JP2007203570A - Laminated film for metal sheet lamination molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated film for metal sheet lamination molding which is excellent in film-making properties, suppresses the bleed-out of low molecular compounds, indicates good adhesion to the metal sheet and excellent molding properties when subjected to can-making working such as drawing, and can produce a metal can having a feeling of gloss after lamination. <P>SOLUTION: The laminated film for metal sheet lamination molding is a biaxially oriented laminated film constituted of a polyester layer A which is made of a wax-containing polyethylene terephthalate (a) composition and has a coefficient of surface orientation of 0.151-0.180 and a polyester layer B which is contacted with the layer A and is made of polyethylene terephthalate (b). The polyester layer A contains 0.01-1.0 wt.% of non-spherical particles, and the polyester layer B contains 0.001-0.05 wt.% of non-spherical particles. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated film for metal plate lamination molding.

  Metal cans are generally painted to prevent corrosion on the inner and outer surfaces, but recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, developed a method to obtain rust resistance without using organic solvents. As one of them, an attempt has been made to cover a metal can with a thermoplastic resin film. That is, a method of laminating a thermoplastic resin film on a metal plate such as tinplate, tin-free steel, or aluminum and then making a can by drawing or the like. As a thermoplastic resin film, a polyethylene terephthalate film has attracted attention as having balanced characteristics, and several proposals based on this have been made. For example, Japanese Patent Application Laid-Open No. 11-151752 and Japanese Patent Application Laid-Open No. 11-151791 propose using a polyester film having a specific melting point and a specific plane orientation coefficient.

  When used on the inner surface of a metal can, when the contents of the can are not liquid, the contents are not firmly attached to the can side wall or the bottom of the can and can be taken out well. In order to impart this property, Japanese Patent Laid-Open No. 2001-220453 proposes to use a polyester film containing a wax.

Japanese Patent Laid-Open No. 11-151752 Japanese Patent Laid-Open No. 11-151791 JP 2001-220453 A

  In recent years, the high-quality appearance of metal cans, that is, the appearance when bonded to a metal plate, in particular, glossiness, has been regarded as important. In addition, it is also required that low molecular weight compounds, such as polyester oligomers, which are unfavorable for food hygiene, come into contact with or are not contained in the contents. However, according to the conventional technique, the bleed-out of the low molecular weight compound cannot be sufficiently reduced while giving the appearance of the metal can gloss.

  The object of the present invention is to reduce the bleed-out of low molecular weight compounds, have excellent film-forming properties, exhibit excellent adhesion to the metal plate without contaminating the step in the step of laminating with the metal plate, and draw processing, etc. An object of the present invention is to provide a laminated film for metal plate laminating and forming that exhibits excellent moldability when performing can manufacturing and can produce a metal can having a glossy feeling after lamination.

  That is, the present invention comprises a polyester layer A comprising a composition of polyethylene terephthalate (a) containing a wax and having a plane orientation coefficient of 0.151 to 0.180, and a composition of polyethylene terephthalate (b) in contact with the layer A. A biaxially stretched laminated film composed of a polyester layer B consisting of the following: a polyester layer A containing 0.01 to 1.0% by weight of non-spherical particles, and a polyester layer B containing spherical particles It is a laminated film for metal plate bonding molding processing characterized by containing 0.01 to 1.0% by weight and 0.001 to 0.05% by weight of non-spherical particles.

  According to the present invention, the film forming property is excellent, the bleed-out of low molecular weight compounds is small, and in the step of laminating with a metal plate, the adhesion with the metal plate is exhibited without contaminating the step, drawing processing, etc. It is possible to provide a laminated film for metal plate laminating and molding that exhibits excellent moldability when performing the can manufacturing process and can produce a metal can having gloss after lamination. This is particularly suitable for bonding to a can body part and a lid part of a metal can for filling a beverage or food, particularly to the inner surface of the can.

  Hereinafter, the present invention will be described in detail.

[Polyester layer A]
The polyester layer A in the present invention is a layer that becomes the non-metal side when the film is bonded to a metal plate.

