JP2006021371A - Laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated polyester film having excellent bending pinhole resistance, impact resistance and aroma retention after bending equal to those of a polyamide biaxially stretched film while keeping the retort resistance, low moisture absorbing properties, dimensional stability and processability like flatness being the features of a polyester film. <P>SOLUTION: The laminated polyester film is a film constituted by alternately laminating layers A comprising a polyester resin (A) and layers B comprising a thermoplastic resin (B) containing at least 90 wt.% of a polyester in a thickness direction so that the number of both layers A and B becomes at least 9 layers in total and characterized by providing an easy adhesive layer at least on one side of the film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laminated polyester film.

  Polyester films represented by polyethylene terephthalate biaxially stretched films have good mechanical strength, thermal characteristics, humidity characteristics, and many other excellent characteristics. They are industrial materials, magnetic recording materials, optical materials, information materials, packaging materials, etc. Used in a wide range of fields.

  However, in packaging material applications where bending pinhole resistance and impact resistance are particularly important, application is limited to a limited range because of its high rigidity.

  Since it is difficult for a packaging material to satisfy various required characteristics with a single material, in many cases, a plurality of materials such as several kinds of plastic films are laminated in a multilayer manner. Among them, the polyamide biaxially stretched film is excellent in flexibility, flex pinhole resistance, and impact resistance. In particular, it is excellent in the property that it is difficult to break when dropped as a packaging bag filled with a food containing liquid or water (bag dropping property), and is widely used as a base film.

  However, polyamide has a high moisture absorption rate and humidity expansion coefficient due to its polymer structure. For this reason, for example, if left as a packaging material at room temperature and humidity, problems such as changes in physical properties such as gas barrier performance and mechanical strength occur over time, and printing unevenness and wrinkles occur during printing and laminating processes. Met. Furthermore, since it is inferior in dimensional stability under severe wet heat conditions such as retort treatment, it can be applied only in a limited range in packaging material applications.

  For this reason, various attempts have been made to impart toughness such as polyamide to polyester having excellent dimensional stability. For example, a flexible polyester film having a specific Young's modulus with improved bending pinhole resistance has been proposed (see, for example, Patent Document 1).

  A polyester film in which polytetramethylene glycol having a specific molecular weight is mixed with polyester at a specific ratio has been proposed (see, for example, Patent Documents 2 and 3).

  Furthermore, a flexible polyester film in which polyethylene terephthalate is added to a modified polybutylene terephthalate containing a specific amount of polytetramethylene glycol (see, for example, Patent Document 4) and two polyesters having different melting points are kneaded to provide flexibility. A method for obtaining an excellent polyester film has been proposed (see, for example, Patent Document 5).

  However, with these proposals, the mechanical properties and transparency of the film deteriorate, and there are problems with the processability of transparent vapor deposition using metal oxides. The pinhole property was insufficient.

Furthermore, a laminated film is also proposed in which five or more layers containing polyester as a main component and polyamide as a main component are alternately laminated (see Patent Document 6). However, since the polyamide is laminated, the bending resistance is satisfactory, but the characteristic that the polyester film can be retort-treated is not sufficient.
JP-A-6-79976 JP-A-7-330926 JP-A-8-41184 JP 2001-11213 A JP 2003-113259 A JP 2004-34299 A

  The object of the present invention is to eliminate the above-mentioned problems, and is equivalent to a polyamide biaxially stretched film while maintaining the processability such as retort resistance, low moisture absorption, dimensional stability and flatness, which are the characteristics of a polyester film. Another object of the present invention is to provide a laminated polyester film having excellent resistance to bending pinholes, impact resistance and fragrance after bending.

  The above-mentioned problem is a film in which a layer A made of polyester (A) and a layer B made of thermoplastic resin (B) containing 90% by weight or more of polyester are alternately laminated in the thickness direction at least on one side. This is achieved by a laminated polyester film characterized in that an easy adhesion layer is provided on the laminated polyester film.

  Since the laminated polyester film of the present invention is configured as described above, impact resistance and bending resistance are maintained while maintaining the characteristics of the polyester film, such as retort resistance, low moisture absorption, dimensional stability, flatness, and transparency. It has excellent characteristics of pinhole property and fragrance retention after bending, and can be preferably used for packaging applications.

  The polyester resin used for the laminated polyester film in the present invention is a generic term for polymers having an ester bond as the main bond in the main chain, and is usually obtained by polycondensation reaction of a dicarboxylic acid component and a glycol component. Can do. Examples of the dicarboxylic acid component include fragrances such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodiumsulfonedicarboxylic acid, and phthalic acid. Aliphatic dicarboxylic acids, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids, and paraoxybenzoic acid and other oxycarboxylic acids And so on. Examples of the glycol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- Examples include aliphatic glycols such as hexanediol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, and aromatic glycols such as bisphenol A and bisphenol S. Among these, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and isophthalic acid are preferably used as the acid component, and ethylene glycol, 1,3-propanediol, 1,4-butanediol, and the like are preferably used as the glycol component. .

  The laminated film of the present invention is obtained by alternately laminating 9 layers or more in the thickness direction of A layers mainly composed of polyester resin (A) and B layers composed of thermoplastic resin (B) containing 90% by weight or more of polyester. It is necessary to be. This is because excellent impact resistance and bending pinhole resistance can be exhibited as compared with a single film or a laminated film of 8 layers or less. This is because the laminated film of the present invention has a large number of interlayer interfaces, and cracks generated by bending and impact are dispersed at the interlayer interfaces, and propagation in the thickness direction is suppressed. In general, increasing the number of laminated layers increases the number of interlayer interfaces, and can improve the characteristics because it can disperse bending deformation and shock absorption, but from the viewpoint of bending pinhole resistance, the number of laminated layers in the present invention. Is more preferably 16 layers or more, and even more preferably 32 layers or more. The upper limit of the number of layers is not particularly limited, but is preferably 1500 layers or less that can maintain the stacking accuracy.

