JP2005068360A - Polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film having excellent mechanical characteristics, capable of being laminated with a metal sheet and having an excellent designability without whitening by thermal treatment even at near or above a melting point. <P>SOLUTION: The polyester film is composed of a polyester composition prepared by compounding 10-90 wt.% of (A) a polyester mainly constituted of ethylene terephthalate, with 90-10 wt.% of (B) a crystalline polyester other than the polyester resin (A), wherein the ratio w/h of a half-value width w(°C) of a temperature-descending recrystallization peak (Tc2) to calorie h (mW), measured with a differential scanning calorimeter (DSC), is ≤1.30 (°C/mW). The crystalline polyester (B) is a polyester preferably selected from a PBT polyester, PEN polyester, PTT polyester, PHT polyester or PPT polyester. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyester film useful for various food packaging, general industrial use, optical use, electrical material use, molding processing film, film laminate metal plate, and the like.

  For example, metal cans, which are one form of food and beverage packaging containers, are excellent in mechanical strength, so that the contents can be stored for a long period of time. It can be easily sterilized, etc., so it is highly reliable for safety and hygiene as a packaging container, and the contents can be stored in a warmed state, and cans can be separated and recovered after use. In recent years, various contents have been filled and used in large quantities.

  The inner and outer surfaces of metal cans for food and drink have thermosetting resins as the main component for the purpose of maintaining the flavor of the contents and preventing corrosion of the metal cans, or improving the cosmetics of the outer surface of the cans and protecting the printed surface. Coatings that apply have been used on metal cans. However, since such metal cans use a large amount of solvent at the time of manufacture, the effects on the environment due to solvent removal during manufacture, sanitary problems due to residual solvent in the coating film, and poor reaction during heat curing. There are problems such as a decrease in flavor due to the remaining oligomer.

  In order to overcome these problems, it has been proposed to laminate a plastic film to a metal, and among other thermoplastic resins, there are other points in terms of adhesive strength, heat resistance, mechanical strength, flavor properties, processability, etc. Since there are many points superior to resin, a polyester film is often laminated on a metal plate. As metal cans obtained by processing such film-laminated metal plates, so-called three-piece cans (hereinafter abbreviated as 3P cans) and two-piece cans (hereinafter abbreviated as 2P cans) have been proposed. The spread of 2P cans is desired from the standpoint of making them seamless.

  As a general manufacturing method of a 2P can, a method of laminating a plastic film, punching a laminated metal plate with a can-making machine, and making a seamless can through a drawing and ironing process is common. In such a can making process, the film is required to have formability that can follow the extension of the metal plate without being cracked or peeled off from the metal plate while being subjected to squeezing and shearing. It is also required that no whitening occurs.

  For such required characteristics, a polyester film in which a polyethylene terephthalate polyester resin having a specific intrinsic viscosity and a polybutylene terephthalate polyester resin having a specific intrinsic viscosity are blended has been proposed.

  For example, by optimizing the semi-crystallization temperature and semi-crystallization time of the polyethylene terephthalate polyester resin and the polybutylene terephthalate polyester resin to be blended, the film followability to the metal deformation and retort whitening are suppressed (for example, Patent Documents 1 and 2).

Also, by optimizing the thermal properties and plane orientation of the polyethylene terephthalate-based polyester resin and polybutylene terephthalate-based polyester resin to be blended, the film's followability to metal deformation and flavor by heat treatment (crystallization treatment) after lamination Improves sex.
At this time, since the degree of crystallinity of the film cannot be increased if the transesterification reaction has proceeded too much between the two types of polyester, for example, the melting time of the resin at the time of film formation and the stretching of the film after that, A device has been devised to reduce the amount of heat applied to the film in the heat treatment process (for example, see Patent Documents 3 and 4).

Furthermore, although it is a blend film of a polyethylene terephthalate (PET) polyester resin and a polybutylene terephthalate (PBT) polyester resin, the PET phase and the PBT phase have independent crystals, so that heat fusion and moldability can be maintained. A polyester film has been proposed. This film can be used for molding transfer, molding container and metal bonding, etc. Also, in order to make PET phase and PBT phase independent crystals, the blended resin is extruded with a pent type extruder into a film. Molding is described (for example, refer to Patent Documents 5 and 6).
Japanese Patent No. 2882985 Japanese Patent No. 3020731 JP 10-195210 A Japanese Patent Laid-Open No. 10-110046 JP 2002-179892 A JP 2002-321277 A

  However, in the study by the present inventors, in the conventional blend type polyester film proposed above, the film is whitened when the film is melted near the melting point or above the melting point and bonded to a metal or the like and then the temperature is lowered. It has been found that the problem arises that the design of the film is lowered. Moreover, it turned out that there exists a problem that the film on a metal plate tends to be damaged.

  In view of the above circumstances, the object of the present invention is to provide a polyester film that has excellent mechanical properties, can be bonded to a metal plate, and does not whiten even if the film is heat-treated near or above the melting point. There is to do. It is another object of the present invention to provide a polyester film having the above-described excellent characteristics and being less likely to be damaged after being laminated on a metal plate.

  The inventors of the present invention have studied the cause of whitening that occurs with a temperature drop after melting near or above the melting point of a polyester film obtained by blending a conventional polyethylene terephthalate-based polyester resin and a polybutylene terephthalate-based polyester resin. As a result, the whitening occurs because the crystal size generated in the temperature lowering process after the film is melted is too large. The increase in the crystal size of the film is caused by the polyester constituting the film (that is, PET polyester resin and PBT type). The dispersion state of the polyester resin is considered to have an influence, and as a result of further research from this viewpoint, the present invention has been completed.

