CA1200751A - Method for production of metal sheet covered with polyester resin film - Google Patents
Method for production of metal sheet covered with polyester resin filmInfo
- Publication number
- CA1200751A CA1200751A CA000411114A CA411114A CA1200751A CA 1200751 A CA1200751 A CA 1200751A CA 000411114 A CA000411114 A CA 000411114A CA 411114 A CA411114 A CA 411114A CA 1200751 A CA1200751 A CA 1200751A
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- resin film
- polyester resin
- metal sheet
- laminated
- sheet
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Abstract
METHOD FOR PRODUCTION OF METAL SHEET COVERED
WITH POLYESTER RESIN FILM
ABSTRACT OF THE DISCLOSURE
A method for the production of a metal sheet covered with polyester resin film which comprises laminating a crystalline and oriented polyester resin film on a metal sheet heated to a temperature above the melting point of polyester resin film and then immediately quenching.
This metal sheet covered with polyester resin film is excellent in corrosion resistance and formability.
WITH POLYESTER RESIN FILM
ABSTRACT OF THE DISCLOSURE
A method for the production of a metal sheet covered with polyester resin film which comprises laminating a crystalline and oriented polyester resin film on a metal sheet heated to a temperature above the melting point of polyester resin film and then immediately quenching.
This metal sheet covered with polyester resin film is excellent in corrosion resistance and formability.
Description
FIELD OF THE INVENTION
___ __ The present invention relates to a method for the production of a metal sheet covered with polyester resin film produced by laminating a crystalline and oriented polyester resin film on the surface of a metal sheet heated to a temperature above the melting point of pol~ester resin film and then rapidly quenching the laminate.
DESCRIPTION OF TH~ PRIOR ART
At present, organic resin film laminated me-tal sheets axe widely used in various fields such as electrical components, furnlture and building materials. In general, there are two well~known methods for continuous l.amination of organic resin film on the surface of the metal sheet. The :Eirst method is one in which an adhesive coated metal sheet is used.
Namely, at first the adhesive in which thermosetting resin is mainly dissolved in a solvent i.s coated on the surface of t:he metal sheet. After curing the adhesive, the organic resin film is laminated on the surface of the metal sheet and then heated in an oven with a large capacity for several rninutes.
After that, the organic resin film laminated metal sheet is cooled.
The second me-thod is one in wh;.ch an adhesive coa-ted organic resin filrn is used. In this case, the or~an.ic resin film is laminated on -the surface of the me-tal sheet and then is also heated in the same type of oven as in the first method.
However r these methods have some problems because a long time is required for curing the adhesive and heating after lamination of the organic resin film. For example, the production speed is low, e.g. 10 to 30 m/min. ~n some cases, the characteristics of the organic resin film such as the corrosion resistance are deteriorated by heating for a long time and the laminated organic resin film may be peeled off from the surface of the metal sheet by severe forming because the formability of thermosetting resin used for the adhesive is not good.
Furthermore, in Laid-Open Japanese Patent Applica--tion No. Sho 53-81530, a modified polyester resin film is used for lamination of the organic resin film on the metal sheet without an adhesive such as thermosetting resin.
In the can producing industry, continuous lacquer coating at high speed on the metal sheet has been investigated in order to decrease the production cost. ~lowever, such process is very difficult to practice industrially, because a lacquer which can be cured by heating for a few seconds has not yet been developed.
Furthermore, the corrosion resistance after forming of the lacquer coated metal sheet is poor as compared with that of the organic resin film laminat~d metal sheetO
~3--~La~
SUMMARY OF I~E INVENTION
It is an object of the present invention to provide a polyester resin fil~ laminated metal sheet having an excellent corrosion resis-tance after forming as compared with that of the lacquer coated metal sheet and other organic resin film laminated metal sheets. It is another object of the in~ention to provide a method for the continuous lamina-tion of a polyester resin film on the surface of A metal sheet at high speeds such as 100 to 600 m/min.
According to a broad aspect of the invention, there is thus provided a method of producing a polyester resin film laminated metal sheet, which comprises laminating a crystalline and oriented polyester resin film to a metal sheet which is heated to a temperature above the melting point of the poly-ester resin fiLm and then rapidly quenching the resulting laminate.
The reason why a polyester resin film laminated metal sheet having an excellent corrosion resistance after forming is obtained according to the method of the present invention is as follows:
In general, a polyester resin film having a crystal-line and oriented structure has an excellent non-permeability to water and steam, but it is not adhered to the metal sheet without a thermosetting resin adhesive. on the contrary, a polyester resin film having an amorphous structure which is obtained by rapidly cooling a crystalline and oriented pol~-ester resin film heated to a temperature above the melting point of polyester resin for a long time strongly bonds to the metal sheet as shown in Japanese Patent Publication ~o.
Sho 49-34180, ~ut it is poor in corrosion resistance because water and vapor easily permeates the film.
r7~ ~
As described above, both polyester resin films have different propert.ies.
Thus, it is belie~ed that one reason why the metal sheet according to the present invention has excellent corrosion resistance after forming is that a thin layer of amorphous polyester resin fîlm having excellent bonding strength to the metal sheet is formed between the upper layer of crystalline and oriented polyester resin film and the sur--face of the metal sheet by rapidly quenching after laminati.ng the crystalline and oriented polyester resin film.
A second reason is that the thicker layer of the crystalline and oriented polyester resin film having the e~cellent non-permeability to water and steam remains after laminating the crystalline and oriented polyester resin fil.m to the surface of the metal sheet.
The polyester resin film laminated metal sheet according to the present invention can be used in applicati.ons wherein excellent corrosion resistance after severe forminq is required, such as drawn cans, drawn and redrawn cans (DR can~
in addition to can ends, instead of lacquered electrotinplate and tin free s-teel having a duplex layer consisting of an upper layer of hydrated chromium oxide and a lower layer of metal.lic chromium. Furthermore, it is also used for the can body adhered by polyester resin film instead of the lac~uered tin free steel can body seamed by nylon adhesive.
