Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
  • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
  • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
  • B65D65/38—Packaging materials of special type or form
  • B65D65/40—Applications of laminates for particular packaging purposes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2007/00—Flat articles, e.g. films or sheets

Definitions

• This disclosure relates to biaxially oriented polyester films, laminates, packaging materials, and top seal materials used in the packaging fields of foods, pharmaceuticals, industrial products, etc.
• Aromatic polyesters such as polyethylene terephthalate (hereinafter sometimes referred to as PET), are widely used as food and beverage containers.
• PET polyethylene terephthalate
• snap-on lids have traditionally been used as the lid material.
• top seal materials as lid materials has been promoted with the aim of making containers easier to open, standardizing lid materials (i.e., mono-materials), and reducing waste by reducing thickness.
• Patent Document 1 proposes that a laminated film using a biaxially oriented polyester film as a base layer and offline-coating a polyester resin layer as a heat-sealable outer layer exhibits good heat-sealability to food trays.
• the purpose of this disclosure is to provide a biaxially oriented polyester film that has a non-slip film surface, and is both transparent and easy to wind when processed.
• inorganic or organic lubricants are sometimes added to the film to provide slipperiness. Reducing the amount of lubricant contained in the film reduces the slipperiness, which may lead to poor processability during film processing.
• a biaxially oriented polyester film as shown in [1] below, has at least an A layer and a B layer, each of which contains polyethylene terephthalate as a main component, and in which the dynamic friction coefficient when the A layer surface is in contact with a metal plate, the dynamic friction coefficient between the A layer surface and the B layer surface, and the haze are controlled within specified ranges, has excellent slipperiness of the film surface, transparency, and winding ability during film processing.
• a biaxially oriented polyester film having at least a layer A and a layer B, wherein the layer A and the layer B each contain a polyethylene terephthalate resin as a main component;
• the lubricant content in the A layer is 0 to 400 ppm by mass, and the lubricant content in the B layer is 500 to 4,500 ppm by mass,
• the weight average particle size of the lubricant is 0.5 to 4.0 ⁇ m;
• the haze value of the biaxially oriented polyester film converted to a thickness of 12 ⁇ m is 4.5% or less,
• the biaxially oriented polyester film, the laminate, the packaging material, or the top seal material of the embodiment is preferably any one of the following [3] to [17].
• the content of the polyethylene terephthalate resin in the layer A is 60 to 100% by mass
• the above-mentioned configuration makes it possible to obtain a biaxially oriented polyester film that has a non-slip surface and is excellent in transparency and windability during film processing.
• this biaxially oriented polyester film as, for example, a material for packaging bags or a top seal material for plastic containers, it is possible to prevent products from falling over due to slipping when stacked and displayed.
• the biaxially oriented polyester film of the embodiment is a biaxially oriented polyester film having at least a layer A and a layer B, each of which contains a polyethylene terephthalate resin as a main component and satisfies the following conditions (a) to (c): (a) The coefficient of dynamic friction when the surface of the layer A of the biaxially oriented polyester film is brought into contact with a metal plate is 0.20 to 1.00. (b) The coefficient of dynamic friction when the surface of the biaxially oriented polyester film on the side of Layer A is brought into contact with the surface of the biaxially oriented polyester film on the side of Layer B is 0.35 to 0.50. (c) The haze value of the biaxially oriented polyester film converted to a thickness of 12 ⁇ m is 4.5% or less.
• biaxially stretched polyester film have at least layer A and layer B, each of which contains polyethylene terephthalate resin as a main component, the lubricant content in layer A is 0 to 400 ppm by mass, the lubricant content in layer B is 500 to 4,500 ppm by mass, the weight average particle size of the lubricant is 0.5 to 4.0 ⁇ m, the haze value converted to a biaxially stretched polyester film thickness of 12 ⁇ m is 4.5% or less, and the ratio of the thickness of layer A to the thickness of the entire biaxially stretched polyester film is 30 to 90%.
• the biaxially stretched polyester films of these embodiments are described below.
• the biaxially oriented polyester film preferably has at least a layer A and a layer B.
• the biaxially oriented polyester film may be a two-layer structure of a layer A and a layer B, or may be a three-layer or more structure including one or more intermediate layers between the layers A and B. That is, the biaxially oriented polyester film may be one consisting of a layer A and a layer B, one consisting of a layer A, a layer B and an intermediate layer, or one including a layer A, a layer B and an intermediate layer.
• the layer A side surface is the surface of layer A.
• the layer B side surface is the surface of layer B.
• the A layer of the biaxially stretched polyester film contains polyethylene terephthalate resin (hereinafter, sometimes referred to as PET resin (a)) as a main component.
• PET resin (a) polyethylene terephthalate resin
• containing as a main component means that the content of PET resin (a) in 100% by mass of the A layer is 60% by mass or more, preferably 70% by mass or more, and most preferably 80% by mass or more.