That is, the present invention
(1) A polyester resin composition comprising 10 to 90% by weight of polyester (A) containing ethylene terephthalate as a main constituent and 90 to 10% by weight of a crystalline polyester resin (B) different from the polyester resin (A). The ratio w / h of the full width at half maximum w (° C.) and the height h (mW) of the recrystallization peak (Tc2) at the time of cooling in the differential scanning calorimeter (DSC) is 1.30 ( (C / mW) or less.
(2) The polyester resin composition is composed of 10 to 70% by weight of polyester (A) whose main constituent is ethylene terephthalate, and the crystalline polyester (B) is polybutylene terephthalate (PBT) or polytetramethylene terephthalate (PTT). Polyester film according to (1) above, which is a polyester selected from polyethylene-2,6-naphthalate (PEN).
(3) The polyester film of (1) or (2) above, wherein the peak temperature of the recrystallization peak is 180 ° C. or higher.
(4) The polyester film according to any one of (1) to (3) above, wherein the reduced viscosity of the polyester film is 0.80 or more.
(5) The polyester film as described in any one of (1) to (4) above, which is for metal plate lamination.
(6) The polyester film as described in any one of (1) to (5) above, which is for molding.

  As is clear from the above description, according to the present invention, the mechanical properties are excellent, the crystallinity is high, and the film alone or a metal plate is bonded, and the film is heat-treated near or above the melting point of the film. Even if it is, the polyester film excellent in the design property which is not whitened can be obtained, and also the polyester film which has this outstanding whitening resistance (design property) and is hard to be damaged can be obtained. The polyester film of the present invention can be used as a film for various kinds of metal wrapping, general industrial use, optical use, electrical material use and molding processing, among them, for general wrapping use, antistatic use, gas barrier use, metal laminate use, heat use. For sealing, anti-fogging, metal deposition, easy tearing, easy opening, bag making packaging, retort packaging, boil packaging, drug packaging, easy adhesion, magnetic recording, capacitor, ink ribbon, transfer Suitable for adhesive labels, stamping foils, gold and silver yarns, tracing materials, mold release, shrink link films and the like, and particularly suitable for metal laminating (a constituent material of a film laminated metal plate).

Hereinafter, the present invention will be described in more detail.
The polyester (A) (hereinafter also referred to as polyester A) having ethylene terephthalate as the main component in the present invention refers to a polyester in which 80 mol% or more of the polyester component is ethylene terephthalate, preferably 90 mol% or more is ethylene. Polyester that is terephthalate.

Here, the polyester is a polymer composed of a dicarponic acid component and a glycol component, and a dicarponic acid component other than terephthalic acid, such as naphthalene dicarponic acid, diphenyl dicarponic acid, diphenyl sulfone dicarponic acid, diphenoxyethane dicarponic acid, Aromatic dicarponic acid such as 5-sodiumsulfoisophthalic acid and phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarponic acid, cyclohexane dicarponic acid, etc. A dicarponic acid component arbitrarily selected from alicyclic dicarponic acid and oxycarponic acid such as p-oxybenzoic acid may be copolymerized. In addition, glycol components other than ethylene glycol, for example, aliphatic glycols such as trimethylene glycol, butanediol, pentanediol, hexanediol and neopentylglycol, alicyclic glycols such as cyclohexanedimethanol, bisphenol A, bisphenol S and the like A glycol component arbitrarily selected from among the aromatic glycols may be copolymerized. In addition, you may use 2 or more types together for these dicarponic acid components and glycol components.
The melting point of the polyester (A) is preferably 240 ° C to 265 ° C.

  Moreover, the reduced viscosity of the polyester (A) is preferably 0.55 to 0.90, and more preferably 0.58 to 0.80. If the reduced viscosity is smaller than this range, it is difficult to obtain a film having mechanical strength that can be used practically, and if it exceeds this range, the thermocompression bonding property of the film to the metal plate is unfavorable.

  In the present invention, the crystalline polyester (B) (hereinafter also referred to as polyester B) is a polybutylene terephthalate (PBT) -based polyester, a polyethylene-2,6-naphthalate (PEN) -based polyester, or a polytrimethylene terephthalate (PTT) -based. One, two or more kinds of polyesters selected from polyester, polyhexamethylene terephthalate (PHT) polyester and polypentamethylene terephthalate (PPT) polyester, preferably polybutylene terephthalate (PBT) polyester Polyethylene-2,6-naphthalate (PEN) polyester, polytrimethylene terephthalate (PTT) polyester, polyhexamethylene terephthalate (PHT) polyester or polyester Pentamethylene terephthalate (PPT) polyester. Here, the polyester is a polymer composed of a dicarponic acid component and a glycol component. These crystalline polyesters are all homopolyesters (ie, polybutylene terephthalate (PBT), polyethylene-2,6-mononaphthalate (PEN), polytrimethylene terephthalate (PTT), polyhexamethylene terephthalate (PHT), polypenta. Methylene terephthalate (PPT)) is preferable, but it may be a copolyester obtained by further copolymerizing the homopolyester with other dicarponic acid component and / or glycol component. Examples of the dicarboxylic acid component as the copolymerization component include diphenyl dicarponic acid, diphenyl sulfone dicarponic acid, diphenoxyethane dicarponic acid, 5-sodium sulfoisophthalic acid, phthalic acid and other aromatic dicarponic acid, Acids, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarponic acids, cyclohexane dicarponic acid and other alicyclic dicarponic acids, P-oxybenzoic acid and other oxycarponic acids, etc. Examples of the dicarpone component selected from the above are listed below. The glycol component includes aliphatic glycols such as ethylene glycol, trimethylene glycol, butanediol, pentanediol, hexanediol, and neopentylglycol, and cyclohexanedimethanol. Alicyclic glycol such as bisph Nord A, include any glycol component selected from among such aromatic glycols such as bisphenol S, these Jikarupon acid component, glycol component may be used in combination of two or more thereof. In addition, the copolymerization amount of these dicarpone components and / or glycol components is in a range that does not impair the high crystallinity of the polyester, and is usually 20 mol% or less based on the entire polyester.

