Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • 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
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
  • B32B15/09—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyesters
• • 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
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
  • C08L61/04—Condensation polymers of aldehydes or ketones with phenols only
  • C08L61/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
  • C08L61/12—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols with polyhydric phenols
• • 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
  • 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
  • C09D167/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • 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
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/08—Anti-corrosive paints

Definitions

• the present invention relates to a seamless can made of a coated metal sheet and a coated metal sheet capable of forming the seamless can.
• the present invention relates to a seamless can excellent in coating coverage and corrosion resistance, effectively preventing metal exposure due to severe drawing and ironing and coating peeling due to heat treatment, and a coated metal sheet capable of forming such a seamless can.
• thermoplastic resin-coated metal plate in which a metal plate such as aluminum is coated with a plastic film (thermoplastic resin film) made of a thermoplastic resin
• thermoplastic resin film thermoplastic resin film
• the organic resin-coated metal sheet is subjected to drawing or drawing and ironing to form a seamless can for filling beverages or the like, or is press-molded to form a can lid such as an easy-open end.
• an organic resin-coated metal sheet having a thermoplastic resin film made of a crystalline polyester resin mainly composed of ethylene terephthalate units as an organic resin coating layer is a seamless can formed by drawing and ironing (hereinafter referred to as a drawing and ironing can).
• a drawing and ironing can Such organic resin-coated metal sheets can be drawn and ironed under dry conditions without the use of coolant (coolant/lubricant).
• Such an organic resin-coated metal sheet can be produced by laminating a pre-formed thermoplastic resin film such as a thermoplastic polyester resin onto the metal sheet by thermal adhesion, or by applying a molten thin film of an extruded thermoplastic polyester resin or the like to the metal sheet. It is manufactured by a film lamination method such as an extrusion lamination method. However, in the film lamination method, it is difficult to control the thickness of the film to be thin due to film formation.
• Patent Document 2 describes a double-sided coated metal plate in which the dry coating amount of the film that will be the inner surface of the can after processing is 90 to 400 mg/100 cm 2 , the glass transition temperature is 50 to 120°C, and the glass transition temperature is 60°C.
• the pencil hardness is H or higher
• the elongation rate is 200 to 600%
• the dynamic friction coefficient is in the range of 0.03 to 0.25
• the dry coating amount of the film that will be the outer surface of the can after processing is 15 to
• a coated metal sheet for drawn and ironed cans 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 60° C. has been proposed.
• the residual stress in the coating film caused by severe processing such as drawing and ironing after forming the can body causes the paint to crack. It was found that the adhesion between the film and the metal substrate (hereinafter sometimes referred to as "coating film adhesion") is remarkably lowered. Such a decrease in adhesion adversely affects various performances such as a decrease in corrosion resistance. This residual stress can be removed by subjecting the can body to heat treatment under specified conditions, which makes it possible to improve adhesion.
• the coating film peels off from the metal substrate, especially in the portion of the can body that is severely processed and thinned.
• the metal exposure occurs in the heat treatment, and the coating film coverage may deteriorate.
• they may be subjected to sterilization treatment under high-temperature and high-humidity conditions such as retort treatment after filling. (retort whitening resistance) is required.
• a polyester-based coating film formed from a polyester-based coating composition has a unique problem of deterioration in workability (embrittlement over time) due to long-term storage under a predetermined environment.
• embrittlement over time due to long-term storage under a predetermined environment.
• the present inventors presume as follows. That is, it is considered that the reorientation of the molecular chains of the polyester resin (transition to an equilibrium state) occurs in the coating film due to the relaxation of enthalpy over time, resulting in embrittlement of the coating film and deterioration of workability.
• Patent Document 2 a polyester-based coating film that can maintain hardness, elongation, etc. even when heat generation near 60 ° C. occurs due to continuous drawing and ironing on the can inner surface side of the coated metal plate.
• a painted metal plate that can withstand drawing and ironing and a drawn and ironed can formed from this painted metal plate are proposed by forming a drawn and ironed can using such a painted metal plate.
• an object of the present invention is to provide a coating film that suppresses the occurrence of coating peeling due to heat treatment after can forming, has high coating film coverage even after heat treatment, and has excellent retort whitening resistance and aging resistance to embrittlement.
• a seamless can such as a drawn and ironed can and a coated metal sheet capable of forming such a seamless can.
• a seamless can having an inner coating film at least on the inner surface side of the can, wherein the inner coating film contains a polyester resin and a resol-type phenol resin and/or amino resin as a curing agent, and the inner coating film
• the membrane has a gel fraction (A) represented by the following formula (1a) of 55% or more and less than 90%.
• Gel fraction (A) (W2a/W1a) x 100 (%) (1a)
• W1a is the weight of the inner coating film isolated from the coated metal substrate cut out from the seamless can
• W2a is the isolated inner coating film immersed in MEK at room temperature for 60 minutes, then taken out and dried. , respectively.
• the resol-type phenolic resin is an m-cresol-based resol-type phenolic resin
• the resol-type phenolic resin is blended in an amount of more than 2 parts by mass and less than 10 parts by mass with respect to 100 parts by mass of the polyester resin.
• the amino resin is a benzoguanamine resin, and the benzoguanamine resin is blended in an amount of 8 parts by mass or more and less than 25 parts by mass with respect to 100 parts by mass of the polyester resin.
• the inner coating film further contains an acid catalyst, and 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.
• the thickness of the central part of the can body is 20 to 75% of the thickness of the central part of the can bottom, and the thickness of the inner coating film at the central part of the can body is the thickness of the inner coating film at the central part of the can bottom. 20 to 75% of the thickness of [7]
• the thickness ratio between the inner coating film and the metal substrate is substantially the same between the can bottom and the can body.
• W6a is the weight of the outer coating film isolated from the coated metal substrate cut out from the seamless can
• W7a is the isolated outer coating film immersed in MEK at room temperature for 60 minutes, then taken out and dried. , respectively.
• L 0 Initial length in the height direction of the coating film isolated from the central part 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
• a coated metal sheet for seamless cans having an inner coating film on at least the inner surface of the can, wherein the inner coating film comprises a polyester resin and a resol-type phenol resin and/or amino resin as a curing agent. and the gel fraction (A) represented by the following formula (1b) of the inner coating film is 55% or more and less than 90%, and the gel content represented by the following formula (2b) of the inner coating film.
• the difference between the gel fraction (B) and the gel fraction (A) is less than 10%.
• the present inventors have found that seamless cans such as drawn and ironed cans made of coated metal sheets on which a polyester coating film is formed have peeling resistance during heat treatment after molding, and polyester coating for retort processing after content filling.
• the coating film peeling resistance, retort whitening resistance, and aging embrittlement resistance of the isolated coating film obtained by the above formula (1) While finding that there is a correlation with the gel fraction (A) of the polyester coating film measured in the state, a suitable range of the gel fraction (A) of the coating film that can be compatible with them and such a coating film A coating film capable of expressing the gel fraction (A) was found.
• the coating film does not peel off during heat treatment.
• the coverage of the internal coating film expressed in ERV conversion is less than 200 mA, which effectively prevents metal exposure, and the coating film coverage is excellent, and the residual stress is removed by heat treatment, improving the coating film adhesion. Therefore, it is possible to exhibit excellent corrosion resistance. Furthermore, it has excellent retort whitening resistance that does not whiten the inner coating even after retort treatment after filling the content, and can prevent embrittlement of the inner coating even after being stored for a long time. , has excellent resistance to embrittlement over time.
• the coated metal sheet of the present invention is excellent in extensibility and workability of the coating film, and even when subjected to severe processing such as drawing and ironing under dry conditions,
• the breakage (sometimes referred to as breakage in the present invention) will occur, and metal exposure is effectively prevented, so even after drawing and ironing, etc., it has high coating coverage and is excellent. It has excellent can manufacturing processability.
• by controlling the gel fraction of the inner coating film formed on the inner surface of the can it is possible to reduce the residual stress generated by drawing and ironing, etc. can be effectively suppressed, and it is possible to provide seamless cans such as drawn and ironed cans that have high coating film coverage even after heat treatment and excellent corrosion resistance.
• Seamless cans such as drawn and ironed cans formed using this coated metal sheet can exhibit excellent retort whitening resistance as described above.
• the coated metal sheet of the present invention can prevent embrittlement of the coating film even after being stored for a long time, and has excellent aging embrittlement resistance that can maintain good workability. .
• the inner coating film on the can inner surface side contains a polyester resin and a resol-type phenol resin and / or amino resin as a curing agent, and the inner coating film of the above formula (1b )
• the gel fraction (A) of the inner coating film measured in the state of the isolated coating film represented by ) is in the range of 55% or more and less than 90%. This is an important feature from the viewpoint of whitening resistance and embrittlement resistance over time. The reason for this will be explained below. First, it will be explained from the viewpoint of coating film peeling resistance during heat treatment.
• a painted metal sheet When a painted metal sheet is used to form a seamless can such as a drawn and ironed can at high speed under dry conditions, the painted metal sheet is subject to severe processing and deformation, accompanied by a temperature rise due to the heat generated during processing. Become. At that time, since the coating film formed on the coated metal sheet is subjected to large deformation during the can manufacturing process, a large residual stress is generated in the coating film during processing. In this state, the molded can body is subjected to heat treatment and heated to a temperature higher than the glass transition temperature of the polyester resin. It is thought that peeling of the paint film occurs due to this, and the metal is exposed. In order to suppress such coating film peeling phenomenon during heat treatment, it is necessary to reduce the residual stress of the coating film that occurs during can manufacturing.
• the present inventors have made intensive studies on the reduction of the residual stress of the coating film generated during processing and the suppression of peeling of the coating film during heat treatment due to it. mass ratio of the coating component that became insoluble in the solvent), more specifically, the gel fraction (A) of the inner coating measured in the state of the isolated coating obtained by the above formula (1b), It was found that the degree of residual stress in the subsequent coating film and, in turn, the coating film peeling phenomenon during heat treatment are greatly affected. As described above, when a painted metal sheet is used to draw and iron a can or the like under dry conditions at high speed, residual stress occurs in the coating film after processing on the painted metal sheet. Residual stress is considered to increase when the base resin such as a resin is highly crosslinked by a curing agent.
