JP4576142B2 - Polyester film for metal plate coating, method for producing the same, and method for producing polyester film-coated metal plate - Google Patents

Description

  The present invention relates to a polyester film for coating a metal plate, a method for producing the same, and a method for producing a polyester film coated metal plate. More specifically, a polyester film excellent in can manufacturing performance (for example, drawing and ironing workability) and suitable for a metal can that is subjected to hot water sterilization, a manufacturing method thereof, and a manufacturing method of a polyester film coated metal sheet It is about.

  Conventionally, the inner surface and outer surface of a metal can have been widely coated with a solution in which various thermosetting resins such as epoxy and phenol are dissolved or dispersed in a solvent for the purpose of preventing corrosion. Has been done. However, this thermosetting resin coating method has a drawback in that it takes a long time to dry the paint, so that productivity is lowered and undesired problems such as environmental pollution due to a large amount of organic solvent often occur.

  In order to avoid such drawbacks, a method of coating a metal plate with a thermoplastic resin by a melt extrusion method is disclosed. (For example, see Patent Document 1)

  However, in the above method, it is difficult to shorten the distance from the T die to the metal plate, and as a result, the thickness of both ends becomes very thick. Therefore, the central portion having a uniform thickness (substantially laminated to the metal plate). This is a laminating method in which the material loss is large and the both ends cut and removed cannot be reused.

  In order to avoid such drawbacks, a method is disclosed in which an unoriented film of polyethylene terephthalate and / or polybutylene terephthalate obtained by cooling and solidifying after melt extrusion is pressed onto a heated metal plate. In this method, the distance from the T die to the metal plate can be shortened. As a result, a central portion having a uniform thickness (a portion that can be substantially laminated on the metal plate) is wider than the above method and cut and removed. Since both the end portions can be recycled, the laminating method can reduce material loss. (For example, see Patent Document 2)

  However, in the above method, when both ends are cut and removed, the film easily breaks, and when the content of polybutylene terephthalate increases (for example, 40% by weight or more), a known chromium-plated mirror surface for polyester film formation When a film is formed at a speed of 30 m / min or more using a roll, a dent exceeding 50 μm is likely to occur on the film surface in contact with the roll, and when this film is laminated, a laminated metal plate in which bubbles due to the dent are present. Thus, there is a drawback that fine film tearing is likely to occur at the time of can making.

  In addition, as a polyester film excellent in canning processing such as drawing, an acid component composed of 80 to 95 mol% of 2,6-naphthalenedicarboxylic acid and 5 to 20 mol% of an aliphatic dicarboxylic acid and a glycol component composed mainly of ethylene glycol And a polyester biaxially stretched film containing a lubricant (preferably silica, alumina, titanium dioxide, calcium carbonate, barium sulfate, silicone resin particles) having an average particle diameter of 2.5 μm or less. (For example, see Patent Document 3)

  However, when trying to obtain a metal can by drawing and ironing the metal plate coated with the biaxially stretched film at a high speed (for example, at a speed of 80 cans / minute), the releasability from the processed punch or die However, film tearing, galling and the like are likely to occur, and the film-coated metal plate has not been satisfactory yet.

  Moreover, as resin used for the resin coating metal plate for squeezing and ironing cans, the dicarboxylic acid component is 50 to 95 mol% terephthalic acid and / or isophthalic acid and / or orthophthalic acid 50 to 5 mol%, and the hydroxy component is mainly composed of ethylene glycol. A resin composition comprising 75 to 99% by weight of a crystalline saturated polyester resin composed of a compound and 25 to 1% by weight of an ionomer resin is disclosed. (For example, see Patent Document 4)

However, when the resin composition is used on the outer surface of a metal can, when the obtained metal can is filled with contents and then subjected to a hot water sterilization treatment such as a paste rise treatment or a retort treatment, an appearance defect (eyeball color tone) As it is easy to generate spots, it has not yet been satisfied as a resin-coated metal plate.
JP-A-57-203545 JP 2001-1447 A JP-A-7-82391 JP-A-7-195617

  The present invention aims to eliminate the drawbacks of the prior art. In other words, the central part with a uniform thickness (the part that can be laminated to a metal plate) is wide, and both ends that have been cut and removed can be recycled, so there is little material loss, and the film breaks when both ends are cut and removed. When the molten resin film is cooled and solidified at a higher speed (for example, at a speed of 30 m / min or more), the film surface in contact with the roll is less likely to have a dent exceeding 50 μm, so that it is excellent in can manufacturing ability and is obtained. Polyester film for metal plate coating, which is less likely to cause poor appearance of the outer surface of the metal can (whitening of the film) due to hot water sterilization performed after filling and sealing the contents in a metal can, its manufacturing method, and polyester film coating The manufacturing method of a metal plate is provided.