  The polyester layer A is composed of a composition of polyethylene terephthalate (a). The polyethylene terephthalate (a) is preferably polyethylene terephthalate substantially free of a copolymer component. Thereby, when laminating to a metal plate, the fault resulting from a laminating roll can be controlled. That is, even when foreign matter is adhered to the laminate roll, the polyester constituting the polyester layer A is hard polyethylene terephthalate (a), and transfer of foreign matter can be suppressed. Thereby, the polyester layer A forms a flat surface with less unevenness due to transfer, and has excellent gloss when bonded to a metal plate. Furthermore, it is possible to prevent low molecular compounds such as oligomers inevitably contained in the polyester layer B from passing through the polyester layer A and bleeding out to the surface of the laminated film for metal bonding molding. This means that when the film of the present invention is used on the inner surface of the metal can, the low molecular weight compound can be prevented from being contained in the contents of the metal can. For example, when the polyester layer B contains a color pigment or a coloring dye, or when the polyester layer B contains an oligomer of polyethylene terephthalate, the polyester constituting the polyester layer A is made of polyethylene terephthalate (a ), It can be suppressed that these low molecular compounds bleed out to the contents side.

  The polyester layer A is a layer that comes into contact with the contents when the metal plate is processed into a can shape. For food hygiene, it is preferable that the polyester layer A does not contain a colorant. Not only that, but in the laminating step with the metal plate, there is a problem that the laminate roll is contaminated. Therefore, it is preferable not to add a colorant to the polyester layer A.

The polyester layer A needs to have a plane orientation coefficient of 0.151 to 0.180 determined by the following formula.
Planar orientation coefficient = [(longitudinal refractive index + lateral refractive index) / 2] −thickness refractive index

  When the plane orientation coefficient is less than 0.151, the low molecular weight compound contained in the polyester layer B passes through the polyester layer A and bleeds out to the content side, contacts the content, and the low molecular weight compound becomes a content. This causes problems such as being contained. On the other hand, when the plane orientation coefficient exceeds 0.180, molding processability is impaired, and problems such as cracking and cutting of the film occur in the can making process.

[particle]
The polyester layer A contains non-spherical particles in an amount of 0.01 to 1.0% by weight, more preferably 0.02 to 0.5% by weight, and particularly preferably 0.03 to 0.1% by weight. This polyester layer A is a layer on the non-metal side. If the non-spherical particles are less than 0.01% by weight, the transportability is inferior in the step of forming a film. If it exceeds 1.0% by weight, the transparency of the film becomes too low, and the metallic luster of the metal plate is impaired when laminated on the metal plate. In addition, when laminating to a metal plate, the surface is too rough, resulting in poor laminating properties and poor adhesion between the metal plate and the film.

[wax]
The polyester composition constituting the polyester layer A of the present invention contains a wax. As waxes, plant waxes such as carnauba wax, candelilla wax, rice wax, tree wax, jojoba oil, palm wax, rosin-modified wax, olicuric wax, sugarcane wax, esparto wax, bark wax, beeswax, lanolin , Animal waxes such as whale wax, ibota wax, shellac wax, mineral waxes such as montan wax, ozokerite, ceresin wax, paraffin wax, microcrystalline wax, petroleum waxes such as petrolactam, Fischer Tropus wax, polyethylene wax, Examples thereof include synthetic hydrocarbon waxes such as oxidized polyethylene wax, polypropylene wax, oxidized polypropylene wax and the like. Of these, polyethylene wax is particularly preferred because of its excellent food hygiene and low handling. The melting point of polyethylene wax is preferably 120 to 140 ° C. By being in this range, even if it goes through the retort sterilization process after filling the contents in the can, the effect of adding the wax is not impaired, and good contents takeout property is expressed. The content of the wax is preferably 0.5 to 2.0% by weight per 100% by weight of the polyester composition of the layer A.

  The polyester of the polyester layer A may be blended with other additives such as a colorant, an antioxidant, a heat stabilizer, an ultraviolet absorber, and an antistatic agent as necessary, as long as the object of the present invention is not impaired. Also good. In particular, for the purpose of obtaining a white appearance, for example, a known technique such as containing titanium oxide can be used. However, it is preferable that the polyester layer A is transparent because the glossiness after laminating the film and the metal plate is excellent.

