the lower part 16 of the can body, and defects of the coating resin are likely to occur. Therefore, if the characteristics of the resin-coated seamless can are controlled at least in the upper part of the can body, it is considered that the quality stability of the entire can is maintained.

[Polyester Resin Layer] In the resin-coated seamless can 10 of the present invention, the dynamic hardness DH represented by the following formula (1) of the polyester resin layer 3 on the inner surface side of the upper part of the can body 12 is: It is characterized by being 20 or less. DH = 37.838 × P / D ² (1) However, P is a load at that time, and D is 29 mgf / se for a 115 ° triangular pyramid indenter on the polyester resin layer of the body of the can.
It is the penetration depth when a load is applied up to 1 g at the speed of c.
When the dynamic hardness is more than 20, it indicates that the polyester resin layer in the body of the can is hard and brittle, and even if it is hard, the impact resistance becomes poor. Further, the fact that the resin is hard is considered to be due to the orientation of the molecular chains or excessive crystallization, so that the internal stress of the resin layer due to the orientation or crystallization increases, and the adhesiveness decreases. Corrosion resistance is poor, which is not preferable. That is, explaining this point,
The dynamic hardness DH of the polyester resin layer on the inner surface side of the can body portion defined by the above formula (1) indicates the brittleness of the resin layer and the orientation of the molecular chains, or the state of crystallization.

In the resin-coated seamless can of the present invention, the dynamic hardness DH of the polyester resin layer containing polyethylene terephthalate on the inner side of the can on the can body is 2
It is maintained at 0 or less, and is characterized by not being excessively oriented or crystallized. As a result, the polyester resin layer is molecularly oriented in the can height direction to some extent by drawing / thinning draw forming and / or ironing, and is also heat-fixed to bond the surface of the metal substrate to the polyester resin layer. It becomes possible to improve the corrosion resistance, impact resistance, etc. by eliminating the factors that hinder the adhesion due to internal stress due to the processing of the polyester resin layer at the interface, but if the molecular orientation or crystallization progresses excessively, the adhesion will be adversely affected. Property is impaired, resulting in poor corrosion resistance, impact resistance and the like.
That is, in order to enhance the adhesion at the adhesive interface between the coating resin layer and the surface of the metal substrate, suppress the undercoat corrosion (UFC) of the seamless can, and enhance the impact resistance (dent resistance) of the coating, In order to control the molecular orientation or crystallization so as not to become excessive, it is necessary to control the dynamic hardness to 20 or less. In addition, in the resin layer covering the inner surface of the can that has a controlled dynamic hardness so that it does not become excessive, the flavor of the contents is adsorbed by the resin when stored as a canned product, and when the canned product is drunk or eaten, it can be opened. It has the effect of preventing a change in taste when the product is cooked.

The resin-coated seamless can of the present invention is
The coating resin layer on the bottom of the can is in a non-oriented state, and since the processing is not severe at the bottom of the can, the orientation of the coated resin layer is maintained.The orientation of the bottom of the can is the coating resin layer before processing. Shows the orientation state of. In order to follow the severe processing of the can body, it is necessary that the orientation state of the coating resin layer before processing is unoriented.To obtain a highly processed resin-coated seamless can, the coating resin before processing must be The orientation of the bottom of the can, which indicates the orientation of the layers, is substantially unoriented. Also,
At the bottom of the can, the adhesive interface between the coating resin layer and the surface of the metal substrate is preserved in the form of the resin-coated metal plate before processing, so the adhesion between the two is sufficient, and corrosion resistance and impact resistance Etc. are kept in a satisfactory state.

The characteristic of the dynamic hardness DH in the polyester resin layer on the inner surface side of the can body of the resin-coated seamless can is imparted by the orientation state of the coated polyester resin before processing, seamless can molding conditions, heat treatment after seamless can molding, etc. Can be applied by. Dynamic hardness DH
To control, using a substantially unoriented polyester resin-coated metal plate laminated extrusion film or cast film, under appropriate temperature conditions, after thinning draw forming and / or ironing process into a seamless cup, It is necessary to alleviate the strain (residual stress) of the coating resin layer of the can body portion due to the above-mentioned processing and to perform heat treatment so as not to excessively grow oriented crystals.

