JP2005262791A - Polyester resin-coated aluminum alloy sheet and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin-coated aluminum alloy sheet excellent in white turbidity resistance, resistance to heat treatment after working, workability and adhesiveness after working and to provide its production method. <P>SOLUTION: This aluminum alloy sheet is produced by coating either one of its surfaces with a polyester resin film having a double layer structure comprising the inner layer contacting the aluminum alloy sheet and the outer layer which does not contact the alloy sheet. The coated polyester resin film has 80-160 MPa of the average of F50 values (stress at 50% elongation by a tensile test) in the 0, 45, 90 and 135 degree directions and has the ratio of maximum value of F50 to minimum value thereof of ≤2.0. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a polyester resin-coated aluminum alloy plate excellent in white turbidity resistance, post-processing heat resistance, workability, and work adhesion, and a method for producing the same. The present invention relates to a polyester resin-coated aluminum alloy plate used in the above and a method for producing the same, and provides a material suitable for use in which heating for sterilization is performed after filling the contents.

Conventionally, a resin-coated aluminum alloy plate has been used as a material for caps and can lids of food and drink containers. These resin coating layers have been formed by the painting / baking process, but it is desired to avoid the use of solvents from the viewpoint of environmental protection, and because the equipment for painting and baking will be large-scale, Resin film laminating technology, which has a low environmental impact and can be processed with simple equipment, is beginning to be applied.
Among them, a method of bonding a polyester resin film is being developed for practical use because the processability and barrier properties of the film are relatively excellent.

However, when the polyester resin-coated aluminum alloy plate as described above is used, the resin film peels off or breaks during processing in drawing and drawing / ironing to give the cap or lid shape was there.
A method of bonding a polyester resin film to a metal plate using an adhesive has been proposed (see, for example, Patent Documents 1 and 2). According to such a method of bonding via an adhesive, strong adhesion is proposed. However, it requires an adhesive application / drying step, and is low in productivity and impractical.
There has also been proposed a method in which after a polyester resin film is bonded, the resin film is melted by heating to a temperature higher than the melting point of the resin film. According to this method, high process adhesion is obtained, and the film processability is improved because the resin film layer is amorphous. However, the resin film becomes cloudy during the sterilization heat treatment after filling the contents, and the appearance is remarkably inferior.

  A method has also been proposed in which the metal plate is heated to a temperature higher than the melting point of the polyethylene terephthalate film, and then the polyethylene terephthalate film is bonded and then rapidly cooled to make the amorphous state only in the vicinity of the interface with the metal plate in the resin coating layer. (See Patent Documents 3 and 4). According to this method, good adhesion can be obtained without using an adhesive, and the surface layer does not become cloudy even by sterilization heating treatment. However, since the amorphous part near the interface becomes cloudy due to the sterilization heating treatment, the appearance is eventually clouded, and in the case of using a biaxially stretched polyester film, the crystalline part is thermally contracted by heating, and the molded part Wrinkles due to heat shrinkage. Furthermore, in order to make only the vicinity of the interface in the resin coating layer amorphous, it is necessary to control the temperature with extremely high accuracy, which is costly and inferior in productivity.

  Moreover, although the polyester resin film can be made into a copolyester by using an ester unit other than the ethylene terephthalate unit, a method for improving processability and suppressing white turbidity due to sterilization heating is also considered, but the film cost increases and is not practical.

Japanese Patent Application Laid-Open No. 61-20736. JP-A-61-149341. Japanese Patent Publication No. 60-47103. Japanese Patent Application Laid-Open No. 60-168643.

  This invention is made | formed in view of the said situation, The objective of this invention is the polyester used for the cap of a food-drink container excellent in white turbidity resistance, post-processing heat processing property, workability, and process adhesiveness, and a can lid The object is to provide a resin-coated aluminum alloy plate and a method for producing the same.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a two-layer structure comprising an inner layer on the side in contact with the aluminum alloy plate and an outer layer on the side not in contact with the aluminum alloy plate on at least one surface of the aluminum alloy plate. A polyester resin-coated aluminum alloy plate coated with a polyester resin film having a structure, wherein the coated polyester resin film has an F50 value of 0, 45, 90, 135 ° direction average value of 80 to 160 MPa, maximum value / The minimum value ≦ 2.0.