,"` I
DET~ILED DESCRIPTIOM OE THE INVENTIO~
In the present invention, the employed polyester resin filrn is prepared by processing polyester resin which is produced by the esteri~ication of at least one saturated polycarboxylic acid by at least one saturated polyalcohol selected from the following polycarboxylic acids and polyalcohols.
Saturated polycarboxylic acids are selected from phthalic acid, isophthalic acidl terephthalic acid, succinic acid, azelaic acid, adipic acid, sebacic acid, 1,4-cyclohexane dicarboxylic acid and trimellitic acid anhydride.
Saturated polyalcohols are selected from ethylene glycol, 1,4-butane diol, 1~5-pentane diol, 1,6-hexane diol, propylene glycol, 1,4-dimethanol cyclohexane, trimethylol propane and pentaerythritol.
In some cases/ additives such as antioxidants, stabilizers, pigments, antistatic agents and corrosion inhibitors are added during the manufacturing process of the polyester resin film used for the present invention.
In -the present invention, the use of polyethylene terephthalate film having biaxial oriented structure is especially desirable from the viewpoint of corrosion resist:ance and economy.
The thickness of the used polyester resin film should be 5 - 100 ~m, ~referably 5 - 50 ~, althou-~h it is not limited to such xange. ~lowever, if the thickness of the employed polyester resin film is below 5 ~m, the excellent corrosion resistance after severe forming in the me-tal sheet according -to the present invention is no-t obtained.
3~ 75~
~ oreo~er, the use of the polyester resin film having a thickness above 100 ~m is not economically suitable for the film to be laminated to the metal sheet, because the polyester resin film used for the present invention is expensive as compared with epoxy phenolic lacquers widely used in the can industry and other organic resin films such as polypropylene film.
The metal sheet used in the present invention is steel sheet or aluminum sheet with or without a surface treatment.
Particularly, tin free steel having an upper layer of hydrated chromium oxide and a lower layer of metallic chromium, lightly tin coated steel sheet, Ni plated steel sheet, Cr plated steel sheet, Cu plated steel sheet, steel sheet covered with hydrated chromium oxide and aluminum she~e-t with chromate treatment and phosphate treatment are suitable as the metal sheet for the present invention, because these metal sheets have excellent bonding strength with respect to the polyester resin film.
Furthermore, the following duplex, triple, composite and alloy plated steel sheets can also be used as the metal sheet in the present invention.
Duplex and triple coated steel sheets are selected from the group consisting of lightly tin coated steel sheet w th Ni plating, chromate treatment, phosphate treatment or tin free steel treatment, Ni plated steel sheet with Cr plating, light Sn plating, chromate treatment, phosphate treatment or tin free steel treatment, Cr plated steel sheet with chromate treatment, Cu plated steel sheet with light tin plating, Ni plating, Cr plating, chromate treatment or tin free steel treatment, and Zn plated steel sheet with chromate treatment, phosphate treatment or silicate treatment.
Composite and alloy coated steel sheets are selected from the group consisting of Ni-Sn plated steel sheet with ~r without chromate treatment and Zn plated steel sheet in which a small amount of at least one metal, hydroxide or oxide of Ni, Co, Fe, Cr and Mo is contained in the plated Zn layer.
In the continuous production of the polyester resin film laminated metal shee~ according to the present invention at high speed, tin free steel sheet covered with a double layer consisting of an upper layer of hydrated chromium oxide having 0.00~ to 0~05 g/m as chrornium and a lower layer of metallir chromium in an amount of 0.01 to 0.2 g/m2, lightl~ tin coated steel sheet having from 0.05 to 1.0 g/m2 of Sn, Cr plated steel sheet having below 0.2 g/m2 of Cr and Ni plated steel sheet having from 0.01 to 3.0 y/m2 of Ni are suitable for use as metal sheet~
As noted above, many kinds of metal sheets with or without a surface treat~ent may be used in the practice of the invention. However, when a polyester resin film laminated metal sheet without a surface treatment is used in applications wherein excellent corrosion resistance after severe forming is required, such as drawn cans, drawn and redrawn cans and can ends where these cans are exposed to hot water or hot steam for the pasteurization of food after the packing of food, a part of the polyester resin film may be peeled off in a severe formed part of the can. On the other hand, in the case of ~
metal sheet covered with a double layer consisting of an upper layer of hydrated chromium oxide and a lower layer of metallic 7Si~
chromium, the laminated polyester resin film is not at all peeled off in a severe formed part even after a treatment with hot water or hot steam.
The presence of optimum amounts of hydrated chromium oxide and metallic chromium are very important for an excellent adhesion of the polyester resin film when the polyester resin film laminated metal sheet is exposed to hot water or hot steam after severe forming. These optimum amounts of hydrated chromium oxide as chromium and metallic chromium range from 0.005 to 0.050 g/m2 and from 0.01 to 0.20 g/m2, respectively.
The temperature of the metal sheet heated just - before the lamination of the polyester resin film which is an important factor in the present invention should be maintained in the range of Tm - Tm + 160C, in which Tm is the melting point of the polyester resin film which exhibits an endothermic peak in an ordinary differential thermal analysis run at a heating rate of 10C/min., in order to get the excellent bonding strength between the polyester resin film and the metal sheet.
.~
If ~he tempcraturc of the metal sheet heated just before the lamination of the pol~.ester resin ~ilm is aboJe Tm + 160C, the corrosion resistance of the polyester resin film laminated metal sheet deteriorates, because the ratio of the non-oriented part to thc oriented part in the laminated polyester resin film will perhaps increase. With a temperature below Tm, the polyester resin film laminated metal sheet having excellent bonding strength is not obtained, because the lower side of the employed polyester resin film in contact with -the metal sheet is not sufEiciently melted.
Furthermore, the quenching conditions after laminating the polyester resin film on the metal sheet is also one of the important factors in the present invention. Namely, the maximum temperature on the surface, which does not contact the surface of the metal sheet, of the laminated polyester resin film should be below TsC, at which the meltin~ oE crystals in the polyester resin film starts, perferably below Ts - 20C.