  The melting point of the polybutylene terephthalate (PBT) polyester is preferably 215 to 235 ° C., the melting point of the polyethylene-2,6-mononaphthalate (PEN) polyester is preferably 260 to 275 ° C., and the melting point of the polytrimethylene terephthalate (PTT) polyester The melting point is preferably 230 to 245 ° C, the melting point of the polyhexamethylene terephthalate (PHT) polyester is preferably 150 to 170 ° C, and the melting point of the polypentamethylene terephthalate (PPT) polyester is preferably 130 to 150 ° C.

  In the present invention, the crystalline polyester (B) is selected from any of polybutylene terephthalate (PBT) polyester, polytrimethylene terephthalate (PTT) polyester, and polyethylene-2,6-naphthalate (PEN) polyester. Of these, polybutylene terephthalate (PBT) -based polyester or polytrimethylene terephthalate (PTT) -based polyester is particularly preferable.

  In the present invention, the reduced viscosity of the crystalline polyester (B) is preferably 0.80 to 2.20, more preferably 0.85 to 1.50. If the reduced viscosity is smaller than this range, a film having mechanical strength that can be practically used cannot be obtained, and if it exceeds this range, the thermocompression bonding property of the film to the metal plate is impaired, which is not preferable.

  In the polyester film of the present invention, the blending ratio (A / B) of polyester A and polyester B is generally 10 to 90% by weight / 90 to 10% by weight, preferably 10 to 70% by weight / 90 to 30% by weight. %, More preferably 35 to 65% by weight / 65 to 35% by weight. If the amount of polyester A exceeds this specified range and the amount of polyester B is small (the amount of polyester B is small), the film forming processability deteriorates. If the amount of polyester B is large (the amount of polyester A is small), the film is whitened when the temperature is lowered after melting the film near or above its melting point. It will be able to be suppressed enough.

  FIG. 1 is a simplified chart showing a recrystallization peak of a crystalline polyester film when the temperature is lowered by a differential scanning calorimeter (DSC). In this figure, when the height from the base line L to the peak top t of the recrystallization peak 1 is h (mW) and the temperature width at the height h / 2, that is, the half width is w (° C.), A ratio w / h (° C./mW) between the value width w and the height h is defined.

  The speed of crystallization in the recrystallization process when the temperature of the polyester film is lowered can be known from the value of the ratio w / h of the half width w and the height h of the recrystallization peak defined as described above. It is considered that the smaller the value of the ratio w / h, the faster the crystallization rate. It is considered that the smaller the value of the ratio w / h is, the more moderately coarsely dispersed the polyester resins (A) and (B) are in the film system, and the faster the crystallization speed of the film is.

  In the polyester film of the present invention, when the value of the ratio w / h is 1.30 ° C./mW or less, the crystallization speed of the film in the cooling process at the time of lowering the temperature near or above the melting point of the film is high. In addition, microcrystals that are small enough not to contribute to the scattering of visible light can be rapidly and abundantly formed inside the film, so that the film is not whitened while maintaining the processing characteristics. On the other hand, when the value of the ratio w / h is larger than 1.30 ° C./mW, the crystal crystallization rate in the cooling process at the time of cooling is slow, so that the microcrystal grows to a size that scatters visible light. Therefore, it is considered that the whitening of the film occurs.

  In the polyester film of the present invention, the value of the ratio w / h of the recrystallization peak at the time of cooling is preferably 1.30 ° C./mW or less, more preferably 1.10 ° C./mW or less, and 1.00 or less. Further preferred. A polyester film having such a preferable ratio w / h exhibits more preferable whitening resistance. The lower limit of the ratio w / h is not particularly defined, but is generally about 0.30 ° C./mW.

  Conventionally, when producing a polyester film of blend type, it is common to mix (dry blend) the polyester chips to be blended before feeding them into the extruder, and then melt and mix the mixed chips into the extruder. However, in this method, since a plurality of polyester chips start to melt substantially at the same time, a plurality of polyesters to be blended are melted and mixed for a long time, and a compatible polyester such as PET and PBT is used. It becomes a finely dispersed state. The polyester film blended with the conventional PET-based polyester resin and the PBT-based polyester resin described in the section of the prior art is manufactured by this method, and the conventional polyester film blended with the PET-based polyester resin and the PBT-based polyester resin. The problem of whitening when the film occurring in step 1 is melted to near or above its melting point and bonded to a metal or the like is that both polyesters (PET polyester resin, PBT polyester resin) constituting the film are copolymerized. In addition, even though they are dispersed in phases that are substantially independent of each other, because they are in a finely dispersed state (ie, they are mutually dispersed because they are completely dispersed), the independence of each crystallinity As a result, crystallization of the film is difficult to proceed, leading to whitening of the film. It is presumed to be. That is, for example, when a blend film of PET (melting point 255 ° C.) and PBT (melting point 220 ° C.) is produced by a single extruder having a single or twin screw, the temperature of the extruder is the melting point of PET having a high melting point. It is necessary to set it above the melting point of PET correspondingly, and is usually set to 280 ° C. or higher in consideration of production stability, etc., but when PBT is heated to such a temperature of 280 ° C. or higher, Decomposition that occurs from around 260 ° C. proceeds more rapidly, and the molecular weight is lowered by the heat of the extruder, so that the compatibility with PET increases and the dispersion proceeds more uniformly and is finely dispersed. Therefore, both of them are easily copolymerized (transesterification) in the process of melting and mixing, and each crystallinity is impaired and the influence of each other is strongly influenced without copolymerization. It is considered that the independence of crystallinity becomes difficult to maintain, and the crystallization speed of the film becomes slow.