  The invention according to claim 2 is a polyester resin coating in which both surfaces of an aluminum alloy plate are coated with a two-layer polyester resin film comprising an inner layer in contact with the aluminum alloy plate and an outer layer on the side not in contact with the aluminum alloy plate. The polyester resin film coated on one surface of the aluminum alloy plate has an F50 value of 0, 45, 90, 135 ° direction average value of 80 to 160 MPa, maximum value / minimum value ≦ 2.0. And on the other side, the coated polyester resin film has an F50 value of 0, 45, 90, and 135 ° direction average value of less than 80 MPa.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the polyester resin film is a copolymer polyester consisting of ethylene isophthalate units and ethylene terephthalate units alone or a mixture of the copolymer polyester and polyethylene terephthalate. The inner layer has a total content of ethylene isophthalate units of 8 to 16 mol%, the thickness of the inner layer is not less than 3 times the center line average roughness of the aluminum alloy plate surface, and the inner layer of ethylene The total content of isophthalate units is I mol%, and is less than 6- (1/3) I μm, and the outer layer has a total content of ethylene isophthalate units of 3 mol% or less, and the thickness of the outer layer Is 6 to 11 μm.

  Invention of Claim 4 is a manufacturing method of the polyester resin coat | covered aluminum alloy plate of Claim 1 or 3, pre-heating an aluminum alloy plate, and pressurizing this heated alloy plate and a polyester resin film When the total content of ethylene isophthalate units in the inner layer is I mol%, the resin-coated aluminum alloy plate sandwiched between rolls and pressure-bonded is then (250-2.5I) ° C. or higher, And it is characterized by post-heating below the melting point of the outer layer and cooling.

  The invention according to claim 5 is the method for producing a polyester resin-coated aluminum alloy plate according to claim 2 or 3, wherein the aluminum alloy plate is preheated and the polyester resin film is pressed on one side of the heated alloy plate. After pressing and pressure-bonding with a roll, heated above the melting point of the polyester resin, cooled, and then preheated again an aluminum alloy plate coated with the polyester resin on one side, and the heated resin of the aluminum alloy plate A polyester resin film is sandwiched between pressure rolls on the surface not coated with the film, and then pressure-bonded. After that, the laminated resin-coated aluminum alloy plate is further added to the total content of ethylene isophthalate units in the inner layer. When it is mol%, it is characterized by being post-heated and cooled at (250-2.5I) ° C. or higher and lower than the melting point of the outer layer.

In the following, the conditions limited in the present invention and the actions associated therewith will be described.
(Average value of F50 values)
When the average value of F50 values in the 0, 45, 90, and 135 ° directions is 80 to 160 MPa, generation of white turbidity and wrinkles in the sterilization heat treatment can be effectively prevented. When the average F50 value is less than 80 MPa, the white turbidity resistance in the sterilization heat treatment decreases, and when the F50 value exceeds 160 MPa, wrinkles are likely to occur in the sterilization heat treatment. Therefore, the average value of F50 values was 80 to 160 MPa. For the same reason, 100 to 135 MPa is preferable.

(F50 value ratio)
By satisfying the maximum value / minimum value of the F50 value ≦ 2.0, it is possible to suppress the occurrence of local wrinkles in the sterilization heat treatment. When the maximum value / minimum value of the F50 value exceeds 2.0, the residual stress in the film produced by the forming process has a strong anisotropy, and local wrinkles are likely to occur due to the sterilization heating treatment. Therefore, the maximum value / minimum value ≦ 2.0, and preferably 1.5 or less.

(The film F50 value on the other side is less than 80 MPa)
In particular, when used for a screw cap, if the film F50 value on the inner surface of the screw cap is less than 80 MPa, characteristics excellent in wear resistance due to repeated opening and closing can be obtained. In the case of 80 MPa or more, the wear resistance is poor.

(Total content of ethylene isophthalate units in the film inner layer is 8 to 16 mol%)
The inclusion of 8% or more provides a melting point difference between the outer layer and the inner layer that can sufficiently ensure the temperature range at which the F50 value of the outer layer can be post-heated at a temperature that does not become less than 80 MPa at an industrial level, and the inner layer sufficiently It flows and good adhesion is obtained. Further, if the deformation resistance of the inner layer is low, the outer layer after molding is easily contracted by sterilization heat treatment. Therefore, the higher the deformation resistance of the inner layer, the higher the heat resistance after processing. The deformation resistance of the inner layer decreases as the total content of ethylene isophthalate units among the ester units in the inner layer increases. Therefore, the total content of ethylene isophthalate units in the inner layer needs to be 16 mol% or less.

(Thickness of the inner layer of the film is 3 times or more of the center line average roughness of the aluminum alloy plate surface, and the total content of ethylene isophthalate units in the inner layer is less than 6- (1/3) I μm )
When the thickness of the inner layer is thin, sufficient work adhesion may not be obtained. The surface of the aluminum alloy plate has surface irregularities corresponding to the irregularities on the surface of the rolling roll. In order for the surface of the aluminum alloy plate and the surface of the film to be fully integrated, a certain amount of inner layer is required. When the amount of the inner layer is small, a gap is formed in the recess of the aluminum plate, and the true adhesion area is reduced. However, sufficient work adhesion cannot be obtained. Therefore, the thickness of the inner layer of the film is preferably at least 3 times the center line average roughness of the aluminum alloy plate surface.
Further, if the deformation resistance of the inner layer is low, the outer layer after molding is easily contracted by sterilization heat treatment. Therefore, the higher the deformation resistance of the inner layer, the higher the heat resistance after processing. The deformation resistance of the inner layer decreases as the thickness of the inner layer increases. Therefore, the thickness of the film inner layer needs to be less than 6- (1/3) I μm, where the total content of ethylene isophthalate units in the inner layer is I mol%.

(Total content of ethylene isophthalate units in the film outer layer is 3 mol% or less)
By mixing the copolymer component with the outer layer, the white turbidity of the resin film can be suppressed. However, the increase of the copolymer component increases the manufacturing cost of the resin film, which is not practical. Although it is necessary to reduce the copolymerization component as much as possible from the cost aspect, considering that the ethylene isophthalate unit contained in the inner layer is included in the outer layer to some extent, the total content of ethylene isophthalate units in the outer layer is 3 mol% or less. It was.

(Outer layer thickness is 6-11 μm)
In order to obtain white turbidity resistance, when the oriented crystal formed at the time of extending | stretching is made to remain in a coating resin film, the workability of a coating resin film is falling compared with an amorphous state. If the molding process such as drawing or ironing is performed in such a state, the coated resin film may be broken.
The triaxiality of stress generated in the coating resin film affects the breaking of the coating resin film. The smaller the stress triaxiality, the larger the processing can be performed without breaking the coated resin film. In order to reduce the stress triaxiality, it is effective to reduce the thickness of the coating resin film. Therefore, the thickness of the outer layer needs to be 11 μm or less, preferably 9 μm or less.
On the other hand, if the thickness of the outer layer is less than 6 μm, the cost required for biaxial stretching increases.

(When the total content of ethylene isophthalate units in the film inner layer is I mol%, it is post-heated at (250-2.5I) ° C. or higher and lower than the melting point of the outer layer)
When the polyester resin film is sandwiched between the pressure rolls and pressure bonded to the surface of the aluminum alloy plate, the aluminum alloy plate is heated by heating the plate temperature of the aluminum alloy plate and the surface temperature of the pressure roll above the glass transition temperature of the inner layer. An alloy plate and a polyester resin film can be bonded together. Even in this state, a certain degree of adhesion is obtained, but the resin-coated film can be easily peeled off by mild processing. The cause of this is that the air entrained between the aluminum alloy plate and the resin film at the time of press-fitting obstructs the close contact between the aluminum alloy plate and the resin film, and the true contact area is reduced. Therefore, in order to obtain high processing adhesion, it is necessary to remove the air that has been caught after the aluminum alloy plate and the resin film are bonded together by pressure bonding. It is possible to remove the entrained air by performing post-heating at a relatively high temperature after bonding by pressure bonding, and as a post-heating, the total content of ethylene isophthalate units in the inner layer is When it is defined as I mol%, it is necessary that it is (250-2.5I) ° C. or higher and lower than the melting point of the outer layer. The melting point here corresponds to a temperature at which the average F50 value is less than 80 MPa.

  As described above, according to the present invention, a polyester resin-coated aluminum alloy plate used for caps and can lids of food and drink containers excellent in white turbidity resistance, post-processing heat resistance, workability, and processing adhesion is obtained. It is done. Moreover, according to the manufacturing method of this invention, the said polyester resin coating aluminum alloy plate can be obtained reliably.

Embodiments of the present invention will be described below.
As an aluminum alloy plate used for the polyester resin-coated aluminum alloy plate of the present invention, any aluminum alloy plate generally used for caps and can lids for food and drink can be used. For example, an aluminum alloy plate such as JIS1200, 3003 can be used for a cap application, and an aluminum alloy plate such as JIS5182 can be used for a can lid application. In order to improve the adhesion to the polyester resin film, it is desirable that the alloy plate is subjected to a chromate treatment, an alumite treatment, or the like on the surface thereof. Recently, a non-porous alumite technique has been developed, and this technique is particularly suitable because a high true contact area can be obtained. Further, when higher work adhesion is required, a silane coupling agent can also be used.

The aluminum alloy plate is usually subjected to a resin coating process in a coil state. The aluminum alloy plate is first heated by a preheating device in the resin coating step. As the heating device, an appropriate device such as a heating roll, an electric furnace, a gas oven, an induction heating device, or an infrared heating device can be used, and these devices can be used in combination as necessary.
The resin film having the above-described predetermined composition coated on the aluminum alloy plate is also coiled and placed in the vicinity of the pressure roll.
The preheated alloy plate is sent to a pressure roll together with the resin film and pressure bonded. At the time of pressure bonding, the resin film may be coated on both surfaces of the aluminum alloy plate, or the resin film may be coated on one surface of the aluminum alloy plate.

The resin-coated aluminum alloy plate coated with the resin as described above is further transferred from the pressure roll to the post-heating step, and subjected to post-heating treatment. As described above, the temperature of the post-heat treatment is set to a range of (250-2.5I) ° C. or higher and lower than the melting point of the outer layer when the total content of ethylene isophthalate units in the inner layer is I mol%. .
High post-heating adhesion can be obtained by the post heating. At that time, if necessary, the post-heating temperature may be selected within the range of the upper and lower limit temperatures, and the heat treatment of the aluminum alloy plate may also be performed. In the post-heating treatment, an appropriate heating device is used as in the preheating.
The resin-coated aluminum alloy sheet produced as described above has excellent properties such as white turbidity resistance, post-processing heat treatment resistance, workability, and work adhesion.

When one side of the aluminum alloy plate is coated with a resin film and post-heated at a temperature equal to or higher than the melting point of the outer layer, the single-side coated aluminum alloy plate is cooled and preheated again, and transferred to the pressure bonding process. When a resin film is pressure-bonded to the surface of the alloy plate that is not coated with resin and the total content of ethylene isophthalate units in the inner layer of the resin film is I mol%, (250-2. 5I) Post-heating is performed in the range of not lower than the temperature and lower than the melting point of the outer layer.
According to this method, one surface is excellent in abrasion resistance, and the other surface is excellent in cloudiness resistance, post-processing heat resistance, workability, and processing adhesion, and is particularly suitable for applications such as screw caps. An alloy plate can be obtained.
In the case of this method, it is advantageous from the viewpoint of suppressing the cost of the resin film that the resin film coated on each surface is the same.

Hereinafter, examples of the present invention will be described in comparison with comparative examples.
A 0.28 mm thick aluminum alloy plate made of a JIS 5182 aluminum alloy plate was subjected to phosphoric acid chromate treatment by a conventional method so that the amount of chromium deposited was 15 mg / m ² .
On the other hand, as the resin film to be coated on the aluminum alloy plate, those made of ethylene isophthalate units and ethylene terephthalate units are used, and the inner layer on the side in contact with the aluminum alloy plate and the outer layer on the side not in contact with the aluminum alloy plate are used. A two-layer polyester film was prepared. This two-layer polyester film is obtained by biaxial stretching and heat treatment after coextrusion molding.

  After heating the said aluminum alloy plate with a preheating apparatus, the pressure roll was passed and the resin film was crimped | bonded to the single side | surface of the aluminum alloy plate. Next, the resin-coated aluminum alloy plate was passed through a post-heating device for post-heating, and then cooled.

  In addition, after heating the aluminum alloy plate with a preheating device, a pressure roll is passed through, a resin film is pressure-bonded to one side of the aluminum alloy plate, and then the single-sided resin-coated aluminum alloy plate is passed through a post-heating device, It cooled after heating beyond the melting | fusing point of the outer layer of a resin film. Thereafter, the single-sided resin-coated aluminum alloy plate was preheated again, and the resin film was pressure-bonded to the surface of the single-sided resin-coated aluminum alloy plate that was not coated with the resin through the pressure roll. Next, the resin-coated aluminum alloy plate was passed through a post-heating device for post-heating, and then cooled.

Table 1 shows the resin-coated aluminum alloy plate obtained in the above process. Table 1 shows the surface roughness of the aluminum alloy plate, the total content of ethylene isophthalate units in the inner layer, and the post-heating temperature after bonding.
The following evaluation tests were performed on the resin-coated aluminum alloy plate shown in Table 1.

(F50 value)
The resin-coated aluminum alloy plate was immersed in an aqueous hydrochloric acid solution to dissolve the aluminum portion, thereby obtaining a coated film. Tensile tests were performed in 0 °, 45 °, 90 °, and 135 ° directions with respect to the longitudinal stretching direction of the film. The tensile test was performed at a tensile speed of 200 mm / min by chucking only 25 mm at each end of the film cut into a width of 15 mm and a length of 100 mm. At that time, the stress (F50 value) at which the elongation becomes 50% was determined, and the result is shown in Table 2.

(White turbidity resistance)
The resin-coated aluminum alloy plate was heat-treated at 210 ° C. for 5 minutes, and the degree of white turbidity was measured with a color difference meter. Color measurement was performed with an L ^* a ^* b ^* optical system, and a color difference ΔE ^* was determined by the following equation.
ΔE ^* = (ΔL ^{* 2} + Δa ^{* 2} + Δb ^{* 2} ) ^1/2
The smaller the color difference ΔE ^* , the smaller the color change (white turbidity) due to heating. If ΔE ^* is 0 to less than 0.5, ○, 0.5 to less than 1.5, 1.5 or more ×. It was determined. Table 2 shows the determination results.

(Heat resistance after processing)
The resin-coated aluminum alloy plate was deep drawn by a deep drawing tester, and before the drawing was completed, the drawing was interrupted and formed into a hat shape. The obtained hat-shaped resin-coated aluminum alloy plate was heated at 150 ° C. for 90 seconds, and the number of wrinkles generated on the flange portion of the cup was counted. The smaller the number of wrinkles, the better the heat resistance after processing, and when the number of wrinkles was 50 or less, it was judged as ◯ if it was 51 to 100, or x when it exceeded 100. Table 2 shows the determination results.

(Processability)
The resin-coated aluminum alloy plate was deep drawn and ironed by a deep drawing tester. The wall part of the obtained resin-coated aluminum alloy cup was observed, and the damage state of the film was observed. The case where no damage was observed on the film was evaluated as “◯”, the case where a crack was partially observed on the film surface was evaluated as “Δ”, and the case where the film was completely broken was determined as “X”. Table 2 shows the determination results.

(Processing adhesion)
The resin-coated aluminum alloy plate was cold-rolled at a rolling reduction of 10%. The adhesiveness of the resin-coated aluminum alloy sheet after rolling was evaluated by a V-shaped tear test. As shown in FIG. 1, about 10 mm of two cuts were introduced into the resin-coated aluminum alloy plate 11 at intervals of 8 mm. Scratches 12 to the extent that the film is cut using a cutter or the like as shown in FIG. Thereafter, the portion 3 between the cuts is bent as shown in FIG. 1 (b), and is immersed in 55 ° C. water for 30 minutes. Thereafter, the portion 13 between the cuts is torn as shown in FIG. At that time, a triangular tearing portion 14 is formed as shown in FIG. The film 15 peeled off from the evaluation surface remains in the tear portion 14. The area of the entire triangular tearing part and the area of the peeled film were measured, and the peeling ratio by (area of peeled film) / (area of the whole tearing part) was calculated. The smaller the peel ratio, the higher the adhesion after processing, and it was judged as ○ when the average peel ratio measured 5 times was 65% or less, and x when exceeding. Table 2 shows the determination results.

