FR2571659A1 - Method of producing a metal sheet coated with a polyester resin film and product obtained - Google Patents

Abstract

The invention relates to a method for producing a metal sheet coated with a polyester resin film. The method consists in laminating a polyester resin film with biaxial orientation which has previously been uniformly coated with a small quantity of an epoxy resin containing an appropriate crosslinking agent, onto a metal sheet covered with a double layer comprising an upper layer of hydrated chromium oxide and a lower layer of chromium metal, this metal sheet having been heated to a temperature of approximately 220 DEG C at a value less than the melting point of the polyester resin film, under conditions in which the surface of the polyester resin film previously coated with an epoxy resin containing the crosslinking agent for the epoxy resin is in contact with the metal sheet. This metal sheet coated with a polyester resin film has excellent corrosion resistance and has excellent adherence of the polyester resin film to the metal sheet after forming under demanding conditions.

Description

 The present invention relates to a method for producing a metal sheet coated with a biaxially oriented polyester resin film. The method comprises laminating the epoxy resin-coated epoxy resin-containing resin film to a double-layered metal sheet comprising an upper layer of chromium oxide hydrate and a lower chromium layer. metal, said metal foil having been heated at a temperature of 2200C to a value below the melting point of the polyester resin film just prior to lamination of the polyester resin film, under conditions in which the side of the polyester resin film previously epoxy resin coating containing an epoxy resin crosslinking agent is in contact with the metal sheet.

 At present metal sheets laminated with an organic resin film are widely used in various fields such as electrical components, furniture and building materials. In general, there are two well-known methods for the continuous lamination of an organic resin film to the surface of the metal sheet.

The first method is a method in which a metal sheet coated with an adhesive is used.

More particularly, the adhesive in which a thermosetting resin is mainly dissolved in a solvent is first applied to the surface of the metal sheet. After crosslinking the adhesive, the organic resin film is laminated to the surface of the metal foil and then heated in a high heat capacity oven for several minutes.

Then, the metal sheet laminated with the organic resin film is cooled.

 The second method is a method in which an organic resin film coated with an adhesive is used. In this case, the organic resin film is laminated on the surface of the metal foil, then it is also heated in the same type of oven as in the first process.

 However, the metal foil laminated with the organic resin film can not be produced at high speed by these methods because a long time is required for the crosslinking of the adhesive and for heating after lamination of the organic resin film. In some cases, the characteristics of the organic resin film are impaired by prolonged heating, and the laminated organic resin film can peel off the surface of the metal foil under severe forming, because the formability of the adhesive is not good.

 Recently, a method of laminating a biaxially oriented polyester resin film to an adhesive-free metal sheet such as a thermosetting resin has been proposed in United States Patent Application No. 398,694 filed July 15, 1982. This method comprises laminating a biaxially oriented polyester resin film to the metal sheet which is heated to a temperature above the melting point of said polyester resin film and to be cooled immediately thereafter. This process is suitable for the continuous lamination of the polyester resin film to the high speed metal foil because a sufficient bond strength of the polyester resin film to the metal foil is achieved by short term heating. applications, the metal sheet laminated with a polyester resin film obtained by this process is heated again at a temperature of 160 to 2000C for about 10 to 30 minutes, because a color printing or varnishing on the other side of the metal sheet with which the polyester resin film is laminated, is carried out before forming. In this case, a part of the polyester resin film can peel off in a shaped area under severe conditions after a water treatment hot or hot steam, because a layer of amorphous polyester resin formed at the interface between the bi-oriented polyester resin film axial and the metal foil by heating to a temperature above the melting point of the polyester resin film is recrystallized by a new long-term heating at a temperature of 160 to 2000C. Therefore, the metal sheet laminated with the polyester resin film produced by this process is not used to an extent sufficient for applications in which lacquer coating or color printing is required.

 In addition, a resin film of the type of a copolymerized polyester is used for lamination with an adhesive-free metal sheet such as a thermosetting resin, in Japanese Patent Application No. Sho 57-22750. However, this resin film is only used for this limited application, because this film is expensive compared to an epoxy-type phenolic lacquer which is widely used in the industry of can making.

 Furthermore, in the can manufacturing industry, the application of high speed varnish layer on the metal foil has been studied in order to reduce the cost price. However, such a process is too difficult to implement industrially, because a varnish that can be crosslinked by heating for a few seconds has not yet been developed. In addition, the corrosion resistance after severe forming of the lacquer-coated metal sheet is low, compared to that of the metal sheet laminated with an organic resin film.

 Accordingly, the first object of the present invention is to find a metal sheet coated with a biaxially oriented polyester resin film having excellent adhesion of the polyester resin film to the metal sheet and excellent corrosion resistance in an area. shaping under severe conditions even after treatment with hot water or hot steam, especially in the shaped part after reheating for the maturation of the color printing ink or a varnish at a temperature of 160 to 200 ° C for a long time, compared to that of the lacquer coated metal sheet and other metal sheets laminated with an organic resin film.