• the gel fraction (A) in the inner coating film of the coated metal plate is considered to represent the gel fraction of the entire inner coating film, that is, the degree of cross-linking (crosslinking degree) of the entire coating film, as will be described later.
• the gel fraction (A) in the inner coating film of the coated metal plate is 90% or more, it indicates that the entire coating film is highly crosslinked. It becomes difficult to prevent peeling.
• the gel fraction (A) is adjusted to less than 90%, the cross-linking degree of the entire coating film is not too high and is moderately controlled. It is believed that the residual stress in the subsequent coating is reduced.
• the coating film When the polyester coating film is subjected to sterilization treatment such as retort treatment, the coating film may whiten due to water absorption, etc., but the degree of cross-linking of the entire coating film is high to some extent, and it has a dense cross-linked structure. In this case, it is thought that whitening of the coating film due to retort treatment can be suppressed by suppressing penetration of moisture into the coating film. Therefore, the whitening phenomenon of the coating film caused by retort treatment is also greatly affected by the degree of cross-linking of the entire coating film, that is, the gel fraction (A) of the inner coating film.
• the degree of cross-linking of the entire coating film that is, the gel fraction (A) of the inner coating film.
• the coating film does not have a dense crosslinked structure, making it difficult to suppress whitening of the coating film.
• the gel fraction (A) is 55% or more, it indicates that the entire coating film has a dense crosslinked structure to some extent, thereby making it possible to suppress whitening of the coating film. That is, by adjusting the gel fraction (A) to 55% or more, it is possible to provide a drawn and ironed can having excellent retort whitening resistance.
• the embrittlement of the polyester-based coating film over time is presumed to be caused by the reorientation of the molecular chains of the polyester resin (transition to an equilibrium state) due to enthalpy relaxation. Since this enthalpy relaxation is due to the molecular motion of the polyester resin, it is considered that the more the polyester resin is crosslinked with the curing agent, the more the molecular motion is suppressed and the enthalpy relaxation less likely to occur. Therefore, this embrittlement phenomenon over time is also greatly affected by the degree of cross-linking of the entire coating film, that is, the gel fraction (A) of the inner coating film.
• the polyester resin If the gel fraction (A) is less than 55%, the polyester resin is not sufficiently crosslinked, making it difficult to suppress embrittlement of the coating film over time. On the other hand, when the gel fraction (A) is 55% or more, molecular motion is suppressed by moderate cross-linking of the polyester resin in the entire coating film, thereby suppressing embrittlement of the coating film over time. It becomes possible.
• the gel It is important that the fraction (A) is in the range of 55% or more and less than 90%. As a result, even after heat treatment after forming seamless cans such as drawn and ironed cans, peeling of the coating film is effectively prevented and the coating film coverage is excellent, as well as retort whitening resistance and aging resistance. It is possible to provide seamless cans, particularly drawn and ironed cans, having a thick coating film.
• the gel fraction (A) is 55% or more and less than 90%, preferably 60 to 88%, more preferably 62% to less than 85%, still more preferably 65 to 84%, particularly preferably 65 to 80%, Most preferably, it is within the range of 68% or more and less than 78%.
• peeling of the coating film may occur during heat treatment.
• the degree of cross-linking of the coating film becomes low, and there is a possibility that the resistance to retort whitening and embrittlement resistance over time may decrease, and the heat resistance of the coating film may also decrease.
• the paint film tends to soften due to the temperature rise when the drawn and ironed can is molded at high speed, and the paint film tends to stick to the mold during molding. .
• the can body sticks to the forming punch, and a phenomenon occurs in which the forming punch and the can body become difficult to separate (poor stripping property). There is a risk that the can body will buckle or break, reducing productivity.
• the coated metal sheet used in the present invention is desirably a double-sided coated metal sheet having an outer coating film on the surface that will be the outer surface of the can after processing, and the outer coating film also desirably contains a polyester resin. Furthermore, it is more desirable to contain a curing agent, preferably an amino resin.
• the gel fraction (A) calculated from the above formula (3b) is 40% or more and less than 90% from the viewpoint of paint film peeling resistance, retort whitening resistance, and aging embrittlement resistance in the outer coating film. , preferably 55% or more and less than 90%, more preferably 60% or more and 88% or less, still more preferably 65 to 85%, particularly preferably 68 to 84%, most preferably 70 to 84% is desirable.
• the difference between the gel fraction (B) of the inner coating film measured in the state of the coated metal substrate obtained by the above formula (2b) and the above-mentioned gel fraction (A) A difference of less than 10% is desirable.
• the polyester-based coating film may have a coating structure in which the curing agent is concentrated near the surface of the coating film. Such a coating film structure is thought to occur when the curing agent is localized on the surface of the coating film during the process of forming the coating film due to the low compatibility between the polyester resin, which is the main ingredient, and the curing agent.
• the above-mentioned gel fraction (B) in the inner coating film of the coated metal plate is obtained by immersing the coated metal substrate in MEK (methyl ethyl ketone), which is a solvent, and calculating the solvent-soluble uncrosslinked component (un Curing component) is extracted, and it is determined from the mass of the coating component that has become insoluble in the solvent.
• MEK methyl ethyl ketone
• un Curing component solvent-soluble uncrosslinked component
• the solvent penetrates into the coating film due to the presence of a dense layer of the curing agent on the coating film surface. Therefore, it becomes difficult to extract the uncrosslinked component existing inside the coating film. Therefore, it can be said that the gel fraction (B) measured by the above method strongly reflects the degree of cross-linking in the vicinity of the coating film surface rather than the degree of cross-linking of the entire coating film.
• the above-mentioned gel fraction (A) is obtained by extracting the uncrosslinked components by immersing the coating film in the state of the isolated coating film isolated from the coated metal substrate in a solvent and making it insoluble in the solvent.
• the coating film has a coating structure in which the aforementioned curing agent is concentrated near the surface of the coating film. Even in the case of , the solvent penetrates into the interior and extracts the uncrosslinked component. Therefore, it can be said that the gel fraction (A) measured by the above method reflects the degree of cross-linking of the entire coating film.
• the compatibility between the polyester resin and the curing agent is high, and the coating film has a coating structure in which the curing agent is uniformly distributed in the coating film. Since it is desirable to have a dense crosslinked structure, it is desirable that the gel fraction (A) and the gel fraction (B) take values close to each other. Specifically, the gel fraction (A) and the gel fraction ( It is desirable that the difference in B) is less than 10%. When the difference between the gel fraction (A) and the gel fraction (B) is 10% or more, it is considered that the coating film surface has a coating structure in which the curing agent is concentrated. It may be difficult to express retort whitening resistance.
• the gel fraction (B) is higher than 45% and 99% or less, preferably higher than 50% and lower than 98%, more preferably higher than 52% and lower than 95%, still more preferably 55 to 94%, particularly preferably It should be in the range of 55-90%, most preferably 58% or more and less than 88%.
• the difference between the gel fraction (A) and the gel fraction (B) is less than 10% in the outer coating film of the coated metal sheet used in the present invention.
• the gel fraction (B) in the outer coating film of the coated metal plate is calculated from the following formula (4b), and the range of the gel fraction (B) is higher than 45% and 99% or less, preferably 50%. higher than 98%, more preferably higher than 52% and lower than 95%, still more preferably 55 to 94%, particularly preferably 55 to 90%, most preferably 58% to 88%. .
• Gel fraction (B) (%) [(W9b-W10b)/(W8b-W10b)] x 100 (4b)
• W8b is the weight of the coated metal plate on which the outer coating film is formed
• W9b is the weight after the coated metal plate is immersed in MEK at 80 ° C. for 60 minutes, taken out and dried
• W10b is the weight.
• Each shows the mass of the metal plate after removing the outer coating film from the coated metal plate. If the gel fraction (B) of the outer coating film is lower than the above range, the degree of cross-linking of the coating film surface is low, and the hardness of the coating film is lowered. External defects may occur.
• the glass transition temperature (Tg) of the inner coating film is 30° C. or higher, preferably higher than 40° C., more preferably higher than 45° C. and 120° C. or lower, still more preferably 50° C. to 110° C., particularly preferably 55° C. It is preferably in the range of higher than 100°C, most preferably higher than 55°C and lower than 90°C. If the Tg is lower than the above range, when the content is filled into the molded can body, the flavor component of the content is likely to be sorbed, and the aroma sorption resistance may be deteriorated. There is a possibility that the barrier property of the film is lowered and the corrosion resistance is deteriorated.
• the Tg exceeds 120°C
• the workability and elongation of the coating film are deteriorated, and metal exposure may occur during molding, resulting in poor can-making workability and residual stress in the coating film. If it becomes large, there is a possibility that the coating film will peel off during the heat treatment.
• the Tg of the outer coating film is also 30° C. or higher, preferably higher than 40° C., more preferably higher than 45° C. and 120° C. or lower, still more preferably 50° C. to 110° C., particularly preferably higher than 55° C. and 100° C. or lower. , and most preferably in the range of greater than 55°C and less than or equal to 90°C.
• the Tg is lower than the above range, the hardness of the coating film becomes low, and there is a possibility that the outer surface defects such as coating film scraping may occur.
• the Tg exceeds 120° C., the workability and elongation of the coating film are lowered, and the metal may be exposed during molding, resulting in poor can-making workability.
• the inner coating is continuous from the bottom to the body on the inner surface of the can. It becomes possible to cover the whole with a film. Furthermore, when a double-sided coated metal sheet having an outer surface coating film is used on the surface that will become the outer surface of the can after drawing and ironing, the entire surface of the can is coated with the outer surface coating film continuously from the bottom to the body of the can outer surface. becomes possible.
