WO2019142781A1

WO2019142781A1 - Biaxially oriented polyester film

Info

Publication number: WO2019142781A1
Application number: PCT/JP2019/000918
Authority: WO
Inventors: 昇玉利; 考道後藤
Original assignee: 東洋紡株式会社
Priority date: 2018-01-22
Filing date: 2019-01-15
Publication date: 2019-07-25
Also published as: TW201936734A; JPWO2019142781A1

Abstract

[Problem] To achieve a polyester film which has excellent pinhole resistance and excellent bag breakage resistance after boiling processing or retort processing, while being not susceptible to cracking of a gas barrier layer during a protective layer formation step and thus exhibiting excellent gas barrier properties. [Solution] A biaxially oriented polyester film which is formed from a polyester resin composition that contains 60-100% by weight of a polybutylene terephthalate resin (A) and 0-40% by weight of a polyester resin (B) other than the polybutylene terephthalate resin (A), and which satisfies the requirements (a) and (b) at the same time. (a) The dimensional change rate of the temperature-dimensional change curve with respect to the film original length at 120°C as determined with use of TMA is from -2.0% to 4.0% in the longitudinal direction of the film. (b) The thermal shrinkage rate of the film at 150°C in the longitudinal direction is from 1.0% to 5.0%.

Description

Biaxially oriented polyester film

The present invention relates to a polyester film used in the field of packaging of food, medicine, industrial products and the like. More specifically, it is mainly composed of polybutylene terephthalate resin which is excellent in pinhole resistance, bag-proof resistance after boiling treatment and retorting treatment, and is excellent in gas-barrier property with little cracking of the gas barrier layer in the protective layer forming step. The present invention relates to a biaxially oriented polyester film.

Since polybutylene terephthalate (hereinafter, polybutylene terephthalate is abbreviated as PBT) resin is more excellent in impact resistance, gas barrier property and chemical resistance than polyethylene terephthalate (hereinafter, polyethylene terephthalate is abbreviated as PET) resin, it is a film for food packaging Applications are also being considered in the field of films such as draw forming films.

For example, in Patent Document 1, a biaxially oriented PBT-based film comprising a polyester-based resin composition in which a polyester resin other than PBT resin is blended in a range of 40% by weight or less with respect to PBT resin The angle between the molecular chain main axes is 30 ° or less, the thermal shrinkage at 150 ° C. is 4.0% or less in both the width direction and the longitudinal direction, and the intrinsic viscosity of the film is 0.80 dl / g or more, 1.2 dl / g It is disclosed that it can be suitably used for retort pouch packaging and water packaging by setting it to g or less.

However, since the thermal contraction rate in the longitudinal direction is suppressed to a low value, it is considered that the film is easily stretched in the longitudinal direction in the protective layer forming step, and the gas barrier property is lowered.

On the other hand, in Patent Document 2, a film mainly composed of PET resin is used as a base material layer, and in a laminated film having at least one metal oxide layer, the thermal shrinkage at 150 ° C. is 0.6 to 3.0%. There is disclosed a packaging member having sufficient impact strength even after hot water treatment such as retort treatment and boiling treatment, and having excellent gas barrier properties.

However, there is no disclosure of specific substrate layer conditions for satisfying the above characteristics.

International Publication No. 2016/171173 International Publication No. 2017/170574

The present invention has been made on the background of the problems of the prior art. That is, the object of the present invention relates to a polyester film used in the field of packaging of food, medicine, industrial products and the like. More specifically, it is possible to obtain a laminated polyester film which is excellent in pinhole resistance, tear resistance after boiling treatment and retort treatment, and is excellent in gas barrier properties with less cracking of the gas barrier layer in the protective layer forming step. is there.

As a result of intensive studies to achieve the above object, the present invention is pin resistant by setting the dimensional change rate and heat shrinkage rate at 120 ° C. of a biaxially oriented stretched film mainly composed of PBT resin as a specific range. The present inventors have found that a laminated polyester film excellent in hole property, bag-proof resistance after being subjected to boiling treatment and retort treatment, and having few cracks in the gas barrier layer in the protective layer forming step and excellent in gas barrier properties can be obtained.