  The laminated thickness of the A layer and the B layer can be arbitrarily changed, but the effect is particularly great when the average thickness of the B layer is preferably 0.02 to 0.5 μm, more preferably 0.05 to 0.15 μm. Become. When the average thickness is larger than 0.5 μm, the B layer alone has sufficient bending resistance and impact resistance, but the effect of dispersing the bending deformation and shock absorption of the A layer is reduced, so Impact resistance and bending-resistant pinhole characteristics are likely to deteriorate. Conversely, when the average thickness is less than 0.02 μm, the film becomes too thin, so that the bending resistance and impact resistance of the B layer alone are reduced. As a result, the impact resistance and the bending pinhole characteristics are likely to deteriorate. By designing the number of layers and the lamination ratio according to the thickness of the film, the effect of the invention can be further enhanced.

  In order to obtain such a laminated polyester film, for example, after laminating two types of resins, ie, a layer A mainly composed of a polyester resin (A) and a layer B composed of a thermoplastic resin (B), in a feed block, three or more layers are laminated. Then, the number of stages of the static mixer is changed and laminated to an arbitrary total number and formed into a sheet shape with a flat die. In the present invention, it is preferable to use a square mixer in which the shape of the flow path from the place where three or more layers in the feed block are laminated to the flat die discharge part is square. When the flow path shape of the static mixer is square, the disturbance of the layer can be reduced when the width is increased in the width direction, and a laminated film with high lamination accuracy can be obtained.

  In the present invention, it is necessary to provide an easy adhesion layer on the laminated film. As a result, excellent bag drop characteristics are exhibited. This is a synergistic effect due to the impact dispersion at the interlayer interface of the film and the presence of the easy-adhesion layer, which improves the adhesive strength of the heat seal part and increases the impact absorption of the seal part.

  As the method for forming the easy-adhesion layer in the present invention, the resin is coated on the film surface (composite melt extrusion method, hot melt coating method, in-line, off-line coating method from a solvent other than water, water-soluble and / or water-dispersible resin). And the like, and the surface lamination method of similar compositions or blends thereof. In particular, an in-line coating method in which orientation crystallization is completed by applying a coating agent on one surface of the film before completion of orientation crystallization, stretching in at least one direction, and heat-treating to complete orientation crystallization. Industrially preferable.

  When providing an easily bonding layer by coating in this invention, it is preferable that it is a composition containing either an acrylic resin, a vinyl resin, a urethane resin, a polyester resin, and those copolymers. Especially, it is more preferable that polyester resin is included from points, such as adhesiveness with the polyester film which is a base material, and heat resistance. Further, when the portion made of the polyester resin component in the coating layer is 60% by weight or more, preferably 80% by weight or more, excellent bag dropping characteristics are exhibited. In addition, it is preferable to use a water-soluble or water-dispersible resin because no organic solvent gas is generated in the heat treatment step after biaxial stretching. The water-soluble or water-dispersible resin in the present invention is not particularly limited as long as it is a resin that can be dissolved or dispersed in water. The water-soluble or water-dispersible herein is a slight amount, and the amount is not particularly limited, but is usually 20% by weight or less, preferably 10% by weight or less, and may contain substances other than water such as various organic solvents. Good.

  In the water-soluble or water-dispersible resin layer of the present invention, various crosslinking agents may be used as necessary. The type is not particularly limited, but typical examples include isocyanate crosslinking agents, isocyanurate crosslinking agents, melamine crosslinking agents, urea crosslinking agents, oxazoline crosslinking agents or epoxy crosslinking agents. Can do. These crosslinking agents may be used alone or in combination of two or more in some cases. In addition, in this invention, although the thickness of the easily bonding layer provided in the film surface is not specifically limited, 0.001-1 micrometer and especially 0.01-0.2 micrometer are preferable.

  In the polyester resin (A), 95 mol% or more of the acid component is terephthalic acid units, 55 to 95 mol% of the glycol component is ethylene glycol units, and 5 to 45 mol% units are butylene glycol units. Ethylene glycol and butylene The total amount of glycol is preferably 90 mol% or more. If the acid component and glycol component are in such ranges, the melting point is preferably 246 ° C. or more, which is excellent in mechanical properties and bending pinhole resistance and can withstand the above-described deposition. Furthermore, it is particularly preferable that 65 to 95 mol% of the glycol component is an ethylene glycol unit and 5 to 35 mol% is a butylene glycol unit because both cost, mechanical properties, heat resistance and bending pinhole resistance can be achieved. .

  The thermoplastic resin (B) constituting the B layer needs to contain 90% by weight or more of polyester from the viewpoint of lamination with the A layer. From the viewpoint of mechanical properties, heat resistance and bending pinhole resistance, 95 mol% or more of the acid component of the polyester as a main component is a terephthalic acid unit, and 20 to 90 mol% of the glycol component is an ethylene glycol unit. A composition in which -80 mol% units are composed of butylene glycol units and the total amount of ethylene glycol and butylene glycol is 90 mol% or more is preferable. When the content of the ethylene terephthalate unit is larger than 90 mol% or the content of the butylene terephthalate unit is smaller than 10 mol%, the film tends to be inferior in impact resistance and bending pinhole resistance, and the ethylene terephthalate unit When the content of is less than 50 mol% or the content of butylene terephthalate units is more than 50 mol%, the film has poor heat resistance, or the difference in thermal properties from the A layer is large. Problems such as curling, deterioration of flatness, and adhesion at the interface are likely to occur. From the viewpoint of film forming properties, it is more preferable that 70 to 95 mol% of the glycol component is an ethylene glycol unit and 5 to 30 mol% is a butylene glycol unit.