• the dry film thickness of the inner coating film is preferably in the range of 0.2 to 20 ⁇ m, preferably 1 to 16 ⁇ m, more preferably more than 2 ⁇ m and 12 ⁇ m or less.
• the dry coating mass is 3 to 300 mg/dm 2 , preferably 15 to 220 mg/dm 2 , more preferably 15 to 150 mg/dm 2 , more preferably greater than 25 mg/dm 2 and less than or equal to 150 mg/dm 2 . It is preferable to be in If the thickness is thinner than the above range, the metal tends to be exposed during molding, resulting in poor coverage of the inner coating film.
• the film thickness is preferably 12 ⁇ m or less, more preferably in the range of 6.5 to 10 ⁇ m.
• the dry coating mass is preferably in the range of 70 mg/dm 2 to 150 mg/dm 2 , preferably 85 mg/dm 2 to 150 mg/dm 2 , more preferably 90 to 140 mg/dm 2 . is.
• the thickness is 1 ⁇ m or more and less than 6.5 ⁇ m, preferably more than 2 ⁇ m and 6.5 ⁇ m. It is preferably less than, more preferably in the range of 2.5-6 ⁇ m.
• the dry coating mass is 15 mg/dm 2 or more and less than 90 mg/dm 2 , preferably more than 25 mg/dm 2 and less than 90 mg/dm 2 , more preferably 30 to 85 mg/dm 2 . be. If the thickness is thinner than the above range, the corrosion resistance is inferior, and if the thickness exceeds the above range, the thickness becomes unnecessarily thick, resulting in poor economy.
• the dry film thickness of the external coating film is 0.2 to 20 ⁇ m, preferably 1 to 16 ⁇ m, more preferably greater than 2 ⁇ m and 12 ⁇ m or less, still more preferably greater than 2 ⁇ m and 6.5 ⁇ m or less. preferred.
• the dry coating mass is from 3 to 300 mg/dm 2 , preferably from 15 to 220 mg/dm 2 , more preferably from 25 mg/dm 2 to 150 mg/dm 2 , still more preferably from 25 mg/dm 2 to 90 mg/dm 2 . A range of less than dm 2 is preferred. If the thickness is thinner than the above range, the metal tends to be exposed during molding, resulting in poor coating coverage of the outer surface.
• the film is thicker than the above range, the residual stress generated during processing increases, and the coating film tends to peel off during heat treatment after drawing, ironing and forming.
• the inner coating film which requires higher coverage, be thicker than the outer coating film.
• the metal plate used as the metal substrate of the coated metal plate is not limited to these, but for example, hot-drawn steel plate, cold-rolled steel plate, hot-dip galvanized steel plate, electro-galvanized steel plate, alloy-plated steel plate, aluminum-zinc alloy-plated steel plate, aluminum plate, tin-plated steel plate, stainless steel plate, copper plate, copper-plated steel plate, tin-free steel, nickel-plated steel plate, ultra-thin tin-plated steel plate, chromium-treated steel plate, etc., and if necessary, various surface treatments, such as phosphate chromate treatment.
• an aluminum plate is preferable among the above metal plates, and as the aluminum plate, in addition to a pure aluminum plate, an aluminum alloy plate, specifically, aluminum in the 3000s, 5000s, and 6000s in "JIS H 4000" An alloy plate can be preferably used, and an aluminum alloy plate is preferred in terms of strength and the like.
• the coating film made of the above-described coating composition has excellent adhesion to the metal substrate, an untreated surface that has not been subjected to surface treatment aluminum alloy plate can also be suitably 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 formability. It should be in the range of ⁇ 0.28 mm.
• the coated metal sheet of the present invention and the inner coating film of the seamless can described later, preferably both the inner and outer coating films, contain a polyester resin as a main agent and a curing agent.
• the content of the polyester resin, preferably the amorphous polyester resin described later is preferably higher than 50% by mass, more preferably 60% by mass or more, still more preferably 70% by mass or more, and 80% by mass. % or more is particularly preferable.
• the content of the polyester resin, preferably the amorphous 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. % or more is particularly preferred.
• a polyester resin is used as the main component (main component) constituting the inner coating film and the outer coating film.
• the content (mass ratio) is the largest.
• the mass ratio of the polyester resin is preferably higher than 50% by mass, more preferably 60% by mass or more, and more preferably 70% by mass or more. More preferably, it is particularly preferably 80% by mass or more.
• 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 terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, and sebacine.
• acids such as dodecanedioic acid and dimer acid, (anhydrous) maleic acid, fumaric acid, unsaturated dicarboxylic acids such as terpene-maleic acid adducts, 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexa alicyclic dicarboxylic acids such as hydroisophthalic acid and 1,2-cyclohexenedicarboxylic acid; One or more of these can be selected and used.
• isophthalic acid 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 It is preferable to use one or more selected from the group consisting of acids.
• the total amount of the polyvalent carboxylic acid components constituting the polyester resin is 100 mol%
• At least one selected from aromatic dicarboxylic acids such as terephthalic acid, orthophthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, or two or more combined at least 70 mol%, preferably at least 80 mol% , more preferably in an amount of 90 mol % or more.
• aromatic dicarboxylic acids such as terephthalic acid, orthophthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, or two or more combined at least 70 mol%, preferably at least 80 mol% , more preferably in an amount of 90 mol % or more.
• terephthalic acid and isophthalic acid are particularly preferable.
• the aromatic dicarboxylic acid At least one selected from certain terephthalic acid, orthophthalic acid, isophthalic acid, and 2,6-naphthalene dicarboxylic acid, or two or more selected from 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol % or more.
• the total content of terephthalic acid and isophthalic acid is preferably 70 mol% or more when the total amount of all polycarboxylic acid components constituting the polyester resin blend is 100 mol%. is 80 mol % or more, more preferably 90 mol % or more.
• the content of isophthalic acid is 2 mol% or more, preferably 5 to 90 mol%, more preferably higher than 10 mol% and 85 mol% or less, still more preferably. It is desirable to be in the range of 15 to 80 mol %, particularly preferably 20 to 80 mol %. As a result, it is possible to densify (high density) the coating film, and as a result, it is possible to improve the aroma adsorption resistance and the can-making processability of the coating film, thereby improving the coating film during molding. The occurrence of defects can be suppressed, leading to improved coating coverage.
• terephthalic acid content is 10 mol% or more, preferably 15 to 90 mol%, more preferably 19 mol% to less than 84 mol%, still more preferably 25 to 80 mol%, particularly preferably 30 to 80 mol%. mol %, most preferably in an amount of 40 to 76 mol %.
• polyester resin when a blend of two or more polyester resins is used as the polyester resin, when the total amount of all polycarboxylic acid components constituting the blend of polyester resin is 100 mol%, isophthalic acid is The content is 2 mol% or more, preferably 5 to 90 mol%, more preferably higher than 10 mol% and 85 mol% or less, still more preferably 15 to 80 mol%, particularly preferably 20 to 80 mol%. is desirable.
• terephthalic acid is 10 mol% or more, preferably 15 to 90 mol%, more preferably 19 mol% to less than 84 mol%, still more preferably 25 to 80 mol%, particularly preferably 30 to 80 mol%, most preferably is preferably contained in an amount of 40 to 76 mol %.
• the polyvalent carboxylic acid component constituting the polyester resin components other than aromatic dicarboxylic acids, such as aliphatic dicarboxylic acids and alicyclic dicarboxylic acids, are added to the residual proportion of the above aromatic dicarboxylic acids, that is, less than 30 mol%.
• the ratio of the aliphatic dicarboxylic acid component or the alicyclic dicarboxylic acid component increases, when the can body is filled with the content, the coating film will absorb the aroma component in the content. As a result, the coating film may become less resistant to odor adsorption, and the retort whitening resistance may also be reduced.
• the proportion of components other than aromatic dicarboxylic acids such as aliphatic dicarboxylic acids in the polyvalent carboxylic acid component constituting the polyester resin is less than 30 mol%, preferably less than 20 mol%, more preferably less than 10 mol%. , more preferably less than 7 mol %, particularly preferably less than 5 mol %, most preferably less than 4 mol %.
• polyester resin when the total amount of all polyvalent carboxylic acid components constituting the blend of polyester resin is 100 mol%, aliphatic dicarboxylic acid and The proportion of cycloaliphatic dicarboxylic acids should be less than 20 mol %, preferably less than 15 mol %, more preferably less than 10 mol %, particularly preferably less than 7 mol %.
• Polyhydric alcohol components constituting the polyester resin include ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3 -butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2- Butyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1-methyl-1,8-octanediol, 3-methyl-1,6-hexanediol, 4-methyl-1, Aliphatic glycols such as 7-heptanediol, 4-methyl-1,8-octanediol, 4-propyl
• Trihydric or higher polyalcohols such as cyclic polyalcohols, trimethylolpropane, trimethylolethane, and pentaerythritol can be used singly or in combination of two or more.
• ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and diethylene glycol are suitable as components constituting the polyester resin. can be used for
• it is selected from ethylene glycol, propylene glycol, 2-methyl-1,3-propanediol, and 1,4-butanediol when the total amount of polyhydric alcohol components constituting the polyester resin is 100 mol%.
• the above 1,4-butanediol is less than 40 mol%, more preferably 30 mol%. less than 20 mol %, more preferably less than 10 mol %.
• 1,4-butanediol is 40 mol % or more, there is a possibility that the aroma adsorption resistance may be deteriorated. Even when a blend of two or more polyester resins is used as the polyester resin, ethylene glycol, propylene glycol, 2-methyl-1, At least one selected from 3-propanediol and 1,4-butanediol, or a combination of two or more selected from 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. Furthermore, considering the aroma sorption resistance, 1,4-butanediol is less than 40 mol%, more preferably less than 30 mol%, still more preferably less than 20 mol%, and particularly preferably less than 10 mol%. desirable.
