JP3041151B2 - Polycarbonate resin-coated metal plate and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycarbonate resin-coated metal sheet mainly intended for use as a material for cans and a method for producing the same. More specifically, the present invention relates to a metal plate in which a lower layer is coated with a polyester resin on one or both sides of a metal plate and a composite resin layer made of a polycarbonate resin on an upper layer, and a method for manufacturing the same. For cans that are not only used as general can materials such as can lids and drawn cans, but also subjected to severe processing, such as drawn and ironed cans and cans that have been stretched after drawing (thinned deep drawn cans) It can be applied as a precoat material.

[0002]

BACKGROUND OF THE INVENTION food cans or Te _Lee emission-free steel is a metal can for materials used in beverage cans (hereinafter, referred to as TFS) and the metal plate such as aluminum is decorated with one or a plurality of times of coating Was. Applying this paint
Not only is the paint baking process complicated, it also requires a large amount of baking time, and in order to discharge a large amount of solvent, it is necessary to lead the discharged solvent to a special incinerator and incinerate it in terms of pollution. Had. In order to solve these problems, it has been studied to laminate a thermoplastic resin film on a heated metal plate. For example, a method of laminating a polyester resin film on a metal plate without using an adhesive (Japanese Patent Publication No. 60-47103). After coating the metal plate with a polyester resin, quenching is performed to reduce the crystallinity of the resin layer to within 30%. (Japanese Patent Publication No. 57-23584). Further, a method of laminating a polyester resin film on which a polymer composition composed of an epoxy resin and a curing agent thereof is applied in advance (Japanese Patent Publication No. 63-13829, Japanese Patent Application Laid-Open No. 61-149341)
No. 1) was developed, and further improvements were made to the laminated polyester resin film.
JP-A-3-87249, Japanese Patent Application No. 2-418199.
The polyester resin-coated metal plate obtained by the method disclosed in No. 1 is processed into a thinned deep-drawing can, and is used for applications in which green tea, oolong tea, black tea, etc. are filled and then retorted at a temperature of 120 to 130 ° C. began. In addition, a plastic laminated metal plate having a stainless steel appearance by laminating various films having an embossed pattern on a metal plate having a certain surface roughness (Japanese Patent Application Laid-Open No. 51-73576) is disclosed.

The polyester resin-coated metal sheet obtained by the method disclosed in Japanese Patent Publication No. 47103/1985 is one of the methods for obtaining a laminate by heat fusion. Although it can be applied as a raw material, it must be used in applications requiring strict workability, such as thin-walled deep-drawing cans. When the can is broken, the degree of orientation of the resin is 0, that is, in a state close to amorphous, when the can is filled at a high speed and continuously after filling the molded can or its contents. When the can collides with the can, when viewed from the inner side of the can, a dent that is deformed in a convex shape is generated, and the resin layer in the dent portion is cracked, and significant local corrosion may occur. Therefore, it is necessary to control the degree of orientation of the polyester resin within a very narrow range, and in fact, a great deal of manufacturing effort is required to obtain stable quality. Further, when the dents are formed under a low temperature condition of 5 ° C. or less, even if the resin layer has an appropriate degree of orientation, there is a risk that the resin layer in that portion is cracked and locally corroded. have.