  The method of mixing the ethylene terephthalate component and the butylene terephthalate component is such that the copolymerized polyester is obtained by polycondensation with terephthalic acid and esterification or transesterification in the presence of ethylene glycol and 1,4-butanediol as a glycol component in the polymerization stage. And the method of polymerizing, pelletizing polyethylene terephthalate and polybutylene terephthalate separately, blending them to have a predetermined mixing ratio during film formation, drying, and mixing by performing melt extrusion, etc. A method of mixing separately polymerized polyesters is preferably used. In order to suppress the transesterification reaction during melt extrusion, a solid or liquid phosphorus compound may be added for the purpose of deactivating the polymerization catalyst in the polyester resin.

  Moreover, in this invention, it is preferable that the difference of melting | fusing point of A layer which has a polyester resin (A) as a main component and B layer which consists of thermoplastic resins (B) is 10 degrees C or less. When the melting point difference is 10 ° C. or less, there is no thickness unevenness of each layer due to a viscosity difference during melt flow and no impact resistance deterioration due to a decrease in interlayer adhesion. Further, from the viewpoint of bending resistance, the melting point difference is preferably 7 ° C. or less, and more preferably 5 ° C. or less.

  In the present invention, the melting point of the polyester resin (A) is preferably 225 to 265 ° C. and the melting point of the thermoplastic resin (B) is preferably 215 to 265 ° C. from the viewpoints of mechanical properties and dimensional stability. Furthermore, from the viewpoint of heat resistance, the melting point of the polyester resin (A) and the thermoplastic resin (B) is preferably in the range of 240 to 265 ° C. In particular, from the viewpoint of heat resistance when depositing a metal compound or metal oxide, the melting point is more preferably 246 to 265 ° C.

  Moreover, it is preferable to add a thermoplastic resin having a glass transition point of 20 ° C. or lower in the thermoplastic resin (B) from the viewpoint of bending pinhole resistance and impact resistance. However, the content is preferably 10% by weight or less in order to prevent deterioration of the transparency and deterioration of the bag dropping characteristics due to interfacial peeling. The thermoplastic resin added to the thermoplastic resin (B) preferably has a glass transition point of 20 ° C. or lower in order to exhibit sufficient impact resistance at room temperature and resistance to bending pinholes. The glass transition point is more preferably 0 ° C. or lower for expressing impact resistance and bending resistance at low temperatures, and even more preferably −30 ° C. or lower.

  A thermoplastic resin having a glass transition point of 20 ° C. or lower added to the thermoplastic resin (B) is not particularly limited, but a thermoplastic elastomer is preferably used. Thermoplastic elastomers are composed of a rubber component (soft segment) that exhibits entropy elasticity at room temperature and a constraining component (hard segment) that flows at high temperature and prevents plastic deformation at room temperature. Polystyrene (hard segment: polystyrene, soft segment: polybutadiene, polyisoprene, hydrogenated polybutadiene, ethylene-propylene copolymer rubber, etc.), polyolefin (hard segment: polyethylene or polypropylene, soft segment: ethylene-propylene copolymer rubber, polybutadiene , Polyisoprene, hydrogenated polybutadiene, etc.), polyester (hard segment: polyester, soft segment: polyether or polyester), polyamide (hard segment: polyamide, soft segment: polyether or polyester), and the like. Of these, polystyrene and polyester are preferred from the viewpoints of impact resistance and bending pinhole resistance. Specific examples of the styrenic elastomer include SBS (styrene-butadiene-styrene copolymer), SEBS (styrene-ethylene / butylene-styrene copolymer), SIS (styrene-isoprene-styrene copolymer), SEP (styrene-ethylene / propylene copolymer). Etc. As the polyester elastomer, elastomers such as Lomod (manufactured by GE Japan), Hytrel (manufactured by Toray DuPont), Anitaire (manufactured by DSM), Perprene (manufactured by Toyobo), and ZTPE (manufactured by Nippon Zeon) can be suitably used. In the polyester system, it is preferable to contain a polyether ester component such as polyoxyalkylene glycol, and among them, a polytetramethylene glycol component-containing elastomer is particularly preferably used. When adding a resin containing a polyoxyalkylene glycol component, a polyester resin is pre-copolymerized with a polyoxyalkylene glycol component, which is a polyether, to form a film, or separately prepared as a polyether ester and blended with the polyester resin May be used.

  In polymerizing the polyester resin constituting the laminated polyester film of the present invention, a reaction catalyst and an anti-coloring agent can be used. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds. A manganese compound, a cobalt compound, an aluminum compound, an antimony compound, a titanium compound, a germanium compound, and the like can be used, and a phosphorus compound or the like can be used as an anti-coloring agent, but is not particularly limited thereto. From the viewpoint of content take-out properties, it is preferable to use an alkali metal compound and / or an alkaline earth metal compound as a reaction catalyst.

  Regarding the addition of the polymerization catalyst, it is preferable to add an antimony compound, a germanium compound and / or a titanium compound as a polymerization catalyst at an arbitrary stage before the production of the polyester is completed. As such a method, for example, taking a germanium compound as an example, a method of adding germanium compound powder as it is, or a glycol which is a starting material of polyester as described in Japanese Patent Publication No. 54-22234 A method in which a germanium compound is dissolved in a component and added can be used.