[Polyester layer B]
The polyester layer B of the present invention is a layer that becomes the metal plate side when the film is bonded to the metal plate. The polyester layer B is composed of a polyester composition composed of polyethylene terephthalate (b).

  The polyethylene terephthalate (a) of the polyester A layer and the polyethylene terephthalate (b) of the polyester B layer in the present invention are polyesters comprising terephthalic acid as a dicarboxylic acid component and ethylene glycol as a diol component. These polyesters may be copolymerized with other components as long as the effects of the present invention are not impaired, and the copolymer component may be an acid component or an alcohol component. As copolymerized dicarboxylic acid components, aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, and alicyclic groups such as cyclohexanedicarboxylic acid Dicarboxylic acid can be illustrated. Examples of the copolymer diol component include aliphatic diols such as butanediol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These may be used alone or in combination of two or more.

  The proportion of the copolymerization component of polyethylene terephthalate (a) is such that the polymer melting point is in the range of 230 to 260 ° C, preferably 235 to 260 ° C, more preferably 240 to 260 ° C. When the polymer melting point is lower than 230 ° C., it is difficult to suppress transfer due to foreign matters on the laminate roll, which will be described later, and the surface has many irregularities and the glossiness is impaired. If the melting point of the polymer exceeds 260 ° C., the crystallinity of the polymer is too large and the moldability is impaired. The polyethylene terephthalate (a) is preferably polyethylene terephthalate substantially free of a copolymer component.

  The proportion of the copolymerization component of polyethylene terephthalate (b) is such that the resulting polymer melting point is in the range of 200-250 ° C, preferably 210-245 ° C, more preferably 215-240 ° C. When the polymer melting point is less than 200 ° C., the heat resistance is inferior, and when the polymer melting point exceeds 250 ° C., the crystallinity of the polymer is too large and the adhesion to the metal plate and the moldability are impaired.

  In order to obtain polyethylene terephthalate (b) satisfying this condition, 5-20 mol%, preferably 7-18 mol%, more preferably 9-16 mol% of isophthalic acid component as a dicarboxylic acid component is a copolymerization component. Copolymerized polyethylene terephthalate included as the above may be used. By co-polymerizing isophthalic acid within the above range, the adhesion to the metal plate can be further improved. If the isophthalic acid component exceeds 20 mol%, the film tends to whiten after retorting, and the appearance after retorting may be impaired.

  The intrinsic viscosity of polyethylene terephthalate (a) and polyethylene terephthalate (b) is preferably 0.50 to 0.80, more preferably 0.54 to 0.70, and particularly preferably 0.57 to 0.65. . When the intrinsic viscosity is less than 0.50, a film having mechanical strength that can be practically used cannot be obtained, and furthermore, it is difficult to suppress transfer due to foreign matter on the laminate roll described later. Problems such as easy component bleeding out to the content side occur. On the other hand, if it exceeds 0.80, moldability is impaired.

  In addition, melting | fusing point of polyester is melting | fusing point obtained by the method of calculating | requiring a melting peak with the temperature increase rate of 20 degree-C / min using the differential scanning calorimeter TA Instruments mDSC. The sample amount is about 10 mg. The intrinsic viscosity of the polyester is a value determined from a measured value at 35 ° C. after being dissolved in o-chlorophenol.

[particle]
The polyester layer B contains 0.01 to 1.0% by weight of spherical particles, preferably 0.02 to 0.5% by weight, and more preferably 0.03 to 0.1% by weight. If it is less than 0.01% by weight, the transportability is inferior in the step of forming a film. On the other hand, if it exceeds 1.0% by weight, the transparency of the film becomes too low, and the metallic luster of the metal plate is impaired when laminated on the metal plate. In addition, when laminating to a metal plate, the surface is too rough, so that the laminating property is inferior, and the adhesion between the metal plate and the film is inferior.

  The polyester layer B contains non-spherical particles in an amount of 0.001 to 0.05% by weight, preferably 0.001 to 0.01% by weight, and more preferably 0.001 to 0.005% by weight. If the non-spherical particles are less than 0.001% by weight, the transportability is inferior in the step of forming a film. If it exceeds 0.05% by weight, the transparency of the film becomes too low, and the metallic luster of the metal plate is impaired when laminated on the metal plate. When the same particles as those contained in the polyester layer A are used for these particles, it is advantageous and preferable for recovering and reusing the portion that did not become a product.