 The second object of the present invention is to find a method of continuously laminating a biaxially oriented polyester resin film to the surface of the metal foil at high speed.

 The first object of the present invention can be achieved by forming double layers consisting of an upper layer of a biaxially oriented polyester resin film and a lower layer of a thin layer of epoxy resin containing a crosslinking agent. for epoxy resin on the double layer coated metal sheet consisting of an upper layer of chromium oxide hydrate and a lower layer of metallic chromium.

 The second object of the present invention can be realized by the continuous lamination of a biaxially oriented polyester resin film pre-coated with epoxy resin containing an epoxy resin crosslinking agent on the metal foil heated at a temperature ranging from 2200C to a This invention is characterized by the use of a biaxially oriented polyester resin film carrying a thin layer of epoxy resin containing an epoxy resin crosslinking agent, which is less than the melting point of the high speed polyester resin film. by heating the metal foil just prior to laminating said polyester resin film at a temperature of 2200C to a value below the melting point of the polyester resin film and by using the double-layer coated metal sheet consisting of upper layer formed of chromium oxide hydrate and in one lower layer formed of metallic chromium.

 The metal foil according to the present invention can be used in applications that require excellent corrosion resistance after severe forming, for example stamped, stamped / re-pressed (ER boxes) as well as box ends. .

 In these applications, these cans are exposed to hot slag or hot steam for the pasteurization of foods after canning foods such as fruit juice, coffee, meat and fish. For example, fruit juices are immediately hot packaged in the can after pasteurization at a temperature of 90 to 1000C and coffee, meat and fish are pasteurized by hot steam at a temperature above 1000C in an autoclave after have been placed in the box at 90 ° C.

 In some applications, color printing or applying a varnish to one side of the metal foil used for the body of these boxes is performed prior to forming, after which these boxes may be used in the applications described above. .

 When the metal sheet laminated with a non-bilayered polyester resin film consisting of hydrated chromium oxide and chromium metal or the metal sheet laminated with a polyester resin film whose polyester resin film is laminated to the metal foil heated to a temperature above the melting point of the polyester resin film is used for applications in which a color printing or the application of a coating of varnish is carried out, a part of the polyester resin film can peel off in On the other hand, in the case of the metal foil according to the present invention, the laminated polyester resin film is in no way peeled off in a region subjected to severe forming even after further heating for the purpose of forming. maturation of a printing ink or varnish followed by treatment with hot water or hot steam.

 In the present invention, the biaxially oriented polyester resin film which is used is prepared by treating, in accordance with a known method, a polyester resin which is produced by esterification of at least one saturated polycarboxylic acid with at least one a saturated polyalcohol chosen between the polycarboxylic acids and the polyalcohols indicated below.

 Saturated polycarboxylic acids are selected from phthalic acid, isophthalic acid, terephthalic acid, succinic acid, azelaic acid, adipic acid, sebacic acid, 2,6-naphthalene acid and the like. dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and trimellitic acid anhydride.

 Saturated polyalcohols are selected from ethylene glycol, 7,4-butanediol; 1,5-pentanediol, 1,6-hexanediol, propylene glycol, 1,4-dimethanolcyclohexane, trimethylolpropane and pentaerythritol.

 In some cases, additives such as antioxidants, stabilizers, pigments, antistatic agents and corrosion inhibitors are added during the process of making the polyester resin film used for the present invention.

 In the present invention, the use of a biaxially oriented polyethylene terephthalate film is particularly desirable from the point of view of corrosion resistance and economy.

 The thickness of the polyester resin film used in the present invention should be 5 to 50 P, especially 10 to 30 lys.

 If the thickness of the polyester resin film used is less than 5 μm, the excellent corrosion resistance after severe forming of the metal sheet according to the present invention is not obtained and the lamination of the thin resin film polyester becomes remarkably difficult. Furthermore, the use of the polyester resin film having a thickness greater than 50 μm is not economically advantageous for the film to be laminated to the metal sheet, because the polyester resin film used for the present invention is expensive compared to epoxy-type phenolic lacquers widely used in the canning industry and other organic resin films such as polypropylene film.

 He is desirable; in the present invention, to use an epoxy resin having an epoxy equivalent of 400 to 4000 for pre-coating one side of the polyester resin film to be laminated to the metal foil. If an epoxy resin having an epoxy equivalent of less than 400 is used, it is impossible to rewind the polyester resin film previously coated with epoxy resin because the adhesiveness of the epoxy resin remains even after the elimination of the epoxy resin. solvent added to continuously coat the polyester resin film with epoxy resin by heating at a temperature of 60 to 1500C in an oven.If an epoxy resin having an epoxy equivalent greater than 4000 is used, the resin layer The shaped epoxy does not have excellent bonding strength to the metal foil and the biaxially oriented polyester resin film.

