JP2000211083A - Polyester laminated film, laminated metal panel using the same and lid for film laminated easy open can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester laminated film excellent in the close adhesiveness with a metal, moldability and heating treatment resistance, capable of being satisfied from an aspect of strength and not generating a feathering phenomenon or a hairing phenomenon at a time of opening, a film laminated metal panel and a lid for an easy open can. SOLUTION: In a polyester laminated film, the crystallizing peak temp. of the laminated film at a time of a temp. rise is 60-110 deg.C and the surface layer on one side of the laminated film is constituted of a polyester layer with a fusion peak temp. of 200-260 deg.C and a crystallizing peak temp. at a time of a temp. rise of 60-110 deg.C and the surface layer on the other side of the laminated film is constituted of a polyester layer with a fusion peak temp. of 180-240 deg.C and a crystallizing peak temp. at a time of a temp. rise of 60-110 deg.C and the fusion peak temp. of the polyester layer on one side is higher than that of the polyester layer on the other side by 5-25 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester laminated film for laminating a lid for an easy-open can (easy-opening can) used for canning of beverages and foods such as soft drinks and beer, and the film is laminated. And a lid for an easy-open can formed by molding the metal plate.

[0002]

2. Description of the Related Art As a method for preventing corrosion of inner and outer wall surfaces of a metal can, there is a method of laminating a thermoplastic film. For example, JP-A-7-227946 discloses a polyester film for laminating a metal material for canning food.

[0003] This polyester-based film has excellent scratch resistance. For example, a film is laminated in a can-making process in which a metal plate is formed into a cylinder and a lid is wound around upper and lower openings of the cylinder. When transferring a metal plate (hereinafter, referred to as a film-laminated metal plate) or processing a film-laminated metal plate by winding or the like, scratches are generated on the film surface of the film-laminated metal plate using the film. Does not reduce the commercial value of the product.

[0004] Further, the polyester-based film is excellent in resistance at the time of winding-up processing and has a small amount of oligomers eluted when a food is filled and heat treatment such as retort treatment is performed after the can is made. Excellent as a polyester film to be laminated on inner and outer wall surfaces.

[0005]

The cans used for the above-mentioned applications include a so-called three-piece can in which a lid is attached to the upper and lower openings of a metal cylinder formed by molding a metal plate into a cylinder. There is a so-called two-piece can formed by deep-drawing a metal plate to form a container portion and winding a lid on the upper surface opening of the container portion.

In the case of a three-piece can, the film-laminated metal plate is simply formed into a cylindrical shape as described above. In the case of a two-piece can, the film-laminated metal plate is drawn and ironed. Will be. Therefore, in order to be applicable to a two-piece can, it is necessary to have good moldability to be formed following the formation of a metal plate and to have excellent adhesion to the metal plate. If the formability of the film is insufficient or the adhesion to the metal plate is insufficient, the film will peel off from the metal plate, a so-called delamination phenomenon will occur, Is torn.

[0007] Further, in both the three-piece can and the two-piece can, a lid for an easy-open can is used as a lid material.
In order to be able to apply to the lid for easy open cans because it is subjected to processing such as crimping (rivet) processing for processing of the container part and the part to be tightened, and attachment of the pull tab used at the time of opening, the film is made of the above-mentioned two-piece can. Similarly, it must be excellent in moldability and adhesion to a metal plate.

Further, in order to be applicable to the lid for the easy-open can, in addition to the case of the above-mentioned two-piece can, a laminated film such as a band or a thread is formed at the end of the opening after the opening. It is required that a so-called feathering phenomenon and a hairing phenomenon do not occur in the form of, and further, for a film laminated on the outer surface of the can lid, a retort treatment performed after can making through the above-described molding process and Appearance is required to prevent whitening and oligomer precipitation even by heat treatment such as printing.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a film having excellent adhesion to metal so that it can be applied as a so-called laminated film for a lid for an easy-open can. Excellent in moldability and heat treatment resistance, satisfactory in strength, and not causing a feathering phenomenon and a hair ring phenomenon at the time of opening, a film laminated metal plate using the same, and forming the metal plate To provide a lid for an easy-open can.