In the present invention, particles having a particle size ratio of 1.0 to 1.2 defined by the following definition are referred to as spherical particles, and particles having a particle size ratio larger than 1.2 are referred to as non-spherical particles.
Particle size ratio = average major axis of particles / average minor axis of the particles

  The average major axis and the average minor axis of the particles are obtained as follows. Observe the cross-section in the transverse direction of the film with a transmission electron microscope. If the particles are individual particles or aggregate type particles, the aggregate is regarded as one particle, and the major axis and minor axis of each particle present in the film Ask for. A value is calculated | required about at least 100 or more of this, and let the average value be an average major axis and an average minor axis, respectively.

Non-spherical particles may be inorganic particles or organic particles. Examples of inorganic particles include silica, alumina, titanium dioxide, calcium carbonate, and barium sulfate. Examples of organic particles include crosslinked polystyrene particles and silicone resin particles. In any case, the average particle size is preferably 1.0 to 3.0 μm, more preferably 1.1 to 2.5 μm. If the average particle size is less than 1.0 μm, the addition amount must be increased in order to obtain film transportability, that is, slipperiness, which is not preferable because transparency is impaired. 3.
If it exceeds 0 μm, it is not preferable because of the coarse particles, resulting in an increase in fly specs, which causes problems such as pinholes and film cutting.

Here, the average particle diameter of the particles is obtained by first obtaining an area equivalent circle diameter from an image magnified 10,000 to 30,000 times with an electron microscope after vapor-depositing a metal on the particle surface. Calculated by fitting.
Average particle size = total area equivalent diameter of measured particles / number of measured particles

  Preferable non-spherical particles are porous silica particles that are aggregated particles of primary particles. Porous silica particles are preferred because they do not easily generate voids around the particles when the film is stretched, and thus have the characteristics of improving the transparency and glossiness of the film.

  The average particle diameter of the primary particles constituting the porous silica particles is preferably 0.001 to 0.1 μm. If the average particle size of the primary particles is less than 0.001 μm, ultrafine particles are generated by crushing at the slurry stage, and this forms an aggregate, which is not preferable because it causes problems in transparency and glossiness. When the thickness exceeds 0.1 μm, the porosity of the particles is lost, and as a result, the feature that the generation of voids is small is lost.

  When porous silica particles are used, the pore volume is preferably 0.5 to 2.0 ml / g, more preferably 0.6 to 1.8 ml / g. When the pore volume is less than 0.5 ml / g, the porosity of the particles is lost, voids are easily generated, and the transparency is lowered, which is not preferable. If it exceeds 2.0 ml / g, crushing and aggregation are likely to occur, and it is difficult to adjust the particle size, which is not preferable.

  When porous silica particles are used, the average particle size is preferably 1.0 to 3.0 μm, more preferably 1.1 to 2.5 μm. If the average particle size is less than 1.0 μm, the addition amount must be increased in order to obtain film transportability, that is, slipperiness, which is not preferable because transparency is impaired. If it exceeds 3.0 μm, the fly specs increase due to the coarse particles, which causes pinholes from this point and causes problems such as cutting of the film, which is not preferable.

  Spherical particles and non-spherical particles may be used at the time of the reaction for producing the polyester, for example, by the transesterification method, at any time during the transesterification reaction or polycondensation reaction, or at any time by the direct polymerization method. In addition, it may be added to the reaction system (preferably as a slurry in glycol). In particular, it is preferable to add porous silica particles to the reaction system at the beginning of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3.

  The spherical particles may be either inorganic particles or organic particles, but inorganic particles are preferred. Examples of inorganic particles include silica, alumina, titanium dioxide, calcium carbonate, and barium sulfate. Preferably, spherical silica, spherical titanium oxide, and spherical zirconium are used. Examples of the organic particles include crosslinked polystyrene particles and crosslinked silicone resin particles, and preferably spherical silicone particles are used.