  Here, as the germanium compound, for example, germanium dioxide, germanium hydroxide hydrate or germanium tetramethoxide, germanium alkoxide compound such as germanium ethylene glycoxide, germanium phenoxide compound, germanium phosphate, germanium phosphite, etc. An acid-containing germanium compound, germanium acetate, or the like can be used. Among these, germanium dioxide is preferably used, and amorphous germanium dioxide is particularly preferably used.

  The antimony compound is not particularly limited, and for example, an oxide such as antimony trioxide, antimony acetate, or the like is used.

  Moreover, although it does not specifically limit as a titanium compound, Titanium tetraalkoxides, such as monobutyl titanate and dibutyl titanate, titanium tetraethoxide, titanium tetrabutoxide, are used preferably.

  For example, in the case of adding germanium dioxide as a catalyst in the production of polyethylene terephthalate, a terephthalic acid component and an ethylene glycol component are transesterified or esterified, and then germanium dioxide and a phosphorus compound are added, followed by high temperature, A method of polycondensation under reduced pressure until a constant diethylene glycol content is obtained to obtain a germanium element-containing polymer is preferably used.

  The film of the present invention preferably contains 0.01 to 0.5% by weight of internal particles, inorganic particles and / or organic particles having an average particle size of 0.01 to 2 μm in order to improve handleability and processability. . Examples of the internal particle precipitation method include the techniques described in JP-A-48-61556, JP-A-51-12860, JP-A-53-41355, JP-A-54-90397, and the like. Can be adopted. In addition, other particles such as JP-B-55-20496 and JP-A-59-204617 can be used in combination. In addition, by using particles having an average particle diameter of 2 μm or less, defects are less likely to occur in the vapor deposition layer when vapor deposition is performed on the obtained film.

  Examples of inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, aluminum oxide, mica, kaolin, clay, and organic particles include styrene, silicone, acrylic Particles containing as constituents acids, methacrylic acids, polyesters, divinyl compounds and the like can be used. Among them, it is preferable to use inorganic particles such as wet and dry silica and alumina, and particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components. Furthermore, two or more of these internal particles, inorganic particles, and organic particles may be used in combination. Among these, inorganic particles can be particularly preferably used, and among them, dry or wet silica is preferably used. The amount of particles added is more preferably 0.01 to 0.1% by weight in terms of gas barrier properties. More preferably, it is 0.01 to 0.05 weight%. When the addition amount of the particles is within such a preferable range, when vapor deposition is performed, pinholes are hardly generated in the vapor deposition layer, and gas barrier properties are excellent.

  Various additives such as antioxidants, ultraviolet absorbers, crystal nucleating agents, thinning agents, thermal stabilizers, infrared absorbers and the like are added to the A layer and the B layer as long as the effects of the present invention are not hindered. May be. The various additives used here preferably have a particle size equal to or less than the thickness of each layer so as not to disturb the lamination interface of the laminated film. It is also possible to provide a layer having these functions on the surface layer of the laminated film.

  When the laminated polyester film of the present invention is used for packaging, the thickness of the entire film is preferably 5 to 30 μm, particularly preferably 10 to 25 μm.

  Next, although the preferable manufacturing method of the laminated | multilayer film of this invention is demonstrated below, this invention is not limited to this. The effects of the present invention can be further enhanced by appropriately adjusting film forming conditions such as stretching temperature, stretching ratio, and heat setting temperature.

  A thermoplastic resin is prepared in the form of pellets and the like, and pre-dried in hot air or under vacuum as necessary. After the resin is supplied to the extruder and heated and melted to the melting point or more in the extruder, the resin extrusion amount is made uniform through a filter or the like by filtering the resin extrusion amount with a gear pump or the like. Further, the resin is formed into a desired shape with a die and then discharged. Generally, the resin is extruded from a slit-shaped die into a sheet shape. The extruded sheet-like polymer is brought into close contact with a casting drum and rapidly cooled and solidified to obtain an unstretched film. The method is not particularly limited, for example, a method of applying static electricity using a wire-like electrode or a tape-like electrode, a casting method in which a water film is provided between a casting drum and an extruded polymer sheet, and the temperature of the casting drum is set to glass of polyester. A method of sticking the extruded polymer below the transition point or a method combining a plurality of these methods can be used. From the viewpoint of productivity and flatness, a method of applying an electrostatic force is preferably used.

  Using such an unstretched film, the film is stretched in the longitudinal direction and then stretched in the width direction, or the stretched film is stretched in the width direction and then stretched in the longitudinal direction, and the longitudinal direction and the width direction of the film are stretched almost simultaneously. Stretching is performed by the simultaneous biaxial stretching method.

  In this stretching method, the stretching ratio employed is preferably 3.0 to 5.0 times in each direction. The stretching speed is desirably 2000 to 500000% / min, and the stretching temperature can be any temperature as long as it is within the temperature range of the glass transition point of the polyester to (glass transition point + 100 ° C.), but preferably Is preferably 80 to 150 ° C., more preferably 80 to 120 ° C. in the longitudinal direction and 70 to 130 ° C. in the width direction. Moreover, you may perform extending | stretching in multiple times with respect to each direction.