  The polyester film of the present invention is used for various applications such as food packaging, general industrial use, optical use, electric material use, metal laminating use and molding processing, and is near or above the melting point of the film. Not only does whitening not occur even after melting, but also excellent formability (formability of the film alone and formability when bonded to a metal plate) and flavor, as well as whitening of the film after molding. It is necessary to avoid it. For that purpose, in order to control the crystallization speed and the crystallinity of the film, it is necessary to sufficiently suppress the copolymerization of polyester A and polyester B (transesterification reaction of both). In the present invention, for example, the polyester A chip and the polyester B chip are not mixed (dry blended), but are put into separate extruders and melted, and the polyester A and the polyester melted by these separate extruders are melted. B is mixed before being extruded from the die, guided to the die, melted, extruded, and formed into a film to shorten the contact time in the molten state of polyester A and polyester B, and polyester A and polyester B Each film is formed into a film while ensuring a dispersion state of “coarse mixing” in which each is dispersed in a relatively large crystal phase state. Such a film in which polyester A and polyester B are dispersed in a relatively large crystalline phase maintains the crystallinity independence of the respective polyesters (polyester A and polyester B). It is considered that the film proceeds rapidly and the ratio (w / h) of the recrystallization peak of the film is 1.30 ° C./mW or less.

  As described above, the polyester film of the present invention is obtained by individually melting the polyester (A) mainly composed of ethylene terephthalate and the crystalline polyester (B) different from the polyester (A), and then in a molten state. These can be manufactured by mixing at a predetermined blending ratio and molding. In the production of a conventional general vinegar polyester film, a material (polyester) constituting a single layer film is put into a single extruder, melted and extruded to be formed into a film. The polyester film described in the patent document exemplified in the column of the prior art uses two or more different raw materials (polyester), but the extruder uses a single extruder and two or more different types. Raw materials (polyester) are melted and mixed together. This is presumed to be a result of considering the stability and economics of the film forming operation, and it seems that it was difficult to produce a higher quality film. On the other hand, the present invention adopts a procedure in which different raw materials (two or more kinds of polyesters) are individually melted, mixed and extruded in a molten state, thereby maintaining the stability of the film formation and maintaining the quality. It has been found that an improved film can be obtained. In the present invention, a method in which individual raw materials (two or more kinds of polyesters) are individually melted in an extruder and mixed in a molten state (a method in which two or more extruders are used in parallel) is preferable. A single extruder is also possible. However, when manufacturing with a single extruder, it is necessary to use an extruder whose compression part (compression zone) of the screw is a double flight type. Here, the “double flight type” means a structure in which the compression part (compression zone) of the screw has a double helix horizontal construction and a subflight with an outer diameter slightly smaller than the outer diameter of the main flight is provided between the main flights. In addition, the solid phase part and the molten part of the polymer are separated by the subflight. Examples of such an extruder in which the compression section (compression zone) has a double flight type screw include UB series (trade name) manufactured by Mitsubishi Heavy Industries, Ltd., and BARR series (trade name) manufactured by Nippon Steel Corporation. Can be mentioned. If the compression part of a screw is a double flight type extruder, it is thought that the polyester film of this invention can be manufactured also with a single extruder for the following reasons. That is, for example, when blending PET and PBT, the PBT that starts melting first and the PET that maintains the solid at that time are separated in the first half flight of the compression section of the extruder. This is because the contact time in the molten state of PBT and PBT can be shortened, and “coarse mixing” can be achieved. In this case, the single extruder is preferably a rapid compression type with a small compression ratio (2.0 or less). This is because if a slow compression type with a large compression ratio (greater than 2.0) is used, the self-heating value in the compression section (compression zone) of the extruder is large even if the apparent set temperature can be set low. Since the temperature of the resin becomes higher than the set temperature, the use of PTT, PBT, PHT, etc., which has a particularly low melting point among the crystalline polyester resins (B), tends to cause their decomposition, which is not preferable. It is.

  In the present invention, the rapid compression type extruder means an L / D of the compression section (compression zone) of less than 25, preferably less than 20, more preferably less than 15, and a slow compression type extruder. Means that the L / D of the compression section (compression zone) is 25 or more. Here, L / D is the ratio of the effective length (L) and outer diameter (D) of the screw in the compression section (compression zone), and the outer diameter (D) is the average outer diameter of the effective length portion of the screw. is there.