• the polyester resin can be obtained by polycondensing one or more of the above polycarboxylic acid components and one or more of the polyhydric alcohol components, or polycondensing polyhydric carboxylic acid components such as terephthalic acid, isophthalic acid, and trianhydride after polycondensation.
• the polyester resin has an acid value of 0.1 mgKOH/g to 40 mgKOH/g, preferably 0.5 mgKOH/g to 25 mgKOH/g, from the viewpoint of curability, retort whitening resistance, adhesion to metal substrates, and the like. , More preferably 1 mg KOH / g to 15 mg KOH / g, more preferably 1.0 mg KOH / g or more and less than 10 mg KOH / g, particularly preferably 1.0 mg KOH / g to 8 mg KOH / g, most preferably 1.0 mg KOH / g or more 5 mg KOH / It is desirable to be in the range of less than g.
• the adhesion between the metal substrate and the coating film may deteriorate.
• the coating film tends to absorb water as compared with the above range, and the retort whitening resistance may be lowered, and the reaction point with the curing agent As the amount increases, the cross-linking density of the coating film increases, and the can-making processability and coating film peeling resistance decrease, which may cause metal exposure and reduce the coating property of the coating film.
• the polyester resin is a blend obtained by blending two or more polyester resins
• the sum of the values obtained by multiplying the acid value and mass fraction of each polyester resin is the average acid value of the blend. (AV mix ), and the average acid value should be within the acid value range described above.
• the hydroxyl value of the polyester resin is not limited to this, but is 20 mgKOH/g or less, preferably 10 mgKOH/g or less, from the viewpoint of can-making processability, coating film peeling during heat treatment, retort whitening resistance, etc. It is more preferably in the range of 1 to 10 mgKOH/g, still more preferably in the range of 2 to 8 mgKOH/g.
• the polyester resin is a blend obtained by blending two or more polyester resins
• the sum of the values obtained by multiplying the hydroxyl value and mass fraction of each polyester resin is the average hydroxyl value of the blend. and the average hydroxyl value should be within the above range.
• the glass transition temperature (Tg) of the polyester resin is 30° C. or higher, preferably higher than 40° C., more preferably higher than 45° C. and 120° C. or lower, still more preferably 50° C. to 100° C., particularly preferably higher than 55° C. to 100° C. Below, it is most preferably in the range of higher than 55° C. and 90° C. or lower. If the Tg is lower than the above range, when the content is filled into a container manufactured by drawing and ironing as described above, the mobility of the resin increases, and the aroma component (flavor component) contained in the content is reduced.
• the amount of sorption of aroma components increases, and there is a risk that the aroma sorption resistance will be inferior, as well as the heat resistance, corrosion resistance, and retort whitening resistance.
• the Tg exceeds 120°C
• the workability and elongation of the coating film will deteriorate, resulting in poor can manufacturing workability, and there is a risk that metal will be exposed during molding, resulting in the coating after molding.
• the residual stress increases, and there is a risk that the resistance to peeling of the coating film during heat treatment will deteriorate.
• a blend of two or more polyester resins with different Tg's can be used, and by blending polyester resins with different Tg's, impact resistance is improved compared to the case where only one polyester resin is used.
• the Tg mix of the polyester resin blend calculated by the following formula (7) should be within the above Tg range.
• Tg mix represents the glass transition temperature (K) of the polyester resin blend
• W1, W2, . . . , Wm represent the mass fraction of each polyester resin (polyester resin 1, polyester resin 2, .
• the number average molecular weight (Mn) of the polyester resin is not limited to this, but from the viewpoint of can manufacturing processability, preferably 1,000 to 100,000, more preferably 3,000 to 50,000, It is more preferably in the range of 5,000 to 20,000, particularly preferably in the range of 10,000 to 20,000. If it is smaller than the above range, the coating film may become brittle and may be inferior in can-making processability.
• the polyester resin is preferably an amorphous polyester resin from the viewpoint of can-making workability, dent resistance, and paintability.
• amorphous as used herein means that a crystalline component does not exhibit a distinct melting point in measurement with a differential scanning calorimeter (DSC).
• DSC differential scanning calorimeter
• the mass ratio of the amorphous polyester resin among all the polyester resin components contained in the inner coating film and/or the outer coating film is preferably higher than 40% by mass, preferably 50% by mass. %, more preferably 60% by mass or more, particularly preferably 70% by mass or more, most preferably 80% by mass or more.
• the coated metal sheet of the present invention and the inner coating film of seamless cans such as drawn and ironed cans are characterized by containing a resol-type phenolic resin and/or amino resin as a curing agent.
• the outer coating film described above contains an amino resin as a curing agent.
• the coating composition forming the inner coating film contains, as described above, the curing agent.
• the curing agent From the viewpoint of hygiene, resol-type phenolic resins and/or amino resins can be used, and in particular, resol-type phenolic resins can be more preferably used from the viewpoints of can-making workability, aroma adsorption resistance, and the like.
• An amino resin capable of forming a transparent coating film without coloration derived from a curing agent is preferably used for the coating composition forming the outer coating film (hereinafter sometimes referred to as "external coating composition”). can be done.
• the resol-type phenolic resin described above causes yellowing of the formed coating film, so care must be taken when using it in a coating composition for forming an external coating film.
• resol type phenolic resin examples include o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol, phenol, m-cresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol and other phenolic compounds are used in combination of one or more, and these phenolic compounds are reacted with formaldehyde in the presence of an alkali catalyst to produce a resol-type phenolic resin. can be used.
• a phenol compound that becomes trifunctional upon reaction with formaldehyde is used as a starting material in an amount of more than 20% by mass, preferably more than 30% by mass, more preferably more than 50% by mass, more preferably more than 50% by mass.
• phenolic compounds that become trifunctional by reaction with formalins include phenol, m-cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol, and one or more of these can be used. can be selected and used.
• the content of these trifunctional phenol compounds is 20% by mass or less, sufficient curability cannot be obtained, and the degree of curing of the coating film may decrease.
• m-cresol is more preferable from the viewpoint of curability.
• the main component is the one with the highest content (mass ratio) among the phenol compounds used as starting materials.
• the m-cresol-based resol-type phenolic resin preferably contains more than 50% by mass, preferably 60% by mass or more, more preferably 80% by mass or more of m-cresol as a starting material.
• the content is less than 70% by mass, preferably less than 50% by mass, more preferably 30% by mass. % is preferable. If it is 70% by mass or more, the curability may deteriorate.
• bifunctional phenol compounds include o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol and 2,5-xylenol.
• methylol groups are alkyl-etherified with alcohols having 1 to 12 carbon atoms (alkoxymethyl ) can be preferably used.
• the ratio of methylol groups to be alkyl-etherified is preferably 50% or more, more preferably 60% or more, and even more preferably 80% or more. If the ratio of alkyl etherification is less than 50%, the compatibility with the polyester resin becomes low, and 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.
• Preferred monohydric alcohols include methanol, ethanol, n-propanol, n- Examples include butanol and isobutanol, and n-butanol is more preferred.
• the number of alkyl-etherified methylol groups is preferably 0.3 or more, preferably 0.5 to 3, on average per phenol nucleus. be. If the number is less than 0.3, the curability with the polyester resin is inferior.
• the number average molecular weight (Mn) of the resol-type phenolic resin is preferably in the range of 500-3,000, preferably 800-2,500.
• the resulting coating film tends to have a high crosslink density, so that the residual stress after molding tends to increase, and the peeling resistance of the coating film may be deteriorated.
• the curability will be inferior, and as a result, there is a possibility that the heat resistance, corrosion resistance, retort whitening resistance, etc. of the coating film will be inferior.
• amino resins include methylolated compounds obtained by reacting amino components such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, and dicyandiamide with aldehyde components such as formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde.
• Amino resins may be mentioned.
• Amino resins obtained by alkyletherifying some or all of the methylol groups of this methylolated amino resin with alcohols having 1 to 12 carbon atoms are also included in the above amino resins. These can be used alone or in combination of two or more.
• Amino resins include methylolated amino resins using benzoguanamine (benzoguanamine resins), methylolated amino resins using melamine (melamine resins), and methylolated amino resins using urea from the viewpoint of hygiene and can-manufacturing processability. Resins (urea resins) are preferred, benzoguanamine resins and melamine resins are more preferred from the viewpoint of curability (reactivity with polyester resins), and benzoguanamine resins are most preferred from the viewpoints of resistance to coating peeling during heat treatment and retort whitening resistance. .
• Benzoguanamine resins include benzoguanamine resins obtained by alkyl-etherifying some or all of the methylol groups of benzoguanamine resins with alcohols such as methanol, ethanol, n-butanol and i-butanol, such as methyl-etherified benzoguanamine resins and ethyl-etherified benzoguanamine resins.
• a 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 are preferred.
• Melamine resins include melamine resins obtained by alkyl-etherifying some or all of the methylol groups of melamine resins with alcohols such as methanol, ethanol, n-butanol and i-butanol, such as methyl-etherified melamine resins and ethyl-etherified melamine resins.
• a 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, or a mixed etherified melamine resin of ethyl ether and butyl ether is preferred.
• Urea resins include urea resins obtained by alkyl-etherifying some or all of the methylol groups of urea resins with alcohols such as methanol, ethanol, n-butanol and i-butanol, such as methyl-etherified urea resins and ethyl-etherified urea. Resins, butyl-etherified urea resins, mixed etherified urea resins of methyl ether and butyl ether, mixed etherified urea resins of methyl ether and ethyl ether, and mixed etherified urea resins of ethyl ether and butyl ether are preferred.
• Examples of functional groups possessed by the melamine resin and benzoguanamine resin described above 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 cross-linking reactions with carboxyl groups (--COOH) and hydroxyl groups (--OH) contained in the polyester resin that is the main ingredient, or in self-condensation reactions between amino resins. , the imino group contributes only to the self-condensation reaction).
• the number of the melamine resin is considered to be larger than that of the melamine resin due to the molecular structure.
• the melamine resin is excellent in curability, the crosslink density of the coating film formed tends to be high, and depending on the blending amount, the coating film may peel off during heat treatment.