  Further, the film is heat-treated after biaxial stretching, and this heat treatment can be performed by any method such as in an oven or on a heated roll. The heat treatment temperature can be any temperature not lower than 120 ° C. and not higher than the melting point of the polyester, but it is preferably a heat treatment temperature of 130 to 220 ° C. from the viewpoint of bending pinhole resistance and impact resistance. From the viewpoint of retort resistance and heat resistance during vapor deposition, it is more preferably 150 to 220 ° C., and in the range of 170 to 210 ° C., in addition to heat resistance, both bending pinhole resistance and impact resistance can be achieved. Even more preferred.

  The heat treatment time can be arbitrarily set within a range not deteriorating other characteristics, but it is usually preferable to carry out for 1 to 30 seconds. Furthermore, it is preferable to provide a heat treatment step in which the film is relaxed in the longitudinal direction and / or the width direction because the shrinkage rate under heating conditions can be suppressed.

  From the viewpoint of bending pinhole resistance, impact resistance, dimensional stability, and mechanical properties, it is preferable to adjust the film forming conditions so that the plane orientation coefficient of the film is 0.12 to 0.17. From the viewpoint of mechanical properties, the plane orientation coefficient is particularly preferably 0.14 to 0.17, and further preferably 0.15 to 0.17.

  In the present invention, it is preferable to subject the film surface to a surface treatment such as a corona discharge treatment because the adhesiveness can be further improved. In particular, when a metal or metal oxide is vapor-deposited to improve gas barrier properties, it is preferable to perform a corona discharge treatment on the surface of the vapor-deposited film in advance because the adhesion between the film and the vapor-deposited layer is improved. When vapor-depositing a metal or metal oxide, particularly preferably used metals and metal oxides include aluminum, aluminum oxide, and silicon oxide. Among these, when aluminum oxide and / or silicon oxide is used, it is preferably used as a transparent gas barrier film.

  The laminated polyester film of the present invention is preferably used as a packaging material by providing a heat seal layer. Laminate with stretched or unstretched polyolefin film called sealant consisting of linear low density polyethylene, low density polyethylene, medium density polyethylene, polypropylene, ethylene propylene copolymer, etc. directly or without adhesive Is preferred. A polyolefin resin may be extrusion laminated sealant. Furthermore, if an aluminum foil is laminated between the laminated polyester film of the present invention and polyolefin, it is particularly preferably used as a high gas barrier packaging material.

  The laminated polyester film of the present invention exhibits excellent impact resistance and flex pinhole resistance while maintaining the low hygroscopicity, dimensional stability, flatness and transparency that are the characteristics of the polyester film, and is used for food packaging, etc. Can be preferably used.

Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.
(1) Composition analysis A sample was dissolved in deuterated chloroform as a solvent, and 400 MHz, ¹ H-NMR (GX-400 pulse FT spectrometer manufactured by JOEL) and 22.5 MHz, ¹³ C-NMR (by nuclear magnetic resonance method) Data obtained using a JOEL FT-900 type pulse FT spectrometer was analyzed and determined.

(2) Melting point, glass transition point Measured with a differential scanning calorimeter (Seiko Denshi Kogyo RDC220). 5 mg of the sample was set in the apparatus, and when the temperature was raised from 25 ° C. to 300 ° C. at 10 ° C./min, the endothermic peak temperature based on melting was taken as the melting point. About resin whose glass transition point is 20 degrees C or less, it heated up to 300 degreeC from -120 degreeC at 10 degree-C / min, and measured the glass transition point.

(3) Number of layers Ultrathin slices were taken from the longitudinal section of the film with a microtome, stained with RuO ₄ , and accelerated with a transmission electron microscope (H-7100FA, manufactured by Hitachi High-Technologies Corporation). Observation was performed at 100 kV (magnification 40,000 times), and the number of layers in the thickness direction of the film was counted by image processing.

(4) Intrinsic Viscosity Intrinsic viscosity [η] was determined from a value calculated from the following formula from a solution viscosity measured at 25 ° C. in orthochlorophenol.
[Η] = ηsp / (C + 2K · C ² )
here,
ηsp = (solution viscosity / solvent viscosity) -1
C is dissolved polymer weight per 100 ml of solvent (g / 100 ml, usually 1.2)
K is the Huggins constant (assuming 0.343)
The solution viscosity and solvent viscosity were measured using an Ostwald viscometer.

(5) Bending-resistant pinhole property According to ASTM F-392 (1999), a film cut into a size of 297 × 210 mm was subjected to a repeated bending test 500 times at a temperature of 23 ° C. using a gel bot tester. The test was performed 10 times, and the average number of pinholes was calculated. The number of pinholes is small, and when the number exceeds three, bent pinholes are likely to occur during transportation.

(6) Impact resistance A film laminated by the following procedure was used. Four sides were sealed at 160 ° C. using an impulse sealer (FA300-10 manufactured by Fuji Impulse Co., Ltd.) so that a bag of 200 mm × 150 mm was filled with 250 ml of 2.5% by weight saline solution. After holding this at 23 ° C. for 24 hours, it was dropped from a 23 ° C. atmosphere and a height of 1.5 m until breakage or water leakage occurred, and the average number of drops when 20 bags were tested was examined. . If the number of drops is less than 2.5, there is a risk of bag breakage during transportation.

[Dry laminating instructions]
Adhesive Takelac A610 manufactured by Mitsui Takeda Chemical Co., Ltd. and curing agent Takenate A50 were mixed at 9: 1 and diluted to 40% by weight with ethyl acetate to obtain an adhesive. An adhesive is applied to the film surface (corona discharge treatment side) so as to have a dry thickness of 3 μm, and laminated with 60 μm of Trefan NO T3931 (general-purpose unstretched polypropylene sealant film manufactured by Toray Synthetic Film Co., Ltd.). Cured for 48 hours at 0C.