 In the present invention, the crosslinking agent that is added to the epoxy resin previously applied to the polyester resin film must be selected from the group consisting of phenolic resin, urea resin, amide resin compounds. , ester resin, acrylic resin and urethane resin. The amount of crosslinking agent that is added to the epoxy resin should be from 5 to 100 parts per 100 parts of epoxy resin. If the amount of crosslinking agent is less than 5 parts per 100 parts of epoxy resin, the previously applied epoxy resin does not cure sufficiently under the effect of heating. When there are more than 100 parts of crosslinking agent per 100 parts of epoxy resin, the formability of the epoxy resin layer after curing becomes remarkably low.

 The amount of epoxy resin containing an epoxy resin crosslinking agent previously applied to the polyester resin film, which is an important factor in the present invention, should be 0.1 to 5.0 g / m 2, preferably 0, 5 to 2.0 g / m 2 after drying at 60 to 1500C.

 It is desirable in the present invention that the epoxy resin containing the epoxy resin crosslinking agent be applied to the biaxially oriented polyester resin film as uniformly and in as thin a layer as possible, because the bond strength of the biaxially oriented polyester resin film is as uniform as possible. the epoxy resin layer to the metal foil and the polyester resin film becomes increasingly weak as the thickness of the epoxy resin layer increases. However, it is very difficult to uniformly apply to the polyester resin film an amount of less than 0.1 g / m 2 of epoxy resin containing a suitable crosslinking agent.

For an amount greater than 5.0 g / m2 of epoxy resin containing a suitable crosslinking agent, applied to the polyester resin film, the bond strength of the epoxy resin layer to the metal foil and the polyester resin film becomes remarkably low in the part that has undergone severe shaping after treatment with hot water or hot steam.

 The drying temperature of the epoxy resin containing a suitable crosslinking agent dissolved in a solvent which is applied to the polyester resin film is also one of the important factors of the present invention. If the temperature is below 600C, a long time is required to remove the solvent that is added to dissolve the epoxy resin and its crosslinking agent. At a drying temperature above 1500C, the reaction between the epoxy resin and the crosslinking agent applied to the polyester resin is accelerated, after which the binding force of the epoxy resin layer to the metal sheet becomes remarkably low.

 It is advantageous in the present invention that an epoxy resin containing a suitable crosslinking agent is dissolved in a solvent. Such a solution is applied to the biaxially oriented polyester resin film and is dried in a period of 5 to 30 seconds at a temperature of 60 to 1500C. For less than 5 seconds the solvent is not sufficiently removed and for a time greater than 30 seconds the high speed production of the laminated metal sheet with the polyester resin film is difficult.

 It is preferred in the present invention that a solvent be added to dissolve the epoxy resin and the crosslinking agent of this resin. A low boiling solvent must be used to dissolve the epoxy resin and its crosslinking agent because it is easily removed by heating at 60-1500C, although this is not a particular limitation. .

 In some cases, a coloring material such as a colorant may be added to the epoxy resin and its crosslinking agent dissolved in a solvent.

 It is contemplated in the present invention that the epoxy resin containing a suitable crosslinking agent is uniformly applied to the metal sheet or strip. However, it is difficult to uniformly apply an epoxy resin containing a suitable crosslinking agent to the metal sheet or strip, because the metal sheet is inferior to the polyester resin film with respect to the polish of its surface.

 In the present invention, the presence of an optimum amount of hydrated chromium oxide and metallic chromium is very important for obtaining excellent bonding strength between the polyester resin film previously coated with epoxy resin containing an agent. suitable cross-linking and the metal foil when said metal sheet laminated with the polyester resin film is exposed to hot water or hot steam after severe forming.

 The optimum range of amounts of chromium oxide hydrate, expressed as chromium, and of chromium metal ranges, respectively, from 3 to 50 mg / m 2 and from 30 to 200 mg / m 2, preferably from 8 to 20 mg / m 2 and from 70 to 150 mg / m 2 on said metal sheet.

 If the amount of chromium oxide hydrate expressed in chromium is less than 3 mg / m 2 or greater than 50 mg / m 2, the adhesion to the metal sheet of the polyester resin film previously coated with epoxy resin containing a suitable crosslinking agent may become low in a severely shaped region, when said metal sheet laminated with the polyester resin film is exposed to hot water or hot steam. When there is less than 30 mg / m 2 of chromium metal, the adhesion of the polyester resin film can also become low, even if the amount of chromium oxide hydrate expressed in chromium is 3 to 50 mg / m 2. Chromium metal deposition in an amount greater than 200 mg / m 2 is not suitable for the high speed continuous production of said laminated metal sheet with a polyester resin film according to the present invention, although the adhesion of said polyester resin film do not become remarkably weak.