~ ore specifically, Ts represents the temperature at which the endothermic reaction of polyester resin film starts, as determined by ordinary differen-tial thermal analy~is ~hich is run at a heating rate of 10C/min.
If the tempera-ture on the surface of the laminated polyester resin film is above ~s r the characteristics of the metal sheet according to the present invention become reMarkably poor.
For e~ample, the appearance of the laminated polyester resin film changes from clear to milky and the corrosion resistance af-tex forming becomes poor.
~12~?~75~
Furthermorc, the cJucnchinc~ time for coolinc3 the metal sheet to bc1ow Ts af~er the lamination of the polyc?ster resin film is also an irnportant Cactor in the prescnt invention.
It should be below 10 seconds In thc case whc--c thc nuenchin time is longer, the corrosion resist-ance or thc ~olyectc~r resin film laminated metal sheet also becomes rernarkably poor, because it is considered that the grea-ter part of the crystalline and oriented structure changes to the non-oriented structure in the laminated polyester resin film.
In the present invention, the method for heating the metal sheet to which the polyester resin film is lamina~ed is not lirnited. However, from the standpoint of continuous and stable production of the polyes-ter resin film laminated metal sheet at high speed, induction heating and/or resistance heating which are used for reflowing tinplate in the conventional process for production of electrotinplate is suitablc as the method for heating the rnetal sheet to be laminated, because the metal sheet to be laminated is rapidly heated and the temperature of the heated metal sheet is easily controlled. Namely, it is desirable in the present invention that the metal sheet to be laminated be heated in the range of from 1 - 20 scconds.
Furthermore, in the present invention, various methods were considered for quenching the metal sheet heated above the meltinc3 point of the polyester resin film after the lamination of the polyester resin film. However, quenchincJ by watcr spray, water in~crsion, liquid nitrogcn oL enlployillg a roller cooled by watcr or liquid nitrogen arc inc3ustrially 75~
suitable as the method for quenching the heated metal sheet after the lamination of polyester resin film. The temperat~lre of water used for quenching the heated metal sheet should be kept below 90C in consideration of the continuous production of the polyester resin film laminated metal sheet according to the present invention, although it should be kept as low as possible.
The present invention is explained in further detail by reference to the following examples.
A cold rolled steel sheet having a thickness of 0.23 mm was electrolytically degreased in a solution of 70 c~/l sodium hydroxide and then pickled in a solution of lO0 g/l sulfuric acid~ The steel sheet, after being rinsed with water, was cathodically treated by using an electrolyte consisting of 30 g/l of Cro3 and l.5 g/l of NaF in water under 20 A/dm2 of cathodic current density at an electrolyte temperature of 30C.
The,thus treated steel sheet was rinsed with hot water having a temperature of 80C and dried. AEter that, a crystalline and oriented polyester resin film (trade mark: MELINEX S made by ICI Co., Ltd.) having a thickness of 20 ~m was laminated on the thus treated steel sheet under'the followin~ conditions and was quenched.
Conditions for the lamination of the polyester resin film:
~lethod for he~ting thc trcatcd stccl shcct ... Resistance heating Temperature of the treated steel sheet just before the lamination ... ~85C
; .
)7~i~
Maxim~ temperature on the surface of the laminat.ed polyester resin film between laminating and quenching ... 150C
Quenching time to 150C on the surface of the laminated polyester resin film ... 2 sec.
The steel sheet was electroplated with 0.3 g/m2 of Sn by using an electrolyte consisting of 25 g/l of stannous sulfate, 15 g/l of phenolsulfonic acid (60% aqueous solution) and 2 g/l of ethoxylated ~-naphthol sulfonic acid in water under 20 A/dm2 of cathodic current density at an electrolyte tempera-ture of 40C after the pretreatment as in Example 1. The tin plated steel sheet was rinsed with water and dried.
After that, a crystalline and oriented polyester resin film (trade mark: LUMIRROR F made by Tore Co., Ltd.) having a thickness of 50 ym was laminated on the thus tin plated steel sheet under the followiny conditions and quenched.
Conclitions for the lamination of the polyester resin film:
Method for heatiny the tin plated steel sheet ... Resistance heating Temperature of the tin plated steel sheet just before the lamination ... 270C
Maximum temperature on the surface of the laminated polyester resin film between laminating and quenching ...-170C
Quenching time to 170C on the surface of the larninated polyester resin film ... 3 sec.
EXP*IPLE 3 The steel sheet was electroplated with 0.6 g/m2 of Ni by using a Watt's bath consisting of 40 g/l of NiC12-6H2O, 250 g~1 of NiSO4 6H2O and 40 g/l of H3BO3 in water under 10 A/dm2 of cathodic current density at a bath temperature of 40C. The Ni plated steel sheet was rinsed with water after chromate treatment by using 30 gjl of sodium dichromate solution under 10 A/dm2 o~ cathodic current density at an electrolyte temperature of 45C and dried.
After that, a crystalline and oriented polyester resin film (trade mark: MELINEX 377 made by ICI Co., Ltd.) having a thickness of 50 ym was laminated on the treated Ni plated steel sheet under the following conditions and quenched.
Conditions for the lamination of the polyester resin film:
Method for heating the Ni plated steel sheet ... Induction heating Temperature of the Ni plated steel sheet just before the lamination ... 320C
Maximum temperature on the surface of the laminated polyester resin film between laminating and quenching ... 185C
Quenching time to 185C on the surface of the laminate polyester resin film ... 4 sec.
The steel sheet was electroplated with 0.7 g/m2 of Ni containing 0.04 g/m2 of Sn by using a Watt's bath usecl 75~L
in Example 3 added 5 g/l of stannous sulfate under the same conditions as in Example 3 after the pretreatment as in Example 1.
The Ni-Sn plated steel sheet was rinsed with water and dried. After that, a crystalline and oriented polyester resin film (trade mark: W 3030 made by Teijin Co., Ltd.) having a thickness of 30 ~m was laminated on the thus Ni-Sn plated steel sheet under the following conditions.