That is, the present invention has the following configuration.
1. A polyester resin composition comprising 60 to 100% by weight of polybutylene terephthalate resin (A) and 0 to 40% by weight of polyester resin (B) other than polybutylene terephthalate resin (A), (a) and (b) A biaxially oriented polyester film that simultaneously satisfies
(A) The dimensional change at 120 ° C. with respect to the film original length of the temperature dimensional change curve measured using TMA (thermal mechanical analyzer) is −2.0% to 4.0% in the longitudinal direction of the film.
(B) The thermal shrinkage at 150 ° C. in the longitudinal direction of the film is 1.0% to 5.0%.
2. The value of piercing strength measured by a piercing strength test according to JIS-Z1707 is 8.0 N or more. The biaxially oriented polyester film as described in.
3. The thickness accuracy of the entire width of the film is 1 to 20%. Or 2. The biaxially oriented polyester film as described in.

The inventor of the present invention is a laminated polyester excellent in pinhole resistance, bag-proof resistance after boiling treatment and retorting treatment by such a technology, and is excellent in gas barrier properties with less cracking of the gas barrier layer in the protective layer forming step. It became possible to obtain a film.

Hereinafter, the present invention will be described in detail.
[Polyester resin composition]
The polyester resin composition used for the film of the present invention contains the PBT resin (A) as a main component, and the content of the PBT resin (A) is preferably 60% by weight or more, and preferably 75% by weight or more. Furthermore, 85 weight% or more is preferable. If it is less than 60% by weight, the pinhole resistance and the bag resistance will be reduced.
The PBT resin (A) used as the main component preferably contains 90 mol% or more, more preferably 95 mol% or more, and still more preferably 98 mol% or more of terephthalic acid as a dicarboxylic acid component. Preferably it is 100 mol%. As a glycol component, 1,4-butanediol is preferably 90 mol% or more, more preferably 95 mol% or more, still more preferably 97 mol% or more, and most preferably 1,4-butane at the time of polymerization. It is not included except by-products generated by the ether bond of diol.

The polyester resin composition used for the film of the present invention contains a polyester resin (B) other than PBT resin (A) for the purpose of adjusting film forming property when performing biaxial stretching and mechanical properties of the obtained film. be able to.
Polyester resins (B) other than PBT resin (A) are polyester resins such as PET, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, or isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, cyclohexane dicarboxylic acid , PBT resin copolymerized with at least one dicarboxylic acid selected from the group consisting of adipic acid, azelaic acid and sebacic acid, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol , 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol and polycarbonate Selected from the group consisting of PBT resin, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid and sebacic acid in which at least one diol component selected from the group is copolymerized PBT resin in which at least one dicarboxylic acid is copolymerized, or 1,3-butanediol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1 At least one diol component selected from the group consisting of 1,6-hexanediol, diethylene glycol, cyclohexane glycol, polyethylene glycol, polytetramethylene glycol and polycarbonate, selected from copolymerized PET resins At least one resin.

Among them, PET resin is high in melting point and excellent in heat resistance, so dimensional change is difficult, and compatibility with PBT resin is also excellent, and transparency is excellent, and polyester resin (B) other than PBT resin (A) is copolymerized PET resins are preferred, and PET is particularly preferred.

The lower limit of the intrinsic viscosity of the PBT resin (A) used in the film of the present invention is preferably 0.8 dl / g, more preferably 0.95 dl / g, and still more preferably 1.0 dl / g.
When the intrinsic viscosity of the PBT resin (A) is less than 0.9 dl / g, the intrinsic viscosity of the film obtained by film formation may be reduced, and the bag breaking strength, the piercing strength and the like may be reduced.
The upper limit of the intrinsic viscosity of PBT resin (A) is preferably 1.3 dl / g. When the above is exceeded, the stress at the time of film stretching becomes too high, and the film forming property may be deteriorated. Furthermore, when using a PBT resin with a high intrinsic viscosity, it is necessary to raise the extrusion temperature because the melt viscosity of the resin is high, but when the PBT resin is extruded at a higher temperature, decomposition products may be easily released. .