 In some applications, the metal sheet laminated with a polyester resin film, in accordance with the present invention, is heated again to a temperature of about 160 to 2000C, because a color printing or varnish application on the On the other side of the metal sheet laminated with the polyester resin film is carried out before forming. In this case, it is very advantageous to use a double layer coated metal foil consisting of a lower layer of chromium metal oxide of 30 to 200 mg / m 2 and a top layer of chromium oxide hydrate of 3 to 50 mg / m 2 expressed in chromium, and having limited amounts of sulfur and fluorine in said chromium oxide hydrate.It is advantageous that the amount of sulfur and fluorine in the chromium oxide hydrate is from 0.1 to 2 , 5 atomic% and 0.5 to 10 atomic%, respectively, with respect to the atomic ratio of sulfur and fluorine to all chromium, oxygen, sulfur and fluorine. The adhesion of said polyester resin film in the severely formed part in a humid atmosphere is then remarkably good.

 Hydrogen also exists in the form of the hydroxyl radical and in the form of bound water in said hydrated chromium oxide. Therefore, the atomic proportion of hydrogen must also be limited. However, it is represented by the atomic proportion of oxygen, because hydrogen exists with the oxygen indicated above, and it is therefore obvious that the atomic proportion of hydrogen is in fact limited in this way.

 It is believed that the excellent adhesion of said polyester resin film to the metal foil is provided mainly by the presence of the hydroxyl radical and bound water in the chromium oxide hydrate.

 Therefore, the presence of a large amount of existing sulfur in the form of a sulfate and fluorine radical is undesirable to ensure the excellent adhesion of said polyester resin film, because the amount of hydroxyl radical or bound water in said hydrated chromium oxide, which is necessary to ensure excellent adhesion of said polyester resin film, is reduced by replacing the hydroxyl radical or the water bound by the sulfate radical or fluorine.

 In the present invention, the reason why the allowable range of atomic proportion of fluorine is greater than that of sulfur is considered to reside in the fact that the fluorine incorporated in the hydrated chromium oxide layer does not disturb the construction. hydrated chromium oxide as much as the sulphate radical, because the fluorine has practically the same volume as the hydroxyl radical or the bound water and the sulphate radical has practically the same volume as the trivalent chromium coordinated by a radical hydroxyl or bound water with a coordination index of 6.

 As mentioned above, the presence of the sulfate and fluorine radical in said hydrated chromium oxide is not desirable from the standpoint of excellent adhesion of said polyester resin film.

However, in order to effectively establish a uniform layer of chromium oxide hydrate with a uniform layer of chromium metal, it is essential to add at least one additive selected from the group consisting of sulfur compounds (for example the acid sulfuric acid, phenolsulphonic acid or sulphate, ammonium or alkali metal sulphate or phenol sulphite, sulphite or thiosulphate) and fluorine compounds (for example a fluoride, fluoborate or fluosilicate of ammonium or of alkali metal or the corresponding acid, that is hydrofluoric, fluoboric, fluosilicic acid, ammonium bifluoride or an alkali metal bifluoride) to the electrolytic solution of chromic acid.

 It is more advantageous to use a chromic acid electrolyte containing only a fluorine compound, as described for example in Japanese Patent Application No. Sho 49-25537, compared to the chromic acid electrolyte containing compounds. sulfur as sulfuric acid, from the point of view described above.

 The foil must be selected from the group consisting of aluminum foils, steel sheets, steel sheets with a deposit of less than 3.0 g / m2 of nickel, steel sheets with a deposit less than 1.0 g / m2 of tin and steel sheets with a deposition of less than 3.0 g / m2 of nickel and less than 1.0 g / m2 of tin, because the foil The metal in question is used for hygienic boxes for food as described above. The amount of nickel deposited must be less than 3.0 g / m 2 in the continuous high speed production of the metal foil. The amount of tin deposited should be limited to less than 1.0 g / m 2. If the amount of tin is greater than 1.0 g / m 2, the adhesion of the polyester resin film becomes remarkably low, because that a large part of the deposited tin remains in the free tin state without formation of tin-iron alloy by heating - just prior to lamination of the polyester resin film. If the amount of nickel and tin deposited is less than 0.01 g / m 2 and 0.05 g / m 2 respectively, the effect exerted by nickel and tin deposited on the characteristics of the metal sheet is apparent penalty, despite the addition of an additional deposition transaction.

 The temperature of the heated metal sheet just prior to lamination of the polyester resin film previously coated with epoxy resin containing its crosslinking agent, which is also one of the important factors of the present invention, must be maintained in the range of 2200C. at a value below the melting point of the polyester resin film, and preferably 230 to 2550C.