This heat treatment is preferably carried out in a 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 of the body of the can decreases. 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 oriented and crystallized during seamless can molding, and by the heat treatment to be performed thereafter,
It is possible to impart properties excellent in heat resistance, impact resistance and corrosion resistance without causing coarse lamella type crystals. The heat treatment operation is performed before or after 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 in the coated polyester resin layer of the can body during can molding, but a short time is generally sufficient, and specifically 1 to 1 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 portion of the can is unoriented. In this state, the adhesive interface with the metal substrate 2 is preserved in substantially the same state. As a result, even when the surface treatment layer on the surface of the metal substrate is cracked, the adhesion with the polyester resin layer is enhanced, the undercoat corrosion (UFC) of the seamless can is suppressed, and the impact resistance (dent resistance) of the coating is also improved. It is possible to obtain the effect of increasing the.

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 carried out so that the dynamic hardness DH of the polyester resin layer containing polyethylene terephthalate in the upper portion of the can body on the inner surface side of the can is 20 or less. Also, it is preferable to perform it in terms of the effect of suppressing the internal strain remaining due to the 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 at least uniaxially, 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 in terms of thermal crystallization prevention, impact resistance and processability. 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 (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. Polyethylene terephthalate / isophthalate having an acid content of 8 to 25 mol% is desirable. 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. When the crystallinity is less than 20%, the adhesion to the metal substrate, the corrosion resistance and the impact resistance are inferior, and the amount of the flavor component adsorbed in the content tends to increase, which is not preferable as a canless 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 (3). Xc = [dc (d-da)] / [d (dc-da)] × 100 (3) In the formula (3), 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, a compounding agent 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, it is important to laminate the polyester resin layer 3 in a substantially non-oriented state in order to make the dynamic hardness DH of the polyester resin layer 3 in the upper part of the can body on the inner surface side of the seamless can 10 to be 20 or less. Become. The metal substrate 2, the polyester resin layer 3, and the resin-coated metal plate 1 used in the present invention 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 substrate 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 cross-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.

[Metal Base] As the metal base, 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, aluminum plating,
An aluminum-coated steel plate subjected to aluminum pressure welding or the like can also 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.

[0038]

The present invention will be described in more detail with reference to the following examples. Table 1 shows the composition of the resin used in each example, and Table 2 shows the conditions, evaluation, etc. of each example.

Example 1 A polyester resin having the composition C shown in Table 1 was charged into a twin-screw extruder, extruded through a T-die to a thickness of 20 μm, and the film cooled with a cooling roll was wound up. It was a cast film. Then, the films thus prepared were heat laminated on both sides of an aluminum alloy plate (plate thickness 0.28 mm, A3004 material, chromic acid / phosphoric acid surface treatment), and immediately water-cooled to obtain a polyester resin-coated metal plate. The temperature of the metal plate before laminating at this time is set to be 15 ° C. higher than the melting point of the polyester resin, and the temperature of the laminating roll is 150 ° C.
C., the strip running speed is 40 m / min. Was laminated with to obtain a resin-coated metal plate.

A wax type lubricant was applied to the polyester resin-coated metal plate thus produced, and a disk having a diameter of 152 mm was punched out to obtain a shallow-drawing cup. Then, this shallow drawn cup was subjected to ironing processing to obtain a seamless cup. The characteristics of this seamless cup were as follows. Cup diameter: 66 mm Cup height: 127 mm Thickness of the can wall portion with respect to the base plate: 45% This seamless cup was subjected to doming molding according to a conventional method, and after heat-treating the polyester resin at Tm-10 ° C for 3 minutes, After cooling the cup, trimming of the opening edge, curved surface printing and baking drying, neck-in processing,
Post processing such as flanging was performed to obtain a 350 cc seamless can.

Example 2 A seamless can was obtained in the same manner as in Example 1 except that the polyester resin having the composition D shown in Table 1 was used.

(Example 3) The polyester resin of composition B shown in Table 1 was used as a surface layer and the polyester resin of composition D as a lower layer, which was put into two twin-screw extruders and passed through a two-layer T-die to obtain the thickness of the surface layer. A seamless can was obtained by the same method as in Example 1 except that a laminate material was obtained by using a cast film extruded so that the thickness of the lower layer was 5 μm and the thickness of the lower layer was 15 μm.

Example 4 A seamless can was obtained in the same manner as in Example 3 except that the polyester resin of composition A shown in Table 1 was used as the surface layer and the polyester resin of composition C was used as the lower layer.

Example 5 A cast film having a polyester resin of composition D shown in Table 1 as a surface layer and a polyester resin of composition E as a lower layer was formed into a TFS steel plate (sheet thickness 0.18 m).
m, the amount of metal chromium was 120 mg / m ² , and the amount of hydrated chromium oxide was 15 mg / m ² ), but the same lamination as in Example 3 was performed.