(Abrasion resistance)
The resin-coated aluminum alloy plate was subjected to a high speed friction test. The abrasion state of the resin film after testing at a friction speed of 400 mm / sec and a pressing load of 100 kg was confirmed. When the generation of wear powder was not observed, it was judged as ◯, and when the generation of wear powder was found, it was judged as Δ.

It is a figure which shows the process of the V-shaped tear test in the Example of this invention. It is a figure which shows the part between the tearing part in the same V-shaped tearing test, and the torn cut.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Resin-coated aluminum alloy plate 12 Scratch 13 Part between cuts 14 Tear part 15 Peeled film

Claims (5)

A polyester resin-coated aluminum alloy plate in which at least one surface of an aluminum alloy plate is coated with a polyester resin film having a two-layer structure including an inner layer in contact with the aluminum alloy plate and an outer layer not in contact with the aluminum alloy plate The polyester resin film thus coated has an F50 value of 0, 45, 90, an average value in the 135 ° direction of 80 to 160 MPa, and a maximum value / minimum value ≦ 2.0. Coated aluminum alloy plate. A polyester resin-coated aluminum alloy plate in which a two-layer polyester resin film comprising an inner layer on the side in contact with the aluminum alloy plate and an outer layer on the side not in contact with the aluminum alloy plate is coated on both sides of the aluminum alloy plate, The coated polyester resin film has an F50 value of 0, 45, 90, 135 ° direction average value of 80 to 160 MPa, maximum value / minimum value ≦ 2.0, and the other surface is coated. The polyester resin film is a polyester resin-coated aluminum alloy plate characterized in that F50 values of 0, 45, 90, and 135 ° direction average values are less than 80 MPa. The polyester resin film is composed of a copolymerized polyester consisting of ethylene isophthalate units and ethylene terephthalate units alone or a mixture of the copolymerized polyester and polyethylene terephthalate, and the inner layer has a total content of ethylene isophthalate units of 8 to 16. The inner layer has a thickness of at least 3 times the center line average roughness of the aluminum alloy plate surface, and the total content of ethylene isophthalate units in the inner layer is I mol%. 3) The outer layer has a total content of ethylene isophthalate units of 3 mol% or less, and the outer layer has a thickness of 6 to 11 μm. Polyester resin coated aluminum alloy plate. 4. The method for producing a polyester resin-coated aluminum alloy plate according to claim 1 or 3, wherein the aluminum alloy plate is preheated, and the heated alloy plate and the polyester resin film are sandwiched between pressure rolls and pressure-bonded. Thereafter, when the total content of ethylene isophthalate units in the inner layer is defined as I mol%, the laminated resin-coated aluminum alloy plate is further heated to (250-2.5I) ° C. or higher and lower than the melting point of the outer layer. A method for producing a polyester resin-coated aluminum alloy plate, characterized by heating and cooling. A method for producing a polyester resin-coated aluminum alloy plate according to claim 2 or 3, wherein the aluminum alloy plate is preheated, and a polyester resin film is sandwiched between pressure heated rolls on one side of the heated alloy plate and pressure bonded. Then, after heating above the melting point of the polyester resin and cooling, the aluminum alloy plate coated with the polyester resin on one side is preheated again, and the heated aluminum alloy plate on the side not coated with the resin film When a polyester resin film is sandwiched between pressure rolls on the surface and pressed and pressure-bonded, and then the laminated resin-coated aluminum alloy plate further has a total content of ethylene isophthalate units in the inner layer of I mol%, (250 -2.5I) A polyester resin-coated adhesive which is post-heated and cooled at a temperature not lower than the melting point of the outer layer and lower than the melting point of the outer layer. Method of manufacturing a Miniumu alloy plate.

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