[0004] JP-A-1-249331, JP-A-3-8
The polyester resin-coated metal plate obtained by the method disclosed in Japanese Patent Application No. 7249 and Japanese Patent Application No. 2-418199 uses a copolymerized polyester resin mainly composed of ethylene terephthalate units having excellent workability for a polyester resin film to be laminated. Thus, the present invention can be applied to a thin-walled deep drawn can requiring strict workability. For example, JP-A-1-249331 discloses a copolymerized polyester resin film in which ethylene terephthalate units having a limited softening onset temperature, crystal melting temperature, elongation at break, etc. occupy 75 to 95%, and Japanese Patent Application No. 3-87249 discloses before and after lamination. Is a material obtained by laminating a copolymerized polyester resin film of the same composition as described above, which has a limited refractive index in the thickness direction and in-plane, on a metal plate via an adhesive layer. In Japanese Patent Application No. 2-418199, a copolyester resin film having the same composition as described above is laminated on a metal plate by thermal bonding, and the plane orientation coefficient of a layer in contact with the metal plate and the plane orientation coefficient of the outermost layer are limited. It is. If these materials are also made and transported in a normal state, and are filled with the contents in a normal state, they can be sufficiently applied to a thinned deep drawn can. However, when an external impact is applied to the molded can, cracks may be formed in the polyester resin layer on the inner surface of the can in the same manner as described above, and the can is locally corroded. In the production of these polyester resin-coated metal sheets, it is necessary to strictly control the lamination conditions in order to control the plane orientation coefficient and the like of the laminated polyester resin layer in an appropriate range. Further, Japanese Patent Application Laid-Open No. 2-418198 discloses a polyester resin-coated metal plate for a thin-walled deep drawn can in consideration of the above-mentioned abnormal work. That is, it is a material obtained by laminating a polyester resin film having the same composition as described above in which the limiting viscosity (IV value) of the laminated polyester resin film is limited on a metal plate. This material is hard to crack in the polyester resin layer on the inner surface of the can even in the abnormal work as described above, and can be used for thinned deep drawn cans. When filling at the following low temperature, when transporting or storing at low temperature, if one of the cans dents due to collision between cans, cracks will enter the polyester resin layer in that part and locally corrode You. That is, the polyester resin-coated metal plate obtained in JP-A-2-418198 is inferior in impact workability at low temperatures, and is difficult to be put into practical use as a can material for filling highly corrosive contents such as carbonated beverages at low temperatures. .

The coated metal structure obtained by the method disclosed in Japanese Patent Publication No. 57-23584 has been studied for the purpose of improving the peeling resistance, molding workability and corrosion resistance. In the composition and the resin structure, the application to the thinned deep-drawing can application is such that the can and the can collide when the molded can or the can is filled with the contents and then the can is conveyed at high speed and continuously. Cracking of the resin layer at the dent cannot be avoided. Further, the configuration of the coated metal plate is greatly different from that of the present invention.

The plastic laminated metal plate having the stainless steel appearance obtained by the method disclosed in JP-A-51-73576 certainly mentions a polycarbonate resin film as one of the laminated plastic films. Aims to find novelty only in the material composition to obtain the stainless steel appearance, and pays attention to the moldability or workability of the resin layer and the adhesion between the metal plate and the resin layer, which are indispensable characteristics as a material for cans. However, it is impossible to apply the method to not only the thinned deep-drawing cans but also general drawing cans. Naturally, the purpose of the invention is significantly different from the present invention.

[0007]

The thermoplastic resin-coated metal sheet obtained by the above-mentioned method has a high quality in consideration of abnormal operations in the above-mentioned can making process and contents filling process. It lacks stability and cannot be a material suitable for applications requiring high workability, such as thinned deep drawn cans. The problem to be solved by the present invention is that even when severe processing such as thinned deep drawing cans and drawn ironing cans is performed, excellent formability, processing adhesion, impact resistance, particularly excellent low temperature impact resistance are obtained. An object of the present invention is to develop a metal plate coated with a polycarbonate resin.

[0008]

In order to solve the above-mentioned problems, the present invention first studied in detail a resin composition having good low-temperature impact workability even without orientation. As a result, it has been found that if a resin having a carbonate bond in the molecule, that is, a polycarbonate resin has a specific elongation at break, it is extremely excellent in low-temperature impact workability. Although it is possible to heat-bond this polycarbonate resin directly to a metal plate,
Even if it is heat-sealed to a metal plate, the processing adhesion is not sufficient, and it is difficult to apply it to applications such as thin-walled deep-drawing cans that require excellent processing adhesion. As a result of examining the surface condition of the metal plate and the resin composition to be interposed between the polycarbonate resin and the metal plate in order to ensure adhesion, a specific polyester resin is interposed at least on the metal plate having a chromium hydrated oxide film. It has been found that, when a polycarbonate resin is heat-sealed, a polycarbonate resin-coated metal sheet excellent in properties such as low-temperature impact workability, work adhesion, and moldability can be obtained. Furthermore, even when heat resistance, flavor properties, and surface appearance after retorting are particularly required, a more preferable configuration of the resin layer has been found.