Conditions for the lamination of the polyester resin film:
Method for heating the Ni-Sn plated steel sheet ... Infrared heating Temperature of the Ni-Sn plated steel sheet just be-Eore the lamination ... 280C
Maximum temperature on the surface of the laminated polyester resin film between laminating and quenching ... 160 DC
Quenching time to 160C on the surface of the laminated polyester resin film ... 2 sec.
The steel sheet was electroplated with 0.3 g/m2 of Ni by using a Watt's bath used in Example 3. After rinsing the Ni plated steel sheet was treated by using an electrolyte consisting of 50 g/l of CrO3 and 0.5 g/l of sulfuric acid in water under 10 A/dm~ of cathodic current density at an electrolyte temperature of 5SC and then rinsed with water and dried.
After that, a crystalline and oriented polyester resin ~ilm ~trade mark: E-5000 made by Toyobo Co., Ltd.) having a thickness of 40 ~3m was lamina-ted on the Ni plated steel sheet haviny metallic chromium and hydrated chromiu3n oxide under the following conditions and was quenched.
Conditions for the lamination of the polyester resin film:
Method for heating the Ni pla-ted steel sheet ... Induction heating Temperature of the Ni plated steel shee-t just before the lamination ... 300C
Maximum temperature on the surface of the laminated polyester resin film between laminating and quenching ... 190C
Quenching time to 190~C on the surface of the laminated polyester resin film ... 6 sec.
~XAMPLL 6 An aluminum sheet (JIS 3004) having a thickness of 0.23 mm was cathodically degreased in a solution of 30 g/l sodium carbonate and then treated in a solution containing 30 g/l sodium dichromate at a solution temperature of 65C. The thus chromate treated aluminum sheet was rinsed with water and drled.
After that, a crystalline and oriented polyester resin film (trade mark: LUMIRROR S10 made by l'ore Co., Ltd.) having a thickness of 20 ~m ~as laminated on the treated aluminum sheet under the following conditions and quenched.
Conditions Eor the lamination of the polyester resin film:
Method for heating the treated aluminum sheet ... Resistance h,eating Temperature o~ the treated aluminum sheet just before the lamination ... 290C
Maximum temperature on -the surface oE the laminated polyester resin film between laminating and quenching ... 180C
Quenching time to 180C on the surface oE the laminated polyester resin film ... 3 sec.
Comparative Example l . . .
The same polyester resin film and the same treat:ed steel shee-t used for Example 1 were prepared. This polyester resin film was laminated to the treated steel sileet under the same conditions as in Example l.
After lamination, the laminated steel sheet was gradually cooled without water quenching.
Comparative Example 2 The same polyester resin film and -the same treated steel sheet used for Example 3 were prepared. This polyester resin film was laminated to the treated steel sheet under the same conditions as in E~ample 3 except for the quenching time to 185C on the surface oE the laminated ~olyester resin film.
Quenching time to 185C ... 15 sec.
lZ0~3751 Comparative Example 3 An aluminum sheet (JIS 3004) having a thickness of 0~23 mm was treated under the same conditions as in Examp:Le 6.
After that, a crystalline and oriented polyester resin film (Trade name: Lumirror S10 made by Tore Co., Ltd.) having a thicXness of 4 ~m was laminated to the treated aluminum sheet under the same conditions as in Example 6.
The characteristics of the resultant metal sheei:
were evaluated by the following test methods, after the measure-ment of the coating weight on the resultant metal sheet by the X-ray fluorescent method, the results of which are shown i.n the Table.
(1) Bonding strength between the metal sheet and the polyester resin film:
The polyester resin film laminated sample was cut to a size of 8 cm x 8 cm, and the polyester resin film laminated side was cut crosswise with a razor. After 6 mm of the sample was extruded by using a conventional Erichsen testing machine, the laminated polyester resin film of the formed part was peeled off by a pincette. Bonding strength was divided into 5 ranks, namely, 5 was excellent, 4 was good, 3 was fair, 2 was poor and 1 was badv
___ __ The present invention relates to a method for the production of a metal sheet covered with polyester resin film produced by laminating a crystalline and oriented polyester resin film on the surface of a metal sheet heated to a temperature above the melting point of pol~ester resin film and then rapidly quenching the laminate.
DESCRIPTION OF TH~ PRIOR ART
At present, organic resin film laminated me-tal sheets axe widely used in various fields such as electrical components, furnlture and building materials. In general, there are two well~known methods for continuous l.amination of organic resin film on the surface of the metal sheet. The :Eirst method is one in which an adhesive coated metal sheet is used.
Namely, at first the adhesive in which thermosetting resin is mainly dissolved in a solvent i.s coated on the surface of t:he metal sheet. After curing the adhesive, the organic resin film is laminated on the surface of the metal sheet and then heated in an oven with a large capacity for several rninutes.
After that, the organic resin film laminated metal sheet is cooled.
The second me-thod is one in wh;.ch an adhesive coa-ted organic resin filrn is used. In this case, the or~an.ic resin film is laminated on -the surface of the me-tal sheet and then is also heated in the same type of oven as in the first method.
However r these methods have some problems because a long time is required for curing the adhesive and heating after lamination of the organic resin film. For example, the production speed is low, e.g. 10 to 30 m/min. ~n some cases, the characteristics of the organic resin film such as the corrosion resistance are deteriorated by heating for a long time and the laminated organic resin film may be peeled off from the surface of the metal sheet by severe forming because the formability of thermosetting resin used for the adhesive is not good.
Furthermore, in Laid-Open Japanese Patent Applica--tion No. Sho 53-81530, a modified polyester resin film is used for lamination of the organic resin film on the metal sheet without an adhesive such as thermosetting resin.
In the can producing industry, continuous lacquer coating at high speed on the metal sheet has been investigated in order to decrease the production cost. ~lowever, such process is very difficult to practice industrially, because a lacquer which can be cured by heating for a few seconds has not yet been developed.