  As described above, the polyester film of the present invention can be produced by a single extruder. However, since the allowable amount of mixing conditions is narrow in a single extruder, a plurality of polyesters are individually separated by separate extruders. The method of melting is preferable. Specifically, as an extruder used for individually melting polyester A and polyester B, the compression ratio is 1.1 to 3.1 (preferably 1.5 to 2.8), L / D. Is an extruder of 20 to 35 (preferably 25 to 30). Such an extruder may be a single screw extruder or a twin screw extruder. Here, L / D is the ratio of the effective length (L) and outer diameter (D) of the screw in the extruder, and the outer diameter (D) is the average outer diameter of the effective length portion of the screw. The compression ratio is calculated by (groove depth of feed zone) / (groove depth of metering zone). The groove depths in the feed zone and metering zone are calculated from the outer diameter of the screw and the groove diameter of the screw, respectively.

  On the other hand, examples of the machine base for mixing individually melted polyester A and polyester B include a single screw extruder, a twin screw extruder, a dynamic mixer, a static mixer (manufactured by Noritake Company), and the like. A single screw extruder and a static mixer are preferred.

  In addition, in the extruder for mixing the melted polyester A and the polyester B, it is not preferable that the melted polyester A and the melted polyester B are uniformly mixed to such an extent that compatibility (transesterification reaction) occurs. Therefore, it is preferable to use one having a small compression ratio, and specifically, one having a compression ratio of 1.1 to 3.8 (preferably 1.3 to 3.0) is suitable. Moreover, it is preferable that the said extruder uses the thing of L / D of the range of 20-35 (preferably 25-30) from the viewpoint of making polyester A and polyester B coarsely mixed, and L of a compression part. / D is preferably 5 to 25) (preferably 10 to 20). The L / D and compression ratio here are the same as those in the above, and the L / D of the compression part (compression zone) is the length (L) and the outer diameter (D) of the compression part (compression zone) of the screw. Is the ratio.

  Moreover, as for the extrusion conditions (molding conditions) of the mixed molten resin, the resin temperature is 265 ° C. or lower, and a region of 275 ° C. or higher (preferably 270 ° C. or higher) is not set in the temperature setting from the cylinder part to the T-die. It is preferable to use conditions. If this condition is not met, the compatibility of the polyesters A and B becomes high when the temperature is high, so that the targeted whitening suppression of the film cannot be achieved, and the viscosity (molecular weight of the film) This is because there is a possibility that the scratch resistance of the produced film may be lowered due to a decrease.

  When the compatibility between polyester A and polyester B is increased, a transesterification reaction occurs between polyester A and polyester B, and a copolymer of polyester A and polyester B is formed. A certain ethylene terephthalate structure is randomized, and its characteristic rigidity is lost, and the main component structure of polyester B is butylene terephthalate structure, trimethylene terephthalate structure, hexamethylene terephthalate structure, pentamethylene terephthalate structure Alternatively, the ethylene-2,6-naphthalate fabrication is randomized, and the high crystallinity that is characteristic thereof is impaired. As a result, the crystallization rate is reduced, and coarse spherulites that cause whitening are easily generated.

  Various means are known as means for suppressing side reactions such as transesterification in a film composition containing polyethylene terephthalate-based polyester and other crystalline polyesters, but are applied in industrial film production. For this purpose, a method of adding an organophosphorus compound (catalyst) is preferable from the viewpoint of inhibiting the polymerization of polyester A and polyester B in the polymerization, and in the present invention, the transesterification reaction can be carried out by adding such an organophosphorus compound (catalyst). The suppression effect can be enhanced.

  In the present invention, the organophosphorus compound (catalyst) preferably has a melting point of 200 ° C. or higher in view of the stability in the extruder (mixer stand). For example, dimethyl methylphosphonate, diphenyl methylphosphonate, phenyl Dimethyl phosphonate, Jetyl phenylphosphonate, Diphenyl phenylphosphonate, Dimethyl pendylphosphonate, Jetyl pendylphosphonate, Diphenylphosphinic acid, Methyl diphenylphosphinate, Phenyl diphenylphosphinate, Phenylphosphinic acid, Phenylphosphite Examples include methyl inacid, phenyl phenylphosphinate, diphenylphosphine oxide, methyldiphenylphosphine oxide, and triphenylphosphine oxide. Among these, those having a molecular weight of 200 or more are particularly preferable. These organic phosphorus compounds can be used singly or in combination of two or more, and the amount of addition varies depending on the type of phosphorus compound, but is generally 0.01 to 0.3 weight based on the total amount of polyester to be blended. % Mild is preferred. The organophosphorus compound is preferably pre-kneaded with a resin in advance, and more preferably pre-kneaded with at least a polyester A chip.

  In addition, when using the polyester film for food applications such as beverage cans, it is necessary to use the organophosphorus compound in an amount and a compound that meet the standards of the FDA (US Food and Drug Administration), the Sanitation Council for Polyolefins, and the like.

  The above has described in detail the method for producing the polyester film of the present invention by separately melting polyester A and polyester B and mixing them in a molten state, but in other methods, polyester A and polyester B Can be formed in a relatively large crystalline phase state (ie, “coarse mixing”), whereby the half-width of the recrystallization peak at the time of cooling in the differential scanning calorimeter (DSC) of the film is 0.00. It goes without saying that such a polyester film is also a polyester film of the present invention as long as it can be prepared to 25 or less.

  In the polyester film of the present invention, the temperature (Tc2) of the recrystallization peak when the temperature is lowered in the differential scanning calorimeter (DSC) is preferably 180 ° C or higher, more preferably 185 ° C or higher, further preferably 190 ° C or higher, most preferably. Is 192 ° C. or higher. When the temperature of the recrystallization peak is such a temperature, the crystallization rate of the film in the cooling process during the temperature lowering from the melting point becomes faster, and a favorable result can be obtained by suppressing the whitening of the film. If the recrystallization peak temperature is too high, such a polyester film has a poor processability, particularly when a laminated metal plate obtained by laminating this to a metal plate causes poor manufacturing of the film. Therefore, the recrystallization peak temperature is preferably 250 ° C. or lower.