Hereinafter, the contents of the present invention will be described in detail. First, in the polycarbonate resin-coated metal plate of the present invention, the polycarbonate resin constituting the upper layer is a polymer mainly composed of a repeating unit having a basic structure represented by the following formula (1). In the formula, R ₁ is an aliphatic hydrocarbon having 2 to 10 carbon atoms or an aromatic hydrocarbon having 6 to 18 carbon atoms. What is important in the present invention is that the elongation at break of the polycarbonate resin is preferably in the range of 70 to 450%, and 100 to 450%.
More preferably, it is in the range of 250%. If the elongation at break is less than 70%, the workability becomes remarkably inferior, and when the dent of the body of a can molded using a polycarbonate resin-coated metal plate is caused by impact, cracks occur in the laminated polycarbonate resin layer. It is not preferable because it may cause On the other hand, if the elongation at break exceeds 450%, a phenomenon in which the resin protrudes from the end face when the coated metal sheet is processed or cut, that is, a film hair tends to occur remarkably, is not preferable. Here, the elongation at break refers to a composite resin film obtained by immersing a polycarbonate resin-coated metal plate of the present invention in 3% dilute hydrochloric acid at 25 ° C. to melt the metal plate, and peeling the metal plate as a sample. The values are measured according to ASTM-D638 except that cracks are observed on the polycarbonate surface or the composite resin film is broken. Further, when the heat resistance of the resin is particularly required, such as when the coated metal plate is used after being painted or printed, an aromatic polycarbonate resin is preferable. In addition, when hot water treatment such as retort treatment is performed, if the polycarbonate resin does not have heat resistance, unevenness occurs at the boundary between a portion where water droplets are attached to the resin surface and a portion where no water droplet is attached, and the surface appearance is impaired. (Hot water trace). From this viewpoint, the polycarbonate resin used in the present invention is preferably an aromatic polycarbonate resin. For example, polydioxydiphenyl-2,2-propane carbonate (bisphenol A polycarbonate), polydioxydiphenylmethane carbonate, polydioxy Diphenylethane carbonate, polydioxydiphenyl-2,2-butanecarbonate, polydioxydiphenyl-2,2-pentanecarbonate, polydioxydiphenyl-3,3-pentanecarbonate, polydioxydiphenyl-2,2hexanecarbonate The aromatic polycarbonate in which the alkyl group or the phenyl group is bonded to the carbon of the central methane of 4,4'-dioxydiphenylmethane carbonate is the upper layer polycarbonate of the present invention. Can be used as a resin, especially heat resistance,
Bisphenol A polycarbonate resin is preferred from the viewpoints of processability, economy and the like. Further, the molecular weight or molecular weight distribution of the resin also affects the properties of the coated metal sheet, but the appropriate molecular weight and molecular weight distribution should be determined in consideration of necessary properties and economy, and there is no particular limitation here.

Next, the polyester resin interposed between the metal plate and the polycarbonate resin layer is selected mainly from the viewpoint of the adhesion between the metal plate and the upper polycarbonate resin layer. The polyester resin used in the present invention is (2)
Alternatively, a polymer mainly composed of a repeating unit having the basic structure represented by the formula (3) is introduced, but other elements are introduced for the purpose of improving properties such as adhesion within a range that does not significantly impair other properties. Good. In the formula, R ₂ is an alkylene group having 2 to 6 carbon atoms, and R ₃ is an alkylene group or an arylene group having 2 to 24 carbon atoms. Furthermore, what is important in the present invention is that the intrinsic viscosity (IV value) of the polyester resin is preferably in the range of 0.3 to 1.8, more preferably in the range of 0.5 to 1.2. IV value is 0.3
If it is less than the above range, when the dents are formed during molding or when the above-mentioned dents are formed, remarkable cracks are generated in the polyester resin layer, and even if the upper layer polycarbonate resin is uniformly coated, corrosion may be concentrated on the crack portion. on the other hand,
If the IV value exceeds 1.8, the melt viscosity becomes high and it becomes difficult to achieve sufficient wetting with other materials, or the adhesion to the metal plate or polycarbonate resin becomes remarkably inferior. Here, the IV value refers to a value obtained by immersing the polycarbonate resin-coated metal plate of the present invention in 3% dilute hydrochloric acid at 25 ° C. to chemically dissolve the metal plate, and scraping only the polyester resin from the composite resin layer. A solution of 0.3 g of sample in 25 ml of orthochlorophenol was added to 35
It is a value measured using an Ostwald BS type viscosity tube at a temperature of ° C. and calculated by the following equation. η _sp / c = [η] + κ [η] ² C (4) where η _sp : specific viscosity [η]: intrinsic viscosity, equivalent to IV value κ: constant (0.247) C: volume concentration (G / 100ml)