• the benzoguanamine resin is inferior to the melamine resin in curability, but the crosslink density of the formed coating film is less likely to increase, and it can be said to be more suitable than the melamine resin from the viewpoint of coating film peeling resistance.
• a mixed amino resin in which melamine resin and benzoguanamine resin are used in combination at a predetermined ratio may be used.
• the blending amount ratio (mass ratio) of the melamine resin and the benzoguanamine resin is 90:10 to 5:95, preferably 80:20 to 10:90, more preferably 80:20 to 20:80, still more preferably 75:25 to 25:75, particularly preferably 70:30 to 30:70.
• the curing agent is desirably 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 resol type phenolic resin as a curing agent, it is 1 to 30 parts by mass, preferably 1.5 to 20 parts by mass, more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the polyester resin (solid content) as the main agent.
• It is preferably blended in the range of 2 to 10 parts by weight, more preferably 2 to 10 parts by weight, most preferably 2.5 to 8.5 parts by weight.
• the amount of the melamine resin to be blended is preferably less than 10 parts by mass, preferably less than 5.5 parts by mass, per 100 parts by mass of the polyester resin.
• the amount is 0.1 parts by mass or more and less than 10 parts by mass, preferably 0.1 parts by mass or more and less than 5.5 parts by mass, more preferably 0.1 part by mass or more and less than 10 parts by mass, based on 100 parts by mass of the polyester resin. 5 to 5.4 parts by mass, more preferably 0.5 to 5 parts by mass, particularly preferably 0.5 to 4 parts by mass, most preferably 1 part by mass or more and less than 4 parts by mass.
• benzoguanamine resin When benzoguanamine resin is used as a curing agent, 4 to 40 parts by mass, preferably 5 to 30 parts by mass, more preferably 6 to 28 parts by mass, and still more preferably 7 to 25 parts by mass with respect to 100 parts by mass of polyester resin, Especially preferably 8 parts by mass or more and less than 25 parts by mass, most preferably 10 to 24 parts by mass.
• the amount is 2 to 25 parts by mass, preferably 2 to 20 parts by mass, more preferably 2 to 20 parts by mass, with respect to 100 parts by mass of the polyester resin. 5 to 15 parts by mass, more preferably 3 parts by mass or more and less than 10 parts by mass.
• the amount of the curing agent is less than the above range, sufficient curability cannot be obtained, the degree of cross-linking of the coating film becomes low, and the gel fraction (A) of the coating film becomes lower than the range described above.
• the heat resistance of the coating film is reduced, the coating film may easily stick to the mold when the seamless can is molded at high speed. Due to this, the can body may buckle or break, resulting in a decrease in productivity.
• an outer surface defect such as scraping of the coating film may occur.
• the amount of the curing agent is larger than the above range, the gel fraction (A) of the coating film may become higher than the range described above, and peeling of the coating film during heat treatment after molding of seamless cans cannot be suppressed. Otherwise, the coating film coverage of seamless cans may deteriorate.
• a curing catalyst it is preferable to incorporate a curing catalyst into 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.
• the curing catalyst conventionally known curing catalysts can be used, such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, phosphoric acid, alkylphosphoric acid, or amine neutralized products thereof.
• Organic sulfonic acid-based and phosphoric acid-based acid catalysts can be used.
• organic sulfonic acid-based acid catalysts are preferably used, and dodecylbenzenesulfonic acid and its amine-neutralized product are particularly suitable.
• the curing catalyst has a solid content of 0.01 to 3 parts by mass, preferably 0.01 to 1.0 parts by mass, more preferably 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the polyester resin. parts, more preferably 0.02 parts by mass or more and less than 0.3 parts by mass, and particularly preferably 0.02 parts by mass or more and less than 0.2 parts by mass.
• the amine-neutralized acid catalyst for example, the amine-neutralized dodecylbenzenesulfonic acid
• the content of the acid catalyst excluding the amine may be within the above range. If the content of the curing catalyst is less than the above range, the effect of accelerating the curing reaction may not be obtained sufficiently.
• the content of the curing catalyst is more than the above range, no further effect can be expected, and the water resistance of the coating film may decrease, resulting in deterioration of corrosion resistance, retort whitening resistance, etc. .
• the acid catalyst since the acid catalyst localizes on the surface of the metal substrate due to acid-base interaction, there is a risk that the adhesion between the coating film and the metal substrate will decrease, causing 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 sheet of the present invention contains at least the polyester resin described above as a main component and the curing agent described above, preferably the curing catalyst (acid catalyst) described above.
• the curing catalyst an acid catalyst
• the component with the highest content is defined as the main agent (main component).
• the content of the above-mentioned polyester resin, preferably the amorphous polyester resin, which is the main ingredient of all the resin components contained in the coating composition is higher than 50% by mass.
• the form of the coating composition that can be used for forming the coating film includes a solvent-based coating composition and a water-based coating composition.
• a solvent-based coating composition is preferred from the viewpoint of coating properties.
• the coating composition is a solvent-based coating composition
• it contains the above polyester resin, a curing agent, and an organic solvent as a solvent.
• the solvent-based coating composition in the present embodiment is a coating made by dissolving the main resin, curing agent, etc. in a known organic solvent, and the mass ratio of the organic solvent in the coating composition. is defined as a coating composition 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 When the coating composition is a water-based coating composition, it contains an aqueous medium as a solvent together with a conventionally known water-dispersible or water-soluble polyester resin and 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 an aqueous medium in the same manner as a 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 total aqueous medium in the aqueous coating composition. By containing the solvent in the above range, the film-forming performance is improved.
• an organic solvent those having amphipathic properties are preferable, and examples thereof include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, ethylene glycol, methyl ethyl ketone, butyl cellosolve, carbitol, butyl carbitol, and propylene glycol monopropyl.
• 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, 3-methyl-3-methoxybutanol and the like.
• the paint composition may contain a lubricant as necessary.
• the blending amount is 0.1 to 20 parts by mass, preferably 0.2 to 10 parts by mass, more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the polyester resin. is preferred.
• Lubricants that can be added to the coating composition include, for example, fatty acid ester waxes, which are esters of polyol compounds and fatty acids, silicone waxes, fluorine waxes such as polytetrafluoroethylene, polyolefin waxes such as polyethylene, and paraffin. Waxes, lanolin, montan wax, microcrystalline wax, carnauba wax, and silicon-based compounds, petroleum jelly, and the like can be mentioned. These lubricants can be used singly or in combination of two or more.
• the coating composition may also contain leveling agents, pigments, antifoaming agents, colorants, and the like, which have conventionally been blended in coating compositions, according to conventionally known formulations.
• other resin components may be contained in addition to the polyester resin as long as the object of the present invention is not impaired.
• 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 coating amount cannot be secured, resulting in poor coverage of the coating film. On the other hand, when the resin solid content is larger than the above range, workability and coatability may be inferior.
• the inner surface coating composition containing the polyester resin as the main agent and the resol-type phenolic resin and/or amino resin as the curing agent is applied to at least the inner surface of the metal plate. Apply so that it becomes a film thickness.
• the outer surface of the metal plate is further coated with the outer surface coating composition containing the polyester resin as the main agent and a curing agent, preferably an amino resin, so as to have the above-described film thickness.
• the baking conditions of the coating composition are appropriately adjusted depending on the type of polyester resin, curing agent, metal substrate, coating amount, etc., but the coating composition described above should be baked at a temperature of 150° C.
• a sufficient degree of curing C. to 350.degree. C., preferably higher than 200.degree. C. to 320.degree. If the baking temperature is lower than the above range, a sufficient degree of hardening may not be obtained. On the other hand, if the baking temperature is higher than the above range, the polyester resin may be thermally decomposed due to excessive heating. If the baking time is shorter than the above range, a sufficient degree of hardening may not be obtained, and if the baking time is longer than the above range, economy and productivity are poor.
• the inner coating film after baking has a gel fraction (A) of 55% or more and less than 90%. It is desirable that the difference in the fraction (B) is less than 10%, so that the residual stress of the coating film after processing can be sufficiently reduced, and peeling of the coating film during heat treatment can be effectively suppressed, and retort whitening resistance is improved. Seamless cans such as drawn and ironed cans with excellent resistance to embrittlement over time can be formed.
• At least the can inner surface side of the metal plate, preferably both sides, is coated by a known coating method such as roll coater coating, spray coating, or dip coating, and then the coating is performed by a heating means such as a coil oven. It can be manufactured by baking.
• a known coating method such as roll coater coating, spray coating, or dip coating
• a heating means such as a coil oven. It can be manufactured by baking.
• a coating film made of another coating composition may be formed depending on the conditions, but it is preferable not to form it from the viewpoint of economy.
• the outermost layer of the can inner surface side of the coated metal sheet used in the present invention is a coating film formed from a coating composition, preferably the inner coating film made of the above-mentioned inner surface coating composition, or the inner surface It is desirable that the layer is formed of a wax-based lubricant, which will be described later, formed on the coating film.
• the outermost layer of the can outer surface side of the coated metal sheet used in the present invention is a coating film formed from a coating composition, preferably the outer surface coating film composed of the above-described exterior coating composition, Alternatively, it is preferably a layer formed on the outer surface coating film and made of a wax-based lubricant, which will be described later.
• the inner coating film and the outer coating film made of the coating composition described above have excellent adhesion to the metal substrate, so that the inner coating film and/or the outer coating film are formed on the metal substrate. It is preferable that it is formed so as to be in direct contact with the certain metal plate.
• the inner coating film located on the inner surface side of the can has the same characteristics as the inner coating film of the above-mentioned coated metal plate, that is, the polyester resin and the curing agent It contains a resol-type phenol resin and/or amino resin, and the gel fraction (A) represented by the above formula (1a) of the inner coating film is 55% or more and less than 90%, preferably 60 to 88%, more preferably is more than 62% and less than 85%, more preferably 65-84%, particularly preferably 65-80%, and most preferably 68% or more and less than 78%.
