JP2001260295A - Polyester laminated film for laminating, laminated film laminate metal plate and metal container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated film for laminating capable of stably coating a surface of a metal plate even by receiving a heat history in a can manufacturing step or the like with excellent heat resistance, having excellent laminating adhesive properties and impact resistance and made of a copolymer polyester containing a specific composition suitably used as a material for molding a metal container for foodstuffs, a laminated film laminating metal plate having excellent moldability and a metal container having excellent corrosion resistance and flavorfulness resistance. SOLUTION: The polyester laminated film for laminating comprises a layer A of a copolymer polyester made of a terephthalic acid-isophthalic acid-dimer acid (molar ratio of 90-98/1-5/1-5) and an ethylene glycol and having a melting point of 235 to 250 deg.C and a layer B of a copolymer polyester made of a terephthalic acid-isophthalic acid-dimer acid (molar ratio of 85-93/1-5/6-10) and an ethylene glycol and having a melting point of 225 to 240 deg.C laminated on the layer A in such a manner that the melting point of the layer A is higher by 3 to 1O deg.C than that of the layer B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film suitable for use as a material for forming a metal container for beverages such as soft drinks, beer, and canned products, and to laminate the laminated film on a metal plate. The present invention relates to a laminated metal sheet laminated and a metal container formed from the laminated metal sheet.

[0002]

2. Description of the Related Art Conventionally, a paint is generally applied to prevent corrosion of the inner and outer surfaces of a metal can, and a thermosetting resin is used as the paint. In the method of applying a thermosetting resin paint, a solvent type paint is used in many cases. The formation of the coating requires heating at 150-250 ° C for several minutes at high temperatures and in the dark for a long time, and a large amount of organic solvent is scattered during baking. Requested.

[0003] In addition, it is inevitable that a small amount of organic solvent remains in the coating film formed under the above-described conditions. When filled, the organic solvent migrates into the foodstuff and can adversely affect the taste and odor of the foodstuff. Furthermore, additives contained in the paint and low-molecular-weight substances caused by incomplete crosslinking reaction may migrate to foodstuffs, and may have the same adverse effects as in the case of the residual organic solvent described above.

As another method, there is a method using a thermoplastic resin film. For example, a polyolefin-based film or a polyester-based film is laminated on heated tin-free steel, and the film-laminated metal plate is used for forming a metal can. The method using a thermoplastic resin film can solve the above problems, such as simplification of the process and prevention of pollution.

However, among the thermoplastic resin films, when a polyolefin film such as polyethylene or polypropylene is used, the heat resistance is inferior and the heat history in the can-making process and the heat history such as retort treatment after the can-making are used. When a history is received, the film may peel off from the film-laminated metal plate.

On the other hand, when a polyester-based film is used as the thermoplastic resin film, the problems of the above-mentioned polyolefin-based film are improved, and this is the most preferable method. On the inner surface side of the can, the polyester film has excellent heat resistance and generates less low molecular weight substances, so it has less adverse effect on the taste and smell of foodstuffs due to the migration of low molecular weight substances than polyolefin films. Excellent in flavor resistance.

However, even when a polyester film containing polyethylene terephthalate as a main component is used for the purpose, it is necessary to improve the finish of the can or to repair a joint portion of the can at the time of can making after lamination. When heat treatment is performed for the purpose of performing, for example, the heat resistance of the polyester-based film is insufficient, and as a result, only the film portion of the film-laminated metal plate undergoes a dimensional change, so that the surplus film is loose, The surface of the plate may not be completely covered.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide excellent heat resistance, to stably coat the surface of a metal plate even when subjected to a heat history in a can-making process, etc. Laminated laminated film composed of copolymerized polyester of specific composition, which is also excellent in impact resistance and is suitably used as a material for forming metal containers for foodstuffs, laminated film laminated metal plate excellent in moldability, and corrosion resistance And to provide a genus container having excellent flavor resistance.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that two types of copolymerized polyesters having different melting points consisting of terephthalic acid / isophthalic acid / dimer acid and ethylene glycol are used. The inventors have found that the above object can be achieved by the laminated film, and have reached the present invention.

[0010] The present invention is as follows. 1. Terephthalic acid / isophthalic acid / dimer acid (molar ratio 9
0-98 / 1-5 / 1-5) and ethylene glycol, melting point 23
A-layer copolyester at 5-250 ° C., and terephthalic acid / isophthalic acid / dimer acid (molar ratio 85-93 / 1-5 / 6-
A polyester laminated film for lamination, wherein a copolymerized polyester consisting of 10) and ethylene glycol having a melting point of 225 to 240 ° C is laminated as a B layer, and the melting point of the A layer is 3 to 10 ° C higher than the melting point of the B layer. 2. 2. The polyester laminated film for lamination according to the above 1, which is a biaxially stretched film. 3. 2. The polyester laminated film for lamination according to the above 1, which contains crosslinked polymer particles and / or inorganic fine particles. 4. A laminated film-laminated metal plate obtained by laminating the layer B of the polyester laminated film according to any one of the above items 1 to 3 on at least one side of a metal plate. 5. 5. A metal container obtained by molding the laminated film-laminated metal plate according to the above item 4.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The copolyester constituting the layer A of the present invention is terephthalic acid / isophthalic acid / dimer acid.
(Molar ratio 90-98 / 1-5 / 1-5) and ethylene glycol, and its melting point is 235-250 ° C. If the melting point is lower than 235 ° C., the heat resistance in the can making process and the like becomes insufficient, and the melting point is 25 ° C.
If the temperature exceeds 0 ° C., the moldability is deteriorated, which is not preferable. The intrinsic viscosity is preferably 0.5 to 1.5,
More preferably, it is 0.55 to 1.2.

In order to further improve the flavor resistance, the copolymerized polyester in the layer A desirably has a small amount of ethylene terephthalate cyclic trimer, which is one of typical oligomers, and preferably 0.7% by weight or less. , More preferably 0.5% by weight or less. For this purpose, after the film is formed, ethylene terephthalate cyclic trimer is extracted and removed from the film with water or an organic solvent, or a copolymerized polyester having a low ethylene terephthalate cyclic trimer content is used.

The copolymerized polyester constituting the layer B is terephthalic acid / isophthalic acid / dimer acid (molar ratio: 85 to 93/1).
~ 5/6 ~ 10) and ethylene glycol with a melting point of 22
5-40 ° C. If the melting point is lower than 225 ° C., the heat resistance becomes insufficient, and the fluidity of the layer B due to the heat history in the can making step and the like increases, and the dimensional change of the layer A increases, which is not preferable. On the other hand, when the temperature exceeds 240 ° C., the laminate adhesion and impact resistance become insufficient, and the reduction or removal of the residual shrinkage stress of the layer A becomes insufficient.

In order to maintain a good balance of heat resistance, laminate adhesion and impact resistance in the laminated film of the layer A and the layer B, and to reduce the dimensional change of the layer A, the melting point of the layer A must be B It needs to be 3-10 ° C. higher than the melting point in the layer.

The method for producing the laminated film is not particularly limited, and includes, for example, a multi-layer extrusion method and an extrusion lamination method. Although it may be unstretched, it is necessary to further improve heat resistance and flavor resistance. Biaxial stretching is preferred. The method for biaxial stretching is not particularly limited, and a known biaxial stretching method (simultaneous or sequential, etc.) can be used. In this case, the stretching ratio in the longitudinal direction is preferably 2 to 5 times, more preferably 2.5 to 4 times, and the stretching temperature is preferably 80 to 120 ° C., and more preferably 9 to 9.
0-110 ° C. The stretching ratio in the transverse direction is preferably 2 to 5 times, more preferably 2.5 to 4 times, and the stretching temperature is preferably 80 to 120 ° C., more preferably 90 to 110 ° C.
° C.

The total thickness of the laminated film is preferably from 4 to 65 μm, more preferably from 5 to 40 μm. If the thickness is less than 4 μm, the corrosion resistance becomes insufficient, and if it exceeds 65 μm, it is economically disadvantageous. The thickness of the A layer is determined from the viewpoints of moldability, dimensional stability and corrosion resistance due to heat history during can making.
It is preferably from 3 to 50 μm, more preferably from 4 to 30 μm.
On the other hand, the thickness of the B layer is from 1 to 1 from the viewpoints of lamination adhesion, impact resistance and heat resistance against heat history during can-making.
It is preferably 5 μm, more preferably 1 to 10 μm.

The residual shrinkage stress due to the biaxial stretching of the layer A is reduced or removed by a heat setting method or the like, so that a dimensional change due to a heat history in a can making process or the like can be reduced. The metal plate laminated with the laminated film was 210
2% dimensional change when heat treated for 2 minutes in an atmosphere of ℃
Or less, more preferably 0.8% or less. By setting the dimensional change rate to 2% or less, the laminated film can stably cover the surface of the metal plate even when the laminated film is heat-treated in a can making process or the like. In addition, it is preferable that the B layer is amorphous or non-oriented by the heat history such as the above-mentioned heat fixing,
As a result, sufficient lamination adhesion can be obtained without preheating the metal plate to the melting point of the layer B, so that the lamination process can be performed at a lower temperature and at a higher speed.

The polyester laminated film of the present invention preferably contains crosslinked polymer particles and / or inorganic fine particles. Molding processability can be improved by containing crosslinked polymer particles and / or inorganic fine particles,
Scratch resistance (scratch resistance) can be imparted.
These may be used alone or in combination of two or more.

The crosslinked polymer particles are not particularly limited as long as they have heat resistance that can withstand the temperature during melt molding of the copolymerized polyester. Examples of the material forming such crosslinked polymer particles include acrylic monomers such as acrylic acid, methacrylic acid, acrylates and methacrylates, and styrene monomers such as styrene and alkyl-substituted styrene. And, divinylbenzene, divinylsulfone, ethylene glycol dimethacrylate,
Copolymers with crosslinkable monomers such as trimethylolpropane trimethacrylate and pentaerythritol tetramethacrylate; melamine resins; benzoguanatemin resins; phenol resins; silicone resins. The crosslinked polymer particles can be produced from these materials by a conventionally known emulsion polymerization method, suspension polymerization method, or the like. In order to adjust the particle size and particle size distribution of the crosslinked polymer particles, pulverization, classification, and the like may be performed.

The inorganic fine particles are not particularly limited as long as they are insoluble and inactive in the copolymerized polyester. Specific examples include silica, alumina, zirconia,
Metal oxides such as titanium oxide; complex oxides such as kaolin, zeolite, sericite, sebiolite; sulfates such as calcium sulfate and barium sulfate; phosphates such as calcium phosphate and zirconium phosphate; carbonates such as calcium carbonate Can be mentioned. These inorganic fine particles may be natural crystals or synthetic crystals. The shape of the particles is not particularly limited.

The particle size of the crosslinked polymer particles and / or inorganic fine particles is preferably 0.5 to 5 μm, more preferably 0.5 to 5 μm.
0.8 to 4 μm. If the particle size is less than 0.5 μm, the effect of improving the slipperiness between the film and the metal at high temperatures is small, and the film is likely to be scratched.If the particle size exceeds 5 μm, the above effect is saturated, This is because there is a tendency that the film is likely to fall off, or the film is easily broken at the time of film formation.

The content of the crosslinked polymer particles and / or inorganic fine particles in the polyester laminated film is preferably 0.3 to 5% by weight, more preferably 0.5 to 3% by weight based on the total amount of the laminated film. is there. If the content is less than 0.3% by weight, the effect of improving the slipperiness between the film and the metal at a high temperature is reduced, and the film is easily scratched.
This is because if the ratio exceeds 2, the above effects tend to be saturated and the film-forming properties of the film tend to be reduced. '

The blending of the crosslinked polymer particles and / or inorganic fine particles into the polyester laminated film may be carried out in the production process of the copolyester, or the above components may be added to the copolyester and melt-kneaded. It is also possible to produce a copolymerized polyester containing the above components at a high concentration, and melt-knead this as a master batch.

The polyester laminated film of the present invention may contain an antioxidant, an ultraviolet absorber, a plasticizer, a pigment,
An antistatic agent, a lubricant, a crystal nucleating agent and the like may be contained.

The laminated film-laminated metal plate of the present invention is obtained by laminating the layer B of the polyester laminated film on at least one side of the metal plate, and has excellent moldability. The metal plate used is not particularly limited, and examples thereof include tin, tin-free steel, and aluminum. The thickness is not particularly limited, but is preferably 100 to 1000 μm, and more preferably 200 to 500 μm.

As a method of laminating the layer B of the polyester laminated film on at least one side of the metal plate, a conventionally known method can be applied and is not particularly limited, but a thermal laminating method is preferable. When laminating a polyester laminated film on both sides of a metal plate,
Lamination may be performed simultaneously or sequentially.
Further, in order to further improve the lamination adhesion of the layer B, a conventionally known adhesive containing a thermosetting resin as a main component may be applied to the layer B in advance and laminated.

The metal container of the present invention can be obtained by molding using the above-mentioned laminated film laminated metal plate. The shape of the metal container is not particularly limited, but is, for example, a can shape, a bottle shape, a barrel shape, or the like. The method of forming the metal container is not particularly limited, but, for example, a drawing method, an ironing method,
A known method such as a drawing and ironing method can be used.

[0028]

The method for measuring the properties of the film according to the present invention will be described below. 1. Dimensional change rate Dimensional change rate of polyester laminated film in heat treatment of laminated film laminated metal plate A 240 μm thick aluminum plate surface-treated with chromium phosphate is preheated to 220 ° C., and the metal plate and the total thickness of 16 μm (A (Layer thickness 8μm and layer B thickness 8μm) Match the layer B side of the polyester laminated film and pass between rubber rolls with a pressure of 500N / cm between rubber rolls at a speed of 10m / min. Then, rapid cooling was performed within 2 seconds to obtain a laminated film-laminated metal plate.
The obtained laminated film laminated metal plate, at least
The film sample portion and the metal plate portion were cut into a 60 mm × 60 mm square so that one side was parallel to the longitudinal direction of the film or the anti-bending direction of the film. Then, the laminated film laminated metal plate sample was blown at a wind speed of 1 to 10 m /
Seconds, suspended from the ceiling in a hot air oven adjusted to a temperature of 210 ℃ so as to be in the middle of the oven, after heat treatment for 2 minutes, remove the layer film laminated metal plate sample from the oven, immediately in water at 25 ℃ or less It was immersed in water for 1 second or more and rapidly cooled. Then, in the film part of the sample,
Read the length in the transverse direction of the film or the direction perpendicular to the anti-bending direction in the film plane, and measure the dimensions after heat treatment (1: unit m
m). From the obtained I, the dimensional change rate was calculated by the following equation.

(Equation 1) Dimensional change rate (%) = (160-Il / 60) × 100

2. Melting point After heating and melting the sample at 300 ° C. for 5 minutes, it was quenched with liquid nitrogen. 10 mg of the sample was used as a sample, and the temperature was increased at a rate of 10 ° C./min.
The endothermic peak temperature based on the appearing crystal melting was measured with a differential scanning calorimeter.

3. Intrinsic viscosity Mixed solvent of phenol / tetrachloroethane (by weight)
In 6/4), the sample was dissolved to a concentration of 0.4 g / d1 and measured at 30 ° C. using an Ubbelohde type viscosity tube.

4. Amount of ethylene terephthalate cyclic trimer Quantitative sample of ethylene terephthalate cyclic trimer was determined by using hexafluoroisopropyl alcohol / chloroform 2/3 (V
/ V), and the copolymerized polyester was precipitated with methanol, and the precipitate was separated by filtration. Then the filtrate was evaporated to dryness and the evaporated to dryness was dissolved in dimethylformamide. The solution was developed by liquid chromatography, and the amount of ethylene terephthalate cyclic trimer in the copolymerized polyester was measured.

5. Determination of oligomer precipitation The laminated film-laminated metal plate obtained as described in 1 above was combined with the film sample part and the metal plate part in an area of 10
It was cut into a square of 0 mm x 100 mm to obtain a sample. This sample
A retort treatment was performed at 120 ° C. for 30 minutes together with 500 cc of distilled water. After the treatment, the laminated film-laminated metal sheet was air-dried, and the state of the film surface was observed by observing all over, and the presence or absence of oligomer precipitation was determined based on the following criteria. Yes:
Oligomer crystals are observed on the film surface. None: No oligomer crystals are observed on the film surface.

(Example) (Production of polyester laminated film) Agglomeration type silica having an average particle size of 1.5 μm was used as a copolymer polyester for layer A.
Terephthalic acid containing 0.4% by weight and having an intrinsic viscosity of 0.7 and an ethylene terephthalate cyclic trimer content of 0.33% by weight, wherein the amount of ethylene terephthalate cyclic trimer is reduced by an extraction method.
A copolymerized polyester composed of isophthalic acid / dimer acid (molar ratio 94/4/2) and ethylene glycol and having a melting point of 240 ° C. was used. On the other hand, as a copolymerized polyester for the layer B, a copolymer of terephthalic acid / isophthalic acid / dimer acid (molar ratio 91/1/8) containing 0.04% by weight of spherical silica having an average particle diameter of 1 μm and ethylene glycol having a melting point of 235 ° C. Polymerized polyester was used. These copolyesters for layer A and layer B were melted by separate extruders, and the melts were laminated in a die and then extruded on a cooling drum to form amorphous sheets. After that, the above amorphous sheet is vertically
The film was stretched by a factor of 3.3 in the transverse direction by a factor of 4.0 and heat-set at 220 ° C to obtain a polyester laminated film having a layer A thickness of 8 µm and a layer B thickness of 8 µm (total thickness 16 µm).

(Production of Laminated Film-Laminated Metal Plate) A 240 μm-thick aluminum plate surface-treated with chromium phosphate is preheated to 220 ° C., and the metal plate and the layer B side of the polyester laminated film are brought into contact with each other. The laminate was passed through a rubber roll with a pressure of 500 N / cm at a speed of 10 m / min and then rapidly cooled within 2 seconds to obtain a laminated film-laminated metal plate. For the obtained laminated film-laminated metal plate, the dimensional change rate due to the heat treatment of the polyester laminated film was measured in accordance with 1 above.
8%. When the presence or absence of oligomer precipitation was observed according to the above item 5, no oligomer precipitation was observed on the film surface.

(Manufacture of Metal Container) When the above-mentioned laminated film-laminated metal plate was used to make a can as a drawn and ironed can, the can was made at a high speed in the can making process, and the film was formed even after the heat treatment in the process. No problems such as spraying or surface exposure of the metal plate occurred. The obtained cans were filled with foodstuffs and retorted at 125 ° C for 30 minutes.
When subjected to a storage test at 6 ° C. for 6 months, it was found to be excellent in corrosion resistance and flavor resistance.

[0037]

The laminated film for laminating comprising the copolyester of the specific composition of the present invention has excellent heat resistance and stably coats the surface of a metal plate even when subjected to a heat history in a can-making process or the like. As a result, it is possible to provide a laminated film-laminated metal plate excellent in moldability and a metal container excellent in corrosion resistance and flavor resistance.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 3E033 BA08 BA09 BA17 BB08 CA03 CA07 CA14 CA20 FA01 3E061 AA15 AB12 AB13 DA01 4F100 AA00H AB01C AK01H AK41A AK41B AK41J AK41K AL01A AL01B BA02 BA03 BA10 BA10 BA01 BA10 BA01 BA10 BA01 BA10 EJ38 GB16 GB23 JA04A JA04B JB02 JD02 JJ03 JK10 JL01 YY00A YY00B

Claims (5)

[Claims] 1. Terephthalic acid / isophthalic acid / dimer acid
A layer of a copolymerized polyester having a melting point of 235 to 250 ° C composed of ethylene glycol (molar ratio of 90 to 98/1 to 5/1 to 5) and terephthalic acid / isophthalic acid / dimer acid (molar ratio of 85 to 93 /
1 ~ 5/6 ~ 10) and ethylene glycol 225 ~ 24
A polyester laminated film for lamination, wherein a layer of a copolymerized polyester at 0 ° C is laminated as a layer B, and the melting point of the layer A is 3 to 10 ° C higher than the melting point of the layer B. 2. The laminated polyester film according to claim 1, which is a biaxially stretched film. 3. The polyester laminated film for lamination according to claim 1, which contains crosslinked polymer particles and / or inorganic fine particles. 4. A laminated film-laminated metal plate obtained by laminating the layer B of the polyester laminated film according to claim 1 on at least one side of a metal plate. 5. A metal container obtained by molding the laminated film-laminated metal plate according to claim 4.