Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D25/00—Details of other kinds or types of rigid or semi-rigid containers
  • B65D25/14—Linings or internal coatings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
  • B21D22/28—Deep-drawing of cylindrical articles using consecutive dies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D51/00—Making hollow objects
  • B21D51/16—Making hollow objects characterised by the use of the objects
  • B21D51/26—Making hollow objects characterised by the use of the objects cans or tins; Closing same in a permanent manner
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D1/00—Rigid or semi-rigid containers having bodies formed in one piece, e.g. by casting metallic material, by moulding plastics, by blowing vitreous material, by throwing ceramic material, by moulding pulped fibrous material or by deep-drawing operations performed on sheet material
  • B65D1/12—Cans, casks, barrels, or drums
  • B65D1/14—Cans, casks, barrels, or drums characterised by shape
  • B65D1/16—Cans, casks, barrels, or drums characterised by shape of curved cross-section, e.g. cylindrical
  • B65D1/165—Cylindrical cans
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D1/00—Rigid or semi-rigid containers having bodies formed in one piece, e.g. by casting metallic material, by moulding plastics, by blowing vitreous material, by throwing ceramic material, by moulding pulped fibrous material or by deep-drawing operations performed on sheet material
  • B65D1/22—Boxes or like containers with side walls of substantial depth for enclosing contents
  • B65D1/26—Thin-walled containers, e.g. formed by deep-drawing operations
  • B65D1/28—Thin-walled containers, e.g. formed by deep-drawing operations formed of laminated material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D25/00—Details of other kinds or types of rigid or semi-rigid containers
  • B65D25/34—Coverings or external coatings
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
  • C08G63/16—Dicarboxylic acids and dihydroxy compounds
  • C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
  • C08G63/181—Acids containing aromatic rings
  • C08G63/183—Terephthalic acids

Definitions

• the present invention relates to a squeezed iron can made of a painted metal plate and a painted metal plate for a squeezed iron can.
• the present invention relates to a squeezed iron can in which film peeling is effectively prevented, and a coated metal plate for a squeezed iron can capable of forming such a squeezed iron can with high productivity.
• An organic resin-coated metal plate in which a metal plate such as aluminum is coated with a thermoplastic resin film has long been known as a material for cans, and this organic resin-coated metal plate is subjected to drawing or ironing. It is also well known to make a seamless can for filling a beverage or the like, or to press-mold it to make a can lid for an easy open end or the like.
• an organic resin-coated metal plate having a thermoplastic resin film made of a crystalline polyester resin mainly composed of ethylene terephthalate units as an organic resin coating layer is used for seamless cans (squeezed iron cans) formed by squeezing. It is used as a can manufacturing material (Patent Document 1 etc.). Since such an organic resin-coated metal plate can be squeezed and ironed under dry conditions without using a coolant (cooling / lubricant), it is possible to squeeze and iron a conventional metal plate using a coolant. In comparison, it has environmental advantages.
• Such an organic resin-coated metal plate is a method in which a preformed film such as a thermoplastic polyester resin is bonded to a metal plate by thermal bonding, or an extrusion in which a molten thin film such as an extruded thermoplastic polyester resin is bonded to a metal plate. It is manufactured by a film laminating method such as a laminating method.
• a film laminating method such as a laminating method.
• it is difficult to control the film thickness to a thin film due to the convenience of film formation, so that the film thickness tends to be thick, which may cause a problem in terms of economy.
• a squeezing can is manufactured under dry conditions from a coated metal plate in which a coating film is formed on the metal plate by a coating method capable of forming a thin film. It is also proposed to do.
• the pencil hardness is H or more
• the elongation rate is 200 to 600%
• the dynamic friction coefficient is within the range of 0.03 to 0.25
• the dry coating amount of the film on the outer surface side of the can after processing is 15 to.
• a coated metal plate for a squeezing can having a pencil hardness of H or higher under test conditions of 150 mg / 100 cm 2 , a glass transition temperature of 50 to 120 ° C., and a glass transition temperature of 60 ° C. has been proposed.
• a squeezed iron In a squeezed iron can formed from a coated metal plate under dry conditions, the adhesiveness between the coating film and the metal substrate is caused by the residual stress in the coating film generated by the harsh squeezing and ironing process after the can body is molded. (Hereinafter, it may be referred to as "coating film adhesion") may be significantly reduced.
• This residual stress can be removed by heat-treating the can body under predetermined conditions, but when such heat treatment is applied, the residual stress of the coating film generated by harsh processing is alleviated at once, and the coating is applied. Shrinkage acts on the interface between the film and the metal substrate, and especially in the part where the processing of the can body is severely thinned, the coating film peels off from the metal substrate, causing metal exposure and reducing the coating film coverage. There was a case.
• Patent Document 2 a coating film capable of exhibiting hardness, elongation, etc. is formed on the inner surface side of the coated metal plate even when heat generation of about 60 ° C. is generated by continuous squeezing and ironing.
• a painted metal plate that can withstand squeezing and ironing, and a squeezed iron can that is molded from this painted metal plate.
• an object of the present invention is to have excellent coating film peeling resistance that does not cause coating film peeling due to heat treatment after molding, suppress metal exposure, have high coating film coating property even after heat treatment, and have corrosion resistance.
• Another object of the present invention is to provide a coated metal plate for a squeezing can, which has a coating film that does not cause the above-mentioned problems.
• a squeezed can having an inner surface coating film on at least the inner surface side of the can, the inner surface coating film contains a polyester resin and a curing agent, and the test conditions of the inner surface coating film at the bottom of the can at 100 ° C.
• a squeezed iron can characterized in that the stress relaxation rate after 10 minutes at the time of 1% elongation in 1 is 50% or more.
• the curing agent contained in the inner coating film is a resol type phenol resin and / or an amino resin.
• the curing agent contained in the inner coating film is an m-cresol-based resol-type phenol resin.
• the inner coating film further contains an acid catalyst. 4.
• the content of the acid catalyst in the inner coating film is less than 0.5 parts by mass with respect to 100 parts by mass of the polyester resin. 5.
• the polyester resin contained in the inner coating film contains ethylene glycol, propylene glycol, 1,4-butanediol, and 2-methyl-1.
• the outer surface coating film is provided on the outer surface side of the can, the outer surface coating film contains a polyester resin and a curing agent, and the stress relaxation rate of the outer surface coating film at the bottom of the can is higher than 40%.
• the thickness of the center of the can body should be 20 to 75% of the thickness of the center of the bottom of the can.
• the thickness of the inner surface coating film at the center of the can body is 20 to 75% of the thickness of the inner surface coating film at the center of the bottom of the can. 9.
• the thickness ratio of the inner surface coating film to the metal substrate is substantially the same at the bottom of the can and the body of the can. 10.
• the heat shrinkage of the inner coating film at the center of the can body which is expressed by the following formula, is 30% or less.
• Heat shrinkage rate (%) ( ⁇ L 1 / L 0 ) ⁇ 100 L 0 : Initial length in the height direction of the coating film isolated from the center of the can body ⁇ L 1 : At a heating rate of 5 ° C./min while applying a load of 5.20 ⁇ 10 5 N / m 2 per unit area.
• the coverage of the inner coating film is less than 200 mA in terms of ERV. Is preferable.
• the present invention is also a coated metal plate for a squeezing can having a coating film on both sides, and the inner surface coating film on the inner surface side of the can after the squeezing and ironing process is a polyester resin and a resole type phenol resin as a curing agent. / Or amino resin is contained, and the outer coating film on the outer surface side of the can after squeezing and ironing contains polyester resin and amino resin as a curing agent, and when the inner coating film is stretched by 1% under the test conditions of 100 ° C.
• the stress relaxation rate after 10 minutes has passed is 50% or more, and the stress relaxation rate after 10 minutes has passed when the outer coating film is stretched by 1% under the test conditions of 100 ° C. is higher than 40%. Painted metal plates for squeezing cans are provided.
• the polyester resin contained in the inner coating film has a total amount of polyhydric alcohol components constituting the polyester resin of 100 mol%
• ethylene glycol and propylene glycol are used.
• 1,4-Butanediol, 2-methyl-1,3-propanediol, and one or more selected from diethylene glycol are preferably contained in an amount of 20 mol% or more in total.
• a squeezed iron can characterized by being made of the coated metal plate for the squeezed iron can.
• the thickness of the center of the can body should be 20 to 75% of the thickness of the center of the bottom of the can.
• the thickness of the inner surface coating film at the center of the can body is 20 to 75% of the thickness of the inner surface coating film at the center of the bottom of the can.
• the coverage of the inner coating film is less than 200 mA in terms of ERV. Is preferable.
• the present inventors have diligently studied the peeling of the coating film due to the heat treatment of the squeezing can made of the coated metal plate. It was found that there is a correlation with the stress relaxation behavior (stress relaxation rate) when the film is stretched under predetermined conditions, and the range of stress relaxation rate that does not cause coating film peeling and such stress relaxation rate are set.
• stress relaxation behavior stress relaxation rate
• the coating film of the inner surface coating film expressed in ERV conversion is less than 200 mA and the metal is exposed even after the heat treatment is performed after the squeezed iron can is formed. Is effectively prevented and has excellent corrosion resistance.
• the coated metal plate that can form such a squeezed iron can has excellent extensibility and workability of the coating film, and is subject to harsh processing such as drawing and ironing under dry conditions.
• the can body is broken (sometimes referred to as broken body in the present invention), and metal exposure is effectively prevented, so that the coating has high coating properties even after drawing and ironing.
• it has excellent can-making processability. That is, in the present invention, a combination of a specific polyester resin and a curing agent is used as the polyester resin and the curing agent constituting the coating film, and the degree of curing and the cross-linking density of the coating film are controlled to be excellent in can making.
• the coated metal plate used for molding the squeezed iron can of the present invention is a coated metal plate having an inner coating film on the surface on the inner surface side of the can after squeezing and ironing, and the inner coating film is a polyester resin. It is an important feature that the inner surface coating film contains a curing agent and has a stress relaxation rate of 50% or more after 10 minutes of elongation at 1% under the test conditions of 100 ° C. As is clear from the measurement method described later, the stress relaxation rate in the present invention was maintained by applying 1% elongation strain to the coating film under test conditions of 100 ° C. using a thermomechanical analyzer or the like.
• the time change of stress is measured in the state, and it is calculated by the following formula (1).
• Stress relaxation rate (%) ( ⁇ 1- ⁇ 2) / ⁇ 1 ⁇ 100 ⁇ ⁇ ⁇ (1)
• ⁇ 1 is the stress when the isolated inner coating film is stretched by 1%
• ⁇ 2 is the stress after 10 minutes have passed.
• the coated metal plate When a squeezed iron can is formed at high speed under dry conditions using a coated metal plate, the coated metal plate is subject to severe processing and deformation while being accompanied by a temperature rise due to processing heat generation. At that time, since the coating film formed on the coated metal plate is greatly deformed by the can making process, residual stress is generated in the coated film after the processing. In particular, when the main resin such as the polyester resin constituting the coating film is highly crosslinked by the curing agent, the stress generated by the processing is difficult to be relaxed and the residual stress tends to be large.
• the large stress relaxation rate in the coating film of the coated metal plate means that when the coated metal plate is molded at high speed and the coating film is processed while being in a high temperature state due to processing heat generation, the stress generated by the processing is immediately generated. It means that it is easily relaxed, that is, the residual stress of the coating film after processing becomes small.
• the coated metal plate used for molding the squeezed iron can of the present invention is a coated metal plate having at least an inner coating film on the surface that becomes the inner surface side of the can after squeezing and ironing, and the inner coating film is a polyester resin.
• the above-mentioned stress relaxation rate of the inner surface coating film is 50% or more, preferably 50 to 95%, more preferably 54 to 90%, still more preferably 54 to 85%, and particularly preferably. It is preferably in the range of 54 to 80%, most preferably 60 to 80%.
• the outer surface coating film is further provided on the surface on the outer surface side of the can after squeezing and ironing, and the outer surface coating film also contains a polyester resin and a curing agent, and the stress relaxation rate of the outer surface coating film is more than 40%. It is preferably in the range of 45 to 95%, more preferably 50 to 90%, still more preferably 54 to 85%, particularly preferably 54 to 80%, and most preferably 60 to 80%.
• the entire can is covered with the continuous inner coating film from the bottom to the body on the inner surface side of the can. It becomes possible to do. Further, when a double-sided coated metal plate having an outer surface coating film is also used on the surface that becomes the outer surface of the can after squeezing and ironing, the entire surface is covered with the continuous outer surface coating film from the bottom to the body on the outer surface side of the can. Is possible. Since the outer coating film on the coated metal plate of the present invention is also excellent in retort resistance, it is possible to obtain a squeezed iron can having excellent retort resistance on the outer surface of the can.
• the bottom of a squeezed iron can has a bottom portion located in the center, a ground contact portion (rim) descending from the peripheral edge of the bottom portion, and an outwardly and upwardly inclined extension from the ground contact portion to be connected to the lower end of the body portion.
• a ground contact portion rim
• an outwardly and upwardly inclined extension from the ground contact portion to be connected to the lower end of the body portion In many cases, it consists of a chime part, but in a squeezed can that is molded from a conventional unpainted metal plate using coolant, a paint for improving the transportability of the can body immediately after molding the can body.
• the glass transition temperature (Tg) of the inner surface coating film is 30 ° C. or higher, preferably higher than 40 ° C., more preferably higher than 50 ° C. and 120 ° C. or lower, still more preferably 60 ° C. to 110 ° C.
• the temperature is preferably higher than 65 ° C., particularly preferably 100 ° C. or lower, and most preferably in the range of 68 to 90 ° C.
• Tg exceeds 120 ° C.
• the can-making processability of the coating film deteriorates, metal exposure may occur due to molding, the coating film of the inner surface coating film becomes inferior, and the corrosion resistance becomes inferior.
• the Tg of the outer coating film is 30 ° C. or higher, preferably higher than 40 ° C., more preferably higher than 50 ° C. and 120 ° C. or lower, still more preferably 60 ° C. to 110 ° C., particularly preferably higher than 65 ° C. and 100 ° C. or lower. Most preferably, it is in the range of 68 to 90 ° C.
• Tg When Tg is lower than the above range, the hardness of the coating film becomes low, which may cause external surface defects such as scraping of the coating film. On the other hand, when Tg exceeds 120 ° C., the can-making processability of the coating film is deteriorated, metal exposure may occur due to molding, and the coating film coverage of the outer surface is inferior.
• the film thickness of the inner coating film is preferably 0.2 to 20 ⁇ m, preferably 1 to 12 ⁇ m, more preferably more than 2 ⁇ m and 12 ⁇ m or less in terms of dry film thickness.
• the weight of the dry coating film is preferably in the range of 3 to 300 mg / dm 2 , preferably 15 to 150 mg / dm 2 , more preferably more than 25 mg / dm 2 and 150 mg / dm 2 or less. If the thin film is thinner than the above range, metal exposure is likely to occur during molding, and the coating film on the inner surface is inferior.
• the film is thicker than the above range, the internal stress generated during processing becomes large, so that the coating film is likely to be peeled off during the heat treatment after the drawing and ironing, and the film becomes thicker than necessary, which is inferior in economy.
• the content to be filled in the squeezing can is an acidic beverage having strong corrosiveness
• it is necessary to make the film thickness relatively thick in order to secure corrosion resistance and it is larger than 6 ⁇ m and 12 ⁇ m or less, preferably 6.5. It is preferably in the range of ⁇ 10 ⁇ m.
• the weight of the dry coating film is preferably larger than 85 mg / dm 2 and 150 mg / dm 2 or less, preferably in the range of 90 to 140 mg / dm 2. If the thin film is thinner than the above range, the corrosion resistance is inferior, and if it exceeds the above range, the coating film is likely to peel off during the heat treatment after squeezing and ironing.
• the content to be filled in the squeezing can is a low-acid beverage having a relatively weak corrosiveness
• corrosion resistance can be ensured even with a relatively thin film, so that it is 1 ⁇ m or more and less than 6.5 ⁇ m, preferably larger than 2 ⁇ m. It is less than 5 ⁇ m, more preferably in the range of 2.5 to 6 ⁇ m.
• the dry coating weight 15 mg / dm 2 or more 90 mg / dm less than 2, preferably greater 90 mg / dm less than 2 than 25 mg / dm 2, preferably to be more preferably in the range of 30 ⁇ 85 mg / dm 2 be.
• the film thickness of the outer coating film is 0.2 to 20 ⁇ m, preferably 1 to 12 ⁇ m, more preferably larger than 2 ⁇ m and 10 ⁇ m or less, still more preferably larger than 2 ⁇ m and 6.5 ⁇ m or less in terms of dry film thickness. Is preferable.
• the weight of the dry coating film is 3 to 300 mg / dm 2 , preferably 15 to 150 mg / dm 2 , more preferably more than 25 mg / dm 2 and 140 mg / dm 2 or less, still more preferably more than 25 mg / dm 2 and 90 mg /.
• the inner surface coating film which is required to have higher coverage, has a thicker film thickness than the outer surface coating film.
• the inner coating film and the outer coating film of the coated metal plate and the squeezing can of the present invention contain a polyester resin and a curing agent as a main agent.
• the content of the polyester resin, preferably the non-crystalline polyester resin described later is preferably higher than 50% by mass, more preferably 60% by mass or more, further preferably 70% by mass or more, and further preferably 80% by mass. % Or more is particularly preferable.
• the content of the polyester resin, preferably the non-crystalline polyester resin is preferably higher than 50% by mass, more preferably 60% by mass or more, further preferably 70% by mass or more, and 80% by mass. It is particularly preferable that it is by mass or more.
• polyester resin In the squeezed iron can and the coated metal plate of the present invention, a polyester resin is used as the main agent (main component) constituting the inner surface coating film and the outer surface coating film.
• the main agent is among the resin components constituting the coating film. It is assumed that the content (mass ratio) is the highest.
• the weight ratio of the polyester resin is preferably higher than 50% by mass, more preferably 60% by mass or more, and 70% by mass or more among the resin components constituting the inner surface coating film and the outer surface coating film. It is more preferably 80% by mass or more, and particularly preferably 80% by mass or more.
• the polyhydric alcohol component (polypoly component) constituting the polyester resin used the polyhydric alcohol component having a non-bulky molecular structure that does not easily cause steric damage of the polymer chain is used, and the total amount of the polyhydric alcohol components constituting the polyester resin. Is preferably contained in an amount of 20 mol% or more when 100 mol% is taken. Examples of such a multivalent alcohol component include, but are not limited to, ethylene glycol, propylene glycol, 1,4-butanediol, 2-methyl-1,3-propanediol, diethylene glycol and the like. It is preferable to contain at least one selected from these, or two or more thereof in an amount of 20 mol% or more in total.
• the bulky polyol is not limited to this, and examples thereof include alicyclic polyols such as 1,4-cyclohexanedimethanol and neopentyl glycol, and such polyhydric alcohols are sterically hindered. It is presumed that stress relaxation due to the rotation of the molecular chain is relatively unlikely to occur.
• the glass transition temperature (Tg) of the polyester resin is 30 ° C. or higher, preferably higher than 40 ° C., more preferably higher than 50 ° C. and 120 ° C. or lower, further preferably 60 ° C. to 110 ° C., particularly preferably higher than 65 ° C. and 100 ° C.
• the temperature is in the range of 68 to 90 ° C.
• the amount of flavor components collected may increase, resulting in inferior flavor acquisition resistance, as well as heat resistance, corrosion resistance, and retort resistance. ..
• Tg exceeds 120 ° C.
• the processability and extensibility of the coating film are lowered, so that the can-making processability is deteriorated, and metal exposure may occur due to molding.
• coating after molding is applied.
• the coating film may be deteriorated, the stress relaxation rate may be lowered, and the coating film peeling resistance may be deteriorated.
• Tg mix represents the glass transition temperature (K) of the polyester resin blend
• Tg1, Tg2, ..., Tgm is the glass transition of each polyester resin (polyester resin 1, polyester resin 2, ... polyester resin m) used.
• W1, W2, ..., Wm represent the mass fraction of each polyester resin (polyester resin 1, polyester resin 2, ... polyester resin m).
• polyvalent carboxylic acid component constituting the polyester resin examples include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, and sebacine.
• aromatic dicarboxylic acids such as acids, dodecandionic acids and dimer acids, unsaturated dicarboxylic acids such as (anhydrous) maleic acid, fumaric acid and terpene-maleic acid adducts, 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid and hexa.
• Hydroisophthalic acid alicyclic dicarboxylic acids such as 1,2-cyclohexendicarboxylic acid, trivalent or higher polyvalent carboxylic acids such as (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, and methylcyclohexcentricarboxylic acid
• polyvalent carboxylic acids isophthalic acid, orthophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, trimellitic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, dimer acid and 1,4-cyclohexanedicarboxylic acid.
• the fragrance is fragrant.
• dicarboxylic acids such as terephthalic acid, orthophthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, or two or more in total, 60 mol% or more, preferably 70 mol% or more, and more. It is preferably contained in an amount of 80 mol% or more, more preferably 90 mol% or more.
• terephthalic acid and isophthalic acid are particularly preferable, and when the total amount of the polyvalent carboxylic acid components constituting the polyester resin is 100 mol%, the total content of terephthalic acid and isophthalic acid is It is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 90 mol% or more.
• the polyhydric alcohol components constituting the polyester resin include ethylene glycol, propylene glycol, 1,4-butanediol, and 2, when the total amount of the polyhydric alcohol components constituting the polyester resin is 100 mol%.
• -At least one selected from methyl-1,3-propanediol and diethylene glycol, or two or more thereof in total is 20 mol% or more, preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 50. It is preferably contained in an amount of mol% or more, particularly preferably 60 mol% or more, and most preferably 70 mol% or more.
• Ether glycols such as triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, tricyclodecaneglycols.
• Hydrocyclic bisphenols, etc., alicyclic polyalcohols, trimethylolpropane, trimethylolethane, pentaerythritol, etc. can be used alone or in combination of two or more. ..
• one or more of the above polyvalent carboxylic acid components and one or more of the polyhydric alcohol components are polycondensed, and after the polycondensation, the polyvalent carboxylic acid components such as terephthalic acid, isophthalic acid, and anhydrous bird are used.
• a method of depolymerizing with merit acid, trimellitic acid, pyromellitic acid, etc., and after polycondensation, acid anhydrides such as phthalic acid anhydride, maleic anhydride, trimellitic anhydride, ethylene glycol bistrimericte dianhydride, etc. are used. It can be produced by a known method such as ring-opening addition.
• the polyester resin has an acid value of 0.1 to 40 mgKOH / g, preferably an acid value of 0.5 to 25 mgKOH / g, more preferably 0.5 to 25 mgKOH / g, from the viewpoints of curability, retort whitening resistance, adhesion to a metal substrate, and the like. It is preferably in the range of 1 to 10 mgKOH / g, more preferably higher than 2 mgKOH / g and 10 mgKOH / g or less, particularly preferably 2.5 to 8 mgKOH / g, and most preferably 3 to 7 mgKOH / g. If the acid value is lower than the above range, the adhesion between the metal substrate and the coating film may decrease.
• the coating film is more likely to absorb water than in the above range, the retort resistance may be lowered, and the reaction point with the curing agent is increased. As the number increases, the crosslink density of the coating film increases, and the can-making processability and the coating film peeling resistance decrease, resulting in metal exposure, which may reduce the coating film property.
• the polyester resin is a blend of two or more types of polyester resins, the sum of the values obtained by multiplying the acid value and the mass fraction of each polyester resin is the average acid value of the blend. (AV mix ), and the average acid value thereof may be within the above-mentioned acid value range.
• the hydroxyl value of the polyester resin is not limited to this, but is preferably 20 mgKOH / g or less, more preferably 10 mgKOH / g or less.
• the number average molecular weight (Mn) of the polyester resin is not limited to this, but is preferably 1,000 to 100,000, more preferably 3,000 to 50,000, from the viewpoint of can-making processability. More preferably, it is in the range of 5,000 to 20,000. If it is smaller than the above range, the coating film becomes brittle and the can-making processability may be inferior, and if it is larger than the above range, the paint stability may decrease.
• the polyester resin is preferably a non-crystalline polyester resin from the viewpoint of can manufacturing processability, dent resistance, and paint formation.
• amorphous means that the melting point of a clear crystalline component is not shown in the measurement by a differential scanning calorimeter (DSC).
• DSC differential scanning calorimeter
• a coating film having excellent solubility in a solvent, easy to make into a paint, and excellent can-making processability and dent resistance can be formed as compared with a crystalline polyester resin. ..
• the hydroxyl value of the polyester resin is not limited to this, but is preferably 20 mgKOH / g or less, more preferably 10 mgKOH / g or less.
• the curing agent used in the present invention one that reacts with a functional group of a polyester resin, for example, a carboxyl group or a hydroxyl group to form a crosslinked structure is used.
• a functional group of a polyester resin for example, a carboxyl group or a hydroxyl group
• examples of such a curing agent include isocyanate compounds, resole-type phenol resins, amino resins, epoxy group-containing compounds, oxazoline group-containing compounds, carbodiimide group-containing compounds, ⁇ -hydroxyalkylamide compounds and the like.
• resol type phenol resin and amino resin are suitable.
• a resol type phenol resin or an amino resin is suitable for the coating composition (hereinafter, may be referred to as “inner surface coating composition”) for forming the inner coating film.
• a resole-type phenol resin can be preferably used from the viewpoint of can-making processability.
• an amino resin capable of forming a transparent coating film without coloring derived from a curing agent is preferably used. Can be done.
• the above-mentioned resole-type phenol resin has a yellowish coating film, care must be taken when using it in a coating composition for forming an outer surface coating film.
• Resol type phenol resin examples include o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol, phenol, m-cresol, m-ethylphenol, and the like.
• a resol-type phenol resin made by mixing one or more of phenol compounds such as 3,5-xylenol and m-methoxyphenol and reacting these phenol compounds with formaldehyde in the presence of an alkaline catalyst. Can be used.
• Phenolic resins are preferred.
• the phenol compound that becomes trifunctional in the reaction with formalins include phenol, m-cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol, and one or more of these. Can be selected and used. If the content of these trifunctional phenol compounds is 50% by mass or less, sufficient curability may not be obtained, and the degree of curing of the coating film may decrease.
• m-cresol is more preferable from the viewpoint of curability, and a resol-type phenol resin containing m-cresol as a starting material in an amount of more than 50% by mass (hereinafter, "m-cresol-based resol type"). (Sometimes referred to as "phenolic resin”) is particularly preferable. Thereby, a sufficient degree of curing of the coating film can be obtained, which is desirable from the viewpoint of heat resistance, corrosion resistance, retort resistance and the like of the coating film.
• the m-cresol-based resol-type phenol resin preferably contains m-cresol as a starting material in an amount of more than 50% by mass, preferably 60% by mass or more, and more preferably 80% by mass or more.
• m-cresol as a starting material in an amount of more than 50% by mass, preferably 60% by mass or more, and more preferably 80% by mass or more.
• the content is less than 50% by mass, preferably less than 40% by mass, more preferably 20% by mass. It is preferably less than%. If it is 50% by mass or more, the curability may be lowered.
• the bifunctional phenol compound include o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol.
• the methylol groups contained therein are alkyl etherified with alcohols having 1 to 12 carbon atoms (alkoxy). What has been methylated) can be preferably used.
• the proportion of the methylol group to be alkyl etherified is preferably 50% or more, more preferably 60% or more, still more preferably 80% or more. If the ratio of alkyl etherification is less than 50%, the compatibility with the polyester resin becomes low, the coating film becomes turbid, and sufficient curability cannot be obtained.
• the alcohol used for alkyl etherification is a monohydric alcohol having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, and suitable monohydric alcohols are methanol, ethanol, n-propanol and n-. Butanol, isobutanol and the like can be mentioned, and more preferably n-butanol. Further, it is preferable that the number of alkyl etherified methylol groups (alkoxymethyl groups) is 0.3 or more, preferably 0.5 to 3 on average, for each alkoxymethyl group per phenol nucleus. be. If the number is less than 0.3, the curability with the polyester resin will be inferior.
• the number average molecular weight (Mn) of the resol-type phenol resin is preferably in the range of 500 to 3,000, preferably 800 to 2,500. If it is smaller than the above range, the crosslink density of the formed coating film tends to be high, so that it becomes difficult to relax stress during molding, and the coating film peeling resistance may be inferior. On the other hand, if it is larger than the above range, the curability becomes inferior, and as a result, the heat resistance, corrosion resistance, retort resistance and the like of the coating film may be inferior.
• amino resin for example, methylol obtained by reacting an amino component such as melamine, urea, benzoguanamine, acetguanamine, steloganamin, spiroganamin, dicyandiamide, and an aldehyde component such as formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Examples include formaldehyde resin.
• the amino resin also includes a part or all of the methylol group of the methylolated amino resin alkyl etherified with an alcohol having 1 to 6 carbon atoms. These can be used alone or in combination of two or more.
• a methylolated amino resin (benzoguanamine resin) using benzoguanamine and a methylolated amino resin (melamine resin) using melamine are preferable from the viewpoints of hygiene, can manufacturing processability, curability and the like.
• benzoguanamine resin a benzoguanamine resin obtained by alkyl etherifying a part or all of the methylol group of the methylolated benzoguanamine resin with an alcohol such as methanol, ethanol, n-butanol, i-butanol, for example, methyl etherified benzoguanamine resin, ethyl ether.
• a benzoguanamine resin Preferable is a benzoguanamine resin, a butyl etherified benzoguanamine resin, a mixed etherified benzoguanamine resin of methyl ether and butyl ether, a mixed etherified benzoguanamine resin of methyl ether and ethyl ether, and a mixed etherified benzoguanamine resin of ethyl ether and butyl ether.
• the methyl etherified benzoguanamine resin is more preferable, and the methyl etherified benzoguanamine resin of the partially etherified type containing an imino group and a methylol group is particularly preferable.
• a melamine resin obtained by alkyl etherifying a part or all of the methylol group of the methylolated melamine resin with an alcohol such as methanol, ethanol, n-butanol, i-butanol, for example, methyl etherified melamine resin, ethyl ether.
• a modified melamine resin a butyl etherified melamine resin, a mixed etherified melamine resin of methyl ether and butyl ether, a mixed etherified melamine resin of methyl ether and ethyl ether, and a mixed etherified melamine resin of ethyl ether and butyl ether.
• the methyl etherified melamine resin is more preferable, and the fully etherified type methyl etherified melamine resin is particularly preferable.
• Examples of the functional group of the above-mentioned melamine resin and benzoguanamine resin include an imino group (> NH), an N-methylol group (> NCH 2 OH), and an N-alkoxymethyl group (> NCH 2 OR; R is an alkyl group).
• These functional groups act as reaction points in the cross-linking reaction with the carboxyl group (-COOH) and the hydroxyl group (-OH) contained in the polyester resin as the main agent, or in the self-condensation reaction between the amino resins (note that).
• the imino group contributes only to the self-condensation reaction).
• the number of the melamine resin is larger in terms of the molecular structure.
• the crosslink density of the formed coating film tends to be high, the stress relaxation rate is low depending on the blending amount, and the coating film peeling may occur during heat treatment.
• the benzoguanamine resin is inferior in curability to the melamine resin, the crosslink density of the formed coating film is unlikely to be high, and it can be said that the benzoguanamine resin is more suitable than the melamine resin from the viewpoint of coating film peeling resistance.
• a mixed amino resin in which a melamine resin and a benzoguanamine resin are used in combination and mixed at a predetermined ratio may be used.
• the blending amount ratio (mass ratio) of the melamine resin and the benzoguanamine resin is 95: 5 to 5:95, preferably 90:10 to 10:90, more preferably 80:20 to 15:85, and further preferably 70. It is desirable to set it from: 30 to 25:75.
• the curing agent is blended in the range of 1 to 40 parts by mass, preferably 1 to 30 parts by mass, and more preferably 2 to 20 parts by mass with respect to 100 parts by mass of the polyester resin.
• a resole-type phenol resin is used as the curing agent, it is 2 to 40 parts by mass, preferably 3 to 30 parts by mass, and more preferably 3 to 25 parts by mass with respect to 100 parts by mass of the polyester resin (solid content) as the main agent. It is more preferable to blend in the range of 3 to 20 parts by mass, and particularly preferably 4 to 15 parts by mass.
• a melamine resin When a melamine resin is used as the curing agent, it is 1 to 15 parts by mass, preferably 1 part by mass or more and less than 10 parts by mass, more preferably 2 to 5.5 parts by mass, particularly with respect to 100 parts by mass of the polyester resin. It is preferable to mix in an amount of 2 to 5 parts by mass.
• a benzoguanamine resin When a benzoguanamine resin is used as the curing agent, it is 4 to 40 parts by mass, preferably 5 to 30 parts by mass, more preferably 6 to 28 parts by mass, and further preferably 8 to 25 parts by mass with respect to 100 parts by mass of the polyester resin. Particularly preferably, it is blended in an amount of 10 to 24 parts by mass.
• the curing agent 2 to 25 parts by mass, preferably 2 to 20 parts by mass, 2.5 to 15 parts by mass with respect to 100 parts by mass of the polyester resin. It is preferable to mix in an amount of 3 parts by mass or more and less than 10 parts by mass.
• the amount of the curing agent is smaller than the above range, sufficient curability cannot be obtained, the degree of curing of the coating film is low, and the heat resistance tends to be low. Therefore, when the squeezed iron can is molded at high speed, the temperature rise becomes more remarkable, and the coating film may easily stick to the mold during molding.
• the can body On the inner surface side of the can, when the can body is pulled out from the molding punch after squeezing and ironing, the can body sticks to the molding punch, causing a phenomenon (poor stripping property) in which the molding punch and the can body are difficult to separate. As a result, the can body may buckle or collapse, resulting in a decrease in productivity.
• the outer surface side of the can there is a possibility that external surface defects such as scraping of the coating film may occur.
• the amount of the curing agent is larger than the above range, the processability of the coating film may be deteriorated, metal exposure may occur during the squeezing and ironing process, and the coating film may be exposed, depending on the type of the curing agent used.
• the crosslink density of the film becomes high, it becomes difficult to relax stress during molding, and it may be difficult to adjust the stress relaxation rate of the above-mentioned inner surface coating film to 50% or more, and as a result, the coating film is coated. There is a risk of deterioration.
• a curing catalyst to the inner surface coating composition and the outer surface coating composition used in the present invention for the purpose of promoting the cross-linking reaction between the polyester resin and the curing agent.
• a conventionally known curing catalyst can be used, for example, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, phosphoric acid, alkylphosphate, or an amine neutralized product thereof.
• Organic sulfonic acid-based and phosphoric acid-based acid catalysts can be used.
• the curing catalyst has a solid content of 0.01 to 3 parts by mass, preferably 0.02 to 1.0 parts by mass, and more preferably 0.02 parts by mass or more and 0.5 parts by mass with respect to 100 parts by mass of the polyester resin. It is desirable that it is less than 10 parts by mass, more preferably 0.03 parts by mass or more and less than 0.3 parts by mass, and particularly preferably 0.04 parts by mass or more and less than 0.2 parts by mass.
• an amine neutralized product of the acid catalyst for example, an amine neutralized product of dodecylbenzene sulfonic acid
• the content of the acid catalyst excluding the amine may be within the above range.
• the effect of promoting the curing reaction may not be sufficiently obtained, while if the content of the curing catalyst is higher than the above range, the effect is more than that.
• the water resistance of the coating film is lowered, and as a result, the corrosion resistance, the retort resistance, and the like may be deteriorated.
• the acid catalyst is localized on the surface of the metal substrate due to the acid-base interaction, which may reduce the adhesion between the coating film and the metal substrate, which causes problems such as peeling of the coating film during can molding. There is a risk.
• the coating composition for forming the coating film of the coated metal plate of the present invention contains at least the above-mentioned polyester resin and the above-mentioned curing agent, and more preferably the above-mentioned curing catalyst (acid catalyst) as the main agent.
• the component having the highest content (mass ratio) is used among the solid components (nonvolatile components excluding volatile substances such as water and solvent) forming the coating film in the coating composition. This is defined as the main agent (main component).
• the content of the above-mentioned polyester resin, preferably the non-crystalline polyester resin, which is the main component is higher than 50% by mass among all the resin components contained in the coating composition.
• examples of the form of the coating composition that can be used for forming the coating film include a solvent-based coating composition and a water-based coating composition.
• a solvent-based coating composition is preferable from the viewpoint of coatability and the like.
• the coating composition is a solvent-based coating composition
• it contains the above-mentioned polyester resin, a curing agent, and an organic solvent as a solvent.
• the solvent-type paint composition in the present embodiment is a paint made by dissolving a main agent resin, a curing agent, etc. in a known organic solvent, and the mass ratio of the organic solvent in the paint composition. Is defined as a coating composition having a content of 40% by mass or more.
• organic solvent examples include toluene, xylene, aromatic hydrocarbon compounds, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, methyl cellosolve, butyl cellosolve, ethylene glycol monoethyl ether acetate, and diethylene glycol monoethyl ether acetate.
• the coating composition is an aqueous coating composition
• it contains an aqueous medium as a solvent together with a conventionally known water-dispersible or water-soluble polyester resin and a curing agent.
• aqueous medium water or a mixture of water and an organic solvent such as an alcohol, a polyhydric alcohol, or a derivative thereof can be used as the aqueous medium, as in the known aqueous coating composition.
• an organic solvent is used, it is preferably contained in an amount of 1 to 45% by mass, particularly preferably 5 to 30% by mass, based on the entire aqueous medium in the water-based coating composition. By containing the solvent in the above range, the film forming performance is improved.
• an organic solvent one having homophilicity is preferable, and for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, ethylene glycol, methyl ethyl ketone, butyl cellosolve, carbitol, butyl carbitol, propylene glycol monopropyl.
• examples thereof include ether, propylene glycol ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and 3-methyl 3-methoxybutanol.
• the coating composition may contain a lubricant, if necessary. It is preferable to add 0.1 part by mass to 10 parts by mass of the lubricant with respect to 100 parts by mass of the polyester resin. By adding the lubricant, it is possible to suppress the damage of the coating film during the molding process and improve the slipperiness of the coating film during the molding process.
• lubricant examples include fatty acid ester wax, which is an esterified product of a polyol compound and a fatty acid, silicon-based wax, fluorine-based wax such as polytetrafluoroethylene, polyolefin wax such as polyethylene, and paraffin.
• fatty acid ester wax which is an esterified product of a polyol compound and a fatty acid
• silicon-based wax fluorine-based wax such as polytetrafluoroethylene
• polyolefin wax such as polyethylene
• paraffin examples thereof include wax, lanolin, montan wax, microcrystallin wax, carnauba wax, and silicon-based compounds, vaseline and the like.
• a leveling agent, a pigment, an antifoaming agent, a colorant and the like which have been conventionally blended in the coating composition, can be added to the coating composition according to a conventionally known formulation.
• other resin components may be contained in addition to the polyester resin as long as the object of the present invention is not impaired.
• polyvinyl acetate, ethylene / vinyl acetate copolymer, polyolefin resin, epoxy resin, polyurethane for example, polyvinyl acetate, ethylene / vinyl acetate copolymer, polyolefin resin, epoxy resin, polyurethane.
• Resin acrylic resin, polyvinyl chloride resin, polyvinyl chloride-vinyl acetate copolymer resin, polyvinyl alcohol, ethylene / vinyl alcohol copolymer, polyvinylpyrrolidone, polyvinylethyl ether, polyacrylamide, acrylamide compound, polyethyleneimine, starch , Arabic gum, methyl cellulose and the like may be contained.
• the polyester resin is contained in an amount of 5 to 55% by mass as a solid content. If the resin solid content is less than the above range, an appropriate amount of the coating film cannot be secured, and the coating film property of the coating film becomes inferior. On the other hand, if the resin solid content is higher than the above range, the workability and coatability may be inferior.
• an inner surface coating composition containing a polyester resin and a curing agent, preferably a resole-type phenol resin, as a main agent is applied to at least the inner surface of the metal plate. More preferably, an outer surface coating composition containing the above-mentioned main agent polyester resin and a curing agent, preferably an amino resin, is further applied to the outer surface of the metal plate.
• the baking conditions of the coating composition are appropriately adjusted depending on the polyester resin, the curing agent, the type of the metal substrate, the coating amount, etc., but the above-mentioned coating composition has a baking temperature of 150 in order to obtain a sufficient curing degree.
• the MEK extraction rate (MEK boiling point, 1 hour), which is an index of the degree of curing, is 50% or less, preferably 1 to 40%, more preferably 2 to 30%. Further preferably, it is preferably in the range of 3 to 25%, particularly preferably 3 to 20%, and when the MEK extraction rate is in the above range, the degree of curing of the coating film is controlled, and the heat resistance of the coating film is high. It is preferable from the viewpoints of property, corrosion resistance, retort resistance, and coating film peeling resistance (stress relaxation rate). When the MEK extraction rate is higher than the above range, the degree of curing of the coating film is low and the heat resistance tends to be low.
• the coating film may easily stick to the mold during molding.
• the can body On the inner surface side of the can, when the can body is pulled out from the molding punch after squeezing and ironing, the can body sticks to the molding punch, causing a phenomenon (poor stripping property) in which the molding punch and the can body are difficult to separate. As a result, the can body may buckle or collapse, resulting in a decrease in productivity.
• the outer surface side of the can there is a possibility that external surface defects such as scraping of the coating film may occur, and the retort whitening resistance may be inferior.
• the MEK extraction rate is lower than 1%, it becomes difficult to set the above-mentioned stress relaxation rate within the above-mentioned range, and there is a possibility that coating film peeling may occur.
• a known coating method such as roll coater coating, spray coating, dip coating, etc. is used to coat at least the inner surface side of the metal plate on at least both sides, and then by heating means such as a coil oven. It can be manufactured by baking.
• the metal plate used as the metal substrate of the coated metal plate is not limited to this, and for example, a hot-stretched steel sheet, a cold-rolled steel sheet, a hot-dip zinc-plated steel sheet, an electric zinc-plated steel sheet, an alloy-plated steel sheet, an aluminum-zinc alloy-plated steel sheet, and aluminum.
• a hot-stretched steel sheet a cold-rolled steel sheet, a hot-dip zinc-plated steel sheet, an electric zinc-plated steel sheet, an alloy-plated steel sheet, an aluminum-zinc alloy-plated steel sheet, and aluminum.
• Examples include plates, tin-plated steel sheets, stainless steel sheets, copper plates, copper-plated steel sheets, tin-free steels, nickel-plated steel sheets, ultra-thin tin-plated steel sheets, chrome-treated steel sheets, etc., and various surface treatments such as phosphoric acid chromate treatment, if necessary.
• zirconium-based chemical chemical treatment coating type treatment in which a water-soluble resin such as polyacrylic acid and a zirconium salt such as zirconium carbonate ammon are combined can be used.
• an aluminum plate is preferable among the above metal plates, and the aluminum plate is not only a pure aluminum plate but also an aluminum alloy plate, specifically, 3000 series, 5000 series, and 6000 series aluminum in "JIS H 4000".
• An alloy plate can be preferably used, and an aluminum alloy plate is suitable from the viewpoint of strength and the like.
• the coating film made of the above-mentioned coating composition has excellent adhesion to the metal substrate, so that no surface treatment is applied.
• the aluminum alloy plate of the above can also be preferably used.
• the thickness of the metal plate is 0.1 to 1.00 mm, preferably 0.15 to 0.40 mm, more preferably 0.15 to 0.30 mm, still more preferably 0.20, from the viewpoint of can body strength and moldability. It should be within the range of ⁇ 0.28 mm.
• the coated metal plate of the present invention on the inner surface coating film formed on the inner surface side of the can after squeezing and / or on the outer surface coating film formed on the outer surface side of the can after squeezing and ironing. If necessary, a coating film composed of another coating composition may be formed. Further, in the coated metal plate of the present invention, since the inner surface coating film and the outer surface coating film made of the above-mentioned coating composition have excellent adhesion to the metal substrate, the inner surface coating film and / or the outer surface coating film is a metal substrate. It is preferable that the metal plate is formed so as to be in direct contact with the metal plate.
• the squeezed iron can of the present invention is a squeezed iron can formed by squeezing and molding from the above-mentioned coated metal plate and having an inner coating film on the inner surface side of the can, and the inner coating film contains a polyester resin and a curing agent.
• the stress relaxation rate after 10 minutes of 1% elongation under the test conditions of 100 ° C. on the inner surface coating film at the bottom of the can is 50% or more.
• the stress relaxation rate of the inner coating film is 50% or more, preferably 50 to 95%, more preferably 54 to 90%, still more preferably 54 to 85%, particularly preferably 54 to 80%, and most preferably 60 to 60 to. It is preferably in the range of 80%.
• the squeezed iron can further has an outer surface coating film on the outer surface side of the can, the outer surface coating film contains a polyester resin and a curing agent, and 1% of the outer surface coating film at the bottom of the can under the test conditions of 100 ° C. It is preferable that the stress relaxation rate after 10 minutes of elongation is higher than 40%.
• the stress relaxation rate of the outer coating film is more than 40%, preferably 45 to 95%, more preferably 50 to 90%, still more preferably 54 to 85%, particularly preferably 54 to 80%, and most preferably 60 to 60. It is preferably in the range of 80%.
• the bottom portion and the can body portion of the squeezed iron can are continuously covered with the inner surface coating film, and further, the can bottom portion and the can body portion on the outer surface side of the can are formed. It is preferable that the outer surface coating film is continuously coated. The stress relaxation rate is reduced and measured with the coating film on the bottom of the iron can because the degree of processing of the bottom of the can is extremely small compared to the body of the can, so the coating film on the coated metal plate before molding is used. This is because it can be approximated to and has similar characteristics.
• the squeezed iron can of the present invention can be manufactured by a conventionally known molding method using the above-mentioned coated metal plate. Since the coating film of the coated metal plate of the present invention has excellent extensibility, processability, and adhesion, the coating film is peeled off at the broken cylinder or the end of the can mouth even during harsh squeezing and ironing. It is possible to form a squeezed iron can without causing a problem. Since the coated metal plate of the present invention is excellent in moldability and lubricity, a squeezed iron can can be formed not only when a coolant is used but also when molding is performed under dry conditions without using a coolant. can do.
• the drawing ratio RD defined by the following formula (3) is in the range of 1.1 to 2.6 in total (up to the squeezing iron can), particularly in the range of 1.4 to 2.6. Is desirable. If the aperture ratio is larger than the above range, the aperture wrinkles become large, and cracks may occur in the coating film to cause metal exposure.
• RD D / d ... (3)
• D represents a blank diameter and d represents a can body diameter.
• the squeezed cup is re-squeezed-one step or several steps of squeezing (squeezing and squeezing) to thin the can body.
• the ironing ratio R represented by the following formula (4) is 25 to 80%, preferably 40 to 80%, more preferably 50 to 80%, still more preferably 55 to 75%, and particularly preferably. It is preferably in the range of 55 to 70%, most preferably higher than 60% and 70% or less. If the squeezing rate is lower than the above range, the wall cannot be thinned sufficiently and the economy is not sufficiently satisfied. On the other hand, if the squeezing rate is higher than the above range, there is a risk of metal exposure.
• R (%) (tp-tw) / tp ⁇ 100 ... (4)
• tp represents the thickness of the original coated metal plate
• tw represents the thickness of the central portion of the side wall of the can body of the squeezed iron can.
• the thickness of the central portion of the can body (the central portion in the height direction, the thinnest portion) is 20 to 75%, preferably 20 to 75% of the thickness of the central portion of the can bottom.
• the thickness is preferably 60%, more preferably 20 to 50%, still more preferably 25 to 45%, particularly preferably 30 to 45%, and most preferably 30% or more and less than 40%.
• the thickness of the metal substrate of the squeezed can is such that the thickness of the metal substrate in the center of the can body is 20 to 75%, preferably 20 to 60%, more preferably 20 to 20% of the thickness of the metal substrate in the center of the bottom of the can.
• the thickness is preferably 50%, more preferably 25 to 45%, particularly preferably 30 to 45%, and most preferably 30% or more and less than 40%.
• the thickness of the coating film located on the can body is reduced by the processing in the same manner as the metal base material. Therefore, the thickness of the coating film at the center of the can body is 20 to 75%, preferably 20 to 60%, more preferably 20 to 50% of the thickness of the coating film at the center of the bottom of the can, which is hardly thinned during can manufacturing. It is more preferably 25 to 45%, particularly preferably 30 to 45%, and most preferably 30% or more and less than 40%.
• the thickness of the metal substrate at the center of the can bottom is 0.10 to 0.50 mm, preferably 0.15 to 0.40 mm, more preferably 0.15 to 0.30 mm, still more preferably 0.20 to 0. A thickness of 28 mm is suitable.
• the film thickness of the inner coating film at the center of the bottom of the can is preferably 0.2 to 20 ⁇ m, preferably 1 to 12 ⁇ m, more preferably larger than 2 ⁇ m and 12 ⁇ m or less in terms of dry film thickness.
• the weight of the dry coating film is preferably in the range of 3 to 300 mg / dm 2 , preferably 15 to 150 mg / dm 2 , more preferably more than 25 mg / dm 2 and 150 mg / dm 2 or less.
• the content to be filled in the squeezing can is a highly corrosive acidic beverage
• it is preferably larger than 6 ⁇ m and 12 ⁇ m or less, preferably in the range of 6.5 to 10 ⁇ m.
• the weight of the dry coating film is preferably larger than 85 mg / dm 2 and 150 mg / dm 2 or less, preferably in the range of 90 to 140 mg / dm 2.
• the content to be filled in the squeezing can is a low-acid beverage having a relatively weak corrosiveness, it is 1 ⁇ m or more and less than 6.5 ⁇ m, preferably larger than 2 ⁇ m and less than 6.5 ⁇ m, more preferably 2.5 to 6 ⁇ m.
• the dry coating weight 15 mg / dm 2 or more 90 mg / dm less than 2, preferably greater 90 mg / dm less than 2 than 25 mg / dm 2, preferably to be more preferably in the range of 30 ⁇ 85 mg / dm 2 be.
• the film thickness of the outer coating film at the center of the bottom of the can is 0.2 to 20 ⁇ m, preferably 1 to 10 ⁇ m, more preferably larger than 2 ⁇ m and 10 ⁇ m or less, still more preferably larger than 2 ⁇ m and 6.5 ⁇ m or less in terms of dry film thickness. It is preferable that it is in the range of.
• As the dry coating weight 3 ⁇ 300mg / dm 2, preferably 15 ⁇ 150mg / dm 2, more preferably 25 ⁇ 140mg / dm 2, more preferably greater 90 mg / dm 2 of less than the range from 25 mg / dm 2 Is preferable.
• the manufacturing error is included in the range, for example, (the thickness of the inner surface coating film / the thickness of the metal substrate) of the can body is the bottom of the can. It means that it is within the range of 0.9 to 1.1 times (thickness of the inner surface coating film / thickness of the metal substrate). The same applies to the outer coating film.
• the processing speed (punch movement speed) of the one-step or several-step ironing process is 1500 mm / sec or more, preferably 3000 mm / sec or more, more preferably 4000 mm / sec or more, still more preferably 5000 mm / sec or more, particularly. It is preferably 6000 mm / sec or more.
• the molding is performed at a high temperature, the stress can be easily relaxed during the molding process, so that the residual stress of the coating film after molding can be reduced, which is also preferable in suppressing the peeling of the coating film during the heat treatment.
• squeezing and ironing if desired, doming forming of the bottom and trimming of the open edge are performed according to a conventional method.
• the coated metal plate is squeezed and ironed, and then the obtained squeezed iron can is subjected to a heat treatment step.
• the stress relaxation rate of the coating film is as high as 50% or more on the inner surface of the can and more than 40% on the outer surface of the can, so that even when heated in the heat treatment step. , The peeling of the coating film is effectively prevented.
• the temperature of the heat treatment needs to be higher than the glass transition temperature of the coating film, and is preferably in the temperature range of 100 to 300 ° C, preferably 150 to 250 ° C.
• the time of the heat treatment is not particularly limited, but it is preferable to heat for 0.1 to 600 seconds, preferably 1 to 300 seconds, and more preferably 20 to 180 seconds.
• the residual stress of the coating film of the squeezed can is not removed by heat treatment, the residual stress is released by isolating the coating film in the central part of the can body (central part in the height direction) with a high degree of processing from the metal substrate and heating it. Since the dimensions change significantly in the direction (mainly in the height direction of the can), whether the residual stress is removed by heat treatment by measuring the amount of dimensional change (heat shrinkage rate) of the isolated coating film due to heating. It can be used as a guide.
• the heat shrinkage rate (with load) represented by the following formula (5) in the inner surface coating film at the center of the can body isolated from the squeezed can is 30% or less, preferably 20% or less, more preferably 15% or less. , More preferably 10% or less.
• the heat shrinkage rate (without load) represented by the following formula (6) is 50% or less, preferably 45% or less, more preferably 40% or less, still more preferably 35% or less.
• the heat shrinkage rate is within the above range, the adhesion to the coating film is improved and excellent corrosion resistance can be exhibited. If the heat shrinkage rate is larger than the above range, the residual stress is not sufficiently removed, and the corrosion resistance may decrease due to the lack of adhesion of the coating film. The film may peel off.
• the outer surface coating film is provided on the outer surface side of the can, it is desirable that the heat shrinkage rate is within the above range even in the outer surface coating film at the center of the can body.
• the amount of dimensional change (shrinkage) due to heating of the isolated coating film can be measured by a thermomechanical folding device (TMA) or the like.
• Heat shrinkage rate (with load) ( ⁇ L 1 / L 0 ) ⁇ 100 (%) ⁇ ⁇ ⁇ (5)
• L 0 is the height direction of the initial length of the coating film isolated from the can barrel central portion (measurement section)
• [Delta] L 1 is a load per unit area 5.20 ⁇ 10 5 N / m 2
• It is the maximum shrinkage amount (maximum value of shrinkage length) in the height direction of the coating film corresponding to L 0 when the temperature is raised from 30 ° C. to 200 ° C. at a temperature rise rate of 5 ° C./min.
• Heat shrinkage rate (no load) ( ⁇ L 2 / L 0 ) ⁇ 100 (%) ⁇ ⁇ ⁇ (6)
• L 0 is the initial length in the height direction of the coating film isolated from the central part of the can body
• ⁇ L 2 is when the temperature is raised from 30 ° C. to 200 ° C. at a heating rate of 5 ° C./min under no load
• L 0 is the maximum shrinkage amount (maximum value of shrinkage length) of the coating film in the corresponding portion in the height direction.
• a printing layer is formed on the can body by a printing / baking step as necessary, and a finishing varnish for protecting the printing layer is formed on the printing layer. Layers are formed. If desired, it is subjected to one-stage or multi-stage neck-in processing and flange processing to obtain a can for winding. Further, after forming a squeezed iron can, the upper part thereof can be deformed to form a bottle shape, or the bottom portion can be cut off and another can end can be attached to form a bottle shape.
• the capacity of the squeezed iron can of the present invention is preferably 150 mL or more, preferably 150 to 2200 mL, more preferably 180 to 1200 mL, still more preferably 300 to 700 mL.
• the coated metal plate of the present invention has excellent can-making processability, it can withstand harsh processing such as the production of squeezed cans, and the coating film does not peel off even in the heat treatment after molding.
• the molding conditions such as the ironing processing speed, it is possible to obtain a squeezed iron can having an inner coating film having a coverage of less than 200 mA in terms of ERV (Enamel Later Value) and having excellent coating film coverage. be able to.
• the coverage of the inner coating film obtained by ERV conversion was measured by filling the obtained squeezed iron can with a saline solution having a concentration of 1% by mass as an electrolytic solution up to the vicinity of the can mouth and measuring the ERV with an enamel heater. 6.
• a metal exposed portion is formed on the outer surface side of the bottom of the can and connected to the anode, while the cathode is immersed in a saline solution filled in the can and at room temperature (about 23 ° C.).
• the current value after applying a DC voltage of 3 V for 4 seconds. In such a measurement, it is shown that the larger the current flows, the more defects exist in the inner coating film which is an insulator, and the larger the area of metal exposure on the inner surface of the can.
• the coverage of the inner coating film in terms of ERV is preferably less than 200 mA, preferably less than 100 mA, and more preferably less than 50 mA.
• the ERV per unit area is a value obtained by dividing the ERV of the squeezed can measured by the above method by the evaluation area (the area where the inner surface of the can body and the bottom of the can and the above-mentioned saline solution are in contact with each other). Is. After molding, the inner surface of the squeezed iron can may be further spray-coated with a correction paint or the like to form another coating film on the inner coating film, but as described above, the inner surface coating may be applied.
• the film Since the film has a high coverage even after molding, it does not need to be spray-painted, and it is preferable that the film is not spray-painted from the viewpoint of economy.
• the outer surface coating film may be located on the surface layer of the bottom portion where the print layer is not formed, but for the purpose of improving the transportability of the can body, the outer surface side of the bottom portion.
• a coating film made of another coating composition may be formed on the outer surface coating film formed on the surface layer of the above.
• the coated metal plate of the present invention can be used for applications other than squeezing iron cans, for example, squeezing cans (DR cans), deep squeezing cans (DRD cans), DTR cans, tensile squeezing ironing cans, can lids, etc. by a conventionally known manufacturing method. Can also be suitably applied.
• a conventionally known shape such as an easy open lid provided with a score for forming an opening for pouring contents and a tab for opening can be adopted, and a fully open type or a partially open type can be adopted. It may be either (stay-on-tab type).
• the various measurement items of the polyester resins A to D followed the following methods.
• the polyester resins A to D are all non-crystalline polyester resins.
• (Measurement of number average molecular weight) It was measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve.
• (Measurement of glass transition temperature) It was measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC).
• DSC differential scanning calorimeter
• 1 g of a solid polyester resin was dissolved in 10 ml of chloroform and titrated with a 0.1 N KOH ethanol solution to determine the resin acid value (mgKOH / g). Phenolphthalein was used as an indicator.
• "dodecylbenzenesulfonic acid (soft type) (mixture)" manufactured by Tokyo Kasei Kogyo Co., Ltd. was used.
• n-butanol solution (solid content 50% by mass) of the resol-type phenol resin was diluted with methyl ethyl ketone to obtain a resol-type phenol resin solution having a solid content of 30% by mass.
• Dodecylbenzene sulfonic acid was neutralized with 2-dimethylaminoethanol and then dissolved in isopropanol to obtain a dodecylbenzene sulfonic acid solution having a solid content of 30% by mass.
• the polyester resin contains polyester resin A, the curing agent contains melamine resin (methyl etherified melamine resin, full ether type, weight average degree of polymerization 1.3), and benzoguanamine resin (methyl etherified benzoguanamine resin, imino group / methylol group). Partially etherified type, weight average degree of polymerization 1.5), dodecylbenzenesulfonic acid was used as a curing catalyst (acid catalyst).
• the melamine resin and the benzoguanamine resin were dissolved in methyl ethyl ketone to obtain a melamine resin solution and a benzoguanamine resin solution having a solid content of 30% by mass.
• Dodecylbenzene sulfonic acid was neutralized with 2-dimethylaminoethanol and then dissolved in isopropanol to obtain a dodecylbenzene sulfonic acid solution having a solid content of 30% by mass.
• 333 parts of the polyester resin A solution 100 parts of the solid content
• 10 parts of the melamine resin B solution (3 parts of the solid content
• 10 parts of the benzoguanamine resin solution (3 parts of the solid content)
• 0.33 parts of the acid catalyst solution solid content
• a phosphoric acid chromate-based surface-treated aluminum plate (3104 alloy, plate thickness: 0.27 mm, chromium weight in the surface-treated film: 20 mg / m 2 ) is used as a metal plate, and first, it is baked on the outer surface side after molding.
• the coating composition for the outer surface was coated with a bar coater and dried at 120 ° C. for 60 seconds so that the weight of the subsequent dry coating film would be 40 mg / dm 2 (about 3 ⁇ m).
• the paint composition for the inner surface is coated on the inner surface on the opposite side with a bar coater so that the weight of the dried coating film after baking is 88 mg / dm 2 (about 6.4 ⁇ m), and 60 at 120 ° C. After drying for seconds, it was prepared by baking at 250 ° C. (the temperature inside the oven) for 30 seconds.
• Paraffin wax was applied to both sides of the painted metal plate prepared by the above method, and then punched into a circle having a diameter of 142 mm to prepare a shallow drawing cup. Next, the shallow drawing cup was subjected to redrawing, ironing (3 steps), and doming under dry conditions using a punch having an outer diameter of ⁇ 66 mm. After that, heat treatment was performed at 201 ° C.
• Example 2 As shown in Table 1, a coating composition for an inner surface was prepared by changing the type of polyester resin and the solid content mixing ratio, and a coated metal plate was prepared in the same manner as in Example 1 except that it was used, and a squeezing can. Was produced.
• Component / propylene glycol component 49/1/12/38 mol%) mixed so as to have a mass ratio of 90:10 (Tg mix : 76 ° C., AV mix : 4 mgKOH / g), and the inner surface coating composition. The thing was prepared.
• a benzoguanamine resin (methyl etherified benzoguanamine resin, partially etherified type containing imino group / methylol group, weight average degree of polymerization of 1.5) is used as a curing agent, and the solid content mixing ratio is changed for the outer surface.
• a coating composition was prepared, a coated metal plate was prepared in the same manner as in Example 1 except that they were used, and a squeezed iron can was prepared.
• Example 5 As shown in Table 1, a mixture of polyester resin A and polyester resin D so as to have a mass ratio of 90:10 was used as the polyester resin, and the above-mentioned benzoguanamine resin (methyl etherified benzoguanamine resin, imino group) was used as the curing agent.
• -A coated metal plate was prepared in the same manner as in Example 1 except that a coating composition for an inner surface was prepared by using a partially etherified type containing a methylol group and a weight average degree of polymerization of 1.5) and changing the solid content mixing ratio. , A squeezed iron can was made.
• Example 6 A coated metal plate was produced in the same manner as in Example 1 except that the average processing speed during ironing (average moving speed of punches during ironing) was 1000 mm / sec when the squeezed iron can was produced. Was produced.
• the coating film characteristics obtained from the inner surface coating composition and the outer surface coating composition used in each Example, Comparative Example, and Reference Example were tested according to the following test method.
• a coating film sample for measurement was prepared as follows.
• Aluminum foil (“Nippakuhoiru” manufactured by Mitsubishi Aluminum Co., Ltd.) so that the coating conditions (paint type, dry coating weight, drying / baking conditions) of the inner coating on the coated metal plate of each example, comparative example, and reference example are the same.
• the non-glossy surface side having a thickness of 12 ⁇ m) was coated with a bar coater, dried at 120 ° C. for 60 seconds, and then baked at 250 ° C. for 30 seconds to form a coating film on aluminum foil.
• the aluminum foil on which the coating film was formed was cut into pieces having a width of 50 mm and a length of 40 mm, and immersed in a diluted hydrochloric acid aqueous solution to dissolve the aluminum foil.
• the film-like coating film was taken out, thoroughly washed with distilled water and dried, and the obtained film-like coating film was cut out to a width of 4 mm and a length of 40 mm to obtain a measurement sample.
• the stress relaxation rate of the obtained measurement sample was measured by a thermomechanical analyzer (TMA).
• TMA thermomechanical analyzer
• the sample was chucked so that the thermomechanical analyzer had no deflection, and then the stress relaxation rate of the obtained measurement sample was measured by the thermomechanical analyzer (TMA).
• TMA thermomechanical analyzer
• the sample was chucked so that there was no deflection in the thermomechanical analyzer so that the distance between the chucks (corresponding to the initial sample length) was 10 mm.
• the temperature of the measurement atmosphere was raised, and after 10 minutes had passed since the temperature reached 100 ° C., the sample was stretched by 1% of the initial length of the sample at a tensile speed of 1 mm / min and held in that state for 10 minutes.
• the stress relaxation rate was calculated by the following formula (1) from the stress ( ⁇ 1) at the time of 1% elongation and the stress ( ⁇ 2) after holding for 10 minutes.
• ⁇ 1 is the stress at 1% elongation
• ⁇ 2 is the stress after holding for 10 minutes.
• the numerical values of ⁇ 1 and ⁇ 2 are correction values obtained by subtracting the numerical values of the stress immediately before 1% elongation after the temperature rise of 100 ° C. from the actual measured values.
• a sample for measurement can be obtained by peeling off the coating film in the form of a metal substrate, drying it, and cutting the obtained film into a width of 4 mm and a length of 40 mm.
• Stress relaxation rate of the inner surface coating film on the bottom of the can Stress relaxation of the inner surface coating film on the inner surface of the can bottom of the squeezed iron cans of Example 4 and Comparative Example 1 after being molded as described in the above section "Preparation of squeezed iron can" and heat-treated at 201 ° C. for 75 seconds. The rate was measured.
• the method for preparing the measurement sample is as follows. From the bottom of the squeezed iron can after the heat treatment, the bottom of the can was cut out so as to have a size of 35 mm in the 0 ° direction and 30 mm in the 90 ° direction with respect to the rolled grain of the metal base material centering on the center of the can bottom.
• the cut-out sample is immersed in boiling hydrogen peroxide solution for 2 to 3 minutes, thoroughly washed with distilled water, and then the film-like coating film on the inner surface side of the can is peeled off from the metal substrate and dried to obtain the film-like coating.
• a sample for measurement was obtained by cutting the film into a width of 4 mm and a length of 35 mm.
• the stress relaxation rate was measured in the same manner as the measurement method described in the above section "Stress relaxation rate of coating film". The results are shown below. Stress relaxation rate of the inner surface coating film on the bottom of the squeezed iron can of Example 4: 67% Stress relaxation rate of the inner surface coating film on the bottom of the squeezed iron can of Comparative Example 1: 45%
• the glass transition temperature of the coating film was measured under the following conditions using a differential scanning calorimeter (DSC). At 2nd-run (heating), the gradient between the outer glass transition start temperature, that is, the straight line extending the baseline on the low temperature side to the high temperature side and the curve of the stepwise change portion of the glass transition is maximized.
• DSC differential scanning calorimeter
• the temperature at the intersection with the tangent line drawn by the point was defined as the glass transition temperature of the coating film (coating film Tg).
• Equipment DSC6220 manufactured by Seiko Instruments Co., Ltd. Sample amount: 5 mg
• Temperature rise rate 10 ° C / min
• Temperature range -80 to 200 ° C (heating, cooling, temperature rising)
• a measurement sample from a painted metal plate or a squeezing can with a coating film formed on both sides, remove the coating film on one side that is not to be measured by scraping it with a sand paver to expose the metal surface.
• the metal substrate metal plate
• the metal substrate is dissolved by a conventional method such as cutting out a coated metal plate and immersing it in a diluted hydrochloric acid aqueous solution, taking out a film-like coating film, thoroughly washing it with distilled water, and drying it. , Measurement samples can be obtained.
• a coating film sample for measurement was prepared as follows.
• Each phosphate chromate-based surface-treated aluminum so as to be the same as the coating conditions (paint type, dry coating weight, drying / baking conditions) of the inner or outer coating on the coated metal plate of each example, comparative example, and reference example.
• a plate (3104 alloy, plate thickness: 0.27 mm, chromium weight in surface treatment film: 20 mg / m 2 ) is coated with a bar coater, dried at 120 ° C for 60 seconds, and then baked at 250 ° C for 30 seconds. To prepare a painted metal plate.
• a 5 cm x 5 cm size test piece is cut out from a coated metal plate, and after measuring the mass of the test piece (W1), 200 ml of MEK (methyl ethyl ketone) is used to put the test piece in boiling MEK (under reflux at 80 ° C.) for 1 hour. It was soaked and MEK extraction was performed at boiling point for 1 hour. The extracted test piece was washed with MEK and then dried at 120 ° C. for 1 hour, and the mass (W2) of the extracted test piece was measured. Further, the coating film was peeled off and removed by a decomposition method using concentrated sulfuric acid, washed and dried, and the mass (W3) of the test piece was measured.
• MEK methyl ethyl ketone
• the MEK extraction rate (mass%) of the coating film of the coated metal plate is calculated by the following formula (7). The results are shown in Table 1.
• MEK extraction rate (%) 100 ⁇ (W1-W2) / (W1-W3) ⁇ ⁇ ⁇ (7)
• the squeezed iron cans and painted metal plates obtained in each Example, Comparative Example, and Reference Example were evaluated according to the following test method.
• the current value (ERV) was measured after immersing the product in a saline solution and applying a voltage of 6.3 V for 4 seconds at room temperature.
• the evaluation criteria are as follows. ⁇ : Current value less than 50 mA (less than 0.18 mA / cm 2 per unit area) ⁇ : Current value 50 mA or more and less than 200 mA (0.18 mA / cm 2 or more and less than 0.70 mA / cm 2 ) ⁇ : Current value 200 mA or more and less than 700 mA (0.70 mA / cm 2 or more and less than 2.50 mA / cm 2 ) ⁇ : Current value 700 mA or more (2.50 mA / cm 2 or more)
• the coating film peeling resistance evaluation is performed by coating the inner and outer surfaces of the can body of the squeezed iron can after molding as described in the above section "Preparation of squeezed iron can" and heat-treating at 201 ° C. for 75 seconds. The presence or absence of film peeling was observed and evaluated. The evaluation criteria are as follows. ⁇ : No peeling of the coating film is observed. ⁇ : Very slight peeling of the coating film is observed in the portion where the processing of the side wall of the can body is severely thinned. X: The coating film is peeled off in a wide range of the part where the processing of the side wall of the can body is severely thinned.
• Peeling strength is 2.0 N / 15 mm or more due to interfacial peeling or cohesive fracture
• Peeling strength is less than 2.0 N / 15 mm due to interfacial peeling 1.0 N / 15 mm or more
• Peeling strength is 1.0 N / 15 mm due to interfacial peeling Less than
• a sample of 10 mm in the circumferential direction of the can body and 20 mm in the height direction of the can body is sampled around the center of the can body (the thinnest part) in the 0 ° direction with respect to the rolled grain of the metal substrate. I cut it out.
• the coating film on the outer surface of the can was removed by sanding to expose the metal surface, and then the metal substrate was dissolved by immersing it in a diluted hydrochloric acid aqueous solution.
• the coating film on the inner surface side of the film-shaped can was taken out, thoroughly washed with distilled water and dried, and the obtained film-shaped coating film was 4 mm wide (in the circumferential direction of the can body) and 20 mm long (can height). A sample for measurement was obtained by cutting out in the direction).
• the measurement sample was chucked into a thermomechanical analyzer so that the distance between the chucks (corresponding to the initial length of the measuring part in the height direction of the coating film) was 5 mm.
• the displacement of the measurement sample was measured under the following conditions, and the heat shrinkage rate in the can height direction with and without load was evaluated.
• Measurement mode Pull mode Load during measurement: 5 mN (5.20 x 105 N / m 2 ) or no load Distance between chucks: 5 mm
• the distance between chucks before measurement (corresponding to the initial length of the measuring part of the coating film) is L 0 , and a load of 5.20 ⁇ 10 5 N / m 2 per unit area is applied and the temperature rise rate is 30 ° C./min.
• ⁇ L 1 be the maximum value (maximum shrinkage length) of the amount of shrinkage in the height direction of the L 0 corresponding portion when the temperature is raised from to 200 ° C., and the value calculated by the formula shown in the following formula (5) is heat.
• the shrinkage rate (with load) was used.
• the amount of displacement was positive for contraction and negative for expansion or expansion. The results are shown below.
• Heat shrinkage rate (with load) ( ⁇ L 1 / L 0 ) ⁇ 100 (%) ⁇ ⁇ ⁇ (5) Heat shrinkage rate (with load) of the inner coating film of the squeezing iron can (without heat treatment) of Example 4: 68% Heat shrinkage rate (with load) of the inner coating film of the squeezing iron can (with heat treatment) of Example 4: 8%
• chuck distance before measuring (corresponding to the measuring unit the initial length of the coating film) L 0, the corresponding L 0 when the temperature was raised from 30 ° C. to 200 ° C. In state with no load heating rate 5 ° C. / min
• the maximum value (maximum shrinkage length) of the amount of shrinkage in the height direction of the portion was defined as ⁇ L 2, and the value calculated by the formula shown in the following formula (6) was defined as the heat shrinkage rate (no load).
• the amount of displacement was positive for contraction and negative for expansion or expansion. The results are shown below.
• Heat shrinkage rate (no load) ( ⁇ L 2 / L 0 ) ⁇ 100 (%) ⁇ ⁇ ⁇ (6) Heat shrinkage of the inner coating film of the squeezed iron can (without heat treatment) of Example 4 (without load): 69% Heat shrinkage rate (without load) of the inner coating film of the squeezing iron can (with heat treatment) of Example 4: 30%
• the corrosion resistance was evaluated at 201 ° C. in the squeezed iron can (without heat treatment) of Example 4 in which the squeezing ironing process and the doming process were performed as described in the above section "Preparation of squeezed ironing can".
• the inner surface coating film at the center of the can body of the squeezed iron can (with heat treatment) of Example 4 after the heat treatment for 75 seconds was performed as follows. Using the above-mentioned squeezing and ironing can, a test piece having a can body circumference of 40 mm and a can height direction of 40 mm was cut out centering on the central portion of the can body (the thinnest part).
• a cross-cut wound reaching a substrate having a length of 4 cm was placed in the test piece with a cutter, immersed in an acidic model solution containing salt, and allowed to elapse at 37 ° C. for 2 weeks to evaluate the corrosion state.
• the model solution used in the test was prepared by adding citric acid to 0.2% of salt and adjusting the pH to 2.5.
• the evaluation criteria are x for those with a maximum width of corrosion under the coating film of 1.5 mm or more per side around the cross-cut part, ⁇ for those with 0.5 mm or more and less than 1.5 mm, and those with less than 0.5 mm. ⁇ .
• the results are shown below. Corrosion state of the squeezed iron can (without heat treatment) of Example 4: ⁇ Corrosion state of the squeezed iron can (with heat treatment) of Example 4: ⁇
• Table 1 shows the composition of the inner surface coating composition and the outer surface composition (type of polyester resin, type of curing agent, solid content mixing ratio), coating of the inner surface coating film and the outer surface coating film of each Example, Comparative Example, and Reference Example.
• the film performance coating film Tg, MEK extraction rate, stress relaxation rate
• evaluation results are shown.
• the squeezed iron can of the present invention does not peel off the coating film during heat treatment, effectively prevents metal exposure, has excellent corrosion resistance, and can be suitably used for beverage containers and the like. Further, the coated metal plate for squeezing iron cans of the present invention has excellent can-making processability and productivity, and has excellent coating film peeling resistance that does not cause coating film peeling even during heat treatment after molding. It can be suitably used for manufacturing iron cans.

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• 2021
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