As the polyester resin used in the present invention, specifically, polyethylene terephthalate / isophthalate obtained by using two kinds of acid components of terephthalic acid and isophthalic acid at the time of synthesis in addition to polyethylene terephthalate and polybutylene terephthalate And a polyester resin such as polyethylene terephthalate / sebacate and polyethylene terephthalate / adipate, or a polyester resin blended with such a resin. The detailed resin composition should be determined according to the required properties. In particular, when corrosion resistance is required for the polycarbonate resin-coated metal sheet of the present invention, it is preferable to use a resin in which a polyethylene terephthalate resin and a polybutylene terephthalate resin are mixed at a weight ratio of 1: 0.1 to 1.7. . The weight ratio of polybutylene terephthalate resin to polyethylene terephthalate resin is 0.1 to 0.1.
When the weight ratio is out of the range of 1.7, the corrosion resistance becomes poor, so that it is not suitable for applications requiring particularly strict workability. When the polycarbonate resin-coated metal plate of the present invention is processed into a can body and the can body is filled with various contents, even if the polycarbonate resin layer is in direct contact with the filled contents, the taste and aroma of the contents are obtained. Has little advantage compared to other resins that hardly changes, but the lower polyester resin layer may slightly affect the taste and aroma of the contents, and the polycarbonate resin of the present invention When a coated metal plate is used on the inner surface of a can and flavor properties are strictly required, a polyethylene terephthalate resin and a polybutylene terephthalate resin are blended in a lower polyester resin layer in a weight ratio of 1: 0.1 to 1.2. Resin is more preferred. If the weight ratio of the polybutylene terephthalate resin to the polyethylene terephthalate resin exceeds 1.2, there is a risk that the adsorption of the flavor component to the resin layer becomes large. Furthermore, when used for sterilization treatment with steam at 100 ° C. or higher, that is, retort treatment, at least the polyester resin on the outer surface of the can is a polyethylene terephthalate resin and a polybutylene terephthalate resin in a ratio of 1: 0.6 to 1.7. It is more preferable to use a resin blended in a weight ratio of If the weight ratio of the polybutylene terephthalate resin to the polyethylene terephthalate resin is less than 0.6, the polyester resin used in the polycarbonate resin-coated metal plate of the present invention is subjected to a heat treatment at a temperature not lower than the crystallization temperature of the polyester resin for a long time of 20 seconds or more. If not, the outer surface of the can after the retort treatment becomes milky white in a spot-like manner, and the surface appearance is remarkably impaired. Further, the adhesion tends to be reduced by the retort treatment, and if it exceeds 1.7, the corrosion resistance becomes inferior. .

In the polycarbonate resin-coated metal sheet of the present invention, the thickness of the upper polycarbonate resin layer and the thickness of the lower polyester resin layer should be determined in consideration of necessary characteristics and economy, and are not particularly limited. However, generally, the thickness of the upper polycarbonate resin layer is 3 to 40 μm, and the thickness of the lower polyester resin layer is 0.2 to 20 μm.

The polycarbonate resin in the upper layer and the polyester resin in the lower layer may be added, if necessary, to a stabilizer, an antioxidant, an antistatic agent, a pigment, a lubricant, a corrosion inhibitor and the like within a range that does not impair the other properties. Such additives may be added.