 If the temperature of the metal foil heated just prior to lamination of said polyester resin film is above the melting point of the polyester resin film, the corrosion resistance in a severely shaped area of the metal sheet laminated with the polyester resin according to the present invention is deteriorated after treatment with hot water or hot steam, because part of the biaxially oriented polyester resin film acquires an amorphous structure on the underside of the resin film biaxially oriented polyester used in contact with the heated metal foil at a temperature above the melting point of the polyester resin film.In addition, in the case of a new heating for the maturation of an ink of printing or varnishing, the adhesion of said polyester resin film to the metal foil becomes remarkably low in a portion having undergone forming. vère after treatment with hot water or hot steam, because the amorphous polyester resin film formed was recrystallized by the reheating.

 Below 2200C, the excellent bonding strength of said polyester resin film to the metal foil is not achieved. In fact, it is considered that the excellent corrosion resistance and excellent bonding strength of said polyester resin film to the metal foil is achieved by laminating the biaxially oriented polyester resin film previously coated with epoxy resin containing its agent. crosslinking without the structural modification of the polyester resin film used.

 In the present invention, the method of heating the metal sheet to which the polyester resin film previously coated with epoxy resin containing its crosslinking agent is laminated, is not limited. However, from the point of view of the continuous and stable production of the metal sheet laminated with a polyester resin film in accordance with the present invention, induction heating and resistance heating, which is used for remelting tinplate in the conventional process of production. electrolytic tinplate and an electrically heated roller are suitable for heating the metal foil to be laminated, because the foil to be laminated is heated rapidly and the temperature of the heated metal foil is easily adjusted. In fact, it is desirable in the present invention that the metal sheet to be laminated is heated for 1 to 30 seconds. A hot steam heated roll is also used for preliminary heating of the metal sheet to be laminated.

 The cooling process after lamination of the polyester resin film on the metal foil is not limited to rapid cooling or gradual cooling, because the characteristics obtained are not modified by both methods.

 The present invention is illustrated in more detail by the following examples.

Example 1
A cold rolled steel sheet having a thickness of 0.21 mm was degreased electrolytically in a solution of 70 g / l of sodium hydroxide and then pickled in a solution containing 100 g / l of sulfuric acid. The steel sheet, after rinsing with water, was cathodically treated using an electrolyte comprising 60 g / l CrO 3 and 3 g / l NaF in water with a cathodic current density of 20 A / sec. dm2 for an electrolyte temperature of 500C.

The steel sheet thus treated was rinsed with hot water having a temperature of 800C, and dried.

 Then, a biaxially oriented polyester resin film previously coated with epoxy resin containing an epoxy resin crosslinking agent, under the following conditions, was laminated to the steel sheet thus treated under the conditions below.

 Epoxy resin primer coating conditions containing an epoxy resin crosslinking agent on the polyester resin film.

Thickness of the polyester resin film to
biaxial orientation ................ 16 m
Composition of the previously coated material
epoxy resin .................... 100
parts
resol produced from paracresol
(crosslinking agent)
parts
equivalent, epoxy resin
epoxy 3000
Drying temperature of the epoxy resin
previously coated ............... 120 C
Drying time of the epoxy resin
beforehand
covered 10
seconds
Quantity of epoxy resin containing the agent
crosslinking for epoxy resin after drying
at 120 C ............................... 1.0 g / m2
Laminating conditions of the polyester resin film prepared under the conditions described above
Method of heating the steel sheet
treated
-------- induction heated roller
Temperature of the treated steel sheet
just before 2450C stratification
Method of cooling the laminate ------
- progressive cooling
Example 2
The steel sheet was electrolytically coated with 0.6 g / m 2 of nickel using a bath of
Watt comprising 40 g / l of NiCl 2 · 6H 2 O, 250 g / l of NiSO 4 · 6H 2 O and 40 g / l of H 3 BO 3 in water with a cathodic current density of 10 A / dm 2 at a bath temperature of 40 ° C. after pretreatment as in Example 1. After rinsing with water, the nickel-coated steel sheet was cathodically treated using an electrolyte comprising 80 g / l CrO 3, 0.35 g / l H 2 SO 4 and 0.6 g / l of HBF4 in water with a cathodic current density of 30 A / dm 2 at an electrolyte temperature of 550 ° C. The steel sheet thus treated was rinsed with hot water at a temperature of 800C, and was dried.

 Next, a biaxially oriented polyester resin film pre-coated with epoxy resin containing an epoxy resin curing agent under the following conditions was laminated to the steel sheet thus treated under the following conditions.