  As described above, suppression of the transesterification reaction between the polyester resins to be blended preferably works to suppress whitening. In the present invention, in particular, the dispersion or / and compatibility of polyester A and polyester B is reduced. That is, the ratio of the recrystallization peak when the temperature is lowered in the target differential scanning calorimeter (DSC) is 1.30 ° C. by making each polyester a “rough mixture” in which a relatively large crystal phase is dispersed. / MW or less, a polyester film excellent in whitening resistance can be obtained. Therefore, a more preferable result can be obtained by adding a crystallization nucleating agent. As such a nucleating agent, both organic fine particles and inorganic fine particles can be used, and examples thereof include silica, kaolin, calcium carbonate, titanium dioxide, polyethylene glycol, and the like, and preferably talc. The addition amount is suitably about 0.0001 to 0.1% by weight per the whole film.

  The reduced viscosity (ηsp / c) of the polyester film of the present invention is preferably 0.80 or more, more preferably 0.85 or more, still more preferably 0.90 or more, and most preferably 0.95 or more. If it is less than 0.80, the hardness of the film after being laminated on the metal plate is insufficient, and it becomes easy to be damaged during processing, and the aluminum or steel plate may be deformed or partially broken during can making. When the reduced viscosity satisfies such a numerical value and the recrystallization peak temperature (Tc2) satisfies the above numerical value, the scratch resistance of the film is further improved.

  The polyester film of the present invention can also be produced by an inflation method, a simultaneous biaxial stretching method, a sequential biaxial stretching method, or the like with a normal film production facility if the above-described conditions are satisfied. Further, the melt-extruded sheet may be used without being stretched, or may be stretched only by one axis.

  Moreover, in this invention, Preferably it heat-processes at 140-270 degreeC after completion | finish of extending | stretching, Preferably it is 140-200 degreeC. At this time, it is possible to improve the adhesiveness of the film to the metal plate and the operability at the time of canning by heat treatment while relaxing at least 2% in the vertical and / or horizontal direction.

  The polyester film of the present invention preferably has a thickness of 3 to 1000 μm, more preferably 5 to 70 μm. Usually, a film is formed by adding a lubricant to polyester. Examples of such lubricants include inorganic lubricants such as silica, kaolin, clay, calcium carbonate, calcium terephthalate, aluminum oxide, titanium oxide, and calcium phosphate, and organic lubricants such as silicone particles. preferable. These are 0.01-5 weight% with respect to the whole total weight of the polyester raw material to blend, Preferably it is 0.02-0.2 weight%. Moreover, in the polyester film of this invention, additives, such as a stabilizer, a coloring agent, antioxidant, an antifoamer, an antistatic agent, can be contained as needed other than a lubricant.

  When producing a film-laminated metal plate using the polyester film of the present invention, the roller or metal plate is heated to 150 to 270 ° C., and the metal plate and the polyester film are bonded together via the roller and then rapidly cooled. What is necessary is to melt and melt at least the surface layer portion of the polyester film in contact with the metal plate. The laminating speed is generally 1 to 200 m / min, preferably 2 to 150 m / min.

The characteristics and tests in this specification were measured and evaluated by the following methods.
1. Reduced viscosity Reduced viscosity (ηsp / c)
0.125 g of the polymer was dissolved in 25 ml of phenol / tetrachloroethane = 6/4 (weight ratio) and measured at 25 ° C. using a Rohde viscosity tube in the evening. The unit is dl / g.

2. The melting point of the polyester, the crystallization temperature of the film, and the half-value width of the crystallization peak. Using DSC3100S manufactured by Mac Science, put the polyester film into the sample pan, cover the pan, and move from room temperature to 280 ° C. in a nitrogen gas atmosphere. The temperature increase was measured at a temperature increase rate of ° C / min. The temperature of the peak top of the melting peak appearing at this time was defined as the melting point of the polyester film, the temperature of the peak top of the low temperature side peak was represented as TmL (° C.), and the temperature of the peak top of the high temperature side peak was represented as TmH (° C.).
Next, the sample having reached 280 ° C. was held as it was for 1 minute, and then the temperature was lowered to room temperature at a rate of 20 ° C./min. The temperature at the peak top of the recrystallization peak at this time was defined as the crystallization temperature Tc2. Further, as shown in FIG. 1, the height h (mW), which is the amount of heat from the base line L to the peak top t of the crystallization peak 1, and the half width w (° C.) at the height h / 2. The ratio w / h (° C./mW) of the half width w and the height h was determined.

3. Film Whitening The film is laminated to an aluminum plate under the following conditions and left in a gear oven at 280 ° C. and 290 ° C. (2 levels) for 1 minute. After that, what was cooled by applying air at 25 ° C. to the film surface of the laminate at a wind speed of 20 m / min was judged visually.
(Lamination condition)
Lamination temperature: 220 ° C
Linear pressure: 10 N / cm

(Evaluation)
◎ ・ ・ ・ ・ No whitening was observed before and after the heat treatment, and the gloss (degree) of the film is high ○ ・ ・ ・ ・ Slight whitening was observed, but the gloss (degree) of the film surface
Δ ··· Whitening was observed and the gloss (degree) of the film surface was low.
× ··· Whitening is remarkable and gloss (degree) of the film surface is low.