Next, as a metal plate used in the present invention, a polyester resin which is a lower layer of the composite resin layer of the present invention is provided with a chromium hydrate oxide film on the surface layer of a sheet-like or belt-like steel plate and an aluminum plate. It is necessary to ensure excellent adhesion to the layer. In particular, a steel sheet in which the lower layer is coated with a double-layered film of chromium metal and the upper layer is a chromium hydrated oxide, so-called TFS, is preferable, and further, one or two or more layers of tin, nickel, zinc, etc. Plating, alloy plating, and TFS film or chromium hydrated oxide film with the above two-layer structure formed on the upper layer, or electrolytic chromic acid treatment and immersion chromic acid treatment on aluminum plate A chromium hydrated oxide film is used.
The amount of chromium hydrated oxide film on the surface layer is 3 mg / m
^{If it is} less than ² or more than 30 mg / m ² , the adhesion to the polyester resin layer, which is the lower layer of the composite resin layer, particularly the adhesion after processing is reduced. Therefore, the amount of the chromium hydrated oxide film is preferably in the range of 3 to 30 mg / m ² as chromium, and more preferably 7 to 25 mg / m ² . The amount of metallic chromium need not be particularly limited, but is preferably in the range of 10 to 200 mg / m ² from the viewpoint of corrosion resistance after processing and adhesion of the polyester resin layer.

Next, a method for producing the polycarbonate resin-coated metal sheet of the present invention will be described. The polycarbonate resin-coated metal plate of the present invention can be manufactured by the following film lamination method or extrusion lamination method. (1) Melting point (Tm) to Tm + of lower layer polyester resin
Unstretched, uniaxially stretched or biaxially stretched on one or both sides of a metal plate having a chromium hydrated oxide film of 3 to 30 mg / m ² heated to a temperature of 150 ° C. A method in which stretched composite resin films are laminated and then slowly or rapidly cooled. (2) 3 to 3 heated to a temperature of Tm to Tm + 150 ° C.
Unstretched, uniaxially stretched or biaxially stretched polyester resin film is laminated on one or both sides of a metal plate having a chromium hydrated oxide film of 0 mg / m ² , or a molten polyester resin is extruded and laminated. A method in which an unstretched, uniaxially stretched or biaxially stretched polycarbonate resin film is laminated on the upper layer at a temperature of Tm to Tm + 150 ° C., or a molten polycarbonate resin is extruded and laminated, followed by slow cooling or rapid cooling. (3) The glass transition temperature (T
g) 3 to 3 ° C. heated to a temperature of + 30 ° C. to Tm + 150 ° C.
A coextruded polycarbonate resin and polyester resin are laminated on one or both sides of a metal plate having a chromium hydrated oxide film of 30 mg / m ^{2 so} that the polyester resin layer is in contact with the metal plate, and slowly cooled or quenched. how to. Here, the melting point is defined as a differential scanning calorimeter (SS1).
0, manufactured by Seiko Denshi Kogyo KK) at a temperature of 10 ° C./min, which indicates the maximum depth of the endothermic peak based on the crystal melting of the resin. If there are two or more endothermic peaks because the resin is a blended product, etc., the melting point is basically the higher temperature indicating the maximum depth of the endothermic peak, but lower if the adhesion force can be ensured. Good as melting point. In addition, the glass transition temperature referred to here is a temperature at a boundary where a resin state becomes a glass or rubber state, a specific volume of the resin at each temperature is measured, and a temperature at which the specific volume-temperature curve starts to bend is determined. Show. Which of these methods is to be used should be determined in consideration of the required characteristics of the coated metal plate, the production amount, and the like, and is not particularly limited. An important factor in these methods is that the polyester resin serving as the lower layer is hot-melted and wets well on the metal plate, a good adhesion between the polyester resin and the metal plate is secured, and the polyester resin and the polycarbonate in the upper layer are secured. Good adhesion between the resins is also ensured by thermal fusion, and for that purpose, the temperature of the metal plate described above is an indispensable requirement. On the other hand, if the heating temperature of the metal plate exceeds Tm + 150 ° C., the polyester resin in the lower layer may be thermally decomposed and properties may be deteriorated, which is not preferable.

The method of heating the metal plate includes a known hot air circulation heat transfer method, a resistance heating method, an induction heating method, a heat roll method, and the like. These methods may be used alone or in combination. Good.

The polycarbonate resin-coated metal plate obtained by the film laminating method or the extrusion laminating method as described above is gradually cooled or quenched. Status,
It should be determined by the processing method, processing conditions, usage, and the like of the polycarbonate resin-coated metal sheet of the present invention. When used on the outer surface of a can to be filled with contents and subjected to retort treatment, it is necessary to select cooling conditions such that the substantially amorphous polyester resin layer existing immediately after coating is finely crystallized. It is preferable from the viewpoint of preventing the surface from being whitened by the treatment.