[0010]

The present invention is as follows. (1) In a polyester laminated film in which a plurality of polyester layers are laminated, the crystallization peak temperature when the temperature of the laminated film is raised is 60 to 110 ° C., and the surface layer on one side of the laminated film has a melting peak temperature of 200 ° C. ~ 260 ° C
A polyester layer having a crystallization peak temperature of 60 to 110 ° C. at the time of temperature rise, and the other surface layer of the laminated film has a melting peak temperature of 180 to 240 ° C. and a crystallization peak temperature at the time of temperature rise. Is composed of a polyester layer of 60 to 110 ° C., and the melting peak temperature of the polyester layer on one side is higher than the melting peak temperature of the polyester layer on the other side by 5 to 5.
A polyester laminated film characterized by being 25 ° C. higher. (2) The polyester laminated film according to the above (1), which is biaxially stretched. (3) A film-laminated metal plate, wherein the polyester laminated film according to (1) or (2) is laminated on a metal plate such that the other side of the film is in contact with the metal plate. (4) The film-laminated metal plate according to (3), wherein the film is rapidly cooled after heat treatment so as to be substantially in an amorphous / non-oriented state. (5) The polyester laminated film according to the above (1) or (2) is laminated such that the other side of the film is in contact with an easy-open can lid, and the crystallinity of the laminated film defined by the following formula is: A lid for a film-laminated easy-open can characterized by being 30% or less.

[0011]

(Equation 2)

(6) A lid for a film-laminated easy-open can according to the above (5), which is formed by molding the film-laminated metal plate according to the above (3) or (4). (7) The above (5) or (6) wherein the polyester laminated film is laminated on the outer surface of the easy open can lid.
A lid for the described film-laminated easy open can. (8) The above (5) or (6), wherein the polyester laminated film is laminated on the inner surface of the easy open can lid.
A lid for the described film-laminated easy open can.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester laminated film of the present invention is a film in which the polyester layer constituting the surface layer is composed of a specific polyester layer as shown below.

First, one side of the polyester laminated film of the present invention, specifically, the polyester layer (hereinafter abbreviated as “polyester layer A”) on the side of the film-laminated metal plate that is not in contact with the metal plate will be described.

The polyester layer A has a melting peak temperature of 2
The crystallization peak temperature at the time of temperature rise is 60 to 260 ° C.
A polyester layer having a temperature of 110 ° C., comprising a polyester composition A.

The reason why the melting peak temperature is 200 to 260 ° C. is to prevent the polyester layer A from being melted in a laminating step with a metal plate as described later. The melting peak temperature is preferably 210 to 25
The temperature is 0 ° C, more preferably 220 to 240 ° C.

The crystallization peak temperature at the time of temperature rise is 60 to
110 ° C. means that the crystallization peak temperature is the crystallization temperature of general polyethylene terephthalate (150 to 17).
0 ° C.), even after laminating the film on a metal plate and then performing a remelt treatment to make the film substantially non-oriented, the polyester in the retort-treated film after can-making does not contain polyester. The crystallization speed is high, and although fine crystals are generated, coarse crystals are hard to grow, so that whitening of the film and generation of white spots are suppressed.
If the crystallization peak temperature at the time of raising the temperature is lower than 60 ° C., the film forming property is reduced. The crystallization peak temperature at the time of raising the temperature is preferably 65 to 105C, more preferably 70 to 100C.