• the content of PET resin (a) may be 100% by mass or less, 99.99% by mass or less, 99.98% by mass or less, 99.9% by mass or less, 98% by mass or less, or 95% by mass or less.
• Layer A may contain a polyester resin (b) other than the PET resin (a) for the purpose of adjusting the mechanical properties of the biaxially stretched polyester film.
• the polyester resin (b) other than the PET resin (a) include polyester resins such as polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and polypropylene terephthalate (PPT); polyester resins copolymerized with dicarboxylic acids such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, cyclohexane dicarboxylic acid, adipic acid, azelaic acid, and sebacic acid; and polyester resins copolymerized with diol components such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6
• the lower limit of the intrinsic viscosity of the resin composition constituting the A layer is preferably 0.45 dl/g, more preferably 0.50 dl/g, and most preferably 0.55 dl/g. By making it 0.45 dl/g or more, the intrinsic viscosity of the biaxially oriented polyester film can be maintained high, and mechanical properties such as puncture strength can be improved.
• the upper limit of the intrinsic viscosity of the resin composition constituting the A layer is preferably 0.80 dl/g, more preferably 0.75 dl/g, and most preferably 0.70 dl/g. By making it 0.80 dl/g or less, it is possible to suppress the stress during film stretching from becoming too high, and good film formability can be obtained.
• the intrinsic viscosity of the A layer is preferably 0.45 to 0.80 dl/g, more preferably 0.50 to 0.75 dl/g, and most preferably 0.55 to 0.70 dl/g.
• the resin composition is a PET resin (a) or a mixture of a PET resin (a) and another resin.
• the intrinsic viscosity of the resin composition can be measured, for example, by dissolving 0.2 g of the resin composition in 50 ml of a mixed solvent of phenol/1,1,2,2-tetrachloroethane (60/40 (weight ratio)) and using an Ostwald viscometer at 30°C. The same applies to the intrinsic viscosity of the resin composition constituting the B layer and the resin composition constituting the intermediate layer, which will be described later.
• Layer A may contain no lubricant or may contain lubricant to the extent that the slipperiness of the film surface can be controlled.
• the lubricant content in 100% by mass of layer A is preferably 0 to 400 ppm by mass, more preferably 0 to 380 ppm by mass, and even more preferably 0 to 350 ppm by mass. By making the content 400 ppm by mass or less, it is possible to impart slipperiness to the film surface. Note that a lubricant content of 0 ppm by mass in layer A means that layer A does not contain a lubricant.
• a lubricant content of 0 to 400 ppm by mass in layer A means that layer A does not contain a lubricant, or that layer A contains a lubricant in a content of more than 0 ppm by mass and 400 ppm by mass or less.
• the lubricant is capable of adjusting the dynamic friction coefficient of the film, and preferably contains at least one inorganic lubricant selected from the group consisting of silica, calcium carbonate, and alumina, more preferably contains at least one inorganic lubricant selected from the group consisting of silica and calcium carbonate, and most preferably contains silica.
• Silica in particular makes it easier to achieve both transparency and slipperiness.
• the lubricant may contain an organic lubricant.
• the weight average particle size of the lubricant in layer A may be the same as or different from the weight average particle size of the lubricant in layer B or the intermediate layer.
• the weight average particle size of the lubricant is preferably 0.5 ⁇ m or more, more preferably 0.8 ⁇ m or more, and even more preferably 1.5 ⁇ m or more.
• the weight average particle size of the lubricant is preferably 4.0 ⁇ m or less, more preferably 3.8 ⁇ m or less, and even more preferably 3.5 ⁇ m or less. This can reduce haze when layer A contains a lubricant.
• the average particle size of the lubricant can be measured, for example, using a laser diffraction particle size distribution measuring device (SALD-2200, manufactured by Shimadzu Corporation). The same applies to the average particle size of the lubricant in layer B and the average particle size of the lubricant in the intermediate layer, which will be described later.
• the pore volume of the lubricant is preferably 1.0 ml/g or more, more preferably 1.1 ml/g or more, and even more preferably 1.2 ml/g or more. This allows the dynamic friction coefficient of the surface of layer A to be increased when layer A contains a lubricant, and also allows haze to be reduced.
• the pore volume of the lubricant is preferably 1.7 ml/g or less, more preferably 1.6 ml/g or less, and even more preferably 1.5 ml/g or less.
• the pore volume of the lubricant can be determined, for example, by using a high-speed specific surface area/pore distribution measuring device (ASAP 2400) manufactured by Shimadzu Corporation, and integrating the pore volume between a specified pore diameter (17 to 3000 ⁇ ) by the BJH method using nitrogen adsorption and desorption (for details, see Shimadzu Review, Vol. 48, No. 1, pp. 35 to 49).