  The average particle diameter of the spherical particles is preferably 0.01 to 2.5 μm. If the average particle size of the particles exceeds 2.5 μm, coarse particles (for example, particles of 10 μm or more) deformed by the molding process will be the starting point, which may cause problems such as pinholes or breakage. The particle diameter is determined in the same manner as in the case of non-spherical particles.

  The polyester layer B may contain other additives such as a colorant, an antioxidant, a heat stabilizer, an ultraviolet absorber, and an antistatic agent as long as the object of the present invention is not impaired. For example, a white pigment such as titanium oxide may be included for the purpose of obtaining a white appearance.

[Layer structure]
The laminated film for metal plate lamination molding processing of the present invention comprises a polyester layer A made of polyethylene terephthalate (a) and a polyester layer B made of polybutylene terephthalate (b1) and polyethylene terephthalate (b2) in contact with the layer A. This is a biaxially stretched laminated film. When laminating with a metal plate, the polyester A layer is disposed on the non-metal side, and the polyester B layer is disposed on the side in contact with the metal. The ratio Ta / Tb between the thickness Ta of the polyester layer A and the thickness Tb of the polyester layer B is preferably 1/10 to 1/5. When Ta / Tb is less than 1/10, the polyester layer A is too thin, and when laminating with a metal plate, foreign matter on the laminating roll is transferred to the film, and unevenness is likely to be formed on the film surface. . Further, when the polyester layer B contains a low molecular compound having a bleed-out property, a problem that the low molecular compound passes through the polyester layer A and comes into contact with the contents is not preferable. If it exceeds 1/5, the polyester layer A is too thick, and the adhesion in the laminating process is impaired, and the molding processability in the can making process is impaired. Further, the curl of the film becomes large, which is not preferable.

  The laminated film for metal plate bonding molding processing of the present invention is laminated on the metal plate so that the polyester layer A becomes the outermost layer. The laminated film for metal plate bonding molding processing of the present invention preferably has a thickness of 6 to 55 μm, more preferably 8 to 45 μm, and particularly preferably 10 to 30 μm. If the thickness is less than 6 μm, tearing or the like tends to occur during molding, which is not preferable.

  Examples of the metal plate to which the laminated film for metal plate laminating molding processing of the present invention is bonded are, for example, metal plates for cans, and specifically, for example, tin, tin-free steel, tin-nickel steel, and aluminum. A board is appropriate. The polyester film is bonded to the metal plate by heating the metal plate above the melting point of the film, bonding the film, cooling it, and making the surface layer (thin layer) of the film in contact with the metal plate amorphous. In addition, the film can be adhered by a primer coating with an adhesive in advance, and this surface can be bonded to a metal plate. As the adhesive, known resin adhesives such as epoxy adhesives, epoxy-ester adhesives, and alkyd adhesives can be used. Moreover, it is good also as a film which has a colored appearance by disperse | distributing a white pigment or a yellow pigment to this adhesive agent.

[Production method]
Polyethylene terephthalate (a) and polyethylene terephthalate (b) can be produced by a conventionally known method. For example, a method in which terephthalic acid, ethylene glycol and a copolymer component are esterified and then the resulting reaction product is subjected to a polycondensation reaction to obtain a copolymer polyester, or dimethyl terephthalate, ethylene glycol and a copolymer component are transesterified. And then the resulting reaction product can be polycondensed to produce a copolyester. If necessary, other additives such as a fluorescent brightening agent, an antioxidant, a heat stabilizer, and an antistatic agent may be blended.

  The laminated film for metal plate lamination molding process of the present invention can be produced using the above polyester in accordance with a conventionally known coextrusion film forming method. First, after drying each of the above-mentioned polyester raw materials as necessary, using a plurality of extruders, a multi-layer multi-manifold die or a feed block, the respective polyesters are laminated to form a molten sheet from a slit-shaped die. Extruded and cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. In the present invention, both may be used together as necessary. Next, the obtained unstretched sheet is stretched biaxially and biaxially oriented. That is, first, the unstretched sheet is stretched in the longitudinal direction by a roll or tenter type stretching machine. The stretching temperature is 60 to 130 ° C., preferably 70 to 120 ° C., and the stretching ratio is 2.9 to 4.0 times, preferably 3.0 to 3.5 times. Next, the film is stretched in the width direction by a tenter type stretching machine. The stretching temperature is 80 to 130 ° C., preferably 90 to 120 ° C., and the stretching ratio is 2.9 to 4.5 times, preferably 3.1 to 4.0 times. Further, heat treatment is performed under a relaxation of 20% or less at a temperature in the range of 140 to 200 ° C., preferably 150 to 190 ° C., to obtain a biaxially stretched film for laminating film for laminating a metal plate of the present invention. Can do.