• the inner coating film containing the polyester resin and the resol-type phenol resin and / or amino resin as a curing agent is represented by the above formula (1a).
• the gel fraction (A) is within the above range, it is possible to achieve both retort whitening resistance, embrittlement resistance over time, and paint film peeling resistance during heat treatment. Further, from the viewpoint of retort whitening resistance, the difference between the gel fraction (A) represented by the above formula (1a) and the gel fraction (B) represented by the above formula (2a) of the inner coating film is Less than 10% is desirable.
• the gel fraction (B) is higher than 45% and 99% or less, preferably higher than 50% and lower than 98%, more preferably higher than 52% and lower than 95%, still more preferably 55 to 94%, particularly preferably It should be in the range of 55-90%, most preferably 58% or more and less than 88%.
• the seamless can further has an outer coating film on the outer surface side of the can, and that the outer coating film also contains a polyester resin, preferably an amino resin as a curing agent.
• the gel fraction (A) represented by the formula (3a) of the outer coating film is 40% or more and less than 90%, preferably 55% or more and less than 90%, more preferably 60% or more and 88% or less, More preferably 65-85%, particularly preferably 68-84%, and most preferably 70-84%.
• the difference between the gel fraction (A) represented by the above formula (3a) and the gel fraction (B) represented by the following formula (4a) of the outer coating film is Less than 10% is desirable.
• the gel fraction (B) is higher than 45% and 99% or less, preferably higher than 50% and lower than 98%, more preferably higher than 52% and lower than 95%, still more preferably 55 to 94%, particularly preferably It should be in the range of 55-90%, most preferably 58% or more and less than 88%.
• the gel fractions (A) and (B) in the coating film of the seamless can are not limited to these, but are measured, for example, from the inner coating film and/or the outer coating film located at the center of the bottom of the seamless can. be able to.
• the center portion of the can bottom of a seamless can is a portion that is relatively less processed in forming a seamless can and has a thickness similar to that of the coated metal plate used for forming.
• the can bottom portion and the can body portion on the inner surface side of the can are continuously coated 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 preferably coated with the above-mentioned It is preferably continuously coated with the outer coating.
• a second feature of the seamless can of the present invention is that the thickness of the inner coating film at the central portion of the can body is 20 to 75% of the thickness of the inner coating film at the central portion of the can bottom.
• the seamless can of the present invention is a drawn and ironed can (DI can), a drawn can (DR can), a deep drawn can (DRD can), and is formed by a conventionally known manufacturing method using the above-described coated metal sheet. ), DTR cans, stretch-drawn and ironed cans, etc.
• drawn and ironed cans are particularly preferred.
• the thickness of the inner coating film located on the can body is reduced by processing to the same thickness as the metal substrate, and the center of the can body (high
• the thickness of the inner coating film in the central part of the can is in the range of 20 to 75% of the thickness of the inner coating film in the central part of the can bottom, which is hardly thinned during can manufacturing. preferably 20 to 60%, more preferably 20 to 50%, still more preferably 25 to 45%, particularly preferably 30 to 45%, most preferably 30 to 40%, especially in drawn and ironed cans. Thickness is preferred.
• the thickness of the outer coating film is 20 to 75% of the thickness of the outer coating film at the center of the can body (central part in the height direction, the thinnest part). is preferably in the range of 20 to 60%, more preferably 20 to 50%, even more preferably 25 to 45%, particularly preferably 30 to 45%, most preferably 30 to 45%, especially in drawn and ironed cans. A thickness of 30-40% is preferred.
• the thickness of the inner coating film at the thinnest portion of the can body is greater than the thickness of the inner coating film at the thickest portion (not thinned portion) of the can body. It is preferably in the range of 80% or less, particularly in a drawn and ironed can, preferably 70% or less, more preferably 60% or less, and even more preferably 55% or less. Furthermore, the thickness of the outer coating film at the thinnest portion of the can body is 80 times the thickness of the outer coating film at the thickest portion (not thinned portion) of the can body. % or less, and particularly in a drawn and ironed can, it is preferably 70% or less, more preferably 60% or less, and even more preferably 55% or less.
• the thickness of the metal substrate at the center of the can bottom of the seamless can 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. A thickness of ⁇ 0.28mm is preferred.
• the type of metal substrate is the same as that of the coated metal plate used for molding.
• the film thickness of the inner coating film at the center of the can bottom of the seamless can is the same as the film thickness described above for the coated metal plate used for molding, and is 0.2 to 20 ⁇ m, preferably 1 to 16 ⁇ m, more preferably 1 to 16 ⁇ m. It is preferably in the range of greater than 2 ⁇ m and less than or equal to 12 ⁇ m.
• the dry coating mass is 3 to 300 mg/dm 2 , preferably 15 to 220 mg/dm 2 , more preferably 15 to 150 mg/dm 2 , more preferably greater than 25 mg/dm 2 and less than or equal to 150 mg/dm 2 . It is preferable to be in
• the film thickness of the inner coating film at the center of the can bottom is greater than 5 ⁇ m and 16 ⁇ m or less, preferably greater than 6 ⁇ m and 12 ⁇ m or less, more preferably. It is preferably in the range of 6.5-10 ⁇ m.
• the dry coating mass is preferably in the range of 70 mg/dm 2 to 150 mg/dm 2 , preferably 85 mg/dm 2 to 150 mg/dm 2 , more preferably 90 to 140 mg/dm 2 . is.
• the film thickness of the inner coating film at the center of the can bottom is 1 ⁇ m or more and less than 6.5 ⁇ m, preferably more than 2 ⁇ m. It is preferably less than 6.5 ⁇ m, more preferably in the range of 2.5-6 ⁇ m.
• the dry coating mass is 15 mg/dm 2 or more and less than 90 mg/dm 2 , preferably more than 25 mg/dm 2 and less than 90 mg/dm 2 , more preferably 30 to 85 mg/dm 2 . be.
• the dry film thickness of the outer coating film at the center of the can bottom is 0.2 to 20 ⁇ m, preferably 1 to 16 ⁇ m, more preferably greater than 2 ⁇ m and 12 ⁇ m or less, further preferably greater than 2 ⁇ m and 6.5 ⁇ m or less. is preferably in the range of The dry coating mass is 3 to 300 mg/dm 2 , preferably 15 to 220 mg/dm 2 , more preferably 25 to 150 mg/dm 2 , still more preferably greater than 25 mg/dm 2 and less than 90 mg/dm 2 . is preferred.
• the seamless can of the present invention can be produced by a conventionally known molding method using the coated metal sheet of the present invention.
• the coated metal sheet of the present invention has excellent paint film coverage without metal exposure without causing breakage or peeling of the paint film at the end of the can even during severe processing such as drawing and ironing.
• Seamless cans such as excellent drawn and ironed cans can be formed.
• the coated metal sheet of the present invention is excellent in formability and lubricity, it can be used not only when using coolant but also when forming under dry conditions without using coolant. Seamless cans can be formed. The method for manufacturing the drawn and ironed can is described in detail below.
• wax-based lubricants include, but are not limited to, fatty acid ester wax, silicon-based wax, white petrolatum, rice wax, beeswax, Japan wax, mineral-derived waxes such as montan wax, Fischer-Tropsch wax, polyethylene and polypropylene.
• wax-based lubricants can be used singly or in combination of two or more.
• a temperature of 100 to 350 ° C. preferably 150 to 250 ° C., more preferably about 200 ° C.
• a wax-based lubricant high-temperature volatile wax-based lubricant that volatilizes at least 50% by mass in a heat treatment (heating) for 10 to 180 seconds
• a wax-based lubricant that volatilizes at least 50% by mass in a heat treatment (heating) for 10 to 180 seconds
• the wax-based lubricant can be easily volatilized and removed by heat treatment, and when printing is applied to the outer surface of a can body, there is no risk of the ink being repelled by the wax-based lubricant, which is desirable in terms of suitability for printing on the outer surface.
• a short-time (10 to 180 seconds) heat treatment at a temperature of 150 to 250° C., preferably about 200° C. is 50% by mass or more, preferably 60% by mass or more, more preferably Desirably, 80% by mass or more, more preferably 90% by mass or more can be removed by volatilization, and the melting point is 20 to 100°C, preferably 25 to 80°C.
• the coating amount of the wax-based lubricant is 1 to 1000 mg/m 2 , preferably 2 to 500 mg/m 2 , more preferably 5 to 200 mg/m 2 per side of the coated metal plate from the viewpoint of moldability and productivity.
• the drawing ratio RD defined by the following formula (8) is in the range of 1.1 to 2.6 in total (up to the drawing and ironing can), especially in the range of 1.4 to 2.6. is desirable. If the drawing ratio is higher than the above range, drawing wrinkles may increase, cracks may occur in the coating film, and the metal may be exposed.
• RD D/d (8) In the formula, D represents the blank diameter and d represents the can body diameter.
• the drawn cup is subjected to redrawing and one-step or several-step ironing (drawing and ironing) to thin the can body.
• the temperature of the forming punch is preferably adjusted to 10 to 100.degree. C., preferably 10 to 80.degree. C., more preferably 15 to 70.degree. If the forming punch temperature is lower than the above range, the wax-based lubricant applied to the coated metal sheet may not exhibit sufficient lubricity, and stripping may be poor when the can body is removed from the forming punch. In addition, there is a possibility that the elongation of the inner coating film is lowered, and the coating film coverage after molding is lowered.
• the drawing rate R represented by the following formula (9) is 25 to 80%, preferably 40 to 80%, more preferably 50 to 80%, still more preferably 55 to 75%, particularly preferably It should be in the range of 55-70%, most preferably greater than 60% and less than or equal to 70%.
• R (%) (tp-tw)/tp x 100 (9)
• tp represents the thickness of the original coated metal plate
• tw represents the thickness of the central portion of the can body of the drawn and ironed can.