  The first invention of the present application is a molten resin film of a polyester resin composition in which a mixing ratio of a polyester having a crystallization temperature (Tc1) of 145 ° C. or less and an olefin polymer is 70:30 to 99: 1 wt%. A polyester film obtained by solidifying with a cooling roll having a surface roughness (Ra) of 0.2 μm or more and less than 4.0 μm and then uniaxially stretching in at least the longitudinal direction, wherein the olefinic polymer in the polyester film An average dispersion diameter is 2 to 10 μm.

  In the second invention of the present application, the mixing ratio of the polyester having the crystallization temperature (Tc1) of 145 ° C. or less and the olefin polymer is 70:30 to 99: 1 wt%, and the average dispersion diameter of the olefin polymer is 2 The method for producing a polyester film for coating a metal plate having a thickness of 10 μm, wherein the polyester film for coating a metal plate is solidified with a cooling roll having a surface roughness (Ra) of 0.2 μm or more and less than 4.0 μm, It is a method for producing a polyester film for covering a metal plate, characterized by being uniaxially stretched at least in the longitudinal direction.

  A third invention of the present application is a polyester film coating in which a polyester film having a crystallization temperature (Tc1) of 145 ° C. or less and a mixing ratio of a polyester and an olefin polymer of 70:30 to 99: 1 wt% is coated. A method for producing a metal plate, wherein the polyester film-coated metal plate is produced by cooling a molten resin film extruded in a layer form from a T die with a surface roughness (Ra) of 0.2 μm or more and less than 4.0 μm. After solidifying with a roll, at least uniaxially stretching in the longitudinal direction, and then cutting and removing both ends to obtain the polyester film, and laminating the polyester film on a heated metal plate This is a method for producing a polyester film-coated metal sheet.

  A fourth invention of the present application is a polyester film for coating a metal plate, wherein the olefin polymer according to claim 1 is polyethylene and / or an ethylene copolymer.

  A fifth invention of the present application is a method for producing a polyester film for metal plate coating, wherein the olefin polymer according to claim 2 is polyethylene and / or an ethylene copolymer.

  A sixth invention of the present application is a method for producing a polyester film-coated metal sheet, wherein the olefin polymer according to claim 3 is polyethylene and / or an ethylene copolymer.

  The method for producing a polyester film-coated metal plate of the present invention can reduce material loss and is not only an economical production method, but also has an appearance and a can-making property (in particular, a can inner surface resin film and a processing punch). This is a production method for obtaining a polyester film-coated metal plate excellent in mold release properties and scratch resistance of the resin film on the outer surface of the can. Furthermore, when the polyester-based film-coated metal plate obtained by the present invention can be made, it is difficult to cause appearance defects (eyeball-like color tone spots) on the outer surface of the metal can by retorting performed after filling the contents. It can be said that it is a very useful polyester film for coating a metal plate, a method for producing a polyester film for coating a metal plate, and a method for producing a polyester film coated metal plate.

  The polyester film for metal plate coating of the present invention is a melt of a polyester resin composition in which the mixing ratio of the polyester having a crystallization temperature (Tc1) of 145 ° C. or less and the olefin polymer is 70:30 to 99: 1 wt%. A polyester film obtained by solidifying a resin film with a cooling roll having a surface roughness (Ra) of 0.2 μm or more and less than 4.0 μm and then uniaxially stretching at least in the longitudinal direction, It is a polyester film for metal plate coating in which the average dispersion diameter of the olefin polymer is 2 to 10 μm.

