JP4799197B2 - Laminated film for metal plate lamination molding - Google Patents

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 for making a can by drawing or the like after laminating a thermoplastic resin film on a metal plate such as tinplate, tin-free steel, or aluminum has been studied.

  The polyethylene terephthalate film has attracted attention as a film having balanced characteristics, and several proposals based on this have been made. For example, Japanese Patent Application Laid-Open Nos. 11-151752 and 11-151791 propose a polyester film having a specific melting point and a specific plane orientation coefficient.

  Moreover, in JP-A-10-195210 and Japanese Patent No. 2882985, a film that does not become cloudy even in a retort sterilization treatment step that is performed after a metal plate laminated with a polyester film is formed into a can shape and filled with contents. A polyester film composed of polyethylene terephthalate and polybutylene terephthalate has been proposed.

Japanese Patent Laid-Open No. 11-151752 Japanese Patent Laid-Open No. 11-151791 JP 10-195210 A Japanese Patent No. 2882985

  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. The present invention provides a laminated film for metal plate laminating and forming that exhibits excellent moldability when performing the can manufacturing process, has a glossy feeling after lamination, and can produce a metal can having a good appearance after retort. It is in.

That is, the present invention comprises a polyester layer A made of polyethylene terephthalate (a) having a melting point of 230 to 260 ° C., polybutylene terephthalate (b1) in contact with this layer A, and polyethylene terephthalate (b2) having a melting point of 210 to 260 ° C. A biaxially stretched laminated film comprising a polyester layer B, wherein the polyester layer A contains 0.01 to 1.0% by weight of non-spherical particles, and the polyester layer B contains 0 non-spherical particles. A laminated film for laminating and forming a metal plate, characterized by containing 0.01 to 1.0% by weight and being laminated to a metal so that the layer B side is in contact with the metal .

  According to the present invention, low-molecular compound bleed-out is small, film-formability is excellent, 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. The present invention provides a laminated film for metal plate laminating and forming that exhibits excellent moldability when performing the can manufacturing process, has a glossy feeling after lamination, and can produce a metal can having a good appearance after retort. Can do.

  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 constituting the polyester layer A is polyethylene terephthalate (a) having a melting point of 230 to 260 ° C., preferably polyethylene terephthalate substantially free of a copolymer component. By using this polyethylene terephthalate (a), it is possible to suppress defects caused by the laminate roll when laminating to a metal plate. That is, even when foreign matter is adhered to the laminate roll, transfer of foreign matter can be suppressed because the polyester constituting the polyester layer A is hard, and the polyester layer A has a flat surface with less unevenness due to transfer. When formed and bonded to a metal plate, it has excellent gloss. 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 metal laminate molding film. 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. When the melting point of the polyethylene terephthalate (a) is less than 230 ° C., it is difficult to suppress transfer due to foreign matters on the laminate roll described later, and the surface has many irregularities and the glossiness is impaired. When the melting point exceeds 260 ° C., the crystallinity of the polymer is too large and the moldability is impaired.

  When the laminated film for metal plate bonding and molding of the present invention is used in a metal can, the laminated film for metal plate bonding and molding of the present invention is bonded to a metal plate and processed into a can shape. Usually, the film is on the outside, but the film may be processed on the inside. In this case, since the polyester layer A becomes a layer in contact with the contents, it is preferable that the polyester layer A does not contain a colorant for food hygiene. 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.

[Polyester layer B]
The polyester layer B in 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 comprising polybutylene terephthalate (b1) and polyethylene terephthalate (b2) having a melting point of 210 to 260 ° C. The melting point of polyethylene terephthalate (b2) is preferably 215 to 260 ° C, more preferably 220 to 260 ° C. When the melting point is less than 210 ° C., the heat resistance is inferior, and when the melting point exceeds 260 ° C., the crystallinity of the polymer is too large and the adhesion to the metal plate and the moldability are impaired.

  In this polyester composition, the blending ratio of polybutylene terephthalate (b1) to polybutylene terephthalate (b2) is preferably 30/70 to 70/30% by weight. When the blending ratio exceeds 70/30, the content of polybutylene terephthalate (b1) is too large, the melting point as a resin is too low, and the heat resistance is inferior. If the mixing ratio is less than 30/70, the amount of polybutylene terephthalate (b1) is too small, and the adhesion to the metal plate will be inferior. When applied, the film is whitened, and the appearance after the retort treatment is impaired.

  In addition, for the purpose of preventing the film from whitening after the retort treatment, a known stabilizer typified by a phosphorus compound is added to suppress the transesterification reaction of polybutylene terephthalate (b1) and polyethylene terephthalate (b2). The crystallization speed may be improved. Examples of the phosphorus compound include trimethyl phosphate, triethylene phosphate, tri-n-butyl phosphate, and orthophosphoric acid.