A wax-type lubricant was applied to the polyester resin-coated metal plate thus produced, and a disk having a diameter of 166 mm was punched out to obtain a shallow drawn cup. Next, this shallow drawing cup was subjected to thinning drawing and ironing processing by stretching to obtain a seamless cup. The characteristics of this seamless cup were as follows. Cup diameter: 66 mm Cup height: 128 mm Thickness of the can wall portion with respect to the base plate: 65% This seamless cup was made into a seamless can by the same method as in Example 1.

Example 6 A polyester resin having the composition F shown in Table 1 was applied to both sides of an aluminum alloy plate (plate thickness 0.28 mm, A3004 material, chromic acid / phosphoric acid surface treatment) heated to 250 ° C. , A φ65 mm extruder was used to perform simultaneous extrusion coating on the inner and outer surfaces so that the thickness was 20 μm, and then cooling was performed to obtain a polyester resin-coated metal plate. Using the resin-coated metal plate thus obtained, a seamless can was obtained by the same method as in Example 1.

(Example 7) A seamless can was obtained in the same manner as in Example 6 except that the polyester resin having the composition G shown in Table 1 was used.

Example 8 A biaxial extruder and a bilayer extruder were used so that the polyester resin having the composition A shown in Table 1 was used as the surface layer and the polyester resin having the composition E was used as the lower layer so that the surface layer was 5 μm and the lower layer was 15 μm. A seamless can was obtained by the same method as in Example 6 except that simultaneous extrusion coating was performed using a die.

Example 9 A seamless can was obtained in the same manner as in Example 8 except that the polyester resin having the composition D shown in Table 1 was used as the surface layer and the polyester resin having the composition C was used as the lower layer.

Comparative Example 1 A seamless can was obtained in the same manner as in Example 1 except that the polyester resin having the composition A shown in Table 1 was used and the heat treatment shown in Table 2 was performed.

Comparative Example 2 A seamless can was prepared in the same manner as in Example 1 except that the polyester resin having the composition B shown in Table 1 was used as the surface layer and the polyester having the composition D was used as the lower layer, and the heat treatment shown in Table 2 was performed. Got

Comparative Example 3 A cast film using the polyester resin having the composition A shown in Table 1 was used as a TFS steel plate (plate thickness 0.18 mm, metal chromium amount 120 mg / m ² , chromium hydrate oxide amount 15 mg / m ^2). The same resin-coated metal plate as in Example 1 except that the metal plate was laminated to (1). Using this resin metal plate, thinning, drawing and ironing as in Example 5 and the heat treatment shown in Table 2 were performed to obtain a seamless cup. Then, the same post-processing as in Example 1 was performed to obtain a seamless can.

Comparative Example 4 A seamless can was obtained by using a resin-coated metal plate in the same manner as in Comparative Example 3 except that the polyester resin having the composition F shown in Table 1 was used and the heat treatment of the seamless cup was not performed.

(Comparative Example 5) A polyester resin having a composition E shown in Table 1 was used as a surface layer and a polyester resin having a composition B was used as a lower layer, except that the heat treatment of the seamless cup was not performed.
A seamless can was obtained in the same manner as in Comparative Example 3.

(Comparative Example 6) A polyester resin having the composition A shown in Table 1 was used to form a cast film, and then 100
The same method as in Example 1 was carried out except that the film was heat-treated at 230 ° C. for 5 seconds to prepare a biaxially-stretched film, and the heat treatment shown in Table 2 was performed after the film was stretched at a temperature of 3 ° C. in the lengthwise and transverse directions by 3 times. Got a seamless can.

(Comparative Example 7) A polyester resin having the composition B shown in Table 1 was used, except that the heat treatment shown in Table 2 was performed.
A seamless can was obtained by the same method as in Example 6.

Comparative Example 8 A polyester resin of composition E shown in Table 1 was used as a surface layer and a polyester resin of composition D as a lower layer was subjected to simultaneous extrusion coating using a twin-screw extruder and a two-layer T die. A seamless can was obtained in the same manner as in Example 6 except that the heat treatment shown was applied.

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

[Measurement of Dynamic Hardness DH] A can height of 70-
Cut 90mm part into 20mm square, then at least 24
Vacuum drying was performed for an hour. Using a Shimadzu ultra-micro hardness meter DUH200, load was applied to a 115 ° triangular pyramid indenter at an ambient temperature of 25 ° C. at a speed of 29 mgf / sec up to about 1 g, and from the depth (D) and load (P) at that time, The hardness was calculated from the dynamic hardness DH = 37.838 × P / D ² . This measurement was repeated 10 times, and the average value after eliminating the abnormal value was defined as the dynamic hardness DH of the sample. The results are shown in Table 2.