  The crystallization temperature (Tc1) of the polyester used in the polyester film for metal plate coating of the present invention is 145 ° C. or less, which is a poor appearance in retort treatment performed after filling the contents (eyeball-like color tone spots ). When the crystallization temperature (Tc1) exceeds 145 ° C., appearance defects (eyeball-like color tone spots) are generated in the retort treatment, which is not preferable.

  The polyester used in the polyester film for coating a metal plate of the present invention is a polyester obtained by polycondensation of a dicarboxylic acid and a diol. Examples of such dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, 5-sodium sulfoisophthalic acid and other aromatic dicarboxylic acids, oxalic acid, succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid. Aliphatic dicarboxylic acids such as acid, maleic acid, fumaric acid and dimer acid, oxycarboxylic acids such as p-oxybenzoic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used. Examples of the diol include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol and neopentylglycol, alicyclic glycols such as cyclohexanedimethanol, and aromatic glycols such as bisphenol A and bisphenol S. Can be used.

  The melting point of the polyester used in the present invention is 180 ° C. or higher. Can manufacturing ability (in drawing and ironing process, the resin on the inner surface of the can ensures the releasability of the processing punch, and the resin on the outer surface of the can suppresses galling. [Vertical scratches in the resin film]).

  The method for producing the polyester used in the polyester film for coating a metal plate of the present invention is not particularly limited. That is, it can be used even if it is produced by either the transesterification method or the direct polymerization method. Further, it may be produced by a solid phase polymerization method in order to increase the molecular weight. Furthermore, the polyester with low oligomer content produced by the reduced pressure solid phase polymerization method is used from the point of reducing the amount of oligomer from the polyester resin in the retort treatment etc. that is performed after filling the contents in the obtained metal can. It is preferable.

  In the polyester film for metal plate coating of the present invention, the olefin polymer blended with the polyester is preferably polyethylene and / or ethylene copolymer. For example, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, Ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer Polymers, ionomers, ethylene-maleic anhydride graft copolymers, ethylene-vinyl alcohol copolymers, and the like can be used. In the present invention, as the olefin polymer blended with the polyester, one kind of resin selected from the above can be used alone, or two or more kinds of resins can be used in combination.

  In the polyester film for coating a metal plate of the present invention, when the polyester and the olefin polymer are blended, the blend ratio needs to be 70:30 to 99: 1% by weight. When the olefin polymer is less than 1% by weight, galling is likely to occur on the outer surface of the can during can making, which is not preferable. Further, when the olefin polymer exceeds 30% by weight, it is not preferable because punch releasability is inferior on the inner surface side of the can and can be easily generated on the outer surface side of the can.

  In the polyester film for coating a metal plate of the present invention, the olefin polymer is dispersed in the polyester film in the form of particles, and the average dispersion diameter is 2 to 10 μm. Necessary to ensure impact. When the dispersion diameter of the olefin polymer is less than 2 μm, it is not preferable because galling is likely to occur on the outer surface of the can during can making. On the other hand, when the thickness exceeds 10 μm, punch releasability is inferior on the inner surface side of the can during can making, and galling is likely to occur on the outer surface side of the can, which is not preferable.

  In order to control the dispersion diameter of the olefin polymer within the above range, as one example of selection of the olefin polymer, two or more types of olefin polymers including a polyolefin having no functional group and a polyolefin containing a functional group may be used. Use together. Specific examples include the combined use of polyethylene and ethylene- (meth) acrylic acid copolymer, and the combined use of ethylene-α-olefin copolymer and ethylene-α-olefin- (meth) acrylic acid copolymer. .

  As a preferable functional group, there can be used a functional group having polarity and having an effect of increasing the affinity with the blended polyester. Examples thereof include a carboxyl group, a glycidyl group, and an acid anhydride group. Specific examples include ethylene-α, β-unsaturated carboxylic acid copolymers such as ethylene- (meth) acrylate copolymers and ethylene- (meth) acrylic acid ester copolymers produced by various production methods and catalysts. can do. However, some or all of the carboxylic acid groups of the α, β-unsaturated carboxylic acid were neutralized with metal ions such as Na, K, Li, Zn, Mg and Ca as a copolymer of vinyl monomers having functional groups. In the case of using an ionomer, it is preferable that the amount of metal ions does not exceed 200 ppm with respect to the total amount of the olefin-based polymer because foreign substances having metal particles as nuclei are likely to be generated in the melt extrusion process.

  In the present invention, when the resin obtained by cutting and removing both ends is reused, the reuse ratio is not particularly limited, but is preferably 5 to 60 (% by weight).

  The polyester film for coating a metal plate of the present invention includes a heat stabilizer, an antioxidant, an ultraviolet absorber, a plasticizer, a pigment, an antistatic agent, a lubricant, a crystal nucleating agent, inorganic or organic particles as necessary. A lubricant or the like may be blended.

  In the polyester film for coating a metal plate of the present invention, a mixture obtained by dry blending a polyester and an olefin polymer or a polymer obtained by melt mixing is melted in a known single or twin screw extruder, and then layered from a T die. It is necessary to solidify the molten resin film extruded into a cooling roll having a surface roughness (Ra) of 0.2 μm or more and less than 4.0 μm.

  When the surface roughness (Ra) of the chill roll is less than 0.2 μm, when the molten resin film is cooled and solidified at a high speed (for example, a speed of 30 m / min or more), the recesses exceeding 50 μm are innumerable on the film surface in contact with the chill roll. When this film is uniaxially stretched at least in the longitudinal direction, the recesses become large, and when this film is laminated to a metal plate, it becomes a laminated metal plate in which bubbles due to the recesses exist, As a result, fine film tearing is likely to occur.

  Conversely, when the surface roughness (Ra) of the cooling roll is 4.0 μm or more, the satin pattern is transferred to the film, and when this film is laminated on a metal plate, a patchy appearance defect occurs on the film. When is used on the outer surface side of the can, the commercial value is lowered.

  At this time, the surface roughness (Ra) of the cooling roll is preferably 0.2 μm or more and 3.5 μm or less, and more preferably 0.2 μm or more and 2.5 μm or less.

  As the surface shape of the cooling roll, a surface finished in a spiral shape, a shape finished in a diamond cut shape, a surface finished in a satin finish or the like can be used. Of these, a roll finished in a satin finish is particularly preferable.

  The average thickness of the central portion after cooling and solidification is preferably 250 μm or less in order to improve the stretchability.

In the present invention, it is preferable to adopt a method in which the laminated molten resin is brought into close contact with static electricity when contacting the cooling roll. In the electrostatic adhesion method, a method in which both end portions and the central portion of the layered resin are made independent is more preferable. Furthermore, when the laminated molten resin contacts the cooling roll, it is more preferable to use a measure (for example, a device such as a vacuum chamber or a vacuum box) for reducing the accompanying flow by reducing the pressure on the opposite side.

  In the present invention, after cooling and solidifying, it is necessary to uniaxially stretch at least in the longitudinal direction and then cut and remove both ends to obtain a polyester film. As longitudinal stretching conditions, it is preferable to stretch 1.3 to 6.0 times in the longitudinal direction at a temperature equal to or higher than the glass transition temperature of polyester. When longitudinal stretching is carried out, when the both ends of the film are cut and removed, the film is hardly broken and productivity can be improved. Further, when both ends of the film are cut and removed and laminated on a metal plate, material loss is reduced, which is economical. Furthermore, in order to improve the thickness distribution and productivity of the polyester film, transverse stretching may be performed after longitudinal stretching. If necessary, the heat shrinkage in the stretching direction of the film may be controlled by heat treatment for 1 to 20 seconds at a temperature of 50 ° C. or higher and a melting point of the polyester −20 ° C. under tension.

  In the present invention, it is preferable that the surface roughness (Ra) of the polyester film is 0.1 μm or less in order to ensure the canability and increase the commercial value of the resulting can. The surface roughness (Ra) is more preferably 0.02 to 0.1 [mu] m in order to ensure laminating properties with the metal plate (in order to suppress deterioration of unwinding property due to film blocking).

  In the present invention, the thickness of the film is not particularly limited.

  In the present invention, the metal plate is not particularly limited, and a steel plate, an aluminum plate, and an aluminum alloy plate are used.

  The mechanical properties such as the plate thickness and tensile breaking strength are not particularly limited, and the steel plate is usually used as a steel plate for cans, specifically for drawn cans, drawn and ironed cans, lids The steel plate used for each application is used. The same applies to the surface treatment applied to the surface of the steel sheet, such as an electrolytic chromic acid-treated steel sheet commonly called TFS-CT, a steel sheet having an electrolytic chromic acid treatment applied to the upper layer of the Ni plating film, and the like.

  The same applies to aluminum plates and aluminum alloy plates, and the mechanical properties such as plate thickness and tensile breaking strength are not particularly limited, and are usually used as aluminum plates for cans, specifically drawn and ironed cans. The aluminum plate used for each use for the lid and the lid is used. As for the surface treatment of the aluminum plate or the aluminum alloy plate, an aluminum plate or an aluminum alloy plate subjected to chromium phosphate treatment or other chemical conversion treatment is used.

  After these metal plates are heated, a polyester film is laminated simultaneously or sequentially on one or both sides of the metal plate using a laminating roll. The heating temperature is preferably a melting point of polyester of −20 ° C. or higher and a melting point of + 150 ° C. or lower. Subsequently, the laminated metal plate is heated and then cooled with water and / or air to obtain a polyester film-coated metal plate. The heating temperature is preferably the melting point of polyester + 10 ° C. or higher and the melting point + 60 ° C. or lower.

  When laminating on both surfaces, the structure and thickness of each polyester film may be the same or different.

  Hereinafter, the present invention will be described based on examples.

[Evaluation methods]
(1) Melting point and crystallization temperature of polyester constituting polyester film Differential scanning calorimeter (DSC) in nitrogen stream using 10 mg of polyester film obtained in Examples 1-9 and Comparative Examples 1-8 When the exothermic / endothermic curve (DSC curve) was measured at a rate of temperature increase of 10 ° C./min with the melting point Tm (° C.) as the peak temperature of the endothermic peak accompanying melting, the peak of the exothermic peak accompanying crystallization The temperature was the crystallization temperature Tc1 (° C.).
(2) Average dispersion diameter of olefin-based polymer The polyester-based films obtained in Examples 1 to 9 and Comparative Examples 1 to 8 were embedded in an epoxy resin and cured, and parallel to each stretching direction using a cryomicrotome. An ultrathin section was prepared by incision at the cross section. This was dyed with ruthenium oxide, held at room temperature for 10 minutes, then carbon-deposited and observed with a transmission electron microscope. The average dispersion diameter of the olefin polymer was determined by a weighted average of the long diameters using an image analyzer (V10, manufactured by Toyobo Co., Ltd.).
(3) Intrinsic viscosity of polyester constituting the polyester film (IV)
It is a value (dl / g) measured by dissolving a raw material resin of a polyester film in orthochlorophenol at 25 ° C.
(4) Cooling roll surface roughness (Ra)
It measured according to JIS B0601 (1982).
(5) Polyester film surface roughness (Ra)
The polyester films obtained in Examples 1 to 9 and Comparative Examples 1 to 8 are cut into 10 cm × 10 cm, and are visually evaluated to have no dents exceeding 50 μm on the film surface in contact with the cooling roll during casting. It evaluated by the following method. In addition, it was set as surface roughness (Ra) (micrometer) with the average value of 20 times measurement.
a. Measuring device: ET-30HK manufactured by Kosaka Laboratory
b. Stitch tip radius: 0.5 μm
c. Stylus load: 5mg
d. Measurement length: 1mm
e. Cut-off value: 0.08mm
(6) Preparation method of polyester film-coated metal plate Aluminum alloy plate heated to 250 ° C. (3004 type alloy plate having a thickness of 0.26 mm) or Ni-plated steel plate (thickness: 0.19 mm and Ni as an adhesion amount on one side) The polyester films obtained in Examples 1 to 9 and Comparative Examples 1 to 8 were simultaneously laminated on both surfaces of 500 mg / m ² and a Ni-plated steel sheet having 6 mg of hydrated chromium oxide film in terms of metal chromium on the upper layer. Then, after heating at 275 ° C., it was quenched in water to obtain a polyester film-coated aluminum plate or a polyester film-coated steel plate.
(7) Releasability of can inner surface resin and processing punch After applying a forming lubricant to the polyester film-coated aluminum plate or polyester film-coated steel plate obtained in Examples 1 to 9 and Comparative Examples 1 to 8, Drawing was carried out by heating to a polyester film of 25 μm on the inner surface side of the can at a plate temperature of 70 ° C. Next, the temperature of the obtained cup was set to 40 ° C., and ironing was performed at a mold temperature of 80 ° C. at a speed of 80 cans / minute, and 400 cans of 350 ml-sized seamless cans were made. The degree of buckling occurring at the top of the 10 cans was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Buckling has not occurred in the can opening. Δ: Buckling has occurred in about 1/3 of the circumference of the can opening. ×: Buckling has occurred in 1/3 or more of the circumference of the can opening. Properties (longitudinal scratches on can outer surface resin)
400 cans were made in the same manner as in (7) above from the polyester film-coated aluminum plates or polyester film-coated steel plates obtained in Examples 1 to 9 and Comparative Examples 1 to 8, and the first 10 cans and the last 10 cans. The degree of occurrence of scratches on the outer surface resin of the can body wall portion formed by the can was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Scratch not generated Δ: Scratch occurred in about 1/3 of the outer surface ×: Severe scratch generated more than 1/3 of the outer surface (9) Appearance observation in retort treatment Obtained in Examples 1-9 and Comparative Examples 1-8 A can obtained from the polyester film-coated aluminum sheet or polyester film-coated steel sheet obtained in the same manner as in the above (7) was heated at 270 ° C. for 40 seconds and then quenched in water, and 200 ml of water was filled. After retorting at 120 ° C. for 30 minutes, the sample was cooled to 50 ° C. within 5 minutes, and the presence or absence of appearance defects (eyeball-like color tone spots) on the outer surface side film of the sample was observed.
○: No eyeball-like color tone occurs.
X: Eyeball-like color tone occurrence.

  The polyester used in Examples 1-9 and Comparative Examples 1-8, the kind and compounding quantity of an olefin polymer are shown in Table 1, the polyester film obtained in Examples 1-9 and Comparative Examples 1-8, and Table 2 shows the measurement and evaluation results of the polyester film-coated metal plate.

[Abbreviations and contents of polyester and olefin polymer used in Examples 1 to 9 and Comparative Examples 1 to 8]
(1) PET: Polyethylene terephthalate (IV: 0.75, average particle diameter
(Containing 2000 ppm of 1.5 μm agglomerated silica)
(2) PBT: Polybutylene terephthalate (IV: 1.20)
(3) CO-PES: Copolyester of terephthalic acid and ethylene glycol / neopentyl glycol (mol% 70/30) (IV: 0.72, 1000 ppm of agglomerated silica having an average particle size of 1.5 μm)
(4) Olefin A: Low density polyethylene (Sumitomo Chemical Co., Sumikasen G40 1: trade name)
(5) Olefin B: ethylene-acrylic acid copolymer (manufactured by Dow Chemical Company, Primacol 3440: trade name)
(6) Olefin C: ethylene-methacrylic acid copolymer (manufactured by Mitsui DuPont Polychemical Co., Ltd., Nucrel N1108C: trade name)
(7) Olefin D: Ethylene-ethyl acrylate copolymer (Mitsui DuPont Polychemical, Evaflex A712: trade name).
(8) Olefin E: Ethylene-1-butene copolymer (manufactured by Nippon Synthetic Rubber, EBM20 41P: trade name)
(9) Olefin F: Styrene-ethylene / butylene-styrene block copolymer (Asahi Kasei Co., Ltd., Tuftec M1913: trade name)

[Example 1]
A mixture in which the mixing ratio of the polyester mixed at a mixing ratio of PET / PBT = 60/40 wt% and the olefin polymer mixed at a mixing ratio of olefin A / olefin B = 50/50 wt% is 90:10 wt%. It is melted at 280 ° C., and cast into a layered cooling roll (circumferential speed 50 m / min) having a surface roughness (Ra) of 1.0 μm using a T die, and the distance between the T die and the cooling roll is 2 cm. The center part and both end parts are electrostatically adhered with separate devices (center part: 4.5 kV, both ends: 6 kV DC power supply is applied), and after cooling and solidification, the preheating temperature is 65 ° C. and the stretching temperature is 100 ° C. The film was stretched 4 times in the direction to obtain a polyester film (thickness of 16 μm and 25 μm).
Next, a 16 μm polyester film was pressure bonded to one side of a 3004 series aluminum alloy plate (thickness 0.26 mm) heated to 250 ° C., and a 25 μm polyester film was pressure bonded to the other side and heated to 275 ° C. A polyester film-coated aluminum plate was obtained by quenching in water.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Example 2]
Polyester films (thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that polyester mixed at a mixing ratio of PET / PBT = 40/60% by weight was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Example 3]
A polyester film (two types having a thickness of 16 μm and 25 μm) was obtained in the same manner as in Example 1 except that a satin-like cooling roll having a surface roughness (Ra) of 0.5 μm was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Example 4]
Polyester films (two types having a thickness of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that a satin-like cooling roll having a surface roughness (Ra) of 3.3 μm was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Example 5]
After cooling and solidifying in the same manner as in Example 1, the polyester was stretched three times in the machine direction at a preheating temperature of 65 ° C. and a stretching temperature of 100 ° C., and then stretched three times in the transverse direction at a preheating temperature of 60 ° C. and a stretching temperature of 100 ° C. System films (two types with thicknesses of 16 μm and 25 μm) were obtained.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Example 6]
Polyester films (thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that an olefin polymer mixed at a mixing ratio of olefin A / olefin C = 50/50 wt% was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Example 7]
Polyester films (thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that an olefin polymer mixed at a mixing ratio of olefin A / olefin D = 50/50 wt% was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Example 8]
Polyester films (thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that an olefin polymer mixed at a mixing ratio of olefin B / olefin E = 50/50 wt% was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Example 9]
Polyester films (thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that a Ni-plated steel plate was used.
Next, a polyester film-coated steel sheet was obtained in the same manner as in Example 1.
As can be seen from Table 2, the method of this example is a method for producing a polyester film-coated metal sheet having an excellent appearance and can-making property, and has a surface smoothness that provides a metal can having excellent retort whitening resistance. It is an excellent polyester film for coating a metal plate and can be said to be a method for producing a polyester film coated metal plate.

[Comparative Example 1]
Polyester films (two types having a thickness of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that PET alone was used as the polyester and was stretched 4 times at a preheating temperature of 90 ° C. and a stretching temperature of 110 ° C.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
As shown in Table 2, this method was a method for producing a polyester film-coated metal plate having excellent canability. However, since eyeball-like color tone spots were generated on the outer surface of the can after retorting, the metal plate was coated. It is not preferable as a production method of a polyester film for coating, a production method of a polyester film for coating a metal plate, and a production method of a polyester film coating metal plate.

[Comparative Example 2]
Polyester films (thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that the olefin polymer was not mixed.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
In this method, as shown in Table 2, galling occurred on the outer surface of the can at the time of can making, and poor mold releasability occurred on the inner surface of the can (see Note 1), so no subsequent evaluation was performed. This method is not preferable as a polyester film for metal plate coating, a method for producing a polyester film for metal plate coating, and a method for producing a polyester film coated metal plate.

[Comparative Example 3]
A polyester film (two types having a thickness of 16 μm and 25 μm) was obtained in the same manner as in Example 1 except that a mixture having a mixing ratio of polyester and olefin polymer of 60: 40% by weight was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
In this method, as shown in Table 2, galling occurred on the outer surface of the can at the time of can making, and a mold releasability failure occurred on the inner surface of the can, so that subsequent evaluation was not performed. This method is not preferable as a polyester film for metal plate coating, a method for producing a polyester film for metal plate coating, and a method for producing a polyester film coated metal plate.

[Comparative Example 4]
Polyester films (thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that olefin A alone was used as the olefin polymer.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
In this method, as shown in Table 2, galling occurred on the outer surface of the can at the time of can making, and a mold releasability failure occurred on the inner surface of the can, so that subsequent evaluation was not performed. This method is not preferable as a polyester film for metal plate coating, a method for producing a polyester film for metal plate coating, and a method for producing a polyester film coated metal plate.

[Comparative Example 5]
Except for using olefin F alone as the olefin polymer, polyester films (two types of thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1, but the discharge became unstable and stable film formation was not possible. The film was abandoned and no further evaluation was performed as shown in Table 2.
This method is not preferable as a polyester film for metal plate coating, a method for producing a polyester film for metal plate coating, and a method for producing a polyester film coated metal plate.

[Comparative Example 6]
Polyester films (two types having a thickness of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that a mirror-like cooling roll having a surface roughness (Ra) of 0.05 μm or less was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
In this method, the appearance of the laminated metal plate was bad (bubbles were generated), and when the can was made, as shown in Table 2, film breakage starting from the bubbles occurred on the inner surface side and the outer surface side, Subsequent evaluation was not performed. This method is not preferable as a polyester film for metal plate coating, a method for producing a polyester film for metal plate coating, and a method for producing a polyester film coated metal plate.

[Comparative Example 7]
Polyester films (thicknesses of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that a mirror-like cooling roll having a surface roughness (Ra) of 4 μm was used.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
In this method, as shown in Table 2, the appearance of the laminated metal plate was bad (the trace pattern of the satin finish spreads in a patchy shape and the transparency was poor), and the elbow shape caused by the trace pattern on the outer surface side of the obtained metal can As a result, the commercial value of the metal can was lowered, and therefore no subsequent evaluation was performed. This method is not preferable as a polyester film for metal plate coating, a method for producing a polyester film for metal plate coating, and a method for producing a polyester film coated metal plate.

[Comparative Example 8]
Polyester films (two types with a thickness of 16 μm and 25 μm) were obtained in the same manner as in Example 1 except that CO-PES alone was used as the polyester.
Then, a polyester film-coated aluminum plate was obtained in the same manner as in Example 1.
This method was a method for producing a polyester film-coated metal plate having an excellent appearance, but as shown in Table 2, galling was generated on the outer surface of the can during can making, and the release property of the punch was poor on the inner surface of the can. Since this occurred, subsequent evaluation was not performed. This method is not preferable as a polyester film for metal plate coating, a method for producing a polyester film for metal plate coating, and a method for producing a polyester film coated metal plate.

注１：比較例２では製缶速度を３０缶／分に低下させた場合は加工ポンチの離型性、外面フィルムのキズ発生程度とも○であった。
注２：比較例８ではポリエステルが非晶性のため融解ピーク及び結晶化ピークはなし。

Note 1: In Comparative Example 2, when the can-making speed was reduced to 30 cans / minute, the releasability of the processed punch and the degree of occurrence of scratches on the outer film were good.
Note 2: In Comparative Example 8, there is no melting peak or crystallization peak because the polyester is amorphous.

  Since the method for producing a polyester film-coated metal sheet of the present invention can reduce material loss, it is not only an economical production method but also an appearance and can-making property (especially a can inner surface resin film and processing). This is a production method for obtaining a polyester film-coated metal plate excellent in punch releasability and scratch resistance of the resin film on the outer surface of the can. Furthermore, when a polyester film-coated metal plate obtained by the present invention is made, it is difficult to cause poor appearance of the outer surface of the metal can (whitening of the polyester film) in the hot water sterilization performed after filling the contents. It can be said that these are extremely useful polyester film for coating a metal plate, a method for producing a polyester film for coating a metal plate, and a method for producing a polyester film coated metal plate.

Claims (2)

For coating a metal plate in which the mixing ratio of the polyester having a crystallization temperature (Tc1) of 145 ° C. or less and the olefin polymer is 70:30 to 99: 1% by weight and the average dispersion diameter of the olefin polymer is 2 to 10 μm. A method for producing a polyester film, wherein the polyester film for covering a metal plate is a satin-like surface having a surface roughness (Ra) of 0.2 μm or more and less than 3.5 μm of a molten resin film extruded in a layer form from a T die. A method for producing a polyester film for covering a metal plate, wherein the film is solidified by electrostatically adhering to a cooling roll at a speed of 30 m / min or more and then uniaxially stretched at least in the longitudinal direction. The method for producing a polyester film for coating a metal plate, wherein the olefin polymer according to claim 1 is polyethylene and / or an ethylene copolymer.