• ASAP 2400 high-speed specific surface area/pore distribution measuring device manufactured by Shimadzu Corporation
• nitrogen adsorption and desorption for details, see Shimadzu Review, Vol. 48, No. 1, pp. 35 to 49.
• the B layer of the biaxially stretched polyester film contains polyethylene terephthalate resin (hereinafter, sometimes referred to as PET resin (a)) as a main component.
• PET resin (a) polyethylene terephthalate resin
• containing as a main component means that the content of PET resin (a) in 100% by mass of B layer is 60% by mass or more, preferably 70% by mass or more, and most preferably 80% by mass or more.
• the content of PET resin (a) may be 100% by mass or less, 99.99% by mass or less, 99.98% by mass or less, 99.9% by mass or less, 98% by mass or less, or 95% by mass or less.
• Layer B may contain a polyester resin (b) other than the PET resin (a) for the purpose of adjusting the mechanical properties of the biaxially stretched polyester film.
• the polyester resin (b) other than the PET resin (a) include polyester resins such as polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and polypropylene terephthalate (PPT); polyester resins copolymerized with dicarboxylic acids such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, cyclohexane dicarboxylic acid, adipic acid, azelaic acid, and sebacic acid; and polyester resins copolymerized with diol components such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6
• the lower limit of the intrinsic viscosity of the resin composition constituting the B layer is preferably 0.45 dl/g, more preferably 0.50 dl/g, and most preferably 0.55 dl/g. By making it 0.45 dl/g or more, the intrinsic viscosity of the biaxially oriented polyester film can be maintained high, and mechanical properties such as puncture strength can be improved.
• the upper limit of the intrinsic viscosity of the resin composition constituting the B layer is preferably 0.80 dl/g, more preferably 0.75 dl/g, and most preferably 0.70 dl/g. By making it 0.80 dl/g or less, it is possible to suppress the stress during film stretching from becoming too high, and good film formability can be obtained.
• the intrinsic viscosity of the B layer is preferably 0.45 to 0.80 dl/g, more preferably 0.50 to 0.75 dl/g, and most preferably 0.55 to 0.70 dl/g.
• the polyester resin contained in layer B may be the same as or different from the polyester resin contained in layer A.
• the B layer preferably contains a lubricant to improve the slipperiness of the film when the A layer and the B layer are in contact with each other and to improve the winding quality of the roll.
• the lubricant content in 100% by mass of the B layer is preferably 500 to 4,500 ppm by mass, more preferably 600 to 3,500 ppm by mass, and even more preferably 800 to 2,500 ppm by mass.
• the lubricant is capable of adjusting the dynamic friction coefficient of the film, and preferably contains at least one inorganic lubricant selected from the group consisting of silica, calcium carbonate, and alumina, more preferably contains at least one inorganic lubricant selected from the group consisting of silica and calcium carbonate, and most preferably contains silica.
• Silica in particular makes it easier to achieve both transparency and slipperiness.
• the lubricant may contain an organic lubricant.
• the weight average particle size of the lubricant in layer B may be the same as or different from the weight average particle size of the lubricant in layer A or the intermediate layer.
• the weight average particle diameter of the lubricant contained in layer B is preferably 0.5 ⁇ m or more, more preferably 0.8 ⁇ m or more, and even more preferably 1.5 ⁇ m or more. If it is 0.5 ⁇ m or more, unevenness can be formed on the surface of layer B of the biaxially oriented polyester film. Therefore, slipperiness can be imparted to layer B of the biaxially oriented polyester film. In addition, when the biaxially oriented polyester film is wound into a roll, blocking with layer A can be suppressed, and the winding quality of the roll can be improved.
• the weight average particle diameter of the lubricant contained in layer B is preferably 4.0 ⁇ m or less, more preferably 3.8 ⁇ m or less, and even more preferably 3.5 ⁇ m or less. If it is 4.0 ⁇ m or less, the occurrence of coarse protrusions on the surface of layer B of the biaxially oriented polyester film can be prevented.
• the pore volume of the lubricant in layer B is preferably 1.0 ml/g or more, more preferably 1.1 ml/g or more, and even more preferably 1.2 ml/g or more. This can reduce haze when layer B contains a lubricant.
• the pore volume of the lubricant in layer B is preferably 1.7 ml/g or less, more preferably 1.6 ml/g or less, and even more preferably 1.5 ml/g or less. This can reduce the dynamic friction coefficient on the surface on the layer B side.
• the difference between the lubricant content in layer A and the lubricant content in layer B is preferably 700 to 4,000 ppm by mass. By having this difference in the above range, it becomes easier to achieve both slip resistance and excellent winding properties. Also, by having the difference be 4,000 ppm by mass or less, haze can be reduced. The difference is more preferably 800 to 3,000 ppm by mass, and even more preferably 850 to 2,000 ppm by mass.
• Layers A and B of the biaxially oriented polyester film may contain additives other than lubricants, such as stabilizers, colorants, antioxidants, antistatic agents, and ultraviolet absorbers.