Pre-coating conditions of the polyester resin film with an epoxy resin containing an epoxy resin crosslinking agent
Thickness of the polyester resin film to
biaxial orientation ............... 12 m
Composition of the pre-coating material
epoxy resin 100 parts
isocyanate resin (
crosslinking) 30 parts
epoxy equivalent of epoxy resin 2000
pre-coating epoxy resin drying temperature * 1000C
drying time of the epoxy resin of
pre-coating 20
seconds
quantity of epoxy resin containing
the appropriate crosslinking agent after
drying at 1000C 0.5 g / m2
Laminating conditions of the polyester resin film prepared under the conditions described above
Method of heating the steel sheet
treated
------- induction heated roller
Temperature of the treated steel sheet
just before 2400C stratification
Method of cooling the laminate ---
gradual cooling
Example 3
The steel sheet was electroplated with 0.3 g / m 2 tin using an electrolyte comprising 25 g / l stannous sulfate, 15 g / l phenolsulfonic acid (60% aqueous solution) and 2 g / l of α-naphthol sulfonic acid ethoxylated in water with a cathodic current density of 20 A / dm 2 at a temperature of the electrolyte of 40 ° C. after the pre-treatment corresponding to Example 1.

After rinsing with water, the tin-coated steel sheet was thermostatically treated using an electrolyte comprising 50 g / l of CrO 3 and 0.5 g / l of
H2S04 in water with a cathodic current density of 25 A / dm 2, at an electrolyte temperature of 500C. The steel sheet thus treated was rinsed with hot water at a temperature of 850C and dried.

 Next, a biaxially oriented polyester resin film pre-coated with epoxy resin containing a suitable crosslinking agent under the following conditions was laminated to the steel sheet thus treated under the conditions set forth below.

Pre-coating conditions of the polyester resin film with an epoxy resin containing an epoxy resin crosslinking agent
Thickness of the polyester resin film to
biaxial orientation 19ysm
Composition of the pre-coating material
epoxy resin 100 parts
urea resin (crosslinking agent
40 parts
golden yellow dye 5 parts
equivalent of epoxy resin
epoxy 550
Drying temperature of 130C pre-coating epoxy resin
Drying time of epoxy resin
5 seconds coating
Quantity of epoxy resin containing an agent
cross-linking for epoxy resin after
drying at 130 C ...................... 2 g / cm2
Laminating conditions of a polyester resin film prepared under the conditions described above
Method of heating the steel sheet
treated ------- induction heating
Temperature of the treated steel sheet
just before the 2550C stratification
Method of cooling the fast cooling laminate to a temperature below 1000C after 5 seconds
Example 4
An aluminum foil (JIS 3004) having a thickness of 0.21 mm was degreased cathodically in a solution of 30 g / l of sodium carbonate.

After rinsing with water, the aluminum foil was cathodically treated using an electrolyte containing 50 g / l of CrO 3, 0.3 g / l of H 2 SO 4 and 0.16 g / l of HBF 4 in water with a cathodic current density of 20 A / dm 2 at an electrolyte temperature of 550 ° C. The aluminum foil thus treated was rinsed with hot water at a temperature of 800C, and dried.

 Next, a biaxially oriented polyester resin film previously coated with epoxy resin containing a suitable crosslinking agent under the following conditions was laminated to the treated aluminum foil under the conditions set forth below.

Pre-coating conditions of the polyester resin film with the epoxy resin containing an epoxy resin crosslinking agent
Thickness of polyester resin film to
biaxial orientation oven
Composition of the pre-coating material
epoxy resin 100 parts
resol produced from paracresol
(crosslinking agent) 10 parts
yellow dye 10 parts
equivalent of epoxy resin
epoxy 1000
Drying temperature of the epoxy resin of
850C pre-coating
Drying time of the pre-epoxy resin
coating 25 seconds
Quantity of epoxy resin containing the agent
crosslinking for epoxy resin after drying
at 800C 1.5 g / m2
Laminating conditions of a polyester resin film prepared under the conditions described above
How to heat the aluminum foil
treated
------- induction heated roller
Temperature of treated aluminum foil
just before the 2500C stratification
Laminate cooling mode -------
gradual cooling
Comparative Example 1
The steel sheet was treated cathodically under the conditions of Example 1 after the pre-treatment according to Example 1. The treated steel sheet was rinsed with hot water, at a temperature of 800C, and dried.

 Then, the treated steel sheet was cured at 210 ° C for 12 minutes after coating with 100 mg / dm 2 of an epoxy-phenolic varnish used for stamped cans.

Comparative Example 2
The steel sheet was electrodeposited with 0.6 g / m 2 of nickel under the conditions of Example 2 after the pre-treatment according to Example 1. After rinsing with water, the steel sheet The nickel coated coating was cathodically treated using an electrolyte containing 30 g / l CrO 3 and 1.5 g / l NaF in water with a cathodic current density of 20 A / dm 2 at a temperature of the electrolyte. 550C. The steel sheet thus treated was rinsed with hot water at a temperature of 800C and dried.