Here, in order to set the melting peak temperature of the polyester layer A and the crystallization peak temperature at the time of raising the temperature to the above ranges, respectively, the polyester contained in the polyester composition A is mixed with the desired melting peak temperature or at the time of the rising temperature. A method of selecting one or two or more such that the crystallization peak temperature is obtained, a method of using a polyester whose polymerization component is selected so as to obtain a desired melting peak temperature or a crystallization peak temperature when the temperature is increased, and the like. Is adopted. In the present invention, the melting peak temperature and the crystallization peak temperature at the time of temperature rise are measured by the methods described later.

The structure of the polyester contained in the polyester composition A is not particularly limited as long as it satisfies the above requirements, but a polyethylene terephthalate copolymer and / or a polybutylene terephthalate copolymer are preferred.

The other copolymer components constituting the polyester include isophthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid,
4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane-1,4-dicarboxylic acid, dimer acid, etc. A dicarboxylic acid component; a glycol component such as propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; p-oxybenzoic acid An oxycarboxylic acid component such as an acid is exemplified. In addition, a small amount of amide bond as a copolymer component other than these,
A compound having a urethane bond, an ether bond, a carbonate bond, or the like may be included.

The above polyester is synthesized by a conventionally known method such as a direct esterification method in which a dicarboxylic acid and a diol are directly reacted; and a transesterification method in which a dimethyl ester of a dicarboxylic acid is reacted with a diol. Each of these methods may be performed by a batch method or a continuous method. Alternatively, a solid-phase polymerization method may be used to increase the molecular weight. The solid phase polymerization method is also preferable from the viewpoint of reducing the content of the cyclic trimer as described below. The polyester synthesized in this way may be included in the polyester composition A alone, or may be included as a mixture of two or more.

In the polyester composition A, the content of the cyclic trimer including the cyclic trimer of ethylene terephthalate is preferably 0.7% by weight or less, more preferably 0.6% by weight or less. More preferably 0.5% by weight
It is as follows. The content of the cyclic trimer is preferably 0.1.
The reason for setting the content to 7% by weight or less is to suppress the precipitation of oligomers on the film. As described below, when manufacturing a lid for an easy-open can, a metal plate on which the film of the present invention is laminated is subjected to a remelt treatment so that the film is in a non-oriented state, and then a lid forming process may be performed. . Oligomers are more likely to precipitate in non-oriented polyester than in oriented polyester. Therefore, if the film contains more than 0.7% by weight of cyclic trimers, for example,
When a metal plate on which this film is laminated is used as a lid of a can filled with food using a lid for an easy-open can formed so that the film becomes an inner surface of the lid, when a heat treatment such as a retort treatment is performed, the polyester layer A Oligomers are eluted in large quantities from, and the oligomers migrate to the food, adversely affecting the taste and flavor of the food. In addition, in an easy-open can lid formed by forming a metal plate on which this film is laminated so that the film becomes an outer surface of the lid, when oligomers precipitate from the polyester layer A,
The appearance is unfavorably impaired.

The method for reducing the content of the cyclic trimer including the ethylene terephthalate cyclic trimer in the polyester layer A to 0.7% by weight or less is not particularly limited. A method of extracting and removing the cyclic trimer with water or an organic solvent, a method of forming the polyester layer A using a polyester having a small amount of the cyclic trimer, and the like can be given. Of these, the method is more economical and preferable.

In the above method, the method for producing the polyester having a low content of the cyclic trimer is not limited.
Solid-state polymerization method; a method of extracting and removing a cyclic trimer after polymerization by heating under reduced pressure or by extraction with water or an organic solvent; and a method combining these methods. In particular, a method for producing a polyester having a low content of cyclic trimer by a solid phase polymerization method, and then extracting the obtained polyester with water to further reduce the cyclic trimer is a method of forming a cyclic trimer in a film forming step. It is most preferable because the amount of body formation can be suppressed.

The polyester composition A may contain a lubricant, inorganic fine particles,
Additives such as incompatible thermoplastic resins, antioxidants, heat stabilizers, ultraviolet absorbers, plasticizers, pigments, antistatic agents, lubricants, and crystal nucleating agents may be included.