  In the range which does not impair the objective of this invention, you may add other additives, such as a coloring agent, antioxidant, a heat stabilizer, a ultraviolet absorber, and an antistatic agent, to the polyester layer B as needed. In particular, there is a case where coloring is performed to obtain a high-grade appearance, in particular, a gold color. For this purpose, a colorant, particularly a yellow colorant, can be added to the film. As the yellow colorant, anthraquinone, isoindolinone, benzimidazolone, quinophthalone, and condensed azo are preferable. In order to adjust the color tone, other components may be used in combination as the colorant, but those having good heat resistance are preferred, and those that are recognized as safe in terms of food hygiene are preferred for their use. .

  The colorant may be contained in the raw material resin polymerization step, and a high-concentration master chip is produced using, for example, a twin screw extruder, and mixed with a chip not containing the colorant to obtain a desired colorant. You may obtain the resin composition containing the coloring agent of a density | concentration. Further, for example, using a screw feeder, the colorant may be directly contained in the extruder in the film forming process as powder.

[polyethylene terephthalate]
The polyethylene terephthalate (a) of the polyester A layer and the polyethylene terephthalate (b2) 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. In order to obtain polyethylene terephthalate (a) satisfying this condition, a homopolymer of polyethylene terephthalate is used, or a copolymerized polyethylene terephthalate containing 1 to 3 mol% of isophthalic acid component as a copolymer component is used as the dicarboxylic acid component. Good. The proportion of the copolymerization component of polyethylene terephthalate (b2) is such that the polymer melting point is in the range of 210-260 ° C. In order to obtain polyethylene terephthalate (b2) satisfying this condition, 1-15 mol%, preferably 1-10 mol%, more preferably 1-5 mol% of isophthalic acid component as a dicarboxylic acid component is used as a copolymerization component. The copolymerized polyethylene terephthalate containing may be used. By copolymerizing isophthalic acid within the above range, the adhesion to the metal plate can be further improved. If the isophthalic acid component exceeds 15 mol%, the film tends to be whitened after retorting, and the appearance after retorting may be impaired.

  The intrinsic viscosities of polyethylene terephthalate (a) and polyethylene terephthalate (b2) are both preferably 0.50 to 0.80, more preferably 0.54 to 0.70, and particularly preferably 0.57 to 0.65. It is. If the intrinsic viscosity is less than 0.50, a film having mechanical strength that can be practically used cannot be obtained, and it becomes difficult to suppress transfer caused by foreign matter on the laminate roll, which will be described later. Is not preferable because it causes problems such as easy bleeding to the contents side. If it exceeds 0.80, the moldability is impaired, which is not preferable.

  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.

[Polybutylene terephthalate]
The polybutylene terephthalate (b1) of the polyester B layer in the present invention is a polyester comprising terephthalic acid as a dicarboxylic component and 1,4-butanediol as a diol component. This polyester is preferably a polyester that has been subjected to a solid-phase polycondensation reaction after a melt polymerization reaction.

  The polybutylene terephthalate may be copolymerized with other components as long as the effects of the present invention are not impaired, and the copolymer component may be a dicarboxylic acid component or a diol component. Copolymerized dicarboxylic acid components include 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. Of these, isophthalic acid, 2,6-naphthalenedigalbonic acid, and adipic acid are preferred. Examples of the copolymer diol component include aliphatic diols such as ethylene glycol 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 is a proportion that results in a polymer melting point of 180 to 223 ° C., preferably 200 to 223 ° C., more preferably 210 to 223 ° C., depending on the type. When the polymer melting point is less than 180 ° C., the crystallinity as polyester is low, and as a result, the heat resistance of the film is lowered. Since the melting point of polybutylene terephthalate homopolymer is 223 ° C., 223 ° C. is the upper limit of the melting point.

  The intrinsic viscosity of the polybutylene terephthalate (b1) is preferably 0.60 to 2.00, more preferably 0.80 to 1.70, and particularly preferably 0.85 to 1.50. An intrinsic viscosity of less than 0.6 is not preferable because a film having mechanical strength that can be used practically cannot be obtained. In terms of productivity of the raw material polyester resin and film, the upper limit of the intrinsic viscosity is 2.0.