Furthermore, the corrosion resistance after forming of the lacquer coated metal sheet is poor as compared with that of the organic resin film laminat~d metal sheetO
~3--~La~
SUMMARY OF I~E INVENTION
It is an object of the present invention to provide a polyester resin fil~ laminated metal sheet having an excellent corrosion resis-tance after forming as compared with that of the lacquer coated metal sheet and other organic resin film laminated metal sheets. It is another object of the in~ention to provide a method for the continuous lamina-tion of a polyester resin film on the surface of A metal sheet at high speeds such as 100 to 600 m/min.
According to a broad aspect of the invention, there is thus provided a method of producing a polyester resin film laminated metal sheet, which comprises laminating a crystalline and oriented polyester resin film to a metal sheet which is heated to a temperature above the melting point of the poly-ester resin fiLm and then rapidly quenching the resulting laminate.
The reason why a polyester resin film laminated metal sheet having an excellent corrosion resistance after forming is obtained according to the method of the present invention is as follows:
In general, a polyester resin film having a crystal-line and oriented structure has an excellent non-permeability to water and steam, but it is not adhered to the metal sheet without a thermosetting resin adhesive. on the contrary, a polyester resin film having an amorphous structure which is obtained by rapidly cooling a crystalline and oriented pol~-ester resin film heated to a temperature above the melting point of polyester resin for a long time strongly bonds to the metal sheet as shown in Japanese Patent Publication ~o.
Sho 49-34180, ~ut it is poor in corrosion resistance because water and vapor easily permeates the film.
r7~ ~
As described above, both polyester resin films have different propert.ies.
Thus, it is belie~ed that one reason why the metal sheet according to the present invention has excellent corrosion resistance after forming is that a thin layer of amorphous polyester resin fîlm having excellent bonding strength to the metal sheet is formed between the upper layer of crystalline and oriented polyester resin film and the sur--face of the metal sheet by rapidly quenching after laminati.ng the crystalline and oriented polyester resin film.
A second reason is that the thicker layer of the crystalline and oriented polyester resin film having the e~cellent non-permeability to water and steam remains after laminating the crystalline and oriented polyester resin fil.m to the surface of the metal sheet.
The polyester resin film laminated metal sheet according to the present invention can be used in applicati.ons wherein excellent corrosion resistance after severe forminq is required, such as drawn cans, drawn and redrawn cans (DR can~
in addition to can ends, instead of lacquered electrotinplate and tin free s-teel having a duplex layer consisting of an upper layer of hydrated chromium oxide and a lower layer of metal.lic chromium. Furthermore, it is also used for the can body adhered by polyester resin film instead of the lac~uered tin free steel can body seamed by nylon adhesive.
,"` I
DET~ILED DESCRIPTIOM OE THE INVENTIO~
In the present invention, the employed polyester resin filrn is prepared by processing polyester resin which is produced by the esteri~ication of at least one saturated polycarboxylic acid by at least one saturated polyalcohol selected from the following polycarboxylic acids and polyalcohols.
Saturated polycarboxylic acids are selected from phthalic acid, isophthalic acidl terephthalic acid, succinic acid, azelaic acid, adipic acid, sebacic acid, 1,4-cyclohexane dicarboxylic acid and trimellitic acid anhydride.
Saturated polyalcohols are selected from ethylene glycol, 1,4-butane diol, 1~5-pentane diol, 1,6-hexane diol, propylene glycol, 1,4-dimethanol cyclohexane, trimethylol propane and pentaerythritol.
In some cases/ additives such as antioxidants, stabilizers, pigments, antistatic agents and corrosion inhibitors are added during the manufacturing process of the polyester resin film used for the present invention.
In -the present invention, the use of polyethylene terephthalate film having biaxial oriented structure is especially desirable from the viewpoint of corrosion resist:ance and economy.
The thickness of the used polyester resin film should be 5 - 100 ~m, ~referably 5 - 50 ~, althou-~h it is not limited to such xange. ~lowever, if the thickness of the employed polyester resin film is below 5 ~m, the excellent corrosion resistance after severe forming in the me-tal sheet according -to the present invention is no-t obtained.
3~ 75~
~ oreo~er, the use of the polyester resin film having a thickness above 100 ~m is not economically suitable for the film to be laminated to the metal sheet, because the polyester resin film used for the present invention is expensive as compared with epoxy phenolic lacquers widely used in the can industry and other organic resin films such as polypropylene film.
The metal sheet used in the present invention is steel sheet or aluminum sheet with or without a surface treatment.
Particularly, tin free steel having an upper layer of hydrated chromium oxide and a lower layer of metallic chromium, lightly tin coated steel sheet, Ni plated steel sheet, Cr plated steel sheet, Cu plated steel sheet, steel sheet covered with hydrated chromium oxide and aluminum she~e-t with chromate treatment and phosphate treatment are suitable as the metal sheet for the present invention, because these metal sheets have excellent bonding strength with respect to the polyester resin film.
Furthermore, the following duplex, triple, composite and alloy plated steel sheets can also be used as the metal sheet in the present invention.
Duplex and triple coated steel sheets are selected from the group consisting of lightly tin coated steel sheet w th Ni plating, chromate treatment, phosphate treatment or tin free steel treatment, Ni plated steel sheet with Cr plating, light Sn plating, chromate treatment, phosphate treatment or tin free steel treatment, Cr plated steel sheet with chromate treatment, Cu plated steel sheet with light tin plating, Ni plating, Cr plating, chromate treatment or tin free steel treatment, and Zn plated steel sheet with chromate treatment, phosphate treatment or silicate treatment.
Composite and alloy coated steel sheets are selected from the group consisting of Ni-Sn plated steel sheet with ~r without chromate treatment and Zn plated steel sheet in which a small amount of at least one metal, hydroxide or oxide of Ni, Co, Fe, Cr and Mo is contained in the plated Zn layer.