As the lubricant, inert inorganic particles such as silica, alumina, kaolin, clay, titanium oxide, calcium phosphate, calcium carbonate, lithium fluoride, barium sulfate, and carbon black can be used. When the lubricant is contained in the polyester composition A in an amount of 0.05 to 1% by weight, the releasability from a mold at the time of molding can be improved. Further, when the laminated film of the present invention is used particularly for the outer surface of an easy-open can lid, it is a preferred embodiment to incorporate 0.01 to 1% by weight of an antioxidant into the polyester composition A. .

The intrinsic viscosity of the polyester composition A when the above-mentioned various components are mixed is preferably in the range of 0.6 to 1.2. When the intrinsic viscosity of the polyester composition A is less than 0.6, the mechanical properties of the obtained film may be deteriorated. When the intrinsic viscosity exceeds 1.2, the quality is excessive and the productivity of the raw material polyester is increased. Is not economical because it falls. In the present invention, the intrinsic viscosity is measured by a method described later.

Next, the other side of the polyester laminated film of the present invention, specifically, the polyester layer (hereinafter abbreviated as "polyester layer B") on the side in contact with the metal plate in the film laminated metal plate will be described.

The polyester layer B has a melting peak temperature of 1
80-240 ° C, the crystallization peak temperature at the time of temperature rise is 60-
A polyester layer having a temperature of 110 ° C., which is composed of a polyester composition B.

The reason why the melting peak temperature is 180 to 240 ° C. is that the polyester layer B must be melted and adhered to the metal plate during the production of the film-laminated metal plate.
This is to suppress the occurrence of the feathering phenomenon and the hairing phenomenon described above in the easy-open can lid formed using the metal plate. The melting peak temperature is preferably 190 to 230 ° C, more preferably 20 to 230 ° C.
0-220 ° C.

The crystallization peak temperature at the time of temperature rise is 60 to
The reason why the temperature is 110 ° C. is to prevent the growth of coarse crystals that cause whitening and spots of whitening of the film by retorting after can-making even if remelting is performed as in the case of the polyester layer A. It is. If the crystallization peak temperature at the time of raising the temperature is lower than 60 ° C., the film forming property is reduced. The crystallization peak temperature at the time of raising the temperature is preferably 65 to 105C, more preferably 70 to 100C.

Here, in order to set the melting peak temperature of the polyester layer B and the crystallization peak temperature at the time of raising the temperature to the above ranges, respectively, the polyester contained in the polyester composition B is mixed with the desired melting peak temperature or at the time of the rising temperature. A method of selecting one or two or more such that the crystallization peak temperature is obtained, a method of using a polyester whose polymerization component is selected so as to obtain a desired melting peak temperature or a crystallization peak temperature when the temperature is increased, and the like. Is adopted.

Further, the melting peak temperature of the polyester layer B is 5 to 2 times lower than the melting peak temperature of the polyester layer A.
It is necessary to select the polyester so that the temperature is lowered by 5 ° C. This is to prevent the polyester layer A from melting when the polyester layer B melts in the production of the film-laminated metal plate.

The structure of the polyester contained in the polyester composition B is not particularly limited as long as it satisfies the above requirements, but a polyethylene terephthalate copolymer and / or a polybutylene terephthalate copolymer are preferred. Further, as other copolymer components constituting the polyester, as in the case of the polyester copolymer component contained in the polyester composition A, isophthalic acid, p
-Β-oxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-dicarboxydiphenyl, 4,
4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-
Sodium sulfoisophthalic acid, cyclohexane-1,
Dicarboxylic acid components such as 4-dicarboxylic acid and dimer acid;
Propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimethanol, ethylene oxide adduct of bisphenol A, glycol components such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., and oxycarboxylic acid components such as p-oxybenzoic acid And the like. In addition, a small amount of a compound having an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be contained as a copolymer component other than these.