[particle]
The polyester layer A contains non-spherical particles in an amount of 0.01 to 1.0% by weight, preferably 0.02 to 0.5% by weight, and more preferably 0.03 to 0.1% by weight. This polyester layer A is a layer that becomes the non-metal side when bonded to a metal. If it is less than 0.01% by weight, the transportability is inferior in the step of forming a film or the step of transporting and processing a metal plate laminated with a film, and problems such as scratching on the film surface occur. In addition, when molding a laminated metal plate, the friction between the mold and the film becomes too great, and the film may be scraped off by the mold, or the mold may be wrinkled or the mold may be worn out. As a result, the molding speed cannot be increased, resulting in poor productivity. When it exceeds 1.0% by weight, the transparency of the film is low, and it is difficult to obtain a preferable gloss when laminated on a metal plate.

  It is preferable that the polyester layer A does not contain substantially spherical particles. Spherical particles are more likely to fall out of the film than non-spherical particles, and if they are contained in a large amount, the laminate roll contacting the polyester layer A tends to become dirty in the laminating step for bonding to a metal plate. Furthermore, when a polyester film containing spherical particles is stretched, voids are generated around the particles. This not only impairs the transparency of the film, but also causes a problem that the low molecular weight compound (for example, a colorant or a polyester oligomer) having a bleedout property contained in the polyester layer B bleeds out through the polyester layer A. . For example, in a metal plate laminated with a film, when the polyester layer A comes into contact with the contents, there is a problem that the low molecular weight compound bleed out from the polyester layer B passes through the polyester layer A and comes into contact with the contents. Arise. Moreover, also when performing a retort process in a sterilization process etc., the low molecular weight compound passes through the polyester layer A similarly from the polyester layer B, and deposits on the surface of the polyester layer A, glossiness is impaired, and the external appearance It causes problems such as inferiority.

  The polyester layer B 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 B is a layer on the 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.

  The polyester layer B preferably further contains spherical particles. The content is preferably 0.005 to 0.1% by weight, more preferably 0.005 to 0.05% by weight. By containing spherical particles in this range, a film that is difficult to be whitened by retort treatment can be obtained. If the spherical particles exceed 0.1% by weight, voids are generated around the particles when the film is stretched, and the low molecular weight compound contained in the polyester layer B tends to bleed out to the surface, which is not preferable. In the process of laminating the film and the metal plate, when the low molecular weight compound bleeds out and adheres to the surface of the polyester layer B, the laminating property and adhesion with the metal plate are inferior.

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. If it exceeds 3.0 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 preferably used for the layer B may be either inorganic particles or organic particles, but inorganic particles are preferable. 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.

[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.

[laminate]
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 at the time of molding, which is not preferable, and if it exceeds 55 μm, the quality is excessive and uneconomical.

  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), polybutylene terephthalate (b1) and polyethylene terephthalate (b2) 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 bonding molding processing of the present invention can be produced using the above-mentioned polyester in accordance with a conventionally known coextrusion film forming method. For example, the following may be performed. 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 40 to 110 ° C., preferably 50 to 100 ° C., and the stretching ratio is 2.5 to 4.5 times, preferably 3.0 to 4.0 times. Next, the film is stretched in the width direction by a tenter type stretching machine. The stretching temperature is 50 to 100 ° C., preferably 60 to 90 ° C., and the stretching ratio is 2.5 to 4.5 times, preferably 3.0 to 4.0 times. Further, heat treatment is performed at a temperature in the range of 90 to 210 ° C., preferably 100 to 200 ° C. under a relaxation of 20% or less, 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) Retort resistance of film The film was retort sterilized at 125 ° C. for 90 minutes, the haze of the film before and after the retort treatment was measured with a Nippon Denshoku Haze Meter NDH2000 type, and the amount of haze change before and after the retort treatment (ΔHz) ) (Unit:%) was calculated.
ΔHz = (haze after retorting) − (haze before retorting)
○: ΔHz is 10 or less Δ: ΔHz is 10-15
×: ΔHz is 15 or more

(4) Curl Measured based on JIS K 7619 (1988) (Measuring method of curl of photographic film). The radius of curvature was determined for a square film with a side of 100 mm, and the curl degree (unit: 1 / m) was calculated by the following formula.
Curling degree (1 / m) = 1 / curvature radius of film [m]
The evaluation was as follows.
○: Curling degree is 250 (1 / m) or less ×: Curling degree is larger than 250 (1 / m)

(5) 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 using a drawing die and punch 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.

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

(7) Appearance after retorting After filling the can that had been deep-drawn in step (5) to a full extent, put it in a retort kettle and pressurize steam at 125 ° C so that steam does not directly hit the sample. Was subjected to a retort treatment for 90 minutes, and the change in the surface appearance of the polyester resin layer at the bottom of the deep-drawn can was visually evaluated.
○: No change.
Δ: Slightly cloudy.
X: It changed to milky white markedly.