The upper limit of the addition amount of the polyester resin (B) other than the PBT resin (A) is preferably 40% by weight or less, more preferably 35% by weight or less, and particularly preferably 15% by weight or less. When the addition amount of the polyester resin (B) other than the PBT resin (A) exceeds 40% by weight, the pinhole resistance and the bag resistance may be impaired, and the transparency and the gas barrier properties may be deteriorated.

The polyester resin composition may contain, if necessary, conventionally known additives such as a lubricant, a stabilizer, a colorant, an antioxidant, an antistatic agent, an ultraviolet absorber and the like.

As a lubricant for adjusting the dynamic friction coefficient of the film of the present invention, in addition to inorganic lubricants such as silica, calcium carbonate and alumina, organic lubricants are preferable, silica and calcium carbonate are more preferable, and silica reduces haze It is particularly preferable in that By these, transparency and slipperiness can be expressed.

The lower limit of the content of the lubricant in the polyester resin composition is preferably 100 ppm by weight, more preferably 800 ppm by weight, and if it is less than 100 ppm by weight, slipperiness may be lowered. The upper limit of the content of the lubricant is preferably 20000 ppm by weight, more preferably 1000 ppm by weight, and particularly preferably 1800 ppm by weight. If it exceeds 20000 ppm by weight, the transparency may be reduced.

[Method of producing biaxially oriented polyester film]
As a suitable method for obtaining the biaxially oriented polyester film of the present invention, a T-die system is preferable from the viewpoint of thickness accuracy in the width direction. In the inflation method, it is difficult to increase the draw ratio due to the manufacturing method, and thickness defects in the width direction may occur.
In addition, as a suitable method for obtaining the biaxially oriented polyester film of the present invention, when casting a molten polyester resin composition on a cooling roll, it is possible to cite a polyester resin composition raw material of the same composition and cast.
Since the PBT resin has a high crystallization rate, crystallization also proceeds during casting. At this time, in the case of casting in a single layer without multilayering, these crystals grow into large size spherulites because there is no barrier that can suppress the growth of crystals. As a result, the yield stress of the obtained unstretched sheet becomes high, and the sheet tends to break when stretched in the longitudinal direction.
Moreover, since crystallization proceeds also during stretching in the longitudinal direction, the film is easily broken at the time of stretching in the width direction, and a film having insufficient tear strength and piercing strength of the obtained biaxially oriented polyester film It becomes.
Furthermore, according to the thickness of the film in the width direction, a large variation occurs in crystal growth and a density difference occurs. As a result, unevenness in stretching stress may occur during subsequent stretching in the longitudinal direction and width direction, and the thickness accuracy of the obtained biaxially oriented polyester film may be reduced.

Specifically, the method for producing a biaxially oriented PBT film of the present invention comprises the molten fluid formed in the step (1) of melting a polyester resin composition containing 60% by weight or more of PBT resin to form a molten fluid The laminated fluid formed in the step (2) of forming a laminated fluid having a lamination number of 60 or more is discharged from a die, brought into contact with a cooling roll and solidified to form a laminated body (3); It has at least the step (4) of axial stretching.
Other steps may be inserted between the step (1) and the step (2) and between the step (2) and the step (3). For example, a filtration step, a temperature change step and the like may be inserted between the step (1) and the step (2). In addition, a temperature change step, a charge addition step and the like may be inserted between the step (2) and the step (3). However, between the step (2) and the step (3), there should not be a step of destroying the laminated structure formed in the step (2).

In the step (1), the method for melting the polyester resin composition to form a molten fluid is not particularly limited, but a suitable method is to cite a method of heating and melting using a single screw extruder or a twin screw extruder. Can.

The method for forming the laminated fluid in step (2) is not particularly limited, but a static mixer and / or a multilayer feed block is more preferable from the viewpoint of facility simplicity and maintainability. Further, from the viewpoint of uniformity in the sheet width direction, one having a rectangular melt line is more preferable. It is further preferred to use a static mixer or multilayer feed block with rectangular melt lines. The resin composition comprising a plurality of layers formed by combining a plurality of polyester resin compositions may be passed through one or more of a static mixer, a multilayer feed block and a multilayer manifold.