The polyester synthesizing method, the additives that can be added to the polyester composition B as required within the range satisfying the above requirements, the intrinsic viscosity of the polyester composition B, and the like are the same as those of the polyester layer A. It is.

In the polyester laminated film of the present invention, the thickness of the polyester layer A is preferably from 3 to 20 μm, and the thickness of the polyester layer B is preferably from 3 to 20 μm. The thickness of the polyester layer A is 3 μm
If it is less than 30, it is not possible to exhibit sufficient mold releasability with a mold in molding processing of an easy open can lid, etc.
If the thickness exceeds 20 μm, the effect for the purpose is saturated, which is economically disadvantageous. Further, if the thickness of the polyester layer B is less than 3 μm, sufficient adhesion to the metal plate cannot be exhibited, and if it exceeds 20 μm, it is economically disadvantageous as in the case of the polyester layer A. However, the thickness of the entire laminated film is 10 to 40 μm
It is preferred that

The laminated film of the present invention is only required to be laminated so that the surface layer on one side is the polyester layer A and the surface layer on the other side is the polyester layer B. A laminated film having a multilayer structure in which a polyester layer having the same composition or a different composition as the polyester layer A or the polyester layer B is further laminated between the layer B and the polyester layer A or the polyester layer B may be used. The lamination method is also not particularly limited, and may be manufactured by a multilayer extrusion method or an extrusion lamination method.

The laminated film of the present invention has a two-layer structure of a polyester layer A and a polyester layer B,
Also in the case of a multilayer structure, the crystallization peak temperature at the time of raising the temperature of the entire laminated film is 60 to 110 ° C. This is to prevent whitening and white spots on the film due to the retort treatment.
The crystallization peak temperature at the time of raising the temperature is preferably 65 to 105.
° C, more preferably 70 to 100 ° C.

The laminated film of the present invention is preferably a biaxially stretched film, and the biaxial stretching method may be any one of sequential biaxial stretching, simultaneous biaxial stretching, and a combination thereof. Good. And in the case of sequential biaxial stretching,
Generally, a method in which the film is stretched in the longitudinal direction and then stretched in the horizontal direction is adopted, but the stretching may be performed in a reverse order. After the biaxial stretching, it is preferable to fix the orientation of the polyester by heat treatment. However, after the biaxial stretching, the polyester may be stretched again in the longitudinal direction and / or the width direction before being subjected to the heat treatment step. Further, there is no restriction on performing a corona discharge treatment or a predetermined coating treatment on one or both surfaces of the film before or after the stretching step.

Further, in the laminated film of the present invention, the force of the film as a whole to shrink is from 0 to 3
g / 4 mm. Even in the case of a biaxially oriented film, the force to shrink is preferably within the range. If the latent shrinkage of the laminated film is large, the film shrinks during the remelting process after forming the film-laminated metal plate, causing a delamination phenomenon or the adhesion between the polyester layer B and the metal plate. This is because when the value is sufficient, only the polyester layer A not in contact with the metal plate shifts, that is, a phenomenon called so-called film shift occurs.

In order to set the force for shrinking the film within the above range, a method of stretching the film at the time of film formation and then performing a heat treatment while relaxing the film at a melting peak temperature of −20 ° C. to fix the orientation is employed. Is done. In the present invention, the force for shrinking the film is measured by a method described later.

The film-laminated metal plate of the present invention is obtained by laminating the above-mentioned laminated film of the present invention so that the polyester layer B is in contact with the metal plate. This is because excellent adhesion can be exhibited by bringing the polyester layer B having adhesiveness into contact with the metal plate.