In the continuous production of the polyester resin film laminated metal shee~ according to the present invention at high speed, tin free steel sheet covered with a double layer consisting of an upper layer of hydrated chromium oxide having 0.00~ to 0~05 g/m as chrornium and a lower layer of metallir chromium in an amount of 0.01 to 0.2 g/m2, lightl~ tin coated steel sheet having from 0.05 to 1.0 g/m2 of Sn, Cr plated steel sheet having below 0.2 g/m2 of Cr and Ni plated steel sheet having from 0.01 to 3.0 y/m2 of Ni are suitable for use as metal sheet~
As noted above, many kinds of metal sheets with or without a surface treat~ent may be used in the practice of the invention. However, when a polyester resin film laminated metal sheet without a surface treatment is used in applications wherein excellent corrosion resistance after severe forming is required, such as drawn cans, drawn and redrawn cans and can ends where these cans are exposed to hot water or hot steam for the pasteurization of food after the packing of food, a part of the polyester resin film may be peeled off in a severe formed part of the can. On the other hand, in the case of ~
metal sheet covered with a double layer consisting of an upper layer of hydrated chromium oxide and a lower layer of metallic 7Si~
chromium, the laminated polyester resin film is not at all peeled off in a severe formed part even after a treatment with hot water or hot steam.
The presence of optimum amounts of hydrated chromium oxide and metallic chromium are very important for an excellent adhesion of the polyester resin film when the polyester resin film laminated metal sheet is exposed to hot water or hot steam after severe forming. These optimum amounts of hydrated chromium oxide as chromium and metallic chromium range from 0.005 to 0.050 g/m2 and from 0.01 to 0.20 g/m2, respectively.
The temperature of the metal sheet heated just - before the lamination of the polyester resin film which is an important factor in the present invention should be maintained in the range of Tm - Tm + 160C, in which Tm is the melting point of the polyester resin film which exhibits an endothermic peak in an ordinary differential thermal analysis run at a heating rate of 10C/min., in order to get the excellent bonding strength between the polyester resin film and the metal sheet.
.~
If ~he tempcraturc of the metal sheet heated just before the lamination of the pol~.ester resin ~ilm is aboJe Tm + 160C, the corrosion resistance of the polyester resin film laminated metal sheet deteriorates, because the ratio of the non-oriented part to thc oriented part in the laminated polyester resin film will perhaps increase. With a temperature below Tm, the polyester resin film laminated metal sheet having excellent bonding strength is not obtained, because the lower side of the employed polyester resin film in contact with -the metal sheet is not sufEiciently melted.
Furthermore, the quenching conditions after laminating the polyester resin film on the metal sheet is also one of the important factors in the present invention. Namely, the maximum temperature on the surface, which does not contact the surface of the metal sheet, of the laminated polyester resin film should be below TsC, at which the meltin~ oE crystals in the polyester resin film starts, perferably below Ts - 20C.
~ ore specifically, Ts represents the temperature at which the endothermic reaction of polyester resin film starts, as determined by ordinary differen-tial thermal analy~is ~hich is run at a heating rate of 10C/min.
If the tempera-ture on the surface of the laminated polyester resin film is above ~s r the characteristics of the metal sheet according to the present invention become reMarkably poor.
For e~ample, the appearance of the laminated polyester resin film changes from clear to milky and the corrosion resistance af-tex forming becomes poor.
~12~?~75~
Furthermorc, the cJucnchinc~ time for coolinc3 the metal sheet to bc1ow Ts af~er the lamination of the polyc?ster resin film is also an irnportant Cactor in the prescnt invention.
It should be below 10 seconds In thc case whc--c thc nuenchin time is longer, the corrosion resist-ance or thc ~olyectc~r resin film laminated metal sheet also becomes rernarkably poor, because it is considered that the grea-ter part of the crystalline and oriented structure changes to the non-oriented structure in the laminated polyester resin film.
In the present invention, the method for heating the metal sheet to which the polyester resin film is lamina~ed is not lirnited. However, from the standpoint of continuous and stable production of the polyes-ter resin film laminated metal sheet at high speed, induction heating and/or resistance heating which are used for reflowing tinplate in the conventional process for production of electrotinplate is suitablc as the method for heating the rnetal sheet to be laminated, because the metal sheet to be laminated is rapidly heated and the temperature of the heated metal sheet is easily controlled. Namely, it is desirable in the present invention that the metal sheet to be laminated be heated in the range of from 1 - 20 scconds.
Furthermore, in the present invention, various methods were considered for quenching the metal sheet heated above the meltinc3 point of the polyester resin film after the lamination of the polyester resin film. However, quenchincJ by watcr spray, water in~crsion, liquid nitrogcn oL enlployillg a roller cooled by watcr or liquid nitrogen arc inc3ustrially 75~
suitable as the method for quenching the heated metal sheet after the lamination of polyester resin film. The temperat~lre of water used for quenching the heated metal sheet should be kept below 90C in consideration of the continuous production of the polyester resin film laminated metal sheet according to the present invention, although it should be kept as low as possible.
The present invention is explained in further detail by reference to the following examples.
A cold rolled steel sheet having a thickness of 0.23 mm was electrolytically degreased in a solution of 70 c~/l sodium hydroxide and then pickled in a solution of lO0 g/l sulfuric acid~ The steel sheet, after being rinsed with water, was cathodically treated by using an electrolyte consisting of 30 g/l of Cro3 and l.5 g/l of NaF in water under 20 A/dm2 of cathodic current density at an electrolyte temperature of 30C.
The,thus treated steel sheet was rinsed with hot water having a temperature of 80C and dried. AEter that, a crystalline and oriented polyester resin film (trade mark: MELINEX S made by ICI Co., Ltd.) having a thickness of 20 ~m was laminated on the thus treated steel sheet under'the followin~ conditions and was quenched.
Conditions for the lamination of the polyester resin film:
~lethod for he~ting thc trcatcd stccl shcct ... Resistance heating Temperature of the treated steel sheet just before the lamination ... ~85C
; .
)7~i~
Maxim~ temperature on the surface of the laminat.ed polyester resin film between laminating and quenching ... 150C
Quenching time to 150C on the surface of the laminated polyester resin film ... 2 sec.