[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 270 ° C. Then, it laminated | stacked on two layers using the feed block, extruded from die | dye, and solidified by cooling, and produced the unstretched film. Here, normal phosphoric acid was added to the polyester layer B so that the amount of phosphorus was 0.03 mol% with respect to 100 mol% of the dicarboxylic acid component of the polyester. Next, the unstretched film was longitudinally stretched 3.2 times at 68 ° C., then transversely stretched 3.7 times at 78 ° C., and heat-set at 185 ° C. to obtain a biaxially oriented laminated film. The thickness of the obtained biaxially oriented laminated film was 12 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 10.5 μm by adjusting the discharge amount of the melt extruder.

In the obtained biaxially oriented laminated film, the polyester layer A contains 0.1% by weight of agglomerated silica (non-spherical) having an average particle size of 2.3 μm as a lubricant, and the polyester layer B is an average particle as a lubricant. It contains 0.1% by weight of aggregated silica (non-spherical) having a diameter of 2.3 μm and 0.01% by weight of true spherical silica (spherical) having an average particle diameter of 1.5 μm.
The obtained biaxially oriented laminated film had excellent performance as a metal plate laminating film as shown in Table 2.

[Example 2]
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 as a lubricant, and the polyester layer B has an average particle size of 2 as a lubricant. Biaxial in the same manner as in Example 1 except that 0.05% by weight of 3 μm agglomerated silica (non-spherical) and 0.01% by weight of true spherical silica (spherical) having an average particle diameter of 1.5 μm are contained. An oriented laminated film was obtained. The obtained biaxially oriented laminated film had a thickness of 12 μm and had excellent performance as a metal plate laminating film as shown in Table 2.

[Example 3]
The polyester composition of the polyester layer A and the polyester layer B is as shown in Table 1, and in the obtained biaxially oriented laminated film, the polyester layer A has 0% aggregated silica (non-spherical) having an average particle diameter of 2.3 μm as a lubricant. The polyester layer B is biaxially oriented in the same manner as in Example 1 except that the polyester layer B contains 0.05% by weight of agglomerated silica (non-spherical) having an average particle size of 2.3 μm as a lubricant. A laminated film was obtained. The obtained biaxially oriented laminated film had a thickness of 12 μm and had excellent performance as a metal plate laminating film as shown in Table 2.

[Comparative Example 1]
A biaxially oriented laminated film was obtained in the same manner as in Example 2 except that the polyester compositions of the polyester layer A and the polyester layer B were as shown in Table 1. The thickness of the obtained biaxially oriented laminated film is 12 μm, and as shown in Table 2, in the process of laminating the film and the metal plate, the laminate roll is very dirty, and the surface of the polyester layer A is caused by the stain. As a result, the gloss of the external appearance of the can obtained by deep drawing was inferior, and the performance as a metal plate laminating film was inferior.

[Comparative Example 2]
In the obtained biaxially oriented laminated film, the polyester layer A contains 0.1% by weight of true spherical silica (spherical) having an average particle size of 1.5 μm as a lubricant, and the polyester layer B has an average particle size of 1 as a lubricant. A biaxially oriented laminated film was obtained in the same manner as in Example 1 except that 0.1% by weight of 5 μm true spherical silica (spherical) was contained. The thickness of the obtained biaxially oriented laminated film is 12 μm, and as shown in Table 2, in the process of laminating the film and the metal plate, the laminate roll is very dirty, and the surface of the polyester layer A is caused by the stain. Therefore, the glossiness of the appearance of the can obtained by deep drawing was not preferred, and the performance as a metal plate laminating film was inferior.

  The metal plate laminating and forming film of the present invention can be used by being bonded to a can body portion or a lid material portion of a metal can for filling a beverage or food, particularly to the outer surface of the can.

Claims (6)

From polyester layer A made of polyethylene terephthalate (a) having a melting point of 230 to 260 ° C., and polyester layer B made of polybutylene terephthalate (b1) in contact with this layer A and polyethylene terephthalate (b2) having a melting point of 210 to 260 ° C. A biaxially stretched laminated film, in which 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. A laminated film for laminating and forming a metal plate, comprising 0% by weight , wherein the layer B is bonded to a metal so that the layer B is in contact with the metal .   The laminated film for metal plate bonding molding according to claim 1, wherein the polyester layer B further contains 0.005 to 0.1 wt% of spherical particles.   The laminated film for metal bonding 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 metal plate bonding according to any one of claims 1 to 3, wherein the polyester layer B is a polyester composition comprising 70 to 30% by weight of polybutylene terephthalate (b1) and 30 to 70% by weight of polyethylene terephthalate (b2). Laminated film for molding process. The laminated film for metal plate bonding forming processing according to claim 1, wherein the polyester layer A does not contain spherical particles. The laminated film for metal plate bonding molding processing according to claim 1, wherein the non-spherical particles are porous silica particles.