The theoretical number of layers in step (2) needs to be 60 or more. The lower limit of the theoretical stacking number is preferably 200, and more preferably 500. If the theoretical number of layers is too small, the distance between layer interfaces will be long and the crystal size will be too large, resulting in breakage at the time of stretching, reduction in mechanical strength and reduction in thickness accuracy. In addition, the degree of crystallinity in the vicinity of both ends of the sheet may be increased, the film formation may be unstable, and the transparency after molding may be reduced. The upper limit of the theoretical number of layers in step (2) is not particularly limited, but is preferably 100,000, more preferably 10,000, and still more preferably 7,000. Even if the theoretical stacking number is extremely increased, the effect may be saturated.

When the lamination in step (2) is performed by a static mixer, the number of theoretical laminations can be adjusted by selecting the number of elements of the static mixer. A static mixer is generally known as a static mixer without a drive (line mixer), and the fluid entering the mixer is sequentially stirred and mixed by the elements. However, when the high viscosity fluid is passed through a static mixer, division and lamination of the high viscosity fluid occur to form a laminated fluid. The high-viscosity fluid is split into two and then merged and stacked each time it passes through one element of the static mixer. For this reason, when the high viscosity fluid is passed through a static mixer with the number of elements n, a layered fluid with the theoretical number of laminations N = 2 is formed.

A typical static mixer element has a structure in which a rectangular plate is twisted 180 degrees, and depending on the direction of twist, there are right and left elements, and the dimension of each element is 1.5 times the length of the diameter Is based on The static mixer that can be used in the present invention is not limited to such.

When the lamination in the step (2) is performed with a multilayer feed block, the number of theoretical laminations can be adjusted by selecting the number of divisions / laminations of the multilayer feed block. A plurality of multilayer feed blocks can be installed in series. Further, it is also possible to use the high viscosity fluid itself supplied to the multilayer feed block as a laminated fluid. For example, when the number of layers of high viscosity fluid supplied to the multilayer feed block is p, the number of divisions / layers of the multilayer feed block is q, and the number of multilayer feed blocks installed is r, the number N of layers of laminated fluid is N = p × (q to the power of r)
In addition, when multilayering by the polyester resin composition of the same composition like this invention, the above-mentioned multilayering apparatus can also be introduce | transduced into the melt line from extrusion to a die | dye only using one extruder. .

In step (3), the laminated fluid is discharged from the die and brought into contact with the cooling roll to solidify.

The lower limit of the die temperature is preferably 255 ° C., more preferably 260 ° C., particularly preferably 265 ° C. If the temperature is lower than the above range, the discharge may not be stable and the thickness may be uneven.
In addition, the PET resin retained in the melt extrusion process of the resin may become unmelted and be mixed in the film, which may deteriorate the quality of the film. The upper limit of the resin melting temperature is preferably 285 ° C, more preferably 280 ° C, and most preferably 275 ° C. If the above is exceeded, decomposition of the resin proceeds and the film becomes brittle.
The upper limit of the die temperature is preferably 320 ° C., more preferably 300 ° C. or less, still more preferably 280 ° C. or less. If the thickness exceeds the above range, the thickness may not be uniform, and the resin may be deteriorated to cause appearance defects due to die lip stains and the like.

The upper limit of the cooling roll temperature is preferably 40 ° C, more preferably 20 ° C or less. When it exceeds the above, the degree of crystallization at the time of cooling and solidification of the molten polyester resin composition may become too high, which may make stretching difficult. The lower limit of the temperature of the cooling roll is preferably 0 ° C., and if it is less than the above, the effect of suppressing crystallization when the molten polyester resin composition is solidified by cooling may be saturated. When the temperature of the cooling roll is in the above range, it is preferable to lower the humidity of the environment near the cooling roll to prevent condensation.

When the molten polyester resin composition is cast on the surface of the cooling roll, the temperature of the surface of the cooling roll rises because the high temperature resin contacts the surface. Normally, chill rolls flow cooling water internally through pipes to cool, but secure a sufficient amount of cooling water, devise piping layout, perform maintenance to prevent sludge from adhering to pipes, etc. It is necessary to reduce the temperature difference in the width direction. In particular, care must be taken when cooling at low temperature without using methods such as multi-layering.
At this time, the thickness of the unstretched sheet is preferably in the range of 15 to 2500 μm. More preferably, it is 500 micrometers or less, More preferably, it is 300 micrometers or less.