The steel sheet was electroplated with 0.3 g/m2 of Sn by using an electrolyte consisting of 25 g/l of stannous sulfate, 15 g/l of phenolsulfonic acid (60% aqueous solution) and 2 g/l of ethoxylated ~-naphthol sulfonic acid in water under 20 A/dm2 of cathodic current density at an electrolyte tempera-ture of 40C after the pretreatment as in Example 1. The tin plated steel sheet was rinsed with water and dried.
After that, a crystalline and oriented polyester resin film (trade mark: LUMIRROR F made by Tore Co., Ltd.) having a thickness of 50 ym was laminated on the thus tin plated steel sheet under the followiny conditions and quenched.
Conclitions for the lamination of the polyester resin film:
Method for heatiny the tin plated steel sheet ... Resistance heating Temperature of the tin plated steel sheet just before the lamination ... 270C
Maximum temperature on the surface of the laminated polyester resin film between laminating and quenching ...-170C
Quenching time to 170C on the surface of the larninated polyester resin film ... 3 sec.
EXP*IPLE 3 The steel sheet was electroplated with 0.6 g/m2 of Ni by using a Watt's bath consisting of 40 g/l of NiC12-6H2O, 250 g~1 of NiSO4 6H2O and 40 g/l of H3BO3 in water under 10 A/dm2 of cathodic current density at a bath temperature of 40C. The Ni plated steel sheet was rinsed with water after chromate treatment by using 30 gjl of sodium dichromate solution under 10 A/dm2 o~ cathodic current density at an electrolyte temperature of 45C and dried.
After that, a crystalline and oriented polyester resin film (trade mark: MELINEX 377 made by ICI Co., Ltd.) having a thickness of 50 ym was laminated on the treated Ni plated steel sheet under the following conditions and quenched.
Conditions for the lamination of the polyester resin film:
Method for heating the Ni plated steel sheet ... Induction heating Temperature of the Ni plated steel sheet just before the lamination ... 320C
Maximum temperature on the surface of the laminated polyester resin film between laminating and quenching ... 185C
Quenching time to 185C on the surface of the laminate polyester resin film ... 4 sec.
The steel sheet was electroplated with 0.7 g/m2 of Ni containing 0.04 g/m2 of Sn by using a Watt's bath usecl 75~L
in Example 3 added 5 g/l of stannous sulfate under the same conditions as in Example 3 after the pretreatment as in Example 1.
The Ni-Sn plated steel sheet was rinsed with water and dried. After that, a crystalline and oriented polyester resin film (trade mark: W 3030 made by Teijin Co., Ltd.) having a thickness of 30 ~m was laminated on the thus Ni-Sn plated steel sheet under the following conditions.
Conditions for the lamination of the polyester resin film:
Method for heating the Ni-Sn plated steel sheet ... Infrared heating Temperature of the Ni-Sn plated steel sheet just be-Eore the lamination ... 280C
Maximum temperature on the surface of the laminated polyester resin film between laminating and quenching ... 160 DC
Quenching time to 160C on the surface of the laminated polyester resin film ... 2 sec.
The steel sheet was electroplated with 0.3 g/m2 of Ni by using a Watt's bath used in Example 3. After rinsing the Ni plated steel sheet was treated by using an electrolyte consisting of 50 g/l of CrO3 and 0.5 g/l of sulfuric acid in water under 10 A/dm~ of cathodic current density at an electrolyte temperature of 5SC and then rinsed with water and dried.
After that, a crystalline and oriented polyester resin ~ilm ~trade mark: E-5000 made by Toyobo Co., Ltd.) having a thickness of 40 ~3m was lamina-ted on the Ni plated steel sheet haviny metallic chromium and hydrated chromiu3n oxide under the following conditions and was quenched.
Conditions for the lamination of the polyester resin film:
Method for heating the Ni pla-ted steel sheet ... Induction heating Temperature of the Ni plated steel shee-t just before the lamination ... 300C
Maximum temperature on the surface of the laminated polyester resin film between laminating and quenching ... 190C
Quenching time to 190~C on the surface of the laminated polyester resin film ... 6 sec.
~XAMPLL 6 An aluminum sheet (JIS 3004) having a thickness of 0.23 mm was cathodically degreased in a solution of 30 g/l sodium carbonate and then treated in a solution containing 30 g/l sodium dichromate at a solution temperature of 65C. The thus chromate treated aluminum sheet was rinsed with water and drled.
After that, a crystalline and oriented polyester resin film (trade mark: LUMIRROR S10 made by l'ore Co., Ltd.) having a thickness of 20 ~m ~as laminated on the treated aluminum sheet under the following conditions and quenched.
Conditions Eor the lamination of the polyester resin film:
Method for heating the treated aluminum sheet ... Resistance h,eating Temperature o~ the treated aluminum sheet just before the lamination ... 290C
Maximum temperature on -the surface oE the laminated polyester resin film between laminating and quenching ... 180C
Quenching time to 180C on the surface oE the laminated polyester resin film ... 3 sec.
Comparative Example l . . .
The same polyester resin film and the same treat:ed steel shee-t used for Example 1 were prepared. This polyester resin film was laminated to the treated steel sileet under the same conditions as in Example l.
After lamination, the laminated steel sheet was gradually cooled without water quenching.
Comparative Example 2 The same polyester resin film and -the same treated steel sheet used for Example 3 were prepared. This polyester resin film was laminated to the treated steel sheet under the same conditions as in E~ample 3 except for the quenching time to 185C on the surface oE the laminated ~olyester resin film.
Quenching time to 185C ... 15 sec.
lZ0~3751 Comparative Example 3 An aluminum sheet (JIS 3004) having a thickness of 0~23 mm was treated under the same conditions as in Examp:Le 6.
After that, a crystalline and oriented polyester resin film (Trade name: Lumirror S10 made by Tore Co., Ltd.) having a thicXness of 4 ~m was laminated to the treated aluminum sheet under the same conditions as in Example 6.
The characteristics of the resultant metal sheei:
were evaluated by the following test methods, after the measure-ment of the coating weight on the resultant metal sheet by the X-ray fluorescent method, the results of which are shown i.n the Table.