The method of laminating the laminated film on the metal plate is not particularly limited, and for example, a dry laminating method, a thermal laminating method and the like can be adopted. Specifically, the polyester layer B of the laminated film is brought into contact with the surface of a metal plate heated to a temperature at which the polyester layer B can be melted at a temperature at which the polyester layer B can be melted, and the polyester film is passed through the nip roll in such a state. Layer B
Is melted. Next, lamination is performed by rapid cooling at 10 to 40 ° C. After passing through the nip roll, heat treatment may be performed at a temperature equal to or higher than the melting point of the polyester layer B, if necessary.

The lamination of the film may be performed on only one side of the metal plate or on both sides. In the case of double-sided lamination, they may be laminated simultaneously or sequentially.

When the film-laminated metal sheet of the present invention is applied to an easy-open can lid, the crystallinity of the film in the easy-open can lid formed from the metal sheet described below is set to 30% or less. In a preferred embodiment, the film-laminated metal plate is heated at a temperature equal to or higher than the melting point of the polyester constituting the film and then quenched. The crystallinity of the film in the film-laminated metal plate after the remelt treatment is 10% or less, and becomes substantially non-oriented. In other words, in the biaxially stretched film in which the polyester is in the oriented state, it is difficult to plastically deform and extend, so it is difficult to form the lid portion, and in severe cases, the delamination phenomenon that the film is peeled off from the metal plate occurs, This is because they can be torn or scraped. On the other hand, in a substantially non-oriented state, the film easily follows the deformation of the metal plate, so that delamination or breakage is unlikely to occur, and molding accompanied by plastic deformation of the metal can be performed.

Here, a non-oriented film generally has a lower strength than a biaxially stretched film, and is more likely to precipitate oligomers and cause whitening. But,
The polyester laminated film of the present invention has a necessary and sufficient strength so as not to be torn or damaged even if it is non-oriented, and does not cause oligomer precipitation or whitening.

The lid for an easy-open can of the present invention is a lid for an easy-open can obtained by molding the above-mentioned film-laminated metal plate of the present invention, and the shape of the lid and the method of molding the lid are not particularly limited.

In the lid for an easy open can of the present invention, the crystallinity defined by the following formula of the laminated film is 30% or less, preferably 25% or less, particularly preferably 20% or less. When the value of the crystallinity exceeds 30%, when subjected to forming such as caulking (rivet) processing at the time of attaching a pull tab, a minute crack (crack) occurs in the film portion, and corrosion of the metal can material on the outer surface of the lid and the like. In this case, the effect of protecting the foodstuffs, which is the contents of the can, is lost on the inner surface of the lid.

[0049]

(Equation 3)

In order to reduce the crystallinity of the film to 30% or less, a remelting treatment performed after the laminating step is a preferred embodiment.

In the easy-open can lid of the present invention, the polyester laminated film of the present invention may be formed on the inner surface side or the outer surface side of the lid. Good. In particular, the polyester laminated film of the present invention does not cause oligomer precipitation or whitening of the film due to retort treatment after can-making even if remelt treatment is performed. In addition, the polyester laminated film of the present invention has no adverse effect due to the transfer of the oligomer to food products, and is therefore suitable for the inner surface of a lid.

Further, when molding into a lid for an easy-open can, a lubricant may be applied to a portion where the molding die contacts as required. When a lubricant is applied, it is necessary to remove the lubricant by volatilization, washing or the like after molding.

[0053]

[Example] <Measurement method> Crystallization peak temperature at elevated temperature After heating and melting the sample at 300 ° C. for 5 minutes, it was quenched with liquid nitrogen, and its 10 mg was measured using a differential scanning calorimeter.
Was heated at a heating rate of 10 ° C./min, and the temperature at the top of the exothermic peak accompanying crystallization was measured, and this was defined as the crystallization peak temperature at the time of heating.

2. Melting peak temperature The sample was heated and melted at 300 ° C. for 5 minutes, quenched with liquid nitrogen, and 10 mg thereof was measured using a differential scanning calorimeter.
Was heated at a rate of 10 ° C./min, and the temperature at the top of the endothermic peak accompanying the melting of the crystal was measured and defined as the melting peak temperature.