  Hereinafter, the present invention will be further described with reference to examples. The film characteristics were measured and evaluated by the following methods.

(1) Melting point The melting peak temperature was determined at a heating rate of 20 ° C./min using a DSC 2920 Modulated DSC manufactured by TA Instruments. The sample amount was about 20 mg.

(2) Intrinsic viscosity After the film was dissolved in o-chlorophenol, the filler such as titanium oxide was removed by a centrifuge and measured at a temperature of 35 ° C. In addition, an intrinsic viscosity is a value of an unstretched film.

(3) Plane orientation coefficient Using a laser refractometer (model 2010 prism coupler) manufactured by Metricon, one film is sandwiched between the pressures of the built-in pressure gauge 40 and measured with a laser beam having a wavelength of 633 nm. On the obtained spectrum chart, the point at which the detector output sharply decreases is read, and this value is taken as the refractive index. About each of the polyester layer A and the polyester layer B, the longitudinal direction refractive index, the horizontal direction refractive index, and the thickness direction refractive index were read, and the plane orientation coefficient was computed using the following formula | equation.
Planar orientation coefficient = [(longitudinal refractive index + lateral refractive index) / 2] −thickness refractive index

(4) Deep drawing workability A sample film was bonded to both sides of a 0.25 mm thick tin-free steel heated to 230 ° C., cooled with water, then cut into a 150 mm diameter disk, and a drawing die and punch were used. Then, deep drawing was performed in four stages to produce a 55 mm diameter side seamless container (hereinafter abbreviated as a can). These cans were observed and tested as follows, and evaluated according to the following criteria. The results of observation of the processing status of the can were visually evaluated according to the following criteria.
○: The film is processed without any abnormality, and no whitening or breakage is observed in the film.
(Triangle | delta): Whitening is recognized by the can upper part of a film.
X: Film breakage is observed in a part of the film.

(5) Glossiness The glossiness of the can in which deep drawing was good in the above (4) was visually evaluated.
◯: Excellent gloss and high-class feeling.
(Triangle | delta): Although it is glossy, a high-class feeling is insufficient.
×: no gloss

(6) Oligomer The can that had been well-drawn in (4) was retort sterilized at 125 ° C. for 90 minutes, the surface was lightly wiped with gauze, and the adhesion of the powder to the gauze was visually evaluated.
○: No powder adheres to the gauze.
Δ: A small amount of powder adhered to the gauze.
X: The powder adhered to the gauze remarkably.
The powder adhering to the gauze was confirmed to be a polyester-based oligomer using NMR or the like.

(7) Contents take-out property The cans that had been well-drawn in (4) above were filled with the contents of 3/2/1% by weight of egg / meat / flour and 125 ° C. for 90 minutes. Retort sterilization treatment, the can was turned upside down, the contents were taken out, and the amount of contents remaining inside the can was determined according to the following.
○: The content remaining in the can is 10% by weight or less of the charged amount. Δ: The content remaining in the can is 10 to 50% by weight of the charged amount.
X: The content remaining inside the can is 50% by weight or more of the charged amount

[Example 1]
The polyester composition of polyester layer A and polyester layer B shown in Table 1 was dried by a conventional method, and the polyester composition forming polyester layer A was melted separately at 280 ° C., and the polyester composition forming polyester layer B was melted separately at 280 ° C. Then, it laminated | stacked on two layers using the feed block, extruded from die | dye, and solidified by cooling, and the unstretched film was created. The polyester composition forming the polyester layer A contains a polyethylene wax having a melting point of 130 ° C. so as to contain 1.5% by weight per 100% by weight of the total polyester composition forming the polyester layer A. In the polyester composition comprising the polyester layer A, the same polyethylene wax as that contained in the polyester layer A was blended so as to contain 0.07% by weight per 100% by weight of the total polyester composition comprising the polyester layer B.