(1) Bonding strength between the metal sheet and the polyester resin film:
The polyester resin film laminated sample was cut to a size of 8 cm x 8 cm, and the polyester resin film laminated side was cut crosswise with a razor. After 6 mm of the sample was extruded by using a conventional Erichsen testing machine, the laminated polyester resin film of the formed part was peeled off by a pincette. Bonding strength was divided into 5 ranks, namely, 5 was excellent, 4 was good, 3 was fair, 2 was poor and 1 was badv
(2) Corrosion resistance against an acidic solut:ion after forming:
The polyester resin film laminated sample was Cllt to a circular blank having a diameter of 80 mm by a punch press, and the blank was deeply drawn to form a cup in which the polyester resin film laminated side was inside at a drawinc~
ratio of 2Ø
50 ml of citric acid adjusted to pll 2.2 was filled into the drawn cup, and the iron or aluminum pick up was measured after aging for 30 days at 55C.
The polyester resin film laminated sample was Cllt to a circular blank having a diameter of 80 mm by a punch press, and the blank was deeply drawn to form a cup in which the polyester resin film laminated side was inside at a drawinc~
ratio of 2Ø
50 ml of citric acid adjusted to pll 2.2 was filled into the drawn cup, and the iron or aluminum pick up was measured after aging for 30 days at 55C.
(3) Discoloration of the laminated polyester res:in film after the retort treatment:
The drawn cup prepared by the method described i:n (2) above was set in a retort into which steam, heated to 125 -130C under a pressure of 1.6 - 1~7 kg/cm2, was blown for 6 hours. After that, the discoloration of the laminated polyester resin film was evaluated by the naked eye.
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. _
The drawn cup prepared by the method described i:n (2) above was set in a retort into which steam, heated to 125 -130C under a pressure of 1.6 - 1~7 kg/cm2, was blown for 6 hours. After that, the discoloration of the laminated polyester resin film was evaluated by the naked eye.
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. _
Claims (18)
1. A method of producing a polyester resin film laminated metal sheet, which comprises laminating a polyester resin film to a metal sheet covered with a double layer con-sisting of an upper layer of hydrated chromium oxide and a lower layer of metallic chromium which is heated to a tempe-rature above the melting point of said polyester resin film and then quenching the resulting laminate.
2. A method according to claim 1, wherein said poly-ester resin film has a crystalline and oriented structure.
3. A method according to claim 2, wherein said poly-ester resin film is produced by esterification of a saturated polycarboxylic acid selected from the group consisting of phthalic acid, iso-phthalic acid, terephthalic acid, succinic acid, azelaic acid, 2,6-naphthalene dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid and trimellitic acid anhydride with a saturated polyalcohol selected from the group consisting of ethylene glycol, 1,4-butane diol, 1,5-pentane diol, 1,6-hexane diol, propylene glycol, 1,4-dimethanol cyclohexane, trimethylol propane and pentaerythritol.
4. A method according to claim 1, wherein said metal sheet is a sheet or strip of steel or aluminum.
5. A method according to claim 1, wherein said metal sheet is a sheet or strip of steel plated with 0.01 to 3.0 g/m2 of nickel.
6. A method according to claim 1, wherein said metal sheet is a sheet or strip of steel plated with 0.05 to 1.0 g/m2 of tin.
7. A method according to claim 1, wherein said metal sheet is a sheet or strip of steel plated with 0.01 to 3.0 g/m2 of nickel and 0.05 to 1.0 g/m2 of tin.
8. A method according to claim 1, wherein said double layer consists of an upper layer of hydrated chromium oxide having 0.005 to 0.05 g/m2 as chromium and a lower layer of metallic chromium in an amount of 0.01 to 0.2 g/m2.
9. A method according to claim 1, wherein the tem-perature of said metal sheet heated just before the lamina-tion of said polyester resin film is maintained in the range of Tm ? Tm + 160°C, Tm representing the melting point of said polyester resin film.
10. A method according to claim 9, wherein said metal sheet is heated to Tm ? Tm + 160°C within 20 seconds using resistance heating, induction heating or both.
11. A method according to claim 1, wherein the maximum temperature on the surface of the laminated polyester resin film is kept below Ts, between the laminating and quenching steps, Ts representing the temperature at which the endothermic reaction of the polyester resin film starts.
12. A method according to claim 11, wherein the maximum temperature on the surface of the laminated polyester resin film is kept below Ts - 20°C.
13. A method according to claims 11 or 12, wherein the quenching time for cooling the laminate to below Ts is below 10 seconds and wherein said quenching is performed by water spray, immersion into water or liquid nitrogen or using a roller cooled by water or liquid nitrogen, the temperature of the water used for quenching being kept below 90°C.
14. A method according to claim 1, wherein the thickness of said polyester resin film is 5 to 100 µm.
15. A method according to claim 14, wherein the thickness of said polyester resin film is 5 to 50 µm.
16. A method according to claim 1, wherein said polyester resin film is a polyester resin film having a biaxially oriented structure.
17. A polyester resin film laminated metal sheet comprising a metal sheet covered with a double layer consist-ing of an upper layer of hydrated chromium oxide and a lower layer of metallic chromium, and a polyester resin film bonded thereto.
18. A polyester resin film laminated metal sheet according to claim 17, wherein said double layer consists of an upper layer of hydrated chromium oxide having 0.005 to 0.05 g/m2 as chromium and a lower layer of metallic chromium in an amount of 0.01 to 0.2 g/m2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000411114A CA1200751A (en) | 1982-09-09 | 1982-09-09 | Method for production of metal sheet covered with polyester resin film |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000411114A CA1200751A (en) | 1982-09-09 | 1982-09-09 | Method for production of metal sheet covered with polyester resin film |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1200751A true CA1200751A (en) | 1986-02-18 |
Family
ID=4123556
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000411114A Expired CA1200751A (en) | 1982-09-09 | 1982-09-09 | Method for production of metal sheet covered with polyester resin film |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1200751A (en) |
-
1982
- 1982-09-09 CA CA000411114A patent/CA1200751A/en not_active Expired
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