The casting in the multilayer structure described above is performed with at least 60 layers, preferably 250 layers or more, and more preferably 1000 layers or more. When the number of layers is small, the spherulite size of the unstretched sheet becomes large, and the effect of improving the stretchability is small, and in addition, the mechanical strength and the thickness accuracy of the obtained biaxially stretched film decrease.

Next, the extending | stretching method of process (4) is demonstrated. The stretching method can be either simultaneous biaxial stretching or sequential biaxial stretching, but it is easy to increase the plane orientation coefficient from the viewpoint of pinhole resistance and tear resistance, and it is easy to improve the uniformity of the film thickness in the width direction Sequential biaxial stretching is most preferable from the viewpoint of high film formation speed and high productivity.

The lower limit of the stretching temperature in the longitudinal direction (hereinafter, MD) is preferably 55 ° C., more preferably 60 ° C. If the temperature is less than 55 ° C., breakage may easily occur, and stretching at a low temperature strengthens the longitudinal orientation, so that the shrinkage stress in the heat setting process becomes large, so molecular orientation in the width direction Distortion may increase, resulting in a decrease in straight straight tearability in the longitudinal direction. The upper limit of the MD stretching temperature is preferably 100 ° C., more preferably 95 ° C. If the temperature exceeds 100 ° C., the mechanical properties may be deteriorated since the orientation is not applied.

The lower limit of the MD stretching ratio is preferably 2.5 times, particularly preferably 2.7 times. If it is less than the above, the mechanical properties may be reduced because orientation is unlikely to take place.
The upper limit of the MD stretching ratio is preferably 3.8 times, more preferably 3.4 times, and particularly preferably 3.0 times. If the above is exceeded, the effect of mechanical strength and thickness unevenness improvement may be saturated.

The lower limit of the stretching temperature in the width direction (hereinafter referred to as TD) is preferably 60 ° C. When the stretching temperature is less than the above, breakage may easily occur. The upper limit of the TD stretching temperature is preferably 100 ° C. If the temperature exceeds the above range, the mechanical properties may be deteriorated since no orientation is applied.

The lower limit of the TD stretch ratio is preferably 3.5 times, more preferably 3.6 times, and particularly preferably 3.7 times. If it is less than the above, the degree of orientation in the width direction is reduced, so that the mechanical strength and the thickness unevenness may be deteriorated. The upper limit of the TD stretching ratio is preferably 5 times, more preferably 4.6 times, and particularly preferably 4.2 times. If the above is exceeded, the effect of mechanical strength and thickness unevenness improvement may be saturated.

The lower limit of the TD heat setting temperature is preferably 185 ° C, more preferably 190 ° C. If it is less than the above, the thermal contraction rate becomes large, the film shrinks in the protective layer forming step, and the laminated gas barrier layer may be cracked, which may result in the deterioration of the gas barrier property. The upper limit of the TD heat setting temperature is preferably 210 ° C. When the temperature exceeds the above range, the film melts, and may not be extremely brittle even if it does not melt, and the thermal shrinkage in the MD direction decreases and the protective layer In the forming step, the film may be stretched, and the laminated gas barrier layer may be cracked, which may lead to a decrease in the gas barrier property.

The lower limit of the TD relaxation rate is preferably 0.5%, and if it is less than the above, breakage may easily occur during heat setting. The upper limit of the TD relaxation rate is preferably 10%, and if it exceeds the above, not only sag may occur to cause thickness unevenness, but also shrinkage in the longitudinal direction at the time of heat setting may be increased. The distortion of molecular orientation may be large, and dimensional stability may be uneven in the width direction.

[Characteristics of biaxially oriented polyester film]
In the biaxially oriented polyester film of the present invention, the lower limit of the film thickness is preferably 3 μm, more preferably 5 μm, and still more preferably 8 μm. If it is less than 3 μm, the strength as a film may be insufficient.
The upper limit of the film thickness is preferably 100 μm, more preferably 75 μm, and still more preferably 50 μm. If it exceeds 100 μm, it becomes too thick and processing for the purpose of the present invention may become difficult.