 Next, a biaxially oriented polyester resin film prepared under the conditions of Example 2 was laminated to the treated steel sheet under the conditions of Example 2.

Comparative Example 3
The steel sheet was electroplated with 0.3 g / m 2 tin under the conditions of Example 3 after the pre-treatment according to Example 1. After rinsing with water, the The tin coated steel was cathodically treated under the conditions of Example 3, then rinsed with hot water having a temperature of 800C and dried. Next, a biaxially oriented polyester resin film having a thickness of 25 μm was laminated to the steel sheet thus treated under the following conditions.

Conditions for lamination of the polyester resin film
Temperature of the treated steel sheet
just before the 2900C stratification
Laminate cooling mode
--- fast cooling by
immersion in water
Comparative Example 4
The aluminum foil was rinsed with water and dried after the pre-treatment carried out as in Example 4.

 Then, a biaxially oriented polyester resin film prepared under the conditions of Example 4 was laminated on the aluminum foil under the conditions of Example 4.

 Adhesion of the polyester resin film to the metal sheet and corrosion resistance after forming were evaluated by the following methods, after measuring the coating weight on the resulting steel sheet and aluminum foil by the X-ray fluorescence method, the results of which are reproduced in the table.

(1) Corrosion resistance after forming
The laminated samples of polyester resin film and the varnished sample were cut into a circular blank with a diameter of 80 mm using a cutting press, and the blank was deeply stamped to form a cup in which the laminated side of the polyester resin film and the varnished side were on the inside, with a draw ratio of 2.0.

 50 ml of 3% citric acid were loaded into the press cup and the iron or aluminum removed after aging for 30 days at 370C.

 (2) Adhesion of the polyester resin film to the metal foil after retort treatment.

 The pressed cup made by the process described in (1) above was placed in a retort in which water vapor heated at 125-1300 ° C was injected for one hour at a pressure of 1.6-1. 7 kg / cm2. Then, the adhesion of the polyester resin film or the lacquer film was evaluated according to a rating scale of 1 to 5 wherein 5 means excellent, 4 means good, 3 means fair, 2 means poor and 1 means bad.

 (3) Adhesion of the polyester resin film to the metal sheet which is heated again before forming, after the retort treatment.

 The laminated polyester resin film sample and the lacquer sample were reheated to a temperature of 2000C for 10 minutes, and then a molded cup was formed by the method described in (1) above. Then, the stamped cup was subjected to the tests under the conditions indicated in (2).

BOARD

Example <SEP> Example <SEP> Example <SEP> Example
<tb> Compara
Compara <SEP> Compara
Ex. <SEP> 1 <SEP> Ex. <SEP> 2 <SEP> Ex. <SEP> 3 <SEP> Ex. <SEP> 4 <SEP> tif <SEP> 1 <SEP> tif <SEP> 2 <SEP> tif <SEP> 3 <SEP> Comparative <SEP> 4
<tb> Steel <SEP> from <SEP> base <SEP> Steel <SEP> Steel <SEP> Steel <SEP> Aluminum <SEP> Steel <SEP> Steel <SEP> Steel <SEP> Aluminum
<tb> Ni <SEP> Sn <SEP> Ni <SEP> Sn
<tb> Metal <SEP> deposited <SEP> (mg / m2) <SEP> Nil <SEP> 0.6 <SEP> 0.3 <SEP> Nil <SEP> Nil <SEP> 0.6 <SEP> 0 , 3 <SEP> None
<tb> * 1 <SEP> Cr <SEP> (mg / m2) <SEP> 110 <SEP> 90 <SEP> 35 <SEP> 50 <SEP> 108 <SEP> 15 <SEP> 38 <SEP> 0
<tb> Crox <SEP> (mg / m2) <SEP> 14 <SEP> 30 <SEP> 7 <SEP> 6 <SEP> 15 <SEP> 12 <SEP> 8 <SEP> 0
<tb> * 2 <SEP> S <SEP> (% <SEP> atomic) <SEP> 0.5 <SEP> 3,4 <SEP> 4,0 <SEP> 1,7 <SEP> 0,5 <SEP> 0.3 <SEP> 3.7 <SEP> 0
<tb> F <SEP> (% <SEP> Atomic) <SEP> 7.0 <SEP> 4.1 <SEP> 0 <SEP> 1.0 <SEP> 6.8 <SEP> 5.6 <SEP > 0 <SEP> 0
<tb> Fe <SEP> @u <SEP> Al <SEP> removed
<tb> (ppm) <SEP> 0.6 <SEP> 0.5 <SEP> 0.3 <SEP> 0.8 <SEP> 8.4 <SEP> 0.7 <SEP> 0.5 <SEP > 3.0
<tb> Adhesion <SEP> of the <SEP> movie
<tb> d @ <SEP> resin <SEP> polyester
<tb> from <SEP> the test <SEP> (2) <SEP> 5 <SEP> 5 <SEP> 5 <SEP> 5 <SEP> 5 <SEP> 4 <SEP> 5 <SEP> 3
<tb> Adhesion <SEP> of the <SEP> movie
<tb> d @ <SEP> resin <SEP> polyester
<tb> from <SEP> the test <SEP> (3) <SEP> 5 <SEP> 4 <SEP> 4 <SEP> 5 <SEP> 5 <SEP> 3 <SEP> 3 <SEP> 2
<tb> Notes: * 1 Cr is chromium metal and Crox is chromium in hydrated chromium oxide formed by chromic acid electrolytic treatment.