3. Intrinsic Viscosity A sample was dissolved in a mixed solvent of phenol / tetrachloroethane (weight ratio: 6/4) to a concentration of 0.4 g / dl, and measured at a temperature of 30 using an Ubbelohde type viscosity tube.

4. Crystallinity of the film In each sample of the polyester laminated film in the lid for the easy open can and the polyester laminated film before lamination, using a Rigaku RINT type X-ray diffractometer,
CuKα as source, tube current 40kV, tube voltage 35mA
The X-ray diffraction intensity of the (100) plane was measured under the conditions described above, and determined by the following equation.

[0057]

(Equation 4)

5. Force to shrink the film A sample obtained by cutting a sample cut into a width of 4 mm and a length of 20 mm using a thermomechanical analyzer, a sample holder interval of 10 mm, an initial load of 5 gf, and a load obtained by increasing the temperature from 30 ° C. at 10 ° C./min. The maximum value of shrinkage was determined from the curve.

Example 1 [Preparation of Polyester Laminated Film] Polyester Layer A
As a raw material for the agglomeration type silica particles (average particle diameter of 1.
5 μm) containing 40% by weight of polyethylene terephthalate containing 0.5% by weight, having an intrinsic viscosity of 0.7 obtained by oligomerization under a high-temperature nitrogen atmosphere, and 0.4% by weight of ethylene terephthalate cyclic trimer; Thereafter, a polyester composition A comprising 60 wt% of polybutylene terephthalate having an intrinsic viscosity of 1.4 and having a molecular weight increased under vacuum in a solid phase was used. The intrinsic viscosity of this polyester composition A was 0.7.

As raw materials for the polyester layer B, the dicarboxylic acid component is composed of 85 mol% of terephthalic acid units and 15 mol% of isophthalic acid units, and the diol component is composed of 40 mol% of ethylene glycol units and 60 mol of butanediol units.
A polyester composition B consisting of a polyester consisting of mol% was used. The intrinsic viscosity of this polyester composition B was 0.7.

The polyester compositions A and B were melted by separate extruders, and the melts were combined in a die, extruded and quenched to obtain an unstretched laminated sheet. This unstretched laminated sheet is subjected to a preheating temperature of 65 ° C and a stretching temperature of 100 ° C.
In the tenter, the film is stretched 4.0 times in the transverse direction at a preheating temperature of 65 ° C. and a stretching temperature of 90 ° C., and then heat-treated at 210 ° C. for 8 seconds, and then heated at 190 ° C. for 5 seconds. %
To obtain a biaxially stretched laminated film having a thickness of 16 μm (the thickness of the polyester layer A is 8 μm and the thickness of the polyester layer B is 8 μm). The crystallization peak temperature of the film at the time of temperature rise is 80 ° C., the melting peak temperature of the polyester layer A is 230 ° C., the crystallization peak temperature at the time of temperature rise is 80 ° C., and the melting peak temperature of the polyester layer B is 205 ° C. The crystallization peak temperature at the temperature was 70 ° C. Further, the force of the film to shrink was 2 g / 4 mm.

[Preparation of Film-Laminated Metal Plate] One side of a preheated aluminum alloy plate was laminated by passing between nip rolls so that polyester layer B of the polyester laminated film prepared above was in contact with the metal plate. An aluminum alloy plate on which the film was laminated was obtained. At the time of lamination, there was no change in initial adhesion, tension fluctuation, winding around a nip roll, and the like, and the suitability for lamination of the film of this example was good. This film-laminated aluminum alloy plate was subjected to a remelt treatment (after the heat treatment, rapid cooling in a water bath at 10 to 40 ° C). At this time, the crystallinity of the film was 8%.

[Preparation of Easy Open Can Lid] The film-laminated aluminum alloy plate prepared above was formed into an easy open can lid, an opening line processing (score processing) was performed, and a pull tab was attached by caulking processing. . During each processing, there is no peeling or tearing of the film,
The releasability from the mold was also good. After sealing and joining the lid thus produced to the can body filled with the beverage,
For 30 minutes. In the resulting beverage can lid, the degree of crystallinity of the film was 25%, there was no whitening or white spots on the film due to retort treatment, and there was no precipitation of oligomers of the film or elution of oligomers from the film into the beverage. Was. Furthermore, there was no hairing phenomenon or feathering phenomenon when opened.

[0064]

As is clear from the above description, the polyester laminated film of the present invention has a lower crystallization peak temperature when the temperature is raised than that of ordinary polyethylene terephthalate. Even if the crystal is made non-oriented, the film is not whitened by the retort treatment, and is suitable for a film laminated to a food container or a beverage can lid to be subjected to retort sterilization or the like. In addition, it is possible to directly adhere to the metal plate by melting the polyester layer on the other side, and to exhibit excellent adhesion.

In the film-laminated metal plate after the remelt treatment, since the film is substantially non-oriented, it can follow the processing involving the plastic deformation of the metal. Suitable for laminated film on board.

Further, the easy-open can lid according to the present invention is characterized in that:
There is no whitening or oligomer precipitation of the film due to the retort treatment, and it has excellent adhesion, and furthermore, it does not cause hairing or feathering at the time of opening. Alternatively, it may be used on the inner surface side of a lid which is required to have no effect on flavor, taste, and the like.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor: hee Nagano 344 Maebata, Kizu, Inuyama-shi, Aichi Prefecture F-term in the Inuyama Plant of Toyobo Co., Ltd. 3E084 AB01 CB01 CB02 CB04 CC01 CC03 CC08 FD08 GB08 GB17 KB01 LA03 4F100 AB01C AB10 AB31 AK41A AK41B AK42 AK42J AL01 AL05 BA02 BA03 BA04 BA05 BA07 BA10A BA10B BA10C BA16 BA26 EJ38A EJ38B EJ41 GB18 JA04 JA04A JA04B JA11 JA13 JK06 JL00 JL01 JN30 YY00 YY00Y

Claims (8)

[Claims] 1. A polyester laminated film in which a plurality of polyester layers are laminated, wherein the crystallization peak temperature when the temperature of the laminated film is raised is 60 to
110 ° C., and the surface layer on one side of the laminated film has a melting peak temperature of 2
The crystallization peak temperature at the time of temperature rise is 60 to 260 ° C.
It is composed of a polyester layer at 110 ° C, and the surface layer on the other side of the laminated film has a melting peak temperature of 1
80-240 ° C, the crystallization peak temperature at the time of temperature rise is 60-
A polyester laminated film comprising a polyester layer at 110 ° C, wherein the melting peak temperature of the polyester layer on one side is higher by 5 to 25 ° C than the melting peak temperature of the polyester layer on the other side. 2. The polyester laminated film according to claim 1, which is biaxially stretched. 3. A film-laminated metal plate, wherein the polyester laminated film according to claim 1 or 2 is laminated on a metal plate such that the other side of the film is in contact with the metal plate. 4. The film-laminated metal plate according to claim 3, wherein the film is quenched after heat treatment so as to be substantially in an amorphous / non-oriented state. 5. The polyester laminated film according to claim 1 or 2, wherein the other side of the film is in contact with a lid for an easy-open can, and the laminated film defined by the following formula has a crystallinity of 30. % Or less, which is a film-laminated easy open can lid. (Equation 1) 6. The lid for a film-laminated easy-open can according to claim 5, wherein the lid is formed by molding the film-laminated metal plate according to claim 3. 7. The film-laminated easy-open can lid according to claim 5, wherein the polyester laminated film is laminated on the outer surface of the easy-open can lid. 8. The film-laminated easy-open can lid according to claim 5, wherein the polyester laminated film is laminated on the inner surface of the easy-open can lid.