  Next, this unstretched film was longitudinally stretched 3.4 times at 85 ° C., then stretched 4.0 times at 100 ° C., and heat-set at 185 ° C. to obtain a biaxially oriented laminated film. The thickness of the obtained film was 20 μm. Here, the thickness of each layer in the biaxially oriented laminated film was adjusted such that the thickness of the polyester layer A was 2 μm and the thickness of the polyester layer B was 18 μm by adjusting the discharge amount of the melt extruder.

  In the obtained biaxially oriented laminated film, the polyester layer B contains 0.1% by weight of agglomerated silica (non-spherical) having an average particle size of 2.3 μm, and the polyester layer B has an average particle size of 1.5 μm. 1% spherical silica (spherical) and 0.005% by weight of agglomerated silica (non-spherical) having an average particle size of 2.3 μm. The obtained biaxially oriented laminated film had excellent performance as a metal plate laminating film as shown in Table 2.

[Example 2]
The same raw material as in Example 1 was used, the amount was changed as shown in Table 1, and the stretching conditions were longitudinally stretched 3.2 times at 90 ° C and then stretched 3.7 times at 105 ° C. A biaxially oriented laminated film was obtained in the same manner as in Example 1 except that. In the obtained biaxially oriented laminated film, the polyester layer A contains 0.05% by weight of agglomerated silica (non-spherical) having an average particle size of 2.3 μm, and the polyester layer B has an average particle size of 1.5 μm as a lubricant. Of spherical silica (spherical) and 0.002% by weight of agglomerated silica (non-spherical) having an average particle size of 2.3 μm. The thickness of the obtained biaxially oriented laminated film was 15 μm. The thickness of each layer in the biaxially oriented laminated film was adjusted such that the thickness of the polyester layer A was 1.5 μm and the thickness of the polyester layer B was 13.5 μm by adjusting the discharge amount of the melt extruder. The obtained biaxially oriented laminated film had excellent performance as a metal plate laminating film as shown in Table 2.

[Example 3]
A biaxially oriented laminated film was obtained in the same manner as in Example 2 except that the raw materials used for the polyester layer A and the polyester layer B were as shown in Table 1. The thickness of the obtained biaxially oriented laminated film was 15 μm. The thickness of each layer in the biaxially oriented laminated film was adjusted such that the thickness of the polyester layer A was 1.5 μm and the thickness of the polyester layer B was 13.5 μm by adjusting the discharge amount of the melt extruder. The obtained biaxially oriented laminated film had excellent performance as a metal plate laminating film as shown in Table 2.

[Example 4]
A biaxially oriented laminated film was obtained in the same manner as in Example 2 except that titanium dioxide particles and 15% by weight based on the polyester layer B were added to the polyester layer B. The thickness of the obtained biaxially oriented laminated film was 20 μm. The thickness of each layer in the biaxially oriented laminated film was adjusted such that the thickness of the polyester layer A was 3 μm and the thickness of the polyester layer B was 17 μm by adjusting the discharge amount of the melt extruder. The obtained biaxially oriented laminated film had excellent performance as a metal plate laminating film as shown in Table 2.

[Comparative Example 1]
In the obtained film, the polyester layer A contains 0.1% by weight of spherical silica (spherical) having an average particle diameter of 1.5 μm, and the polyester layer B is a spherical silica having an average particle diameter of 1.5 μm as a lubricant. A biaxially oriented laminated film was obtained in the same manner as in Example 2 except that 0.1% by weight of (spherical) was contained. The thickness of the obtained film was 15 μm. The thickness of each layer in the biaxially oriented laminated film was adjusted such that the thickness of the polyester layer A was 1.5 μm and the thickness of the polyester layer B was 13.5 μm by adjusting the discharge amount of the melt extruder. In the obtained biaxially oriented laminated film, since the lubricant of the polyester layer A is spherical, the laminate roll is soiled in the step of laminating the film and the metal plate. There was a transfer due to this, and the glossiness of the appearance of the can obtained by deep drawing was inferior, and the performance as a metal plate laminating film was inferior.