(7) Retort shrinkage The film was cut into a size having a width of 10 mm and a length of 200 mm in the longitudinal direction, and each sample was marked with an oil pen at an interval of about 150 mm. After adjusting the humidity for 12 hours under conditions of 23 ° C. and 65% RH, the interval (L1) was measured using a universal projector. A 3 g clip was suspended from one end of the sample, and a retort treatment was performed at 115 ° C. for 30 minutes using a retort treatment machine. The water on the surface of the sample taken out was wiped off with gauze, humidity was adjusted for 24 hours under the conditions of 23 ° C. and 65% RH, and the mark interval (L2) was measured using a universal projector. (%) Was calculated.
R (%) = {(L1-L2) / L1} × 100
When the retort shrinkage rate is 3% or more, application in retort processing becomes difficult.

(8) Fragrance retention Transparent vapor deposition was performed by the following method, and a sealant film was dry laminated on the vapor deposition surface side. The dry lamination was performed in the same manner as the impact resistance test. A sample bag was prepared by cutting 0.5 mm in the longitudinal direction and 50 mm in the machine direction and placing 0.5 ml of d-limonene in a three-side seal with an impulse sealer and sealing the remaining one side. The sample bag was twisted 180 ° twice and then placed in a 200 ml glass bottle and sealed with aluminum foil and parafilm. After standing at room temperature for 1 week, it was opened at random and two panelists sniffed directly, and evaluated in two stages, with ○ being passed and × being rejected.
○: It smells.
X: It does not smell.

  [Transparent vapor deposition processing] The raw film is set on an unwinding device of a continuous vacuum vapor deposition machine and travels through a cooling metal drum to wind the film. At this time, the pressure of the continuous vacuum vapor deposition machine is reduced to 0.133 Pa or less, the aluminum crucible is charged into the alumina crucible from the lower part of the cooling drum, the metal aluminum is heated and evaporated, and oxygen is added to the vapor. While being supplied and subjected to an oxidation reaction, the film was adhered and deposited on the easily adhesive surface of the film to form an aluminum oxide film having a thickness of 30 nm to obtain a transparent deposited film.

Example 1
Polyethylene terephthalate and polybutylene terephthalate were polymerized in the following manner.

[Polymerization of polyethylene terephthalate]
To 194 parts by weight of dimethyl terephthalate and 124 parts by weight of ethylene glycol, 0.1 part by weight of magnesium acetate tetrahydrate and 0.05 part by weight of antimony trioxide were added, and the ester exchange reaction was carried out while distilling methanol at 140-230 ° C. went. Next, the mixture was transferred to a polycondensation reaction can, and after adding 0.05 part by weight of ethylene glycol solution of phosphoric acid and stirring for 5 minutes, the reaction system was gradually heated from 230 ° C. to 290 ° C. while stirring the low polymer at 30 rpm. And the pressure was reduced to 100 Pa. When the polymerization reaction was carried out for 3 hours and the predetermined stirring torque was reached, the polycondensation reaction was stopped, discharged into cold water in the form of a strand, and immediately cut to obtain polyethylene terephthalate pellets having an intrinsic viscosity of 0.63. In addition, when transitioning to a polycondensation reaction after the transesterification reaction, an ethylene glycol slurry of aggregated silica particles having an average particle diameter of 1.0 μm is added, and a polycondensation reaction is similarly performed to prepare a particle master having a particle concentration of 2% by weight. did.

[Polybutylene terephthalate polymerization]
A mixture of 100 parts by weight of terephthalic acid and 110 parts by weight of 1,4-butanediol was heated to 140 ° C. in a nitrogen atmosphere to obtain a uniform solution. Then, 0.067 parts by weight of tetra-n-butyl orthotitanate and 0.067 parts by weight of monohydroxybutyltin oxide were added, the temperature was raised to 160 ° C. to 230 ° C., and the esterification reaction was carried out while distilling off the generated water and tetrahydrofuran. went. The esterification reaction product was transferred to a polycondensation reaction can, 0.09 part by weight of tetra-n-butyl titanate, 0.13 part of 'Irganox 1010' manufactured by Ciba Geigy Japan as a stabilizer and 0.026 part by weight of phosphoric acid Was added. Next, the reaction system was gradually heated from 230 ° C. to 250 ° C., and the pressure was reduced from normal pressure to 133 Pa or less. After 2 hours and 50 minutes, the polycondensation reaction was completed, discharged into cold water in the form of a strand, and immediately cut to obtain polybutylene terephthalate pellets having an intrinsic viscosity of 0.90. Thereafter, the reaction vessel was charged into a rotary reaction vessel and subjected to solid phase polymerization at 190 ° C. under a reduced pressure of 67 Pa for 8 hours to obtain a polybutylene terephthalate resin having an intrinsic viscosity of 1.20. The resulting polybutylene terephthalate had a melting point of 230 ° C.
By mixing 76.5% by weight of polyethylene terephthalate thus obtained, 20% by weight of polybutylene terephthalate, and 3.5% by weight of the particle master, a layer A is formed, and 80% by weight of polyethylene terephthalate and polybutylene terephthalate are mixed. 19% by weight and 1% by weight of Hytrel 3078 (glass transition temperature: -72 ° C.) manufactured by DuPont Co., Ltd. were mixed to form a B layer. Using these raw materials, a film was formed as follows.
The raw material resin of each layer dried in vacuum was melt-extruded using two single-screw melt extruders so that the ratio of the discharge amount was A layer: B layer = 4: 1, and 5 layers of A layer were formed in the feed block. The B layers are merged so that four layers are alternately stacked, and after being divided into 129 layers by providing a square mixer, electrostatic application is performed on a hard chrome plated drum cooled to 25 ° C. from a T-shaped die. While being extruded, an unstretched sheet was obtained. The melting temperature of the A and B extruders was 280 ° C. The sheet was preheated to 95 ° C. on the roll and then stretched 3.6 times in the longitudinal direction, and then cooled once with a cooling roll. One side of this uniaxially stretched film was subjected to corona discharge treatment in air, and the following coating coating solution was applied to the discharge treatment surface side with a rod coater. The coating thickness was set to 0.05 μm after the orientation crystal was completed.