[0018]

EXAMPLES Examples and comparative examples of the present invention will be described below.

Example 1 A biaxially stretched composite resin film composed of a polyester resin in which the upper layer is a bisphenol A polycarbonate resin and the lower layer is a 1: 1 weight ratio of a polyethylene terephthalate resin and a polybutylene terephthalate resin (each resin the thickness of the layer: 12 [mu] m, the polyester resin melting point: a 252 ° C.), induction strip TFS heated to 280 ° C. by heating rolls (metallic chromium amount: 110 mg / m ^2, hydrated chromium oxide content: chromium as 18 mg / m ² , board thickness: 0.
26 mm, board width: 250 mm, temper: T-5) were laminated on both sides using a pair of silicon rolls, and immersed and cooled in water after 3 seconds. The breaking elongation of the polycarbonate resin in the obtained polycarbonate resin-coated TFS is 11
The IV value of the polyester resin was 0.72.

Example 2 An unstretched composite resin film (polycarbonate resin layer) consisting of a polyester resin in which the upper layer is a bisphenol A polycarbonate resin and the lower layer is a mixture of a polyethylene terephthalate resin and a polybutylene terephthalate resin in a weight ratio of 1: 0.2. Thickness: 20 μm, thickness of polyester resin layer: 10 μm, melting point of polyester resin: 25
4 ° C.) was heated to 290 ° C. with an induction heating roll to obtain a strip-shaped TFS (amount of chromium metal: 60 mg / m ² , hydrated chromium oxide: 25 mg / m ² as chromium, plate thickness: 0.26 mm,
It was laminated on both sides of the temper degree: T-5) and immediately quenched in water. In the obtained polycarbonate resin-coated TFS, the breaking elongation of the polycarbonate resin was 105%, and the IV value of the polyester resin was 0.58.

Example 3 A biaxially stretched composite resin film composed of a polyethylene terephthalate / isophthalate copolymerized polyester resin containing an upper layer of bisphenol A polycarbonate resin and a lower layer of 88 mol% of terephthalic acid and 12 mol% of isophthalic acid as acid components. Polycarbonate resin layer thickness: 15μ
m, the thickness of the polyester resin layer: 10 μm, and the melting point of the polyester resin: 228 ° C.)
Then, lamination was performed under the same conditions as in Example 1. In the obtained polycarbonate resin-coated TFS, the elongation at break of the polycarbonate resin was 110%, and the I of the polyester resin layer was
The V value was 0.62.

Example 4 Polyethylene terephthalate resin and polybutylene terephthalate resin coextruded from an extruder were used in the following manner:
A composite resin composed of a polyester resin and a bisphenol A polycarbonate resin blended at a weight ratio of 0.7 (each thickness: 15 μm, melting point of the polyester resin: 25)
3 ° C.) so that the polyester resin layer is
It was laminated on a belt-like TFS (plate thickness: 0.26 mm, temper degree: T-5, amount of chromium metal: 150 mg / m ² , amount of chromium hydrated oxide: chromium: 7 mg / m ² ) heated to 0 ° C. And immediately quenched into water. The breaking elongation of the polycarbonate resin in the obtained polycarbonate resin-coated TFS was 113%, and the IV value of the polyester resin was 0.64.

Example 5 A strip-shaped steel sheet having a thickness of 0.26 mm and a temper degree of T-5 was degreased and pickled by a known method, and then tin sulfate 80 g / l and phenolsulfonic acid (65% aqueous solution) 60 g. / l, ethoxylated α-naphthol 0.06 g / l tin plating bath, bath temperature 45 ° C, cathode current density 20 A / dm ² , 1.
5g / m ² tin plating, washed with water, chromic anhydride 50g /
l, sulfuric acid 0.5 g / l chromic acid solution, bath temperature 50 ° C
Under a condition of a cathode current density of 40 A / dm ² , a TFS film (metal chromium content: 90 mg / m ² , chromium hydrated oxide content: 13 mg / m ² as chromium) was formed on both surfaces, washed with hot water and dried tin plating An unstretched composite resin film in which the upper layer is a bisphenol A polycarbonate resin on both sides of the steel sheet and the lower layer is a polyethylene terephthalate resin and a polybutylene terephthalate resin in a weight ratio of 1: 1.5 (polycarbonate resin layer thickness: 7 μm, polyester Resin layer thickness: 5
μm, melting point of polyester resin: 250 ° C.) in the same manner as in Example 1 except that the temperature of the steel sheet was 255 ° C. The breaking elongation of the polycarbonate resin in the obtained polycarbonate resin-coated tin-plated steel sheet was 120.
%, IV value of the polyester resin was 0.73.