4). 2. Hardness of film Scrub the film surface of the laminated plate heated and cooled with a sharp tip of the pencil lead. At that time, the highest pencil hardness that was not scratched was evaluated.

5). Can-making film 3. Laminate on an aluminum plate under the conditions of 240 ° C, and after processing at 240 ° C, observe the presence of damage such as peeling, cutting and cracking of the film after molding the can body visually and with a fluorescent microscope (magnification 80 times). The evaluation was made based on the following criteria.

◎ ... 95 out of 100 cans are not damaged.
○ ······ No damage to 94 dents out of 100 cans.
Δ ············ 70 to 79 out of 100 cans were not bruised.
× ································· 31 out of 100 cans were damaged

Hereinafter, the present invention will be described more specifically with reference to examples.
(Example 1)
Polyethylene terephthalate (reduced viscosity 0.75, catalyst is germanium dioxide) in which silica (Silicia 310 manufactured by Fuji Silysia) was added in advance during the polymerization as polyester A was 60 mm ¢ extruder I (L / D = 29, compression ratio 4. 2) and melted at 275 ° C. Polyesterene terephthalate (1200S manufactured by Toray Industries, reduced viscosity 1.30) and organophosphorus compound (ADK STAB PEP-45: manufactured by Asahi Denka Kogyo Co., Ltd.) 300 ppm as polyester B were separated into another 60 mmφ extruder II (L / D = 29). The mixture was put into a compression ratio of 4.2) and melted at 240 ° C. Thereafter, 90 mmφ extruder III (L / D = 25, compression part) in the molten state so that the amount ratio (I / II) = 4/6 (weight ratio) of the melted product from extruder I and extruder II L / D = 12, compression ratio 1.5), charged, mixed, melted and extruded from a T-die to obtain an unstretched sheet having a thickness of 200 μm. At this time, the temperature of the cylinder part and the filter part (200 mesh) of the extruder III is 260 ° C., the temperature from the screw tip of the extruder to the T-die is 255 ° C., and the temperature of the resin discharged from the T-die is 257 ° C. It was made to become. The pressure of the resin immediately before entering the T-die was set to 8.8 MPa (90 kgf / cm ² ).
Then, this unstretched sheet is guided to a roll stretching machine, stretched 3.3 times in the longitudinal direction at 70 ° C., and further stretched 3.5 times in the transverse direction at 95 ° C. with the tenter. A film having a thickness of 17 μm was obtained by heat setting at 150 ° C. while relaxing 3% in the lateral direction.

(Example 2)
Polypropylene terephthalate (Toray Industries, 1200S, reduced viscosity) obtained by pre-kneading 300 ppm of an organic phosphorus compound (Adeka Stub PEP-45: manufactured by Asahi Denka Kogyo Co., Ltd.) with polyester B as a raw material of the extruder II in Example 1 A film was obtained in exactly the same manner except for 1.30). The temperature of the resin exiting the T-die was 258 ° C.

(Comparative Example 1)
In Example 1, the temperature of the filter part of the extruder III is 285 ° C., the temperature from the screw tip of the extruder III to the T-die is 282 ° C., and the temperature of the resin finally coming out of the T-die is 266. A film was obtained in the same manner as in Example 1 except that the temperature was changed to ° C.

(Example 3)
A film was obtained in the same manner as in Example 1 except that the compression ratio of the extruder III was 4.0. The conditions such as temperature setting were all the same as in Example 1, but the temperature of the resin exiting the T-die was 263 ° C.

(Comparative Example 2)
The polyesters A and B used in Example 1 and the organophosphorus compound were charged as pellets into Extruder III (L / D = 25, compression ratio 4.0) so as to have the same composition ratio as Example 1, and temperature conditions Was obtained in the same manner as in Example 1 except that the film was extruded in the same manner as in Example 1. The temperature conditions were set the same as in Example 1, but the temperature of the grease from the T-die was 265 ° C.

Example 4 A film was obtained in the same manner as in Example 1 except that polytrimethylene terephthalate (reduced viscosity 0.98) was used instead of polybutylene terephthalate. The temperature of the resin exiting the T-die was 260 ° C.

(Example 5)
A film was obtained in the same manner as in Example 1 except that a static mixer (N20 manufactured by Noritake Company Limited, element number 12, cylinder temperature 258 ° C.) was used instead of the extruder III. The temperature of the resin exiting the T-die was 258 ° C.

(Example 7)
A film having a thickness of 38 μm was obtained in the same manner as in Example 1, and then molded at 90 ° C. using a mold to produce a liquid crystal surface cover for mobile phones having a depth of 5 mm × width 50 mm × length 50 mm. did. It was confirmed that it was not whitened and was good for molding.

(Comparative Example 3)
Polyethylene terephthalate and polybutylene terephthalate containing true spherical silica having an average particle diameter of 1.5 μm were mixed (dry blended) at 42:58 (weight ratio), and the extruder III (L / D = 25, L / D of the compression part) D = 12, compression ratio 4.0) was added as pellets, and a 12 μm film was obtained in the same manner as in Comparative Example 2 except that all temperature conditions were 290 ° C. The temperature of the fats and oils which came out of T-die was 290 degreeC. It should be noted that only one DSC melting point peak could be seen due to the high resin temperature.