The lower limit of the intrinsic viscosity of the biaxially oriented PBT film of the present invention is preferably 0.80 dl / g, more preferably 0.85 dl / g, still more preferably 0.90 dl / g, particularly preferably 0 It is .95 dl / g. Impact strength, puncture resistance, etc. will be improved as it is more than the above.
The upper limit of the intrinsic viscosity of the biaxially oriented PBT film is preferably 1.2 dl / g, more preferably 1.1 dl / g. When it exceeds the above, the stress at the time of stretching becomes too high, and the film forming property is deteriorated.

The biaxially oriented PBT film of the present invention preferably has a resin of the same composition throughout the entire film.

The lower limit of the degree of plane orientation (ΔP) of the biaxially oriented polyester film of the present invention is preferably 0.145, more preferably 0.148, still more preferably 0.151. If it is less than the above range, the plane orientation may be weak, the puncture strength may be reduced, and the resistance to breakage may be reduced.
The upper limit of ΔP of the biaxially oriented polyester film of the present invention is preferably 0.200. If the above is exceeded, the improvement effect may be saturated.

The upper limit of the thermal shrinkage after heating at 150 ° C. for 15 minutes in the MD direction of the biaxially oriented polyester film of the present invention is 5.0%, preferably 4.0%, more preferably 3.3%. is there. Within the above range, the expansion and contraction of the film can be suppressed in the protective layer forming step where tension is applied, and the deterioration of the gas barrier properties due to the cracking of the gas barrier layer can be suppressed. When it exceeds the above, the film may be shrunk in the protective layer forming step to cause cracking of the gas barrier layer and as a result, the gas barrier properties may be lowered.
The lower limit of the heat shrinkage after heating at 150 ° C. for 15 minutes in the MD direction of the biaxially oriented polyester film of the present invention is 1.0%, and 2.0% is particularly preferable. Within the above range, the expansion and contraction of the film can be suppressed in the protective layer forming step where tension is applied, and the deterioration of the gas barrier properties due to the cracking of the gas barrier layer can be suppressed. If it is less than the above, the film may be stretched in the protective layer forming step to cause cracking of the gas barrier layer and as a result, the gas barrier properties may be reduced.

The upper limit of the dimensional change rate at 120 ° C. in the MD direction assuming a protective layer forming step measured using TMA of the biaxially oriented polyester film of the present invention is 4.0%, preferably 3.0%. . Within the above range, elongation of the film can be suppressed in the protective layer forming step where tension is applied, and deterioration in gas barrier properties due to cracking of the gas barrier layer can be suppressed. When it exceeds the above, the film may be stretched in the protective layer forming step to cause cracking of the gas barrier layer and as a result, the gas barrier properties may be lowered. The lower limit of the dimensional change at 120 ° C. in the MD direction of the biaxially oriented polyester film of the present invention is −2.0%, preferably 0%. The shrinkage | contraction of a film is suppressed in the protective layer formation process to which tension | tensile_strength is applied as it is in the said range, and the fall of the gas barrier property by the crack of a gas barrier layer can be suppressed. If it is less than the above, the film may be shrunk in the protective layer forming step to cause cracking of the gas barrier layer and as a result, the gas barrier properties may be reduced.

The lower limit of the puncture strength of the biaxially oriented polyester film of the present invention is preferably 8N. When it is less than the above, the strength may be insufficient when used as a bag. The upper limit of the piercing strength is preferably 20N. If the above is exceeded, the improvement effect may be saturated.

As a means for improving the processability of the biaxially oriented polyester film of the present invention, it is effective to adjust the slipperiness of at least one side of the film. The upper limit of the dynamic friction coefficient of at least one surface of the film is preferably 0.4 or less, preferably 0.39 or less, and most preferably 0.38 or less.

The upper limit of the haze per thickness of the biaxially oriented polyester film of the present invention is preferably 0.66% / μm, more preferably 0.60% / μm, still more preferably 0.53% / μm. . If the above is exceeded, the quality of printed characters and images may be impaired when the film is printed.

A printing layer may be laminated on the biaxially oriented polyester film of the present invention.
As a printing ink which forms a printing layer, resin-containing printing ink of an aqueous | water-based and solvent type can use it preferably. Here, examples of the resin used for the printing ink include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins and mixtures thereof. For printing inks, known are antistatic agents, light blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, antifoaming agents, crosslinking agents, blocking agents, antioxidants, etc. Additives may be included.

It does not specifically limit as a printing method for providing a printing layer, Well-known printing methods, such as an offset printing method, a gravure printing method, the screen-printing method, can be used. For drying of the solvent after printing, known drying methods such as hot air drying, hot roll drying, infrared drying and the like can be used.

In addition, the biaxially oriented polyester film of the present invention may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, surface roughening treatment, as long as the object of the present invention is not impaired. Anchor coating treatment, printing, decoration, etc. may be given.

An inorganic thin film layer or a gas barrier layer such as a metal foil such as aluminum foil can be provided on at least one side of the biaxially oriented polyester film of the present invention.

In the case of using an inorganic thin film layer as the gas barrier layer, the inorganic thin film layer is a thin film made of metal or inorganic oxide. The material for forming the inorganic thin film layer is not particularly limited as long as it can be made into a thin film, but from the viewpoint of gas barrier properties, inorganic oxide such as silicon oxide (silica), aluminum oxide (alumina), and a mixture of silicon oxide and aluminum oxide Are preferably mentioned. In particular, a composite oxide of silicon oxide and aluminum oxide is preferable from the viewpoint of achieving both the flexibility and the compactness of the thin film layer.

In this composite oxide, the mixing ratio of silicon oxide and aluminum oxide is preferably in the range of 20 to 70% of Al by weight ratio of metal components. When the Al concentration is less than 20%, the water vapor gas barrier properties may be lowered. On the other hand, if it exceeds 70%, the inorganic thin film layer tends to be hard, and the film may be broken during secondary processing such as printing or laminating, and the gas barrier properties may be lowered. Here, silicon oxide refers to various silicon oxides such as SiO and SiO ₂ or a mixture thereof, and aluminum oxide refers to various aluminum oxides such as AlO and Al ₂ O ₃ or a mixture thereof.

The thickness of the inorganic thin film layer is usually 1 to 100 nm, preferably 5 to 50 nm. If the film thickness of the inorganic thin film layer is less than 1 nm, satisfactory gas barrier properties may not be obtained in some cases. On the other hand, even if it exceeds 100 nm and is excessively thick, the corresponding improvement effect of gas barrier properties is obtained It is rather disadvantageous in terms of bending resistance and manufacturing cost.

There is no restriction | limiting in particular as a method to form an inorganic thin film layer, For example, well-known vapor deposition, such as a physical vapor deposition method (PVD method), such as a vacuum evaporation method, sputtering method, ion plating method, or a chemical vapor deposition method (CVD method) The law may be adopted as appropriate. Hereinafter, a typical method of forming an inorganic thin film layer will be described by taking a silicon oxide / aluminum oxide based thin film as an example. For example, when using a vacuum evaporation method, a mixture of SiO ₂ and Al ₂ O ₃ or a mixture of SiO ₂ and Al is preferably used as an evaporation raw material. Usually, particles are used as the vapor deposition raw material. At this time, the size of each particle is preferably such that the pressure at the time of vapor deposition does not change, and the preferred particle diameter is 1 mm to 5 mm. For heating, a method such as resistance heating, high frequency induction heating, electron beam heating, or laser heating can be adopted. In addition, reactive vapor deposition using means such as introduction of oxygen, nitrogen, hydrogen, argon, carbon dioxide gas, water vapor or the like as a reaction gas, or addition of ozone or ion assist may be employed. Furthermore, film forming conditions can be arbitrarily changed, such as applying a bias to the deposition target (laminated film to be deposited) or heating or cooling the deposition target. Such vapor deposition material, reaction gas, bias of the vapor-deposited body, heating / cooling, etc. can be similarly changed also in the case of employing the sputtering method or the CVD method. Furthermore, the printing layer may be laminated on the above-mentioned inorganic thin film layer.

In the present invention, it is preferable to provide a protective layer on the gas barrier layer. The gas barrier layer made of a metal oxide is not a completely dense film, but minute defects are scattered. By coating a specific resin composition for a protective layer to be described later on the metal oxide layer to form a protective layer, the resin in the resin composition for the protective layer penetrates into the defect portion of the metal oxide layer, As a result, the effect of stabilizing the gas barrier properties can be obtained. In addition, the gas barrier performance of the laminated film is also greatly improved by using a material having gas barrier properties for the protective layer itself.

Examples of the protective layer include those obtained by adding an epoxy-based, isocyanate-based or melamine-based curing agent to a urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, or polybutadiene-based resin. . Examples of the solvent (solvent) used when forming the protective layer include aromatic solvents such as benzene and toluene; alcohol solvents such as methanol and ethanol; ketone solvents such as acetone and methyl ethyl ketone; ethyl acetate and acetic acid Ester solvents such as butyl; polyhydric alcohol derivatives such as ethylene glycol monomethyl ether; and the like.

In the urethane resin, the polar group of the urethane bond interacts with the inorganic thin film layer and also has flexibility due to the presence of the noncrystalline portion, so that the damage to the inorganic thin film layer is suppressed even when a bending load is applied. It is preferable because it can be
The acid value of the urethane resin is preferably in the range of 10 to 60 mg KOH / g. More preferably, it is in the range of 15 to 55 mg KOH / g, further preferably in the range of 20 to 50 mg KOH / g. When the acid value of the urethane resin is in the above range, the liquid stability is improved when the aqueous dispersion is prepared, and the protective layer can be uniformly deposited on the high polarity inorganic thin film, so the coat appearance is good. It becomes.

The urethane resin preferably has a glass transition temperature (Tg) of 80 ° C. or more, more preferably 90 ° C. or more. By setting the Tg to 80 ° C. or more, the swelling of the protective layer due to molecular motion in the wet heat treatment process (temperature increase to heat retention to temperature decrease) can be reduced.

From the viewpoint of improving gas barrier properties, it is more preferable to use a urethane resin containing an aromatic or aromatic aliphatic diisocyanate component as a main component.
Among these, it is particularly preferable to contain a metaxylylene diisocyanate component. By using the above-mentioned resin, the cohesive force of the urethane bond can be further enhanced by the stacking effect between the aromatic rings, and as a result, good gas barrier properties can be obtained.

In the present invention, the proportion of the aromatic or araliphatic diisocyanate in the urethane resin is preferably in the range of 50 mol% or more (50 to 100 mol%) in 100 mol% of the polyisocyanate component (F). The proportion of the total amount of aromatic or araliphatic diisocyanates is preferably 60 to 100 mol%, more preferably 70 to 100 mol%, and still more preferably 80 to 100 mol%. As such a resin, "Takelac (registered trademark) WPB" series commercially available from Mitsui Chemicals, Inc. can be suitably used. If the proportion of the total amount of aromatic or araliphatic diisocyanates is less than 50 mol%, good gas barrier properties may not be obtained.

It is preferable that the said urethane resin has a carboxylic acid group (carboxyl group) from a viewpoint of affinity improvement with an inorganic thin film layer. In order to introduce a carboxylic acid (salt) group into a urethane resin, for example, a polyol compound having a carboxylic acid group such as dimethylol propionic acid or dimethylol butanoic acid may be introduced as a copolymerization component as a polyol component. Moreover, after synthesize | combining a carboxylic acid group containing urethane resin, if it neutralizes with a salt formation agent, the urethane resin of a water dispersion can be obtained. Specific examples of the salt forming agent include ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, trialkylamines such as tri-n-butylamine, N-methylmorpholine, N-ethylmorpholine, etc. And N-dialkylalkanolamines such as -alkyl morpholines, N-dimethyl ethanolamine, N-diethyl ethanolamine and the like. These may be used alone or in combination of two or more.

Layers of other materials may be laminated on the biaxially oriented polyester film of the present invention, and as the method, the biaