JP2012251140A - Polyester film for three-piece can lamination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film excellent in adhesion with a metal sheet and molding processability, a film laminated metal sheet, and a metal container.SOLUTION: This polyester film for three-piece can lamination includes polyester composition. The polyester composition mainly contains polyethylene terephthalate. A polyoxyalkylene glycol component where the number of repetitions of 2 or more C alkylene oxide unit is three or more is contained, as the 2 or more C alkylene oxide unit originating in the polyoxyalkylene glycol component, by 2-20 mol% to the whole acid component of the polyester component in the polyester composition. The polyester film contains 0.75-1.2 wt.% of spherical PMMA particles to the whole amount of the polyester composition, the density of the film is 1.37 g/cmor higher, and the surface orientation coefficient is 0.161-0.167.

Description

The present invention relates to a polyester film used for the purpose of preventing corrosion of metal containers such as soft drinks, beer, and canned foods, and a metal container formed by forming the film laminated metal plate, particularly for a three-piece can. The present invention relates to a suitably used polyester film.
More specifically, adhesion to the metal plate, transportability of the metal plate, canability (for example, bending, joining, joint repair, flanging, top lid attachment, contents filling, bottom lid attachment, retort sterilization) The present invention relates to an excellent polyester film, a film laminated metal plate obtained by laminating the film on a metal plate, and a metal container formed by molding the film laminated metal plate.

  Conventionally, the inner surface and outer surface of a metal can have been widely coated with a solution in which various thermosetting resins such as epoxy and phenol are dissolved or dispersed in a solvent for the purpose of preventing corrosion. Has been done. However, this method of coating the thermosetting resin has poor productivity due to the long time required to dry the paint, and also has undesirable problems such as adverse effects on the human body and environment due to the use of a large amount of organic solvent. .

In order to solve such a problem, a polyester film in which a polyethylene terephthalate-polytetramethylene glycol ether block copolymer and a polyethylene terephthalate resin are mixed and crosslinked PMMA particles are added is known. (For example, refer to Patent Document 1).

  By using this film, this scratch resistance was improved, and it was also seen in the case of a coating film method in which an organic film having excellent lubricity and scratch resistance was formed on the surface of the polyester film by the coating method. As described above, since only a part of the solvent remains in the organic coating layer, when the food container is filled with a metal container manufactured using this film, the organic solvent adversely affects the taste and smell of the food product. There is no problem. Further, there is no problem that the low molecular weight substance is eluted from the organic coating layer and has the same adverse effect as the remaining organic solvent.

  However, in the film, there was a concern that particles were dropped during the can making process, adversely affecting the film properties after can making, and reducing the production efficiency.

Further, it comprises a polyester composition having a melting point of 220 to 250 ° C. mainly composed of a copolymer polyester composed of an ethylene terephthalate component and an ethylene isophthalate component, and has a density of less than 1.385 g / cm ³ and a plane orientation coefficient of less than 0.130. A biaxially oriented polyester film, wherein the polyester composition is a carbon derived from the polyoxyalkylene glycol component with a polyoxyalkylene glycol component having 3 or more repeating alkylene oxide units having 3 or more carbon atoms. The alkylene oxide unit having 2 or more is contained in an amount of 2 to 20 mol% based on the total acid component of the polyester composition, 0.05 to 1.0 wt% of inert particles, and 0.1% of wax. A polyester containing 01 to 0.15% by weight and 0.01 to 1.0% by weight of an antioxidant. A laminated polyester film for laminating a metal plate made of a steal composition is known (for example, see Patent Document 2).

  However, this film has a problem that the heat resistance and the scratch resistance are not sufficient as a three-piece can laminate film, and further the flavor of the contents is impaired.

The reason for this is that this film has a good formability of being formed following the formation of a metal plate for application to a drawn iron can with a high work deformation rate, and has excellent adhesion to the metal plate. This is because it is designed to meet the requirements, and there is no repair process for the joint of the can. Further, the use of the copolyester has the disadvantage that the crystallization of the film does not proceed and the components of the contents are adsorbed.
As a further reason, in order to apply a film laminated metal plate to a two-piece can, a remelt process is performed in which, after laminating, heating is performed at a temperature equal to or higher than the melting point of the polyester constituting the film in order to remove the orientation of the polyester film, followed by rapid cooling. Sometimes it is broken.
Japanese Patent No. 3248450 JP 2006-199017 A

  The object of the present invention is to solve the problems of the prior art. That is, it is providing the polyester laminated film excellent in the adhesiveness with a metal plate, and a moldability, a film lamination metal plate, and a metal container.

  As a result of intensive studies to achieve the above object, the present inventors have found that polyoxyalkylene glycols mainly composed of polyethylene terephthalate, spherical PMMA particles, and alkylene oxide units having 2 or more carbon atoms are repeated 3 or more. By controlling the density of the polyester film containing a specific amount of ingredients, it is suitable for the can manufacturing process of three-piece cans, and particles are not dropped during the can manufacturing process, adversely affecting the coating properties after can manufacturing. In addition, the inventors have found that a film for laminating can be obtained that does not reduce production efficiency and does not impair the flavor of the contents.

The present invention is as follows.
1. The polyester film for laminating three-piece cans of the present invention is a polyester film for laminating three-piece cans comprising a polyester composition, wherein the polyester composition is mainly composed of polyethylene terephthalate and has 2 or more carbon atoms. The polyoxyalkylene glycol component having a repetition of 3 or more is used as an alkylene oxide unit having 2 or more carbon atoms derived from the polyoxyalkylene glycol component, and 2 to the total acid component of the polyester component in the polyester composition. -20% by mole, 0.75-1.2% by weight of spherical PMMA particles with respect to the total amount of the polyester composition, and the density of the film is 1.37 g / cm ³ or more. The plane orientation coefficient is 0.161 to 0.167. And it is characterized in Rukoto.
2. In this case, it is preferable that the tensile elongation of the film is 144 to 200 MPa.
3. In this case, a metal plate characterized by laminating the polyester film is preferable.
4). In this case, a metal container characterized by forming a metalate metal plate is preferable.

  According to the present invention, it has excellent adhesion to the metal plate, is not damaged when the laminated metal plate is transferred, and can be made (for example, bending, joining, joint repair, flanging, top lid mounting, contents filling, bottom lid A polyester film for 3-piece cans with little particle dropout during mounting and retort sterilization) and can-making processes is obtained, and the appearance of a 3-piece can obtained by molding a metal plate obtained by laminating the film is also improved. It is possible to provide a very useful polyester film suitable for repairing a welded part, a film laminated metal plate, and a metal container obtained by molding a film laminated metal plate without impairing the flavor of the contents.

Hereinafter, the present invention will be described in detail.
The polyethylene terephthalate in the present invention is a polyester having terephthalic acid as a main component as an acid component.
Moreover, other copolymerization components can be included in the range which does not inhibit the purpose.
Among other copolymerizable components that can be used, dicarboxylic acid components include naphthalene dicarboxylic acid, diphenylsulfone dicarboxylic acid, aromatic dicarboxylic acids such as 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, Aliphatic dicarboxylic acids such as decanedicarboxylic acid, maleic acid, fumaric acid and dimer acid, oxycarboxylic acids such as p-oxybenzoic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used.
The amount of the above dicarboxylic acids and their ester derivatives that can be used is preferably 7 mol% or less, more preferably 5 mol% or less. If the amount of other dicarboxylic acids and their ester derivatives used exceeds 8 mol%, the thermal stability of the polyester is deteriorated, and the flavor of the contents is impaired.

In addition, as the glycol component of the polyethylene terephthalate of the present invention, components that can be used in addition to the ethylene glycol component include aliphatic glycols such as propanediol, butanediol, pentanediol, hexanediol, and neopentylglycol, cyclohexanedimethanol, and the like. Aromatic glycol such as alicyclic glycol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol S, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can be used.
In addition, a small amount of a compound containing an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be included. Here, the amount of other glycol components that can be used is preferably 7 mol% or less, and more preferably 5 mol% or less. If the amount of other dicarboxylic acids and their ester derivatives used exceeds 8 mol%, the thermal stability of the polyester is deteriorated, and the flavor of the contents is impaired.

  It does not specifically limit about the manufacturing method of the polyethylene terephthalate of this invention. That is, it can be used even if it is produced by either the transesterification method or the direct polymerization method. Further, it may be produced by a solid phase polymerization method in order to increase the molecular weight. In addition, the amount of oligomers from the polyester resin in the retort treatment, etc. that is carried out after filling the can into the can is reduced, and from the standpoint of aroma retention that prevents the flavor of the content from being impaired, and contamination of the can manufacturing line From the viewpoint of prevention, it is preferable to use a polyester having a low oligomer content produced by a solid phase polymerization method under reduced pressure or in an inert gas atmosphere.

  Here, for example, the content of the oligomeric cyclic trimer including ethylene terephthalate cyclic trimer is preferably 0.7% by weight or less.

  The intrinsic viscosity of the polyester of the present invention is preferably 0.6 to 1.2. If the intrinsic viscosity is less than 0.6, the mechanical properties of the resulting film may be deteriorated, and even if the intrinsic viscosity exceeds 1.2, no further effect of improving the mechanical properties can be obtained. In addition, the productivity at the time of production of the polyester is lowered, which is not economical.

  In the production of the polyester in the present invention, as the polymerization catalyst, antimony oxide, germanium oxide, titanium compound, etc. are used, and in addition to the polymerization catalyst, the polyester resin composition of the present invention is used to form a melt-extruded film. In order to provide electrostatic adhesion, Mg salt such as magnesium acetate and magnesium chloride, Ca salt such as calcium acetate and calcium chloride, Mn salt such as manganese acetate and manganese chloride, Zn salt such as zinc chloride and zinc acetate, Co salt such as cobalt chloride and cobalt acetate should be added within the range of 300 ppm or less as the total amount of each metal ion, and phosphoric acid ester derivatives such as phosphoric acid or phosphoric acid trimethyl ester and phosphoric acid triethyl ester as phosphorous atoms within 200 ppm or less. Is also possible. When the total amount of metal ions other than the above polymerization catalyst exceeds 300 ppm and the amount of phosphorus exceeds 200 ppm, not only is the resulting polyester colored significantly, but the heat resistance and hydrolysis resistance of the polyester may also decrease. Therefore, it is not preferable.

  At this time, when the molar ratio of the total phosphorus amount to be added and the total metal ion amount is 0.4 to 1.0, the polyester having the best balance of heat resistance, hydrolysis resistance, and electrostatic adhesion Is preferable. Here, molar ratio of addition amount = (total amount of phosphorus in phosphoric acid, phosphoric acid alkyl ester or derivative thereof (molar atom)) / (total amount of Mg ion, Ca ion, Mn ion, Zn ion, Co ion ( Mole atom)). When the molar ratio is less than 0.4, the composition of the present invention is markedly colored, and heat resistance and hydrolysis resistance are lowered. If it exceeds 1.0, sufficient electrostatic adhesion cannot be obtained.

The polyester composition of the present invention needs to contain a polyoxyalkylene glycol component composed of alkylene oxide units having 2 or more carbon atoms and having 3 or more repeating units.
By containing the above components, voids generated around the spherical PMMA particles to be added are reduced as much as possible, elasticity of the polyester composition at room temperature and low temperature is imparted, and molding adhesion to the metal plate is improved. Along with being able to.
In particular, it is possible to suppress the heat shrinkage rate at the time of repairing the joint portion of the metal plate, improve the adhesion with the repair resin, or suppress whitening in the retort treatment after canning.
Examples of polyoxyalkylene glycols comprising alkylene oxide units having 2 carbon atoms include polyethylene glycol (2 carbon atoms), polytrimethylene glycol (3 carbon atoms), polytetramethylene glycol (4 carbon atoms), polyhexamethylene Glycol (6 carbon atoms) can be used, and one of these components may be used alone, or two or more components may be mixed and used. A polyoxyalkylene glycol having an average molecular weight in the range of 500 to 3000 can be suitably used, and an average molecular weight in the range of 800 to 2000 is more preferable. At this time, polytetramethylene glycol is preferred.

  The amount of the polyoxyalkylene glycol component contained in the polyester composition of the present invention is such that the amount of the alkylene oxide unit having 2 or more carbon atoms derived from the polyoxyalkylene glycol component is the total acid component of the polyester composition. It is preferable that it is 2-20 mol% with respect to. An alkylene oxide unit having 2 or more carbon atoms derived from a polyoxyalkylene glycol component means a structural unit in which both ends of an alkylene chain form an ether bond with an adjacent alkylene chain with an oxygen atom interposed therebetween. More preferably, it is 3-15 mol%, Most preferably, it is 3-10 mol%.

The method for incorporating the above polyoxyalkylene glycol component into the polyester composition of the present invention is not particularly limited. For example, a polyester composition obtained by adding a polyoxyalkylene glycol component at the stage of producing a polyester composition in the same manner as other raw materials and then terminating the polyester synthesis reaction may be used, or a polyoxyalkylene glycol may be used. Another copolyester obtained by copolymerization of may be melt-mixed with the polyester composition of the present invention. In the present invention, the latter method of melt mixing is preferable because the effect of improving the moldability and tearability of the can is exhibited more efficiently. In particular, the polyalkylene terephthalate-polytetramethylene oxide block copolymer is melt-mixed. The method is the most preferred form.
In particular, as a method for adding a polyoxyalkylene glycol composed of an alkylene oxide unit having 2 carbon atoms to a polyester composition, for example, a method of adding a polyalkylene terephthalate-polytetramethylene oxide block copolymer to polyethylene terephthalate. can give. Examples of the polyalkylene terephthalate include polybutylene terephthalate, and polybutylene terephthalate is preferable.
At this time, the ratio of polyoxyalkylene glycol in the block copolymer is preferably 5 to 40% by weight.

As described above, the polyester film of the present invention can be used for three-piece cans even when the manufacturing conditions are severe, such as when the metal deformation ratio is increased or the processing speed is increased when a metal container is manufactured by drawing and ironing. In order to impart the slipperiness and scratch resistance of the laminated metal plate, it is necessary to contain spherical PMMA particles in the range of 0.75 to 1.2% by weight, preferably 0.85 to 1.1% by weight. %.
Even if it contains an amount exceeding 1.2% by weight, the effect of preventing scratches is not changed, and the dropout of the particles may be worsened.

The average particle diameter of the spherical PMMA particles is preferably 1.0 to 3.0 μm. This is because if the thickness is less than 1.0 μm, the effect of improving scratch resistance and slipperiness of the film cannot be sufficiently exhibited. On the other hand, if it exceeds 3.0 μm, the effect of improving scratch resistance is saturated, while particles are likely to fall off during the can making process.
The average particle size of the particles was measured by a 50% weight average by a Coulter counter method.

The thermal decomposition temperature of the spherical PMMA particles is preferably 290 ° C. or higher, and deformation of the particles is less likely to occur during film formation, and void formation can be suppressed.

  Here, as the spherical PMMA (polymethyl methacrylate) particles, it is preferable to use crosslinked polymer particles or the like.

In addition to the spherical PMMA particles, the following particles may be used in combination so long as the effect is not impaired.
Examples thereof include silica, alumina, kaolin clay, titanium oxide, calcium phosphate, calcium carbonate, lithium fluoride, barium sulfate, and carbon black. Moreover, as the crosslinked polymer particles, acrylic monomers such as acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, styrene monomers such as styrene and alkyl-substituted styrene, and divinylbenzene, Copolymers with crosslinking monomers such as divinyl sulfone, ethylene glycol dimethacrylate, trimethylolpropane trimethyl acrylate, pentaerythritol tetramethyl acrylate, melamine resins, benzoguanamine resins, phenol resins, silicon-containing resins, etc. Can be illustrated.

  The spherical PMMA particles may be added to the polyester film in the production process of the polyester composition, or the polyester composition and the inert particles may be melt-kneaded. Moreover, you may add with the masterbatch containing a high concentration inert particle at the time of manufacture of a polyester film. The polyester film used in the present invention preferably has a coefficient of dynamic friction between the film and the metal at 80 ° C. of 0.45 or less. If the dynamic friction coefficient is 0.45 or less, the metal plate can be transported and can be made (for example, bending, joining, joint repair, flanging, top lid attachment, contents filling, bottom lid attachment, retort sterilization). Become a practical level. In order to lower the dynamic friction coefficient, it can be achieved by adding inert particles in the above-mentioned range, but it is also preferable to use a combination of inorganic particles and crosslinked polymer particles or polyester incompatible thermoplastic resins. This is an embodiment.

  In the polyester film of the present invention, in addition to the particles, if necessary, an incompatible thermoplastic resin, an antioxidant, a heat stabilizer, an ultraviolet absorber, a plasticizer, a pigment, an antistatic agent, a lubricant, You may contain additives, such as a crystal nucleating agent.

  The content of the antioxidant with respect to the polyester film of the present invention is preferably 0.01 to 1.0% by weight. If the content of the antioxidant is less than 0.01% by weight, the effect of substantially preventing thermal degradation is insufficient, and conversely, even if the content exceeds 1.0% by weight, the effect of more than that is It cannot be expected and it will only be economically disadvantageous.

The density of the film of the present invention is preferably 1.37 g / cm ³ or more, and by making it within this range, dropping of particles during the can making process can be suppressed.

  The plane orientation coefficient of the film of the present invention is preferably 0.161 to 0.167. If it is less than 0.161, the flavor of the contents is impaired, and if it exceeds 0.167, the film is produced. It becomes difficult.

  The film according to the present invention preferably has a tensile elongation of 144 to 200 MPa, and by setting this range, the occurrence of film cracks when the laminated metal can is dropped can be suppressed.

  Although the thickness of the laminated polyester film of this invention is not specifically limited, 10-50 micrometers is preferable from the point of a coating effect (rust prevention property) and a moldability, and also economical efficiency. If the film thickness is less than 10 μm, the coating effect cannot be obtained, and if it exceeds 50 μm, the film quality is excessive, which is economically undesirable.

The production method of the polyester film of the present invention is not particularly limited, but after forming the base material layer and the adhesive layer using an inflation film production apparatus and a T-die film production apparatus, respectively, the laminate can be bonded by an extrusion laminating method. A multilayer film may be formed by coextrusion from the beginning.
Here, in order to obtain the required range of the present invention, it is preferable to perform uniaxial stretching or biaxial stretching after forming an unstretched film by an extrusion method. By using a stretched film, crystal orientation occurs, and strength and excellent processability can be obtained.

  However, as the stretching conditions at that time, it is one of the requirements of the present invention to provide an appropriate temperature and a stretching ratio within the range where the film does not melt in the preheating and stretching temperatures in the stretching process. Desirable to obtain a film with few voids. If the heat is insufficient, the interfacial stress between the PMMA particles and polyethylene terephthalate due to orientation increases and the voids become high, and the dropout of the particles may become remarkable. If the temperature is high, it is difficult to form protrusions on the film surface, and scratch resistance and can-making properties may be deteriorated.

Taking the case of the longitudinal stretching temperature at the time of sequential biaxial stretching as an example, a preferable temperature range can be exemplified by 70 to 120 ° C. as the preheating temperature at the longitudinal stretching and 100 to 130 ° C. as the stretching temperature. Examples of the preheating temperature at the time of transverse stretching include 80 to 120 ° C., and the degree of heat fixation includes 225 to 235 ° C.

In addition, regarding the draw ratio, it is preferable to take an appropriate range. If the ratio is low, the target strength and surface protrusion may not be obtained, or the flavor of the contents may be impaired. If the ratio is high, production is difficult. Since it may become, it is not preferable. Preferred stretching ratios for sequential biaxial stretching include 3 to 6 times in the longitudinal direction and 6 to 10 times in the transverse direction, preferably 3.5 to 4.1 times in the longitudinal direction and transverse direction. It is 3.7 to 4.3 times.

The polyester film of the present invention may be provided with an adhesive layer on one side. For the layer having adhesiveness, a method of providing a resin layer having adhesiveness or a coating method can be used by a co-extrusion method at the time of film production.
When the coextrusion method is used, copolymerized polyethylene terephthalate, polybutylene terephthalate, or a mixed resin thereof can be used.
When using the coating method, an organic solvent-soluble resin composition or a water-dispersed resin composition can be used, and a dispersible resin composition is preferred.

  The water-dispersed resin composition itself is a resin composition that is insoluble in water but can be dispersed or dissolved in an aqueous solvent, and known ones can be used.

  The thickness of the adhesive layer B is preferably 0.02 to 2.0 μm. When the adhesive layer is formed by a coating method, it may be either a stretched film during film formation (in-line) or a film after film formation (off-line).

  The water-dispersed resin composition itself is a resin composition that is insoluble in water but can be dispersed or dissolved in an aqueous solvent, and known ones can be used.

The method for laminating the layer made of the water-dispersed resin composition on the polyester film is not limited, and for example, a melt extrusion method, a coating method, or the like can be used. When the coating method is used, it is preferable not to use an organic solvent because an adverse effect on the human body and the environment can be reduced.
The thickness of the resin layer B made of the water-dispersed resin composition is preferably controlled to 0.02 to 0.1 μm. When the resin layer B is laminated by the coating method, either a stretched film during film formation (in-line) or a film after film formation (off-line) may be used.

  The film-laminated metal container of the present invention may be subjected to printing or the like as necessary, and may be subjected to a remelt treatment again after a can-making process or a printing process.

  In the present invention, a surface-treated steel plate such as tin-free steel, an aluminum plate, an aluminum alloy plate, or a surface-treated aluminum plate or aluminum alloy plate can be used as the metal plate to be used.

  The method for laminating the laminated polyester film of the present invention on a metal plate is not particularly limited, and for example, a dry laminating method, a thermal laminating method or the like can be employed. In the case of the dry laminating method, an adhesive is applied to one side of the film, and the adhesive layer is heated and pressure-bonded to a metal plate. In the case of the thermal laminating method, specifically, the metal plate is heated to the melting point or more of the laminate surface of the film, the film is brought into contact with the surface of the metal plate, and the nip roll is passed in this state. Subsequently, it laminates by making it quench-harden at 10-40 degreeC.

  Moreover, the lamination of the film may be performed only on one side of the metal plate or on both sides. In the case of double-sided lamination, it may be laminated at the same time or sequentially.

The polyester film of the present invention preferably has an adhesion strength with a metal plate of 10 N / 15 mm or more. If the adhesion strength is less than 10 N / 15 mm, the molding processability during can making may be reduced, and peeling of the film and the metal plate may occur during the molding process. The adhesion strength between the film and the metal plate is measured by the following method.
[1]. Production of Film Laminated Metal Plate After laminating a metal plate preheated to 170 ° C. through a nip roll so that the resin layer (II) layer side of the laminated polyester film of the present invention is in contact with the metal plate, 10 to 40 ° C. Quench in a water bath to obtain a film-laminated metal plate.
[2]. Heat treatment A film-laminated metal plate is heated at 230 ° C. and then quenched in water to obtain a laminated metal plate.
[3]. Adhesion strength A part of the metal part is dissolved and removed from the remelt metal plate with dilute hydrochloric acid, and only the film is taken out. With this as a trigger, the film / metal plate is peeled off. After sufficiently peeling, a reinforcing material is applied so that the film does not stretch, and cutting is performed to a width of 15 mm. The peel strength of the sample is measured using a tensile tester at a pulling speed of 50 mm / min.

  The film-laminated metal container of the present invention is a metal container formed by appropriately forming the polyester film-laminated metal plate of the present invention, and the shape of the container and the method of forming the metal container are not particularly limited. Specifically, the present invention can be applied to a so-called three-piece can in which the top cover is wound and filled with contents.

  In the metal container of the present invention, the polyester film of the present invention may be molded so as to be on the inner wall surface side of the metal container, or may be molded so as to be on the outer wall surface side. When the polyester film of the present invention is used for the outer wall surface, a resin coating film containing a pigment or a colorant may be applied in advance in order to conceal the surface of the film to be bonded to the metal.

EXAMPLES Hereinafter, although an Example is given and the content and effect of this invention are demonstrated concretely, this invention is not limited to a following example, unless it deviates from the summary.

Various evaluation methods in the present invention are shown below.

(1) Thermal properties of polyester 10 mg of a sample obtained by heating and melting a polyester composition at 300 ° C. for 5 minutes and then rapidly cooling with liquid nitrogen was used in a nitrogen stream using a differential scanning calorimeter (DSC). The peak temperature of the endothermic peak accompanying melting when the exothermic / endothermic curve (DSC curve) was measured at a temperature elevation rate of ° C./min was defined as the melting point Tm (° C.).

(2) Composition of polyester A polyester resin sample was dissolved in deuterated chloroform containing 15% by weight of trifluoroacetic acid, and 1H-NMR was measured. In the case of a laminated film, the lower layer resin layer was removed with a solvent or the like, and the remaining upper layer sample was dissolved in the same manner, and 1H-NMR was measured. The composition ratio was determined from the integrated intensity of the peaks derived from each component.

(3) Intrinsic viscosity (IV)
According to JIS K 7367-5, a value (dl / g) measured at 25 ° C. using a phenol / tetrachloroethane-60 / 40 mixed solvent as a solvent using a capillary viscometer (Ubbelohde clay meter).

(4) Plane orientation coefficient of film A modified plate analyzer is attached to the eyepiece side of an Abbe refractometer according to JIS K 7142, using NaD line as a light source and methylene iodide as a medium at 25 ° C, The refractive index in the triaxial direction of the thickness is measured. Nx (refractive index in the vertical direction), Ny (refractive index in the horizontal direction), and Nz (refractive index in the thickness direction), and Nx, Ny, and Nz are substituted into the following equation (1) to obtain the plane orientation coefficient (AO). Asked.
AO = (Nx + Ny) / 2−Nz (1)

(5) Density of film It measured at 25 degreeC using the density gradient tube according to JISK7112.

(6) Tensile elongation of film Measured at 23 ° C. according to JIS K 7127.

(7) Haze of film It measured at 23 degreeC according to JISK7105.

(8) Coefficient of dynamic friction Measure the coefficient of dynamic friction when a film sample is set on a 1.5 kg weight slider having a contact area of 50 mm x 70 mm and slid on a tin-free steel plate at 80 ° C at a speed of 250 mm / min. did.

(9) Laminate adhesion Adhesive layer (II) on both sides of a metal plate coated with a polyurethane adhesive “Adcoat” manufactured by Toyo Ink Co., Ltd. and a curing agent as an adhesive layer on a polyester film and heated to 170 ° C. ) Were pressed between the nip rolls so that they contact each other, further heated to 230 ° C., and then rapidly cooled in water.

(10) Adhesion strength A part of the metal part is dissolved and removed from the laminated metal plate with dilute hydrochloric acid, and only the film is taken out. With this as a trigger, the film / metal plate is peeled off. After sufficiently peeling, a reinforcing material was pasted so that the film did not stretch and cut to a width of 15 mm. The peel strength of the sample was measured using a tensile tester at a pulling speed of 50 mm / min.

(11) Scratch resistance In a dyeing fastness friction tester manufactured by Toyo Seiki Co., Ltd., a friction piece with a load of 400 g on which a film sample is set is tinned at 80 ° C. under a reciprocating distance of 100 mm at 30 reciprocations per minute. The scratches on the film surface after rubbing the free steel plate for 1 minute were observed with the naked eye and evaluated according to the following criteria. Note that Δ and above are practical.
○: Scratches are hardly recognized.
Δ: Scratches are partially observed.
X: Scratches are observed on the entire surface.

(12) Separability With a dyeing fastness friction tester manufactured by Toyo Seiki Co., Ltd., a 400 g load set with aluminum foil having a thickness of 0.05 mm was applied to a 100 mm reciprocating distance of 30 reciprocations per minute. Under the conditions, the surface of the aluminum foil after rubbing the film at 20 to 40 ° C. for 1 minute was observed with the naked eye and evaluated according to the following criteria. Note that Δ and above are practical.
○: Dirt is hardly recognized.
(Triangle | delta): Dirt is recognized partially.
X: Dirt is recognized on the entire surface.

(13) Repairability The ink adhesion of the printing and laminating samples obtained as described above was measured using a grid pattern peeling (2 mm square x 25 pieces, using Nichiban's cello tape (registered trademark) 18 mm width). , 90 ° peeling method), and judged according to practicality, and then classified according to the next rank.
0 cross-section peeling parts ...
１〜 1-5 ...
６ 6-15 ...
以上 More than 15 ...

(14) A 9 cm square sample of the laminated metal plate used for crack laminate adhesion is cut out. A weight (600 g) having a tip diameter of 10 mm is dropped from a height of 4 cm to a surface corresponding to the outer surface of the sample, and an impact is applied. Next, the sample was placed on a glass container filled with 7% dilute hydrochloric acid (with the convex portion of the sample immersed), and the corrosion state of the convex portion was visually observed after 3 days. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Corrosion of the convex part is not generated ×: Corrosion of the convex part is generated

  Next, the kind and content of polyester used for the Example and the comparative example are demonstrated.

(1) Resin A: Ethylene terephthalate (PET, IV = 0.67, containing 0.2% by weight of amorphous silica particles)
82 parts by weight of ethylene glycol (ethylene glycol / terephthalic acid molar ratio = 2) with respect to 100 parts by weight of terephthalic acid in a reactor equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying column, and a stirring blade .2), with respect to the acid component, 0.05 mol% of germanium oxide as the Ge element, 0.05 mol% of magnesium acetate as the Mg element, and amorphous silica particles having an average particle diameter of 1.5 μm (Fuji Silysia, Silysia) 0.23 parts by weight were charged, nitrogen was introduced with stirring, the pressure inside the system was kept at 0.3 MPa, and the esterification reaction was carried out while distilling off the water generated at a temperature of 230 ° C. to 250 ° C. went. After completion of the reaction, at 250 ° C., 0.04 mol% of trimethyl phosphate is added as the P amount, the pressure is gradually reduced while the temperature is raised, and a polycondensation reaction is performed under a vacuum of 275 ° C. and 1.0 hPa or less. Obtained. Subsequently, this polyester was heat-treated at 220 ° C. under a vacuum of 1.0 hPa for 12 hours to obtain polyester A-2 (PET). The polyester obtained had an intrinsic viscosity of 0.67 (dl / g) and an ethylene terephthalate cyclic trimer of 0.4% by weight.

(2) Resin B: Polyethylene terephthalate / isophthalate (repeating unit of ethylene isophthalate: 8.0 mol% (PET-I (8)), IV = 0.74, containing 0.2% by weight of amorphous silica particles)
90 parts by weight of terephthalic acid, 10 parts by weight of isophthalic acid, 82 parts by weight of ethylene glycol (ethylene glycol / total acid component) were added to a reactor equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying column, and a stirring blade. Amorphous silica particles having a molar ratio of 2.2), 0.05 mol% of germanium oxide as the Ge element, 0.05 mol% of magnesium acetate as the Mg element, and an average particle diameter of 1.5 μm with respect to the acid component 0.23 parts by weight were charged, nitrogen was introduced with stirring, the pressure inside the system was maintained at 0.3 MPa, and the esterification reaction was performed while distilling off the water generated at a temperature of 230 ° C. to 250 ° C. outside the system. . After completion of the reaction, at 250 ° C., 0.04 mol% of trimethyl phosphate is added as the P amount, the pressure is gradually reduced while the temperature is raised, and a polycondensation reaction is performed under a vacuum of 275 ° C. and 1.0 hPa or less. Obtained. Subsequently, this polyester was heat-treated at 200 ° C. under a vacuum of 1.0 hPa for 12 hours to obtain polyester A-1 (PET-I (10)). The polyester obtained had an intrinsic viscosity of 0.74 (dl / g) and an ethylene terephthalate cyclic trimer of 0.4% by weight.

(3) Resin C: Polytetramethylene terephthalate-polytetramethylene oxide block copolymerized polyester (IV = 0.75)
In a reaction apparatus equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying column, and a stirring blade, 75 parts by weight of 1,4-butanediol, polytetramethylene glycol with respect to 100 parts by weight of dimethyl terephthalate (Average molecular weight 1000) 75 parts by weight and normal butyl titanate 0.05 parts by weight were charged, and transesterification was carried out while distilling methanol produced at 190 ° C. to 230 ° C. out of the system. After completion of the reaction, 0.05 part by weight of tetranormal butyl titanate and 0.025 part by weight of phosphoric acid were added, and a polycondensation reaction was performed at 250 ° C. under reduced pressure (1.0 hPa or less). Polytetramethylene terephthalate-polytetramethylene oxide block copolymer, polytetramethylene oxide ratio 40% by weight, intrinsic viscosity 0.75) were used.

(4) Resin D: Polyester containing 5% by weight of crosslinked PMMA particles Polyester methacrylate particles crosslinked with trimethylolpropane trimethacrylate with respect to 95 parts by weight of polyester resin A (manufactured by Nippon Shokubai Co., Ltd., part number Eposter MA1002, 5 parts by weight of an average particle diameter of 2 to 3 μm was melt-kneaded with a twin-screw extruder to obtain a polyester resin containing 5% of crosslinked polymethyl methacrylate particles.

Example 1
A polyester resin composition prepared by mixing Resin A / Resin C / Resin D at a ratio (wt%) of 75.5 / 4.5 / 20 was melt-extruded by a T-die method to form an amorphous sheet, and then at 78 ° C. Preheated, stretched 3.7 times in the longitudinal direction at 128 ° C. in 3.7 steps, stretched 4.0 times in the transverse direction at 115 ° C., and heat-set at 228 ° C. for 4 seconds to obtain a polyester film having a thickness of 12 μm. One side of the polyester film was coated with an adhesive (a mixture of polyurethane adhesive “Adcoat” and curing agent manufactured by Toyo Ink Co., Ltd.) and a curing agent at a solid content of 4 g / m ² , dried, and then aged at 40 ° C. for 24 hours. The film thus obtained was degreased, laminated on both sides of a cold-drawn steel plate heated to 170 ° C. by a thermal laminating method, and rapidly cooled in a water bath at 10 to 40 ° C. to obtain a laminated steel plate. Further, the film laminated metal plate was heated at 230 ° C. and then quenched in water.

Tables 1 and 2 show the characteristics of the obtained polyester film and laminated steel sheet.
The polyester film and laminated steel sheet obtained in this example have good slipperiness between the film and metal at high temperature, excellent scratch resistance, excellent transparency, and high quality as a metal laminating film and laminated steel sheet. Met.
Using the polyester film obtained in this example on the inner surface of the can body and the inner and outer surfaces of the bottom lid, a can was made as a three-piece can, which was manufactured at a high speed without scratching the surface of the film during the can making process. Can be made, no particles fall out in the can, and even after repairing the joint, the film looks good, and even if the molded can is filled with coffee and retort processed, it can be transferred from the film of oligomers, organic solvents, etc. There was no change in taste and smell, and the product value was high.

(Example 2)
A polyester film was obtained in the same manner as in Example 1 except that the ratio (wt%) of resin A / resin C / resin D was 78.5 / 4.5 / 17.

(Comparative Example 1)
The same method as in Example 1, except that the ratio of resin B / resin C / resin D was 75.5 / 4.5 / 20 (weight%) as the raw material, and the heat setting temperature after stretching was 150 ° C. Thus, a polyester film was obtained.

(Comparative Example 2)
A polyester film was obtained in the same manner as in Example 1 except that the ratio of resin A / resin D was 80/20 (wt%).

(Comparative Example 2) A polyester film was obtained in the same manner as in Example 1 except that the ratio of resin A / resin C was 95.5 / 4.5 (wt%).

(Comparative Example 4)
A polyester film was obtained by the same method as in Example 1 except that the same resin as in Example 1 was melt-extruded as a raw material to form an amorphous sheet and then stretched 3.4 times in two stages in the longitudinal direction.

  The polyester film for a three-piece can of the present invention has adhesion to a metal plate, transportability of the metal plate, and can-making properties (for example, bending, joining, joint repair, flanging, top lid attachment, content filling, bottom filling Since it is excellent in lid mounting and retort sterilization), the present invention can be used for a wide range of applications such as soft drinks, beer, metal containers such as canned foods, and contributes greatly to the industry.

Claims (4)

A polyester film for laminating three-piece cans comprising a polyester composition,
The polyoxyalkylene glycol component in which the polyester composition is mainly composed of polyethylene terephthalate and the repeating of the alkylene oxide unit having 2 or more carbon atoms is 3 or more has 2 carbon atoms derived from the polyoxyalkylene glycol component. The alkylene oxide unit is contained in an amount of 2 to 20 mol% based on the total acid component of the polyester component in the polyester composition, and spherical PMMA particles are added in an amount of 0.75 to 1.5% based on the total amount of the polyester composition. A polyester film for three-piece can lamination, containing 2% by weight, having a density of 1.37 g / cm ³ or more, and having a plane orientation coefficient of 0.161 to 0.167.   A polyester film for three-piece can lamination, wherein the film has a tensile elongation of 144 to 200 MPa.   A metal plate obtained by laminating the polyester film according to claim 1.   A metal container formed by molding the laminated metal plate according to claim 3.