[Coating coating composition]
As acid components, terephthalic acid: 29 mol parts, isophthalic acid: 7 mol parts, trimellitic acid: 10 mol parts, sebacic acid: 3 mol parts, as glycol components, ethylene glycol: 14 mol parts, neopentyl glycol: 19 mols Part, 1,4-butanediol: polyester resin A containing 18 parts by mole (glass transition temperature: 20 ° C.): 95 parts by weight N-methylolated melamine compound (MW-12LF (manufactured by Sanwa Chemical Co., Ltd.)): 5 parts by weight (solid content ratio)
Subsequently, both ends of the film were gripped and passed through a stenter-type transverse stretching heat treatment machine, and stretched 3.5 times in the film width direction at a preheating of 75 ° C. and a stretching temperature of 100 ° C. Further, while applying 5.0% relaxation in the width direction, a heat treatment was performed at 205 ° C. for 3 seconds, the film was cooled, and a film having a thickness of 12 μm was obtained.

(Example 2)
Layer A by mixing 76.5% by weight of polyethylene terephthalate used in Example 1, 20% by weight of polybutylene terephthalate 'Torcon 1200S' (melting point 223 ° C) manufactured by Toray Industries, Inc., and 3.5% by weight of particle master. The B layer was 100% by weight of polyethylene terephthalate used in Example 1. The film forming conditions and the coating solution composition for in-line coating were the same as in Example 1, and a film having a thickness of 12 μm was obtained.

Example 3
As the polyester resin, 76.5% by weight of polyethylene terephthalate used in Example 1, 20% by weight of polytrimethylene terephthalate “Corterra CP509201” (melting point 228 ° C.) manufactured by Shell Chemicals, and 3.5% by weight of particle master Were mixed to obtain a layer A. The layer B was 80% by weight of polyethylene terephthalate and 20% by weight of polybutylene terephthalate used in Example 1. The film forming conditions and the in-line coating composition were the same as in Example 1, and a film having a thickness of 12 μm was obtained.

Example 4
As the polyester resin, 96.5% by weight of polyethylene terephthalate / dimer acid copolymerized polyester prepared by the following method and 3.5% by weight of particle master were mixed to form layer A. The layer B was 100% by weight of polyethylene terephthalate used in the examples. The in-line coating composition and film forming conditions were the same as in Example 1 to obtain a film having a thickness of 12 μm.
[Polymerization of polyethylene terephthalate / dimer acid copolymer polyester]
8 parts by weight of hydrogenated dimer acid “PRIPOL 1009” manufactured by Unikema Co. was added to 150 parts by weight of terephthalic acid and 87 parts by weight of ethylene glycol, and the temperature was raised to 140 ° C. in a nitrogen atmosphere to obtain a uniform solution. Then, it heated up and pressurized to 160-230 degreeC and 0.2 MPa, and esterification was performed, distilling the water to produce | generate. After moving to a polycondensation reactor, 0.05 parts by weight of ethylene glycol solution of phosphoric acid and 0.05 parts by weight of antimony trioxide were added and stirred for 5 minutes, and then the reaction system was stirred while stirring the low polymer at 30 rpm. The temperature was gradually raised from 230 ° C. to 290 ° C. and the pressure was reduced to 100 Pa. When the polymerization reaction was carried out for 3 hours and the predetermined stirring torque was reached, the polycondensation reaction was stopped, discharged into cold water in the form of a strand, and immediately cut to obtain a copolyester having an intrinsic viscosity of 0.72 (melting point 245 ° C.).

(Example 5)
In the A layer, the polyethylene terephthalate used in Example 1 was 76.5% by weight, the polybutylene terephthalate was 20% by weight, and the particle master was 3.5% by weight. The layer B was made of 80% by weight of polyethylene terephthalate and 20% by weight of polybutylene terephthalate used in Example 1. The in-line coating composition and film forming conditions were the same as in Example 1 to obtain a film having a thickness of 12 μm.

(Example 6)
A raw material composition, film forming conditions, and in-line coating composition were the same as in Example 1 except that the number of square mixers was changed to a nine-layer laminated film, and a film having a thickness of 12 μm was obtained.

(Example 7)
The raw material composition, film forming conditions, and in-line coating composition were the same as in Example 1 except that the number of square mixers was changed to form a laminated film of 2049 layers, and a film having a thickness of 12 μm was obtained.

(Example 8)
A film having a thickness of 12 μm was obtained in the same manner as in the raw material composition and film forming conditions of Example 1 except that the in-line coating coating solution had the following composition and was diluted with water to a solid concentration of 3% by weight.
[Formulated paint composition]
Acrylic resin copolymerized with methyl methacrylate (40 mole parts), ethyl acrylate (58 mole parts), acrylic acid (1 mole part), and N-methylolacrylamide (1 mole part) (glass transition temperature 20 ° C.): 90 parts by weight Oxazoline: Oxazoline-based crosslinking agent “Epocross” WS-500 (manufactured by Nippon Shokubai Co., Ltd.): 10 parts by weight (solid content ratio)
(Comparative Example 1)
96.5% by weight of polyethylene terephthalate used in Example 1 and 3.5% by weight of particle master were mixed to obtain a raw material. A film having a thickness of 12 μm was obtained by performing in-line coating under the same film forming conditions and coating composition as in Example 1 except that the feed block and the square mixer were not provided and a single layer film was used.