• the thickness of the central part of the can body (the central part in the height direction, the thinnest part) is 20 to 75%, preferably 20 to 75%, of the thickness of the central part of the can bottom. 60%, more preferably 20 to 50%, still more preferably 25 to 45%, particularly preferably 30 to 45%, and most preferably 30 to 40%.
• the thickness of the metal substrate of the drawn and ironed can is 20 to 75%, preferably 20 to 60%, more preferably 20 to 75% of the thickness of the metal substrate at the center of the can bottom.
• a thickness of 50%, more preferably 25-45%, particularly preferably 30-45%, most preferably 30-40% is suitable.
• the thickness of the coating film located on the body of the can becomes as thin as the metal base due to the working. Therefore, as described above, the thickness of the coating film in the central part of the can body is 20 to 75%, preferably 20 to 60%, more preferably 20% of the thickness of the coating film in the central part of the can bottom, which is hardly thinned during can manufacturing.
• a thickness of ⁇ 50%, more preferably 25-45%, particularly preferably 30-45%, most preferably 30-40% is suitable.
• the thickness of the thinnest portion of the can body is 80% or less of the thickness of the thickest portion (the least thinned portion) of the can body, preferably It is suitable that the thickness is 70% or less, more preferably 60% or less, still more preferably 55% or less.
• the thickness ratio of the inner coating film to the metal substrate in the can body is the same regardless of the position of the can body. It is characterized by being substantially the same throughout the trunk. The same applies to the outer coating film.
• the processing speed (moving speed of the punch) of the one-stage or several-stage ironing process is 2000 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 Preferably, it should be 6000 mm/sec or more.
• molding at a high temperature can further reduce the residual stress of the coating film after molding, which is also preferable for suppressing peeling of the coating film during heat treatment.
• doming of the bottom and trimming of the opening edge are performed according to conventional methods.
• the resulting seamless can such as a drawn and ironed can is preferably subjected to a heat treatment step.
• the above-mentioned gel fraction (A) of the coating film is controlled to be less than 90%, so even when heated in the heat treatment process , peeling of the paint film is effectively prevented.
• the residual stress of the coating film caused by processing can be removed.
• the heat treatment temperature must be higher than the glass transition temperature of the coating film, preferably in the range of 100 to 300°C, preferably 150 to 250°C.
• the heat treatment time is not particularly limited, but it is preferable to heat for 0.1 to 600 seconds, preferably 1 to 300 seconds, more preferably 10 to 180 seconds.
• the coating film at the central part of the can body (central part in the height direction), which is highly processed, can be isolated from the metal substrate and heated. Since the dimension changes greatly in the direction in which the stress is released (mainly in the height direction of the can), the residual stress is removed by heat treatment by measuring the amount of dimensional change (thermal shrinkage) of the isolated coating film due to heating. It can be used as a measure of whether the The heat shrinkage rate (with load) represented by the following formula (5) in the inner coating film on the central part of the can body isolated from the seamless can is 30% or less, preferably 25% or less, more preferably 20% or less.
• the thermal shrinkage ratio (without load) represented by the following formula (6) is 50% or less, preferably 45% or less, and more preferably 40% or less.
• the thermal shrinkage ratio is within the above range, the coating film adhesion is improved, and excellent corrosion resistance can be exhibited. If the heat shrinkage rate is larger than the above range, the residual stress may not be sufficiently removed and the coating adhesion may be insufficient, resulting in a decrease in corrosion resistance. The film may peel off. Further, in the case where the outer surface coating film is provided on the outer surface of the can, it is desirable that the heat shrinkage ratio of the outer surface coating film at the center of the can body is also within the above range.
• the amount of dimensional change (amount of shrinkage) due to heating of the isolated coating film can be measured using a thermomechanical analyzer (TMA) or the like.
• Thermal shrinkage rate (with load) ( ⁇ L 1 /L 0 ) x 100 (%) (5)
• L 0 is the initial length in the height direction of the coating film isolated from the central part of the can body (measurement part)
• ⁇ L 1 is the load of 5.20 ⁇ 10 5 N / m 2 per unit area
• It is the maximum amount of shrinkage (maximum value of shrinkage length) in the height direction of the coating film of the portion corresponding to L0 when the temperature is increased from 30°C to 200°C at a temperature increase rate of 5°C/min.
• Thermal contraction rate (without load) ( ⁇ L 2 /L 0 ) x 100 (%) (6)
• L 0 is the initial length in the height direction of the coating film isolated from the center of the can body (measurement part)
• ⁇ L 2 is the temperature increase rate of 5 ° C./min under no load from 30 ° C. to 200 ° C. This is the maximum amount of shrinkage (maximum value of shrinkage length) in the height direction of the coating film at the portion corresponding to L0 when the temperature is raised.
• the can body After the heat treatment, the can body is quenched or left to cool, and if necessary, a printing layer is formed on the can body by a conventionally known method, and a finishing varnish layer is formed on the printing layer to protect the printing layer. It is formed. If desired, it is subjected to one-step or multi-step neck-in processing and flange processing to form a can for seaming. Also, after forming a seamless can such as a drawn and ironed can, the upper part can be deformed into a bottle shape, or the bottom part can be cut off and another can end can be attached to form a bottle shape.
• the capacity of the seamless can such as the drawn and ironed can of the present invention is preferably 150 mL or more, preferably 150 to 2200 mL, more preferably 180 to 1200 mL, and still more preferably 300 to 700 mL.
• the inner coating film of the coated metal sheet of the present invention has excellent can-making workability, it can suppress the occurrence of metal exposure even during severe processing such as drawing and ironing, and the coating can be applied even during heat treatment after forming.
• the inner coating film has a coverage of less than 200 mA in terms of ERV (Enamel Rate Value). It is possible to obtain a seamless can such as a drawn and ironed can having excellent coating film coverage.
• the coverage of the inner coating film obtained by ERV conversion was obtained by filling the obtained drawn and ironed can with a salt solution having a concentration of 1% by mass as an electrolytic solution to the vicinity of the can mouth, and measuring the ERV with an enamel meter.
• 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 a voltage of 6.3 V is applied at room temperature (20°C). is the current value after applying the DC voltage for 4 seconds.
• the more current flows the more defects are present 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 ERV-equivalent coverage of the inner coating film of seamless cans such as drawn and ironed cans is desirably less than 200 mA, preferably less than 100 mA, and more preferably less than 50 mA.
• the ERV per unit area (cm 2 ) is preferably less than 0.70 mA/cm 2 , preferably less than 0.35 mA/cm 2 , more preferably less than 0.18 mA/cm 2 .
• the ERV per unit area is the value obtained by dividing the ERV of the seamless can measured by the above method by the evaluation area (the total area where the inner surface of the can body and can bottom is in contact with the above saline solution). is.
• the inner surface of a seamless can such as a drawn and ironed can after molding, if necessary, the inner surface may be further spray-coated with a correction paint or the like to form another coating film on the inner coating film.
• the inner coating film since the inner coating film has a high degree of coverage even after molding, it is not necessary to spray coat, and from the economical point of view, it is preferable not to spray coat.
• the outermost layer on the inner surface side of the drawn and ironed can of the present invention is a coating film composed of a coating composition, preferably the inner coating film composed of the above-described inner coating composition, or the inner coating film described above. It is preferably an applied layer of wax-based lubricant, more preferably the inner coating.
• the outermost layer of the outer surface of the can bottom is a coating film made of a coating composition, preferably the outer coating film, or a layer of a wax-based lubricant applied on the outer coating film, more preferably It is desirable that the outer coating film is positioned on the outermost layer of the bottom of the can.
• the coated metal sheet of the present invention can be used for drawn and ironed cans by severe forming, it can be used for purposes other than drawn and ironed cans, such as drawn cans (DR cans), deep drawn cans (DRD cans), It can be suitably applied to DTR cans, seamless cans such as stretch-drawn and ironed cans, and can lids.
• the shape of the can lid can adopt a conventionally known shape such as an easy-open lid provided with a score for forming an opening for pouring out the contents and a tab for opening. (stay-on-tab type).
• polyester resins A to D are all amorphous polyester resins.
• NACURE 5925 manufactured by King Industries, amine-neutralized dodecylbenzenesulfonic acid solution, 25% by mass of active ingredient
• An n-butanol solution of a resol-type phenolic resin (solid content: 50% by mass) was diluted with methyl ethyl ketone to obtain a resole-type phenolic resin solution with a solids content of 25% by mass.
• a butanol solution of benzoguanamine resin A (solid content: 70% by mass) was dissolved in methyl ethyl ketone to obtain a benzoguanamine resin solution with a solid content of 25% by mass.
• 400 parts of polyester resin B solution solid content: 100 parts
• 60 parts of benzoguanamine resin solution solid content: 15 parts
• 0.4 parts of acid catalyst solution solid content: 0.10 parts
• a chromate phosphate-based surface-treated aluminum plate (3104 alloy, plate thickness: 0.27 mm) was used as the metal plate .
• the external surface coating composition was applied with a bar coater to a thickness of about 3 ⁇ m) and dried at 120° C. for 60 seconds.
• the inner surface coating composition was applied to the opposite inner surface side with a bar coater so that the dry coating mass after baking was 88 mg/dm 2 (about 6.4 ⁇ m). After drying for a second, baking was performed for 30 seconds at 250° C. (the temperature inside the oven).
• paraffin wax which is a high-temperature volatile wax-based lubricant (which can be volatilized and removed by 50% by mass or more by short-time heat treatment at a temperature of about 200 ° C.) is applied ( Application amount: about 50 mg/m 2 per side), and punched into a circular shape with a diameter of 142 mm to form a shallow drawn cup.
• the shallow-drawn cup was subjected to redrawing, ironing (three steps), and doming under dry conditions using a punch (with temperature control) having an outer diameter of ⁇ 66 mm. After that, heat treatment is performed at 201° C.