• the biaxially oriented polyester film may have an intermediate layer between the A layer and the B layer as necessary.
• the intermediate layer preferably contains a polyethylene terephthalate resin (hereinafter, sometimes referred to as PET resin (a)) as a main component.
• PET resin (a) polyethylene terephthalate resin
• “containing as a main component” means that the content of the PET resin (a) in 100% by mass of the intermediate layer is 60% by mass or more, preferably 70% by mass or more, and most preferably 80% by mass or more.
• the content of the PET resin (a) may be 100% by mass or less, 99.99% by mass or less, 99.98% by mass or less, 99.9% by mass or less, 98% by mass or less, or 95% by mass or less.
• the intermediate layer may contain a polyester resin (b) other than the PET resin (a) for the purpose of adjusting the mechanical properties of the biaxially stretched polyester film.
• polyester resins such as polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and polypropylene terephthalate (PPT); polyester resins copolymerized with dicarboxylic acids such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, cyclohexane dicarboxylic acid, adipic acid, azelaic acid, and sebacic acid; and polyester resins copolymerized with diol components such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6
• the lower limit of the intrinsic viscosity of the resin composition constituting the intermediate layer is preferably 0.45 dl/g, more preferably 0.50 dl/g, and most preferably 0.55 dl/g. By making it 0.45 dl/g or more, the intrinsic viscosity of the biaxially oriented polyester film can be maintained high, and mechanical properties such as puncture strength can be improved.
• the upper limit of the intrinsic viscosity of the resin composition constituting the intermediate layer is preferably 0.80 dl/g, more preferably 0.75 dl/g, and most preferably 0.70 dl/g. By making it 0.80 dl/g or less, it is possible to suppress the stress during film stretching from becoming too high, and good film formability can be obtained.
• the intrinsic viscosity of the intermediate layer is preferably 0.45 to 0.80 dl/g, more preferably 0.50 to 0.75 dl/g, and most preferably 0.55 to 0.70 dl/g.
• the polyester resin contained in the intermediate layer may be the same as or different from the polyester resin contained in the A or B layers.
• the intermediate layer may contain no lubricant or may contain a lubricant to improve the slipperiness of the film and improve the winding quality of the roll.
• the lubricant content in 100% by mass of the intermediate layer is preferably 0 to 2,500 ppm by mass, more preferably 0 to 2,000 ppm by mass, and even more preferably 0 to 1,500 ppm by mass.
• the total amount of lubricant contained in the A layer, the B layer, and the intermediate layer is preferably 4,500 ppm by mass or less, more preferably 3,500 ppm by mass or less, and even more preferably 2,500 ppm by mass or less, relative to the entire biaxially oriented polyester film.
• the total amount of lubricant contained in the A layer, the B layer, and the intermediate layer is preferably 200 ppm by mass or more, more preferably 500 ppm by mass or more, and even more preferably 1,000 ppm by mass or more, relative to the entire biaxially oriented polyester film.
• the lubricant is capable of adjusting the dynamic friction coefficient of the film, and preferably contains at least one inorganic lubricant selected from the group consisting of silica, calcium carbonate, and alumina, more preferably contains at least one inorganic lubricant selected from the group consisting of silica and calcium carbonate, and most preferably contains silica.
• Silica in particular makes it easier to achieve both transparency and slipperiness.
• the lubricant may contain an organic lubricant.
• the weight average particle size of the lubricant in the intermediate layer may be the same as or different from the weight average particle size of the lubricant in layers A and B.
• the weight average particle size of the lubricant is preferably 0.5 ⁇ m or more, more preferably 0.8 ⁇ m or more, and even more preferably 1.5 ⁇ m or more.
• the weight average particle size of the lubricant is preferably 4.0 ⁇ m or less, more preferably 3.8 ⁇ m or less, and even more preferably 3.5 ⁇ m or less. This can reduce haze when the intermediate layer contains a lubricant.
• the pore volume of the lubricant is preferably 1.0 ml/g or more, more preferably 1.1 ml/g or more, and even more preferably 1.2 ml/g or more. This can reduce haze when the intermediate layer contains a lubricant.
• the pore volume of the lubricant is preferably 1.7 ml/g or less, more preferably 1.6 ml/g or less, and even more preferably 1.5 ml/g or less.
• the intermediate layer may contain additives other than the lubricant, such as stabilizers, colorants, antioxidants, antistatic agents, and ultraviolet absorbers.
• the thickness of the biaxially oriented polyester film is preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, and even more preferably 7 ⁇ m or more. By making it 3 ⁇ m or more, the strength of the film can be maintained.
• the upper limit of the thickness is preferably 100 ⁇ m or less, more preferably 75 ⁇ m or less, and even more preferably 50 ⁇ m or less. By making it 100 ⁇ m or less, processing becomes easier.
• the ratio of the thickness of layer A to the overall thickness of the biaxially oriented polyester film is preferably 30-90%, and more preferably 35-70%.
• the thickness ratio of layer A be 30% or more, the dynamic friction coefficient of the surface on the layer A side can be increased. This is thought to be due to the fact that if layer A, which contains PET resin (a) as its main component, is relatively thick, the true contact area of the surface on the layer A side when a load is applied tends to be large.
• the thickness ratio of layer A be 90% or less, it becomes easier to ensure the thickness of layers other than layer A.
• the thickness of layer A is preferably equal to or greater than the thickness of the intermediate layer. This allows the dynamic friction coefficient of the surface of layer A to be increased.
• the thickness of layer A is preferably equal to or greater than 1.0 times the thickness of the intermediate layer.
• the thickness of layer A is preferably equal to or less than 10 times the thickness of the intermediate layer, more preferably equal to or less than 6 times, and even more preferably equal to or less than 5 times. This allows the thickness of the biaxially oriented polyester film to be reduced.
• the thickness of layer B is preferably smaller than that of layer A. This increases the dynamic friction coefficient of the surface on the A layer side and decreases the dynamic friction coefficient of the surface on the B layer side.
• the thickness of layer B is preferably less than 1.0 times the thickness of layer A, more preferably 0.9 times or less, even more preferably 0.7 times or less, and most preferably 0.6 times or less.
• the thickness of layer B is preferably 0.1 times or more the thickness of layer A, more preferably 0.2 times or more, even more preferably 0.3 times or more, and most preferably 0.4 times or more. This makes it easier for layer B to retain the lubricant.
• the puncture strength of the biaxially oriented polyester film is preferably 0.60 N/ ⁇ m or more, more preferably 0.62 N/ ⁇ m or more, and even more preferably 0.64 N/ ⁇ m or more. By setting it to 0.60 N/ ⁇ m or more, for example, when the biaxially oriented polyester film is used as a lid material for plastic containers for food use, it can be used suitably without breaking even if external stress is applied to the lid material.
• the upper limit of the puncture strength is preferably 1.00 N/ ⁇ m or less, more preferably 0.97 N/ ⁇ m or less, and even more preferably 0.94 N/ ⁇ m or less.
• the puncture strength (N/ ⁇ m) is the puncture strength converted to a thickness of 1 ⁇ m, as described in the examples below.
• the haze value of the biaxially oriented polyester film converted to a thickness of 12 ⁇ m is preferably 4.5% or less, more preferably 4.3% or less, even more preferably 4.0% or less, and most preferably 3.8% or less. By making it 4.5% or less, transparency is high, and for example, when the biaxially oriented polyester film is used as a lid material for a plastic container or a packaging material, the contents can be clearly seen, the print can be clearly seen, and the appearance can be good.
• the haze value of the biaxially oriented polyester film converted to a thickness of 12 ⁇ m may be 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more.
• the dynamic friction coefficient when the surface of the A layer side of the biaxially oriented polyester film is in contact with a metal plate is preferably 0.20 or more, more preferably 0.23 or more, and even more preferably 0.25 or more.
• the dynamic friction coefficient is preferably 1.00 or less, more preferably 0.80 or less, and even more preferably 0.60 or less.
• the film has excellent surface slip resistance, and for example, when used as a lid material for plastic containers, even when the plastic containers are stacked and displayed so that the bottoms and the A layer are in contact, the containers are less likely to collapse due to slipping.
• the dynamic friction coefficient can be measured by the method described in the examples below.
• the value of the dynamic friction coefficient when the B layer surface of the biaxially oriented polyester film is in contact with a metal plate is preferably smaller than the value of the dynamic friction coefficient when the A layer surface of the biaxially oriented polyester film is in contact with a metal plate. This makes it easier to achieve both slip resistance and excellent winding properties.
• the value of the dynamic friction coefficient when the B layer surface is in contact with a metal plate is preferably 0.9 times or less, more preferably 0.5 times or less, even more preferably 0.3 times or less, and most preferably 0.2 times or less, of the value of the dynamic friction coefficient when the A layer surface is in contact with a metal plate.
• the said factor may be 0.01 times or more, and the said factor may be 0.03 times or more.
• the dynamic friction coefficient when the A layer surface and the B layer surface of the biaxially oriented polyester film are brought into contact is preferably 0.35 or more, more preferably 0.37 or more, and even more preferably 0.39 or more. It is preferably 0.50 or less, more preferably 0.48 or less, and even more preferably 0.45 or less. By setting the dynamic friction coefficient in the range of 0.35 or more and 0.50 or less, the sliding properties between the films are improved, and the winding quality of the film roll is improved.
• the dynamic friction coefficient can be measured by the method described in the examples below.
• the heat shrinkage rate of the biaxially oriented polyester film in the machine direction (hereinafter sometimes referred to as MD direction) and width direction (hereinafter sometimes referred to as TD direction) after heat treatment at 150°C for 15 minutes is preferably 0.1 to 2.5%, more preferably 0.2 to 2.0%, and even more preferably 0.3 to 1.8%. By keeping it at 2.5% or less, it is possible to suppress dimensional changes when heated in the secondary processing step and reduce the occurrence of wrinkles.
• a printing layer may be laminated on the surface of layer B of the biaxially oriented polyester film.
• the printing ink for forming the printing layer water-based and solvent-based resin-containing printing inks can be preferably used.
• the resin used in the printing ink include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures of these.
• the printing ink may contain known additives such as antistatic agents, light blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoamers, crosslinking agents, anti-blocking agents, and antioxidants.
• the printing method for forming the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used.
• known drying methods such as hot air drying, heated roll drying, and infrared drying can be used.
• Layer B of the biaxially oriented polyester film may be subjected to a slip-reducing corona discharge treatment, a glow discharge treatment, a flame treatment, a surface roughening treatment, or may be subjected to a known anchor coat treatment, printing, decoration, etc., as long as it does not impair the objectives of this disclosure.
• a layer of another material may be laminated to layer B of the biaxially oriented polyester film. This can be done by laminating the biaxially oriented polyester film to the layer of another material after film formation, or by laminating the biaxially oriented polyester film to the layer of another material during film formation.
• the present disclosure further provides a laminated body including the biaxially oriented polyester film and the sealant film of the embodiment.
• the laminated body is usually formed by extrusion lamination or dry lamination.
• the sealant film preferably includes a heat-sealable resin layer.
• the thermoplastic copolymer forming the heat-sealable resin layer may be any copolymer capable of sufficiently exhibiting sealant adhesiveness, and may be polyethylene resins such as high density polyethylene (HDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE), polypropylene resin, ethylene-vinyl acetate copolymer, ethylene- ⁇ -olefin random copolymer, ionomer resin, polyester resin, etc.
• the sealant film may be composed of a heat-sealable resin layer.
• the sealant film or heat-sealable resin layer may be a single layer or a multilayer, and may be selected according to the required function.
• the sealant film or heat-sealable resin layer may also contain various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.
• the total thickness of the sealant film is preferably 5 to 100 ⁇ m, and more preferably 10 to 60 ⁇ m.
• the biaxially oriented polyester film and laminate of the embodiment can be used in the packaging field for foods, medicines, industrial products, etc. In particular, they can be suitably used as top seal materials for packaging containers.
• the present disclosure further provides a top seal material comprising a biaxially oriented polyester film according to an embodiment.
• a top seal material comprising a biaxially oriented polyester film according to an embodiment.
• it is preferable to use it with the surface of Layer B facing the packaging container and the surface of Layer A as the outer surface of the top seal material.
• the layer configuration of the top seal material for packaging containers, where the boundary between layers is represented by / is, for example, non-slip surface layer/sealant layer, non-slip surface layer/gas barrier layer/protective layer, non-slip surface layer/gas barrier layer/protective layer/adhesive layer/sealant layer, non-slip surface layer/gas barrier layer/protective layer/adhesive layer/resin layer/adhesive layer/sealant layer, non-slip surface layer/adhesive layer/resin layer/gas barrier layer/protective layer/adhesive layer/sealant layer, non-slip surface layer/gas barrier layer/protective layer/printing layer/adhesive layer/sealant layer, non-slip surface layer/printing layer/gas barrier layer/protective layer/adhesive layer /sealant layer, non-slip surface layer/printing layer/gas barrier layer/protective layer/adhesive layer
• the present disclosure further provides a package including the biaxially oriented polyester film of the embodiment.
• the package include packaging products, various label materials, lid materials, sheet molded products, laminated tubes, etc.
• packaging products include packaging bags, etc.
• T-die method Method of manufacturing biaxially oriented polyester film
• the T-die method is preferred from the viewpoint of thickness accuracy.
• the stretch ratio is difficult to increase due to the manufacturing method, and thickness defects in the width direction may occur.
• a typical manufacturing process of the T-die method will be described.
• the T-die method includes: (1) a process of melt-extruding a polyester resin composition into a sheet and cooling it on a cooling roll to form an unstretched sheet; (2) a stretching process of stretching the formed unstretched sheet in the MD direction and in the TD direction perpendicular to the MD direction; (3) a heat setting process of heating and crystallizing the film after the stretching; (4) a heat relaxation process (sometimes called a relaxation process) of removing residual strain in the heat-set film; and (5) a cooling process of cooling the film after heat relaxation.
• the upper limit of the resin melting temperature in the extruder is preferably 310°C, and more preferably 300°C. If it is 310°C or lower, decomposition of the resin can be suppressed, preventing the film from becoming brittle and preventing deterioration of film quality due to thermal degradation.
• the lower limit of the resin melting temperature in the extruder is preferably 230°C, and more preferably 240°C. If it is 230°C or higher, not only will it be possible to extrude the resin, but it will also be possible to ensure stable extrusion and good thickness accuracy.
• the upper limit of the cooling roll temperature is preferably 40°C, and more preferably 20°C or less. If it is 40°C or less, the crystallinity of the molten polyester resin composition does not become too high when it is cooled and solidified, making it easier to stretch, and it is also possible to suppress the decrease in transparency due to crystallization.
• the lower limit of the cooling roll temperature is preferably 0°C. If it is 0°C or more, it is possible to fully exert the effect of suppressing crystallization when the molten polyester resin composition is cooled and solidified. Furthermore, when the temperature of the cooling roll is in the above range, it is preferable to reduce the humidity of the environment near the cooling roll to prevent condensation.
• the thickness of the unstretched sheet is preferably in the range of 15 to 2500 ⁇ m. More preferably, it is 500 ⁇ m or less, and most preferably, it is 300 ⁇ m or less.
• the stretching method can be either simultaneous biaxial stretching or sequential biaxial stretching, but in order to increase the puncture strength, it is necessary to increase the degree of planar orientation, and in that respect sequential biaxial stretching is preferred.
• the lower limit of the MD stretching temperature is preferably 90°C, more preferably 95°C, and particularly preferably 100°C. At 90°C or higher, breakage can be further suppressed.
• the upper limit of the MD stretching temperature is preferably 140°C, more preferably 135°C, and particularly preferably 130°C. At 140°C or lower, the degree of planar orientation can be increased, and the puncture strength can be increased.
• the lower limit of the stretching ratio in the MD direction is preferably 2.8 times, more preferably 2.9 times, and particularly preferably 3.0 times. If it is 2.8 times or more, the degree of planar orientation can be increased, and the puncture strength can be increased. Furthermore, if it is 2.8 times or more, thickness unevenness can be suppressed, and slack in the film roll can be prevented.
• the upper limit of the stretching ratio in the MD direction is preferably 4.5 times, more preferably 4.4 times, and particularly preferably 4.3 times. If it is 4.5 times or less, the effect of improving mechanical strength and thickness unevenness can be sufficiently obtained.
• the lower limit of the TD stretching temperature is preferably 100°C, more preferably 105°C, and particularly preferably 110°C. If it is 100°C or higher, breakage is less likely to occur.
• the upper limit of the TD stretching temperature is preferably 140°C, more preferably 135°C, and particularly preferably 130°C. If it is 140°C or lower, the degree of planar orientation can be increased, and the puncture strength can be increased.
• the lower limit of the stretching ratio in the TD direction is preferably 3.8 times, more preferably 3.9 times, and particularly preferably 4.0 times. If it is 3.8 times or more, the degree of planar orientation can be increased, and the puncture strength can be increased.
• the upper limit of the stretching ratio in the TD direction is preferably 5.0 times, more preferably 4.9 times, and particularly preferably 4.8 times. If it is 5.0 times or less, the effect of improving the mechanical strength and thickness unevenness can be sufficiently obtained.
• the lower limit of the heat setting temperature is preferably 170°C, more preferably 180°C, and particularly preferably 190°C. If it is 170°C or higher, the thermal shrinkage rate can be reduced.
• the upper limit of the heat setting temperature is preferably 240°C, more preferably 230°C, and particularly preferably 220°C. If it is 240°C or lower, it is possible to prevent the film from melting, and also to increase the degree of planar orientation and the puncture strength.
• the lower limit of the relaxation rate in thermal relaxation is preferably 0.5%, more preferably 1.0%, and particularly preferably 2.0%. If it is 0.5% or more, the thermal shrinkage rate in the TD direction can be kept low.
• the upper limit of the relaxation rate is preferably 10%, more preferably 8%, and particularly preferably 6%. If it is 10% or less, the occurrence of sagging can be prevented, and flatness can be improved.
• Biaxially oriented polyester films were evaluated using the following measurement methods. Unless otherwise specified, measurements were performed in a measurement room with an environment of 23°C and a relative humidity of 65%.
• the mass of the thread (weight) around which the upper film was wound was 3.5 kg, and the size of the base area of the thread was 39.7 mm2 .
• the pulling speed in measuring the friction coefficient was 200 mm/min.
• the dynamic friction coefficient thus determined is referred to as "dynamic friction coefficient (A layer/metal plate)" in the examples and tables.
• the mass of the thread (weight) around which the upper film was wound was 1.5 kg, and the size of the base area of the thread was 39.7 mm2 .
• the pulling speed in measuring the friction coefficient was 200 mm/min.
• the dynamic friction coefficient thus determined is referred to as "dynamic friction coefficient (A layer/B layer)" in the examples and tables.
• the heat shrinkage rate was measured using a dimensional change test method in accordance with JIS C2151 (2019), except that the test temperature was 150°C and the heating time was 15 minutes.
• the plastic container used and the load during the measurement are as follows: Polystyrene lunch box container ("PS container”), length 230 mm x width 195 mm x height 25 mm (manufactured by Fukusuke Kogyo Co., Ltd.), load 200 g Polypropylene tray container (“PP container”), length 190 mm x width 140 mm x height 31 mm (manufactured by Chuo Kagaku Co., Ltd.), load 200 g A-PET clean cup container (“A-PET container”), diameter ⁇ 101 mm x height 35 mm (manufactured by Rispack), load 100 g
• the angle at which the container began to slide was evaluated according to the following criteria. ⁇ : The sliding angle is 26° or more. ⁇ : The sliding angle is less than 26°.
• silica particles were used as Silica 310 (average particle size 2.7 ⁇ m, pore volume 1.60 ml/g) manufactured by Fuji Silica Co., Ltd.
• each resin composition was melted at 280°C, laminated in a configuration of A layer/intermediate layer/B layer by the feed block method, cast from a T-die at 280°C, and adhered to a cooling roll at 10°C by electrostatic adhesion to obtain an unstretched sheet.
• the unstretched sheet obtained was then stretched 3.5 times in the MD direction at a temperature of 115°C, then passed through a tenter to stretch 4.0 times in the TD direction at 120°C, and subjected to a heat setting treatment at 215°C for 3 seconds and a 7% relaxation treatment for 1 second to obtain a biaxially oriented polyester film with a thickness of 12 ⁇ m.
• the physical properties and evaluation results of the obtained film are shown in Table 1.
• Examples 2 to 4 biaxially stretched polyester films having a thickness of 12 ⁇ m were obtained by film formation in the same manner as in Example 1, except that the content of silica particles contained in the resin compositions constituting the A layer, intermediate layer, and B layer, and the layer thickness ratio of A layer/intermediate layer/B layer were changed as shown in Table 1. The physical properties and evaluation results of the obtained films are shown in Table 1.
• Example 5 A biaxially stretched polyester film having a thickness of 12 ⁇ m was obtained by film formation in the same manner as in Example 1, except that the silica particles in Example 5 were changed to Silicea 420 (average particle size 3.1 ⁇ m, pore volume 1.25 ml/g) manufactured by Fuji Silysia Ltd. The physical properties and evaluation results of the obtained film are shown in Table 1.
• Comparative Example 1 Comparative Example 1 was carried out in the same manner as in Example 1, except that the content of silica particles in layer B was changed to the content of silica particles shown in Table 2. The physical properties and evaluation results of the obtained film are shown in Table 2. The dynamic friction coefficient (layer A/layer B) of the obtained film was too large to be measured. In addition, the film winding property was also poor.
• Comparative Example 2 In Comparative Example 2, the same procedure as in Example 1 was carried out except that the content of silica particles in the A layer was changed to the content of silica particles shown in Table 2. The physical properties and evaluation results of the obtained film are shown in Table 2. The obtained film had a small dynamic friction coefficient (A layer/metal plate) and lost its slipperiness. In addition, the start angle of inclined sliding was small in all plastic containers, and the results were poor.
• Comparative Example 3 In Comparative Example 3, the same procedure as in Example 1 was carried out except that the thickness ratio of the A layer and the B layer was changed to the thickness ratio shown in Table 2. The physical properties and evaluation results of the obtained film are shown in Table 2. Since the A layer of the obtained film was thin, the dynamic friction coefficient (A layer/metal plate) was small, and the slipperiness was lost. In addition, the inclined sliding was also poor, with the sliding start angle being small in all plastic containers.
• Comparative Example 4 was performed in the same manner as in Example 1, except that the content of silica particles in layer B was changed to the content of silica particles shown in Table 2. The physical properties and evaluation results of the obtained film are shown in Table 2. Since the obtained film had a high content of silica particles, the haze was deteriorated.
• Comparative Example 5 The same procedure as in Example 1 was repeated except that in Comparative Example 5, the silica particles were changed to Silisia 530 (average particle size 2.7 ⁇ m, pore volume 0.80 ml/g) manufactured by Fuji Silysia Ltd. The physical properties and evaluation results of the obtained film are shown in Table 2. The obtained film had a poor haze because the pore volume of the silica particles was small and coarse protrusions were easily formed.
• Comparative Example 6 In Comparative Example 6, the same procedure as in Example 1 was carried out, except that the silica particles were changed to Silicea 250 (average particle size 5.0 ⁇ m, pore volume 1.80 ml/g) manufactured by Fuji Silysia Co., Ltd. The physical properties and evaluation results of the obtained film are shown in Table 2. The obtained film had a large pore volume of the silica particles and was easily crushed, so the dynamic friction coefficient (A layer/B layer) was too large to be measured. In addition, the film winding property was also poor.

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