(Comparative Example 4)
30% by weight of polyethylene terephthalate (reduced viscosity 0.76 (extreme viscosity 0.67)) containing 0.1% by weight of silica having an average particle size of 1.0 μm and polybutylene terephthalate (Made by Engineering Engineering Plastics, Novado Wool 5009AS) ) 70% by weight was charged into the extruder. This extruder had a slow compression screw of 75 mmφ, L / D = 45, compression ratio 3.5, L / D = 30 in the compression part. Further, a 12 μm film was obtained in the same manner as in Example 1 except that the temperature conditions were all 265 ° C. The temperature of the resin from T Sendai was 290 ° C. DSC showed two melting point peaks, but because of the large compression ratio and slow compression screw, the half-value width of the recrystallization peak at the time of cooling was large, and many whitenings were observed.

(Comparative Example 5)
50% by weight of polyethylene terephthalate (reduced viscosity 0.80 (ultimate viscosity 0.70)) containing 0.1% by weight of silica having an average particle size of 1.0 mm and polybutylene terephthalate (Made by Mitsubishi Engineering Plastics, Novado Wool) 5010) 50 wt% was used and charged into the extruder. This extruder was extruded from a T-die with a pent type extruder (Ikegai Koki Kikai, PCM-45). The temperature conditions of the extruder were all 280 ° C., and the resin temperature coming out of the T-die was 280 ° C. The film was stretched 3.4 times longitudinally at 68 ° C, then stretched 4.0 times at 80 ° C with a tenter, and then heat-fixed with a tenter at 240 ° C for 1 second, followed by 5% width relaxation at 160 ° C and thickness. A film of 25 μm was obtained. Although two melting point peaks were observed by DSC, the temperature was slightly high, and the half-width of the recrystallization peak at the time of temperature decrease was large due to the twin screw extruder, and many whitenings were observed.

(Examples 7 and 8)
A film was obtained in the same manner as in Example 1 except that the amounts of the resins from Extruder I and Extruder II were 85:15 and 20:80 (weight ratio), respectively.

Example 9
Example 1 except that polyhexamethylene terephthalate having a reduced viscosity of 0.85 was used instead of polybutylene terephthalate, and the ratio of the resins from Extruder I and Extruder II was 90:10 (weight ratio). In the same manner as above, a film was obtained.

(Example 10)
Implemented except that polyethylene-2,6-naphthalate having a reduced viscosity of 0.88 was used in place of polybutylene terephthalate, and the ratio of resins from Extruder I and Extruder II was 90:10 (weight ratio). In the same manner as in Example 1, a film was obtained.

(Example 11)
A film was obtained in the same manner as in Example 2 except that the heat setting was 220 ° C.

(Comparative Examples 6 and 7)
A film was obtained in the same manner as in Comparative Example 4 except that only polypropylene (terephthalate) containing 0.1 wt% silica or only polypropylene (terephthalate) containing 0.1 wt% silica was used as a raw material.

(Example 12)
In the same manner as in Example 1, except that the polyesters A and B and the organophosphorus compound in Example 1 were charged into the extruder as pellets so as to have the same composition ratio and extruded under the same temperature conditions as in Example 1. Got. This extruder had a screw of 90 mmφ, L / D = 25, compression ratio 1.5, L / D = 12 of the compression part, and a double flight type compression part. The temperature conditions were set the same as in Example 1, but the temperature of the resin exiting the T-die was 257 ° C.
Table 1 shows the production conditions of the polyester films produced in Examples 1 to 5, 7 to 12 and Comparative Examples 1 to 7, and Table 2 shows the characteristic values and test results.

  The polyester film of the present invention is used as various food packaging, general industrial, optical, electrical material and molding films. Specifically, for general packaging, antistatic, gas barrier, metal laminating, heat sealing, antifogging, metal deposition, easy tearing, easy opening, bag making packaging, retort packaging, boil packaging, medicine packaging Suitable for use, easy adhesion, magnetic recording, capacitor, ink ribbon, transfer, adhesive label, stamping foil, gold and silver thread, -tracing material, mold release, shrink link, etc. In particular, it is particularly suitable for molding processing (molding material when a single film is molded into a target article) and metal laminating (a constituent material of a film laminated metal plate).

It is a schematic diagram of the chart which shows the recrystallization peak at the time of the temperature fall by the differential scanning calorimeter (DSC) of a polyester film. FIG.

Explanation of symbols

1 DSC chart L Baseline w Half width (° C)
h Height (mW)
h / 2 1/2 of the height
t Peak Top

Claims (6)

  It consists of a polyester-based resin composition in which 10 to 90% by weight of a polyester (A) containing ethylene terephthalate as a main constituent and 90 to 10% by weight of a crystalline polyester resin (B) different from the polyester resin (A) are blended. The film is a differential scanning calorimeter (DSC) having a ratio w / h of a half width w (° C.) to a height h (mW) of a recrystallization peak (Tc2) at the time of temperature reduction of 1.30 (° C./mW). ) Polyester film characterized by   The polyester resin composition is composed of 10 to 70% by weight of polyester (A) whose main constituent is ethylene terephthalate, and the crystalline polyester (B) is polybutylene terephthalate (PBT), polytetramethylene terephthalate (PTT), polyethylene- The polyester film according to claim 1, which is a polyester selected from any of 2,6-naphthalate (PEN).   The peak temperature of Tc2 of Claim 1 is 180 degreeC or more, The polyester film characterized by the above-mentioned   The polyester film according to claim 1 or 2, wherein the reduced viscosity of the polyester film is 0.80 or more.   The polyester film according to any one of claims 1, 2, and 3 is for metal plate lamination.   The polyester film according to any one of claims 1, 2, and 3 is for molding processing.