(Comparative Example 2)
Except not performing inline coating and the corona treatment before that, it formed into the film by the same raw material composition and film forming conditions as Example 1, and obtained the film of 12 micrometers.

(Comparative Example 3)
The A layer and B layer raw materials were the same as the A layer and B layer compositions of Example 1. A film having a thickness of 12 μm was obtained by applying in-line coating under the same film forming conditions except that a square mixer was not provided and a three-layer structure was used.

(Comparative Example 4)
Except not performing inline coating and the corona treatment before that, it formed into the film by the raw material composition and film forming conditions similar to Example 2, and obtained the film of 12 micrometers.

(Comparative Example 5)
Layer A was 96.5 wt% 5-sodium sulfoisophthalic acid copolymerized polyethylene terephthalate prepared as follows, and the particle master was 3.5 wt%. For layer B, nylon 6′CM1021FS ′ (melting point: 225 ° C.) 100% by weight manufactured by Toray Industries, Inc. was used. Inline coating was performed under the same film forming conditions and coating composition as in Example 1 except that the extrusion temperature of the B extruder was 250 ° C., and a film having a thickness of 12 μm was obtained.
[Polymerization of 5-sodiumsulfoisophthalic acid copolymerized polyethylene terephthalate]
To 190 parts by weight of dimethyl terephthalate, 4 parts by weight of dimethyl 5-sodiumsulfoisophthalate, and 124 parts by weight of ethylene glycol, 0.1 parts by weight of magnesium acetate tetrahydrate and 0.05 parts by weight of antimony trioxide were added. The transesterification was carried out while distilling methanol at 230 ° C. Next, the mixture was transferred to a polycondensation reaction can, and after adding 0.05 part by weight of ethylene glycol solution of phosphoric acid and stirring for 5 minutes, the reaction system was gradually heated from 230 ° C. to 290 ° C. while stirring the low polymer at 30 rpm. And the pressure was reduced to 100 Pa. The polymerization reaction was carried out for 2 hours and 45 minutes, and when the predetermined stirring torque was reached, the polycondensation reaction was stopped, discharged into cold water in the form of a strand, and immediately cut to obtain copolymer polyester pellets having an intrinsic viscosity of 0.72.

  The compositions and properties of the films thus obtained are shown in Table 1 and Table 2, respectively. The film of the present invention has excellent resistance to bending pinholes and impact resistance, is excellent in retort resistance and aroma retention after bending, and can be suitably used as a packaging film. On the other hand, the comparative example which is not the present invention was inferior in any of bending pinhole resistance, impact resistance, retort resistance and aroma retention after bending, and was insufficient as a packaging film.

Abbreviations in the table are as follows.
PET: polyethylene terephthalate PBT: polybutylene terephthalate PTT: polytrimethylene terephthalate PET / DA: dimer acid copolymerized polyethylene terephthalate PET / SSIA: 5-sodium sulfoisophthalic acid copolymerized polyethylene terephthalate N6: nylon 6
Tm: melting point Tg: glass transition temperature

  The laminated polyester film of the present invention is excellent in impact resistance, flex pinhole resistance and retort resistance and can be preferably used for packaging applications, but is not limited thereto.

Claims (9)

A film in which A layer mainly composed of polyester resin (A) and B layer composed of thermoplastic resin (B) containing 90% by weight or more of polyester are alternately laminated in the thickness direction, and at least one side A laminated polyester film characterized in that an easily adhesive layer is provided on the laminated polyester film. The laminated polyester film according to claim 1, wherein the difference between the melting point of the A layer mainly composed of the polyester resin (A) and the melting point of the B layer composed of the thermoplastic resin (B) is 10 ° C or less. The melting point of the polyester resin (A) is 225 to 265 ° C, and the melting point of the polyester which is the main component of the thermoplastic resin (B) is 215 to 265 ° C. Polyester film. 95 mol% or more of the acid component of the polyester resin (A) is terephthalic acid units, 55 to 95 mol% of the glycol components are ethylene glycol units, and 5 to 45 mol% units are butylene glycol units. Ethylene glycol and butylene The laminated polyester film according to any one of claims 1 to 3, wherein the total amount of glycol is 90 mol% or more. 95 mol% or more of the acid component of the polyester which is the main component of the thermoplastic resin (B) is a terephthalic acid unit, 20 to 90 mol% of the glycol component is an ethylene glycol unit, and 10 to 80 mol% unit is a butylene glycol unit. The laminated polyester film according to any one of claims 1 to 4, wherein the total amount of ethylene glycol and butylene glycol is 90 mol% or more. The laminated polyester film according to any one of claims 1 to 5, wherein a thermoplastic resin having a glass transition temperature of 20 ° C or less is contained in the B layer by 10 wt% or less. The laminated polyester film according to claim 1, wherein the easy adhesion layer is provided by coating. The laminated polyester according to any one of claims 1 to 7, wherein the easily adhesive layer is formed of a resin selected from an acrylic resin, a vinyl resin, a urethane resin, a polyester resin, and a copolymer thereof. the film. The laminated polyester film according to claim 1, which is used as a packaging material.