[Crystallinity] The upper part of the can body of a seamless can was cut out and the metal was dissolved to isolate a free film. After vacuum drying for at least 24 hours, the density of the sample was measured, and the crystallinity of the resin film was calculated and displayed by the density method.

[Adhesion Evaluation] A cross-cut was put on the inner surface film of the can body of the seamless can with a cutter, and cellophane tape (manufactured by Nichiban Co., Ltd .: 24 mm width) was attached to that portion, and the cellophane tape was peeled off. For the evaluation, the peeled state of the polyester resin coating after peeling the cellophane tape was visually observed. The evaluation results are shown in Table 2 with the following symbols. ○: There was no film peeling ×: There was film peeling

[Cross-Cut Evaluation] 3 cm × 3 cm was cut out from the inner surface of the upper part of the can body of a seamless can, the cross-cut was made with a cutter, the sample was dipped in a 0.1% sodium chloride aqueous solution, and the mixture was stored at 50 ° C. for one week. The corrosion condition was observed. The evaluation was carried out based on the size of film peeling from the cross-cut portion and the size of corrosion under the film. The evaluation results are shown in Table 2 with the following symbols. ◯: Film peeling or under-film corrosion of less than 1 mm was observed. ×: Film peeling or under-film corrosion of 1 mm or more was observed.

[Pack Evaluation] A can filled with cola was left to stand sideways, and then at 5 ° C., on the can axis perpendicular to the rolling direction of the metal plate, at the end of the can bottom side of the neck-in portion of the can. A weight of 1 kg having a spherical surface having a diameter of 65.5 mm was dropped from a height of 40 mm so that the spherical surface hits, and shocked. Then, a storage test was performed at a temperature of 37 ° C. to evaluate the state of the inner surface of the can after one year. Further, the sample was dropped vertically from a height of 50 cm, and then a storage test was performed at a temperature of 37 ° C. to observe the state of the inner surface of the can after one year. In particular, corrosion of the can neck and the bottom of the can was observed and shown in Table 2.

[Evaluation of Retort Treatment] After filling with distilled water at 95 ° C., retort treatment was performed at 135 ° C. for 30 minutes, the temperature was returned to room temperature, the distilled water was extracted, and the corrosion state of the inner surface of the can was observed.
The results are shown in Table 2.

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

EFFECT OF THE INVENTION The resin-coated seamless can of the present invention has excellent corrosion resistance and impact resistance by controlling the dynamic hardness DH of the polyester resin layer in the can body upper part on the inner surface side of the can to be 20 or less. And a resin-coated seamless can having flavor and flavor resistance.

[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.

[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: bottom of can 12: Can body 13: Neck 14: Flange part 15: Upper part of can body 16: Lower part of can body

Continued front page    F-term (reference) 3E061 AA16 AB13 AC01 AC09 AD01                       AD04 BA01 BB14 DA02                 3E062 AA04 AB02 AB14 AC07 JA07                       JA08 JB04 JB11 JB23 JB25                       JC02 JC09 JD03                 4F100 AB01A AB10 AB31 AK41B                       AK41C AK41D AK41E AK42B                       AK42C AK42D AK42E AL01B                       AL01C AL01D AL01E AL05B                       AL05C AL05D AL05E BA05                       BA06 BA10B BA10D GB16                       GB23 JA06B JA06C JA06D                       JA06E JA12B JA12C JA12D                       JA12E JB01 JK10 JK12B                       JK12D YY00B YY00C YY00D                       YY00E

Claims (6)

[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 represented by the following formula (1) is used. A resin-coated seamless can having a dynamic hardness DH of 20 or less at the upper part of the can body. DH = 37.838 × P / D ² (1) P: load, D: when a load P is applied to the polyester resin layer of the can body part with a 115 ° triangular pyramid indenter at a speed of 29 mgf / sec up to 1 g Penetration depth 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 thinned by drawing / thinning drawing and / or ironing so that the thickness of the can body is 20 to 85% of the thickness of the can bottom. The resin-coated seamless can according to claim 1 or 2. 4. The polyester resin layer comprises two layers, the surface layer (A) comprises polyethylene terephthalate / isophthalate having an isophthalic acid content of 15 mol% or less, and the lower layer (B) comprises an isophthalic acid content of 8 to 25 mol. %
4. The resin-coated seamless can according to claim 1, comprising the polyethylene terephthalate / isophthalate. 5. 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. 6. The resin-coated seamless can according to claim 1, wherein the polyester resin layer on the upper part of the can body has a crystallinity of 20 to 55% by a density method. .