* 2 S represents the sulfur present in the form of the sulphate radical and F represents the fluorine incorporated into the hydrated chromium oxide formed.

Claims (15)

 A method of laminating a biaxially oriented polyester resin film which has been previously coated with an epoxy resin-containing epoxy resin resin to a double layer coated metal sheet comprising an oxide top layer of hydrated chromium and a lower layer of metallic chromium, characterized in that it consists in heating the metal foil at a temperature ranging from 2200.degree. C. to a value below the melting point of said polyester resin film, and then in bringing in the surface of said polyester resin film coated with epoxy resin containing the appropriate crosslinking agent in contact with the metal foil.  2. A process according to claim 1, characterized in that the polyester resin film is prepared by treatment of polyester resin produced by esterification of a saturated polycarboxylic acid selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, succinic acid, azelaic acid, adipic acid, sebacic acid, 226-naphthalenedicarboxylic acid, 1,4-cyclohexane dicarboxylic acid and acid anhydride trimellitic with a saturated polyhydric alcohol selected from the group consisting of ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, propylene glycol, 1,4-dimethanolcyclohexane, trimethylolpropane and pentaerythritol.  3. A process according to claim 2, characterized in that the polyester resin film is a biaxially oriented polyethylene terephthalate film.  4. Process according to claim 1, characterized in that the epoxy resin has an epoxy equivalent of 400 to 4000.  5. Process according to claim 1, characterized in that the crosslinking agent of the epoxy resin consists of at least one compound selected from the group consisting of a phenolic resin, a urea resin, an amide resin, a resin of ester, an acrylic resin and a urethane resin.  6. A process according to claim 1, characterized in that the amount of epoxy resin crosslinking agent added to the latter resin is from 5 to 100 parts per 100 parts of. epoxy resin.  7. A method according to claim 1, characterized in that the drying temperature of the epoxy resin containing the epoxy resin crosslinking agent previously applied to the polyester resin film is 60 to 1500C.  The method of claim 1, characterized in that the amount of said epoxy resin containing said epoxy resin crosslinking agent pre-applied to the polyester resin film is 0.1 to 5.0 g / m 2, preferably from 0.5 to 2.0 g / m2 after drying at a temperature of 60 to 1500C.  9. The method of claim 1, characterized in that the metal foil is a sheet or strip of steel or aluminum.  10. A process according to claim 1, characterized in that the metal foil is a sheet or steel strip coated with 0.01 to 3.0 g / m2 of nickel.  He. Process according to claim 1, characterized in that the metal foil is a sheet or steel strip coated with 0.05 to 1.0 g / m2 of tin.  12. A method according to claim 1, characterized in that the metal foil is a sheet or steel strip coated with 0.01 to 3.0 g / m 2 of nickel and from 0.05 to 1.0 g / m 2 'tin.  13. Process according to claim 1, characterized in that the double layer comprises a chromium oxide top layer hydrated at 3-50 mg / m 2 and preferably 8-20 mg / m 2, expressed as chromium, and a lower layer metal chromium of 30 to 200 mg / m2 and preferably 70 to 150 mg / m2.  74. Process according to claim 1, characterized in that the atomic ratio of sulfur and fluorine to total chromium, oxygen, sulfur and fluorine in the hydrated chromium oxide forming an upper layer of said layer double a, respectively, a value of 0.1 to 2.5 atomic% and 0.5 to 10 atomic%.  The method of claim 1, characterized in that the temperature of the bilayer-coated metal sheet consisting of a top layer of chromium oxide hydrate and a lower layer of metallic chromium, heated just prior to stratification of said chromium oxide. polyester resin film, is maintained in the range of 230 to 2550C.  16. Process according to claim 1, characterized in that the thickness of the polyester resin film is from 5 to  Metal sheet laminated with a polyester resin on one or both sides thereof according to claim 1.