Comparative Example 1 An unstretched bisphenol A polycarbonate resin film (thickness: 25 μm) was laminated on both sides of a strip-shaped TFS similar to that in Example 1 heated to 300 ° C., and immediately quenched in water. The elongation at break of the polycarbonate resin in the obtained polycarbonate resin-coated TFS was 103%.

Comparative Example 2 88 mol% of biaxially stretched terephthalic acid, isophthalic acid 1
Polyethylene terephthalate containing 2 mol% as an acid component /
An isophthalate copolymerized polyester resin film (thickness: 25 μm, melting point: 228 ° C.) was laminated on both sides of a strip-shaped TFS similar to that of Example 1 heated to 240 ° C., and immediately cooled in water. Obtained polyester resin coated TFS
Of the polyester resin was 0.60.

Comparative Example 3 A primer consisting of 75 parts of an epoxy resin (epoxy equivalent 3000) and 25 parts of paracresol-based resol was previously applied to one surface of a biaxially stretched copolyester resin film as in Comparative Example 2 at 100 ° C. The film dried in ( ¹ ) was laminated on both sides of a strip-shaped TFS similar to that in Example 1 heated to 240 ° C. so that the primer-coated surface was in contact with the TFS surface. After 3 seconds, it was immersed in water and cooled. Obtained polyester resin coated TFS
Of the polyester resin was 0.58.

The resin-coated metal sheets obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were processed into thin-walled deep-drawing cans under the following molding conditions, and were subjected to doming, necking, and flanging in a conventional manner. Processed. [Molding conditions] Drawing process Blank diameter: 187 mm Drawing ratio: 1.50 Redrawing process Primary redrawing ratio: 1.29 Secondary redrawing ratio: 1.24 Tertiary redrawing ratio: 1.20 Curvature radius at corner of die in redrawing process: 0.4 mm Wrinkle holding load in process: 6000 kg Average Thinning Ratio of Can Body Part: -20% based on the thickness of the resin-coated metal plate before molding The characteristics of the thin-walled deep-drawn cans obtained under the above molding conditions were evaluated by the following methods. The results are shown in Tables 1 and 2. (1) Processing Adhesion of Laminated Resin Layer The presence or absence of peeling of the laminated resin layer in each forming step of the thinned deep drawn can performed under the above-mentioned forming processing conditions was visually evaluated. (2) Workability of the laminated resin layer The obtained thin-drawing deep-drawing can is filled with 3% saline, a DC voltage of 6.3 V is applied to the can, and the degree of exposure of the metal surface is determined by the flowing current value. That is, the workability was evaluated based on the degree of cracking of the laminated resin layer at the time of forming into a thinned deep drawn can. (3) Impact resistance of the laminated resin layer The width of the obtained thin-walled deep-drawn can in the circumferential direction is 30 from the can body.
mm, 4 samples of length 120mm, 10mm from the bottom of the can
At a position, a rod (weight 1 kg) having a steel ball having a tip diameter of 1/2 inch on the outer surface of the can is dropped from a height of 40 mm,
Apply a sponge impregnated with 3% saline to the convex part on the inner surface,
A DC voltage of 6.3 V was applied to the sample, the flowing current value was measured, and the impact resistance of the laminated resin layer was evaluated by the average value of the current value at each position. (4) Resistance to low-temperature impact workability of the laminated resin layer The sample prepared by the method shown in (3) above was immersed in ice water for 5 minutes, taken out, and placed in a sample having a temperature of 5 ° C. The impact processing was applied from the outer surface side of the can in the same manner as in the above), the current value was measured in the same manner, and the low-temperature impact workability of the laminated resin layer was evaluated.

[0028]

[Table 1] (Note) PC: Bisphenol A polycarbonate resin P / PB: Polyester resin blended with polyethylene terephthalate and polybutylene terephthalate in parentheses P-PI: Polyethylene with terephthalic acid 88 mol% and isophthalic acid 12 mol% as acid components Terephthalate / isophthalate copolymerized polyester resin

[0029]

[Table 2]

[0030]

As described above, the polycarbonate resin-coated metal sheet of the present invention is excellent in workability, work adhesion, impact resistance, especially low-temperature impact resistance, and can not only endure severe molding but also form. Even if impact processing is applied from the outside to the can body and the contents filled with the contents at a low temperature, cracks hardly enter the laminated resin layer,
It is a material for cans with excellent corrosion resistance, and is widely used not only for thin-walled deep-drawn cans subjected to severe processing but also for drawn cans, drawn ironed cans, can lids, screw caps, etc. Also, the manufacturing method does not require strict temperature control, and is a method suitable for high-speed and stable production.

Claims (9)

(57) [Claims] 1. A polycarbonate resin having one or both sides of a metal plate having a chromium hydrated oxide film of 3 to 30 mg / m ² as chromium, and an upper layer mainly composed of a repeating unit having a basic structure represented by the following formula (1): A polycarbonate resin-coated metal plate, wherein the lower layer is coated by heat fusion with a composite resin layer composed of a polyester resin mainly composed of a repeating unit of the following formula (2) or (3): Wherein R ₁ is an aliphatic hydrocarbon having 2 to 10 carbon atoms or an aromatic hydrocarbon having 6 to 18 carbon atoms, In the formula, R ₂ is an alkylene group having 2 to 6 carbon atoms, and R ₃ is an alkylene group or an arylene group having 2 to 24 carbon atoms. 2. The polycarbonate resin-coated metal plate according to claim 1, wherein the polycarbonate resin in the upper layer is an aromatic polycarbonate resin having an elongation at break of 70 to 450%. 3. The polycarbonate resin-coated metal plate according to claim 1, wherein the polycarbonate resin in the upper layer is bisphenol A polycarbonate resin. 4. The polycarbonate resin-coated metal sheet according to claim 1, wherein the lower layer polyester resin is a polyester resin having an intrinsic viscosity of 0.3 to 1.8. 5. The polyester resin of the lower layer is mainly composed of a blended resin in which a polyethylene terephthalate resin and a polybutylene terephthalate resin are mixed in a weight ratio of 1: 0.1 to 1.7. 3. Polycarbonate resin coated metal plate of 3 or 4. 6. The lower polyester resin layer on one side of a metal plate is mainly composed of a blended resin in which a polyethylene terephthalate resin and a polybutylene terephthalate resin are blended in a weight ratio of 1: 0.1 to 1.2, and the other surface is formed. The lower polyester resin layer mainly comprises a blend resin obtained by mixing a polyethylene terephthalate resin and a polybutylene terephthalate resin in a weight ratio of 1: 0.6 to 1.7. 3 or 4 polycarbonate resin-coated metal plate. 7. The melting point (Tm) of the lower layer polyester resin.
A non-stretched, uniaxially stretched or biaxially stretched composite resin film comprising a polycarbonate resin as an upper layer and a polyester resin as a lower layer is laminated on one or both sides of a metal plate heated to a temperature of ~ Tm + 150 ° C. Item 10. A method for producing a polycarbonate resin-coated metal sheet according to Item 1. 8. The melting point (Tm) of the lower layer polyester resin.
2. The method according to claim 1, wherein the polyester resin is coated on one or both sides of a metal plate heated to a temperature of from Tm to 150 [deg.] C., and a polycarbonate resin is further coated thereon at a temperature of Tm to Tm + 150 [deg.] C. A method for producing a polycarbonate resin-coated metal plate. 9. A co-extruded upper layer of a polycarbonate resin and a lower layer of a composite resin of a polyester resin on one or both sides of a metal plate heated to a temperature of (glass transition temperature (Tg) + 30 ° C. to Tm + 150 ° C.) of the lower layer polyester resin. The method according to claim 1, wherein the polyester resin layer is laminated so that the polyester resin layer is in contact with the metal plate.