[Comparative Example 2]
The polyethylene waxes contained in the polyester layer A and the polyester layer B are as shown in Table 1, and the stretching conditions are as follows: longitudinal stretching at 2.8 times at 100 ° C., and transverse stretching at 2.8 times at 110 ° C. A biaxially oriented laminated film was obtained in the same manner as Example 1 except for the above. In the obtained biaxially oriented laminated film, the polyester layer A contains 0.05% by weight of agglomerated silica (non-spherical) having an average particle size of 2.3 μm, and the polyester layer B is a true lubricant having an average particle size of 1.5 μm as a lubricant. It contained 0.05% by weight of spherical silica (spherical) and 0.002% by weight of agglomerated silica (non-spherical) having an average particle size of 2.3 μm. The thickness of the obtained biaxially oriented laminated film was 15 μm. The thickness of each layer in the biaxially oriented laminated film was adjusted such that the thickness of the polyester layer A was 1.5 μm and the thickness of the polyester layer B was 13.5 μm by adjusting the discharge amount of the melt extruder. Since the obtained biaxially oriented laminated film has a small plane orientation coefficient of the polyester layer A, the laminate roll is very dirty in the process of laminating the film and the metal plate. Due to the transfer, the gloss of the can obtained by deep drawing was inferior in gloss, and after retorting, oligomer bleed out was observed on the film surface, and the metal plates were bonded together. The film was inferior in performance.

[Comparative Example 3]
A biaxially oriented laminated film was obtained in the same manner as in Example 2 except that the polyester composition of polyester layer A and polyester layer B and the polyethylene wax contained in each layer were as shown in Table 1. The thickness of the obtained biaxially oriented laminated film was 15 μm. The thickness of each layer in the biaxially oriented laminated film was adjusted such that the thickness of the polyester layer A was 1.5 μm and the thickness of the polyester layer B was 13.5 μm by adjusting the discharge amount of the melt extruder. Since the obtained biaxially oriented laminated film had a small plane orientation coefficient of the polyester layer A, the laminating rolls were very dirty in the process of laminating the film and the metal plate. Furthermore, since the melting point of the polyester constituting the polyester layer A is too low, transfer due to dirt on the laminate roll is seen on the surface of the film. Therefore, the gloss of the appearance of the can obtained by the deep drawing process. Was inferior. Moreover, after the retorting treatment, oligomer bleed-out was observed on the film surface, and the performance as a metal plate laminating film was poor. Moreover, since the addition amount of the polyethylene wax contained in the polyester layer A is too small, the contents can be taken out easily.

  As is clear from the results in Table 2, the can using the polyester film of the present invention has excellent deep drawing workability, excellent process suitability during lamination, gloss after lamination, and appearance after retort. It was.

  The laminated film for metal plate bonding molding processing of the present invention can be used by being bonded to a can body portion or a lid material portion of a metal can such as a soft drink or a food can.

Claims (5)

  Polyester layer A comprising a composition of polyethylene terephthalate (a) containing wax and having a plane orientation coefficient of 0.151 to 0.180, and polyester layer B comprising the composition of polyethylene terephthalate (b) in contact with this layer A The polyester layer A contains 0.01 to 1.0% by weight of non-spherical particles, and the polyester layer B contains 0.01 to 1 spherical particles. A laminated film for metal plate laminating and molding, characterized by containing 0.0% by weight and 0.001 to 0.05% by weight of non-spherical particles.   The laminated film for metal bonding molding according to claim 1, wherein the ratio Ta / Tb of the thickness Ta of the polyester layer A and the thickness Tb of the polyester layer B is 1/10 to 1/5.   The laminated film for metal bonding molding according to claim 1, wherein the polyester layer B is polyethylene terephthalate copolymerized with an isophthalic acid component.   The laminated film for metal lamination molding according to claim 1, wherein the wax is a polyethylene wax having a melting point of 120 to 140 ° C.   The laminated film for metal plate bonding molding processing according to any one of claims 1 to 3, wherein the laminated film is used by being bonded to a metal so that the polyester layer B side is in contact with the metal.