• Examples 2 to 10, Comparative Examples 1 to 5 As shown in Table 1, except for changing the composition of the inner surface coating composition and the outer surface coating composition (type of polyester resin, type of curing agent, solid content blending ratio of polyester resin / curing agent / acid catalyst) A coated metal plate was produced in the same manner as in Example 1, and a drawn and ironed can was produced.
• benzoguanamine resin B mixed etherified benzoguanamine resin of methyl ether and ethyl ether, full ether type
• melamine resin methyl etherified melamine resin, full ether type
• p-cresol-based resol-type phenolic resin a resol-type phenolic resin containing p-cresol as the main component of the starting material
• the properties of the coating film obtained from the inner surface coating composition used in each example and comparative example were tested according to the following test method.
• a test piece having a size of 5 cm ⁇ 5 cm was cut out from the coated metal plate and immersed in a diluted hydrochloric acid aqueous solution to dissolve the aluminum plate (metal base). Then, the film-like isolated coating film was taken out, sufficiently washed with distilled water and dried, and this was used as an isolated coating film sample for measurement. After measuring the mass (W1) of the sample, the sample was immersed in 30 ml of MEK (methyl ethyl ketone) at room temperature (about 20°C) for 1 hour. After that, remove the solvent-insoluble portion of the sample (MEK-insoluble portion) onto an aluminum petri dish, dry it under the conditions of 120 ° C for 30 minutes, and cool it to room temperature.
• MEK methyl ethyl ketone
• An isolated coating film sample for measurement can be obtained by dissolving the metal substrate by the above method or the like.
• a test piece is cut out from a coated metal plate or the bottom of a drawn and ironed can, soaked in boiled hydrogen peroxide water for several minutes, thoroughly washed with distilled water, and then peeled off the film-like coating from the metal substrate. It can also be taken and dried and used as an isolated coating sample for measurement.
• Gel fraction (A) of can bottom inner surface coating film For the drawn and ironed cans of Examples 2 and 3 after molding as described in the above section "Preparation of drawn and ironed cans" and heat treatment at 201 ° C. for 75 seconds, the gel fraction of the can bottom inner coating film (A) was measured. The average processing speed during the ironing process (average moving speed of the punch during the ironing process) was about 5500 mm/sec. A method for preparing an isolated coating film sample for measurement is as follows.
• a 5 cm x 5 cm size test piece is cut out from the coated metal plate, and after measuring the weight of the test piece (W3), 400 ml of MEK (methyl ethyl ketone) is used, and the test piece is placed in boiling MEK (under reflux at 80 ° C.) for 1 hour. It was soaked and MEK extracted for 1 hour at the boiling point. After washing the extracted test piece with MEK, it was dried at 120° C. for 30 minutes, and the mass (W4) of the extracted test piece was measured. Further, the coating film was peeled off and removed by a decomposition method with concentrated sulfuric acid, washed and dried, and the mass (W5) of the test piece was measured.
• MEK methyl ethyl ketone
• coated metal plates and drawn and ironed cans obtained in each example and comparative example were evaluated according to the following test methods.
• Retort whitening resistance evaluation-2 (drawn and ironed can) was formed as described in the above section "Production of drawn and ironed can", and after heat treatment at 201 ° C. for 75 seconds, the drawn and ironed can was evaluated as follows. I went to the street of The average processing speed during the ironing process (the average moving speed of the punch during the ironing process) was about 1000 mm/sec. 300 ml of water was poured into the can, which was placed in an autoclave and subjected to retort treatment at 125° C. for 30 minutes.
• Retort whitening resistance of the drawn and ironed can of Example 3 ⁇ Retort whitening resistance of the drawn and ironed can of Example 9: ⁇ Retort whitening resistance of the drawn and ironed can of Comparative Example 2: ⁇ Retort whitening resistance of the drawn and ironed can of Comparative Example 3: ⁇
• Coated metal sheets for evaluation were prepared as follows using the inner surface coating compositions used in Examples and Comparative Examples. Each phosphoric acid chromate-based surface-treated aluminum plate (3104 alloy, plate thickness: 0 .27 mm), dried at 120° C. for 60 seconds, and then baked at 250° C. for 30 seconds to prepare a coated metal plate for evaluation. This coated metal plate is cut into a size of 3.5 ⁇ 3 cm so that the rolling direction of the aluminum plate is the long side, and the short side is so that the surface coated with the coating composition for the inner surface of the test piece is outside.
• Evaluation criteria for both initial workability and aging workability are as follows. Table 1 shows the results. ⁇ : Less than 0.4 mA ⁇ : 0.4 mA or more and less than 1.0 mA ⁇ : 1.0 mA or more and less than 2.5 mA ⁇ : 2.5 mA or more
• a metal exposed portion was formed on the outer surface of the can bottom of the drawn and ironed can, and the can body was connected to the anode of the enamelrator. After immersing it in a saline solution and applying a voltage of 6.3 V for 4 seconds at room temperature (approximately 20° C.), the current value (ERV) was measured. Evaluation criteria are as follows. Table 1 shows the results.
• ⁇ 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)
• Heat shrinkage rate evaluation The evaluation of the heat shrinkage rate was performed on the drawn and ironed can (without heat treatment) of Example 3, which was subjected to drawing and ironing and doming as described in the above section "Production of drawn and ironed cans", and then 201 in an oven.
• the inner coating film on the central part of the can body of the drawn and ironed can (with heat treatment) of Example 3 after heat treatment at °C for 75 seconds the following procedure was carried out.
• the average processing speed during the ironing process (average moving speed of the punch during the ironing process) was about 5500 mm/sec.
• a sample of 10 mm in the circumferential direction of the can body and 20 mm in the can height direction is centered on the center of the can body (the thinnest portion) in the 0° direction with respect to the rolling grain of the metal substrate. cut out.
• the can was immersed in a diluted hydrochloric acid aqueous solution to dissolve the metal substrate.
• the film-like coating on the inner surface of the can is taken out, thoroughly washed with distilled water and dried, and the obtained film-like coating is 4 mm wide (circumferential direction of the can body) and 20 mm long (can height). direction) to obtain a sample for measurement.
• the sample for measurement was chucked in a thermomechanical analyzer so that the chuck-to-chuck distance (corresponding to the initial length of the measurement portion in the height direction of the coating film) was 5 mm.
• the amount of displacement of the measurement sample was measured under the following conditions, and the heat shrinkage rate in the can height direction was evaluated with and without load.
• Apparatus TMA/SS6100 manufactured by Seiko Instruments Inc. Heating rate: 5°C/min Temperature range: 30-200°C Measurement mode: tension mode Load during measurement: 5 mN (5.20 ⁇ 10 5 N/m 2 ) or no load Distance between chucks: 5 mm
• the distance between the chucks before measurement (corresponding to the initial length of the measurement part of the coating film) is L 0 , and the temperature is raised to 30°C at a rate of 5°C/min while applying a load of 5.20 ⁇ 10 5 N/m 2 per unit area.
• ⁇ L 1 is the maximum amount of shrinkage (maximum shrinkage length) in the height direction of the portion corresponding to L 0 when the temperature is raised from 1 to 200 ° C
• the value calculated by the formula shown in the following formula (5) is Shrinkage rate (with load).
• contraction was taken as a positive value, and expansion or elongation as a negative value. The results are shown below.
• Thermal shrinkage rate (with load) ( ⁇ L 1 /L 0 ) x 100 (%) (5) Heat shrinkage rate (with load) of the inner coating film of the drawn and ironed can (without heat treatment) of Example 3: 66% Heat shrinkage rate (with load) of the inner coating film of the drawn and ironed can (with heat treatment) of Example 3: 18%
• L 0 is the distance between chucks before measurement (corresponding to the initial length of the measurement part of the coating film), and L 0 corresponds to when the temperature is raised from 30 ° C. to 200 ° C. at a heating rate of 5 ° C./min in a no-load state.
• the maximum amount of shrinkage (maximum shrinkage length) in the height direction of the part was defined as ⁇ L2 , and the value calculated by the following formula (6) was defined as the thermal shrinkage rate (without load).
• contraction was taken as a positive value, and expansion or elongation as a negative value. The results are shown below.
• Example 3 The evaluation of corrosion resistance was performed on the drawn and ironed can (without heat treatment) of Example 3, which was subjected to drawing and ironing and doming as described in the section "Production of drawn and ironed can" above, and then at 201 ° C. in an oven. After heat treatment for 75 seconds, the inner surface coating film on the central portion of the can body of the drawn and ironed can (with heat treatment) of Example 3 was treated as follows. The average processing speed during the ironing process (average moving speed of the punch during the ironing process) was about 5500 mm/sec.
• test piece of 40 mm in the can body circumferential direction and 40 mm in the can height direction was cut out centering on the can body central portion (thinned portion).
• a 4 cm-long cross-cut scratch was made on the test piece with a cutter to reach the base material, and the test piece was immersed in an acidic model solution containing salt and aged at 37°C for 2 weeks to evaluate the state of corrosion.
• the model solution used in the test was prepared by adding 0.2% sodium chloride and adding citric acid to adjust the pH to 2.5.
• Table 1 shows the formulation of the internal coating composition and external coating composition of each example and comparative example (type of polyester resin, type of curing agent, solid content blending ratio), coating of internal coating film and external coating film Membrane properties (gel fraction (A), gel fraction (B)) and evaluation results are shown.
• the seamless can such as a drawn and ironed can of the present invention has a coating film that is excellent in retort whitening resistance and embrittlement resistance over time, does not peel off the coating film during heat treatment, and effectively prevents metal exposure. Since it has coating film coverage and corrosion resistance, it can be suitably used for filling food and drink that require retort sterilization as contents. Also, the coated metal sheet for seamless cans of the present invention has a coating film that is excellent in retort whitening resistance, embrittlement resistance over time, and coating film peeling resistance that does not cause coating film peeling even during heat treatment after molding. Therefore, it can be suitably used for producing seamless cans such as drawn and ironed cans filled with food and drink that require retort sterilization as contents.

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• 2022
  • 2022-08-02 TW TW111128955A patent/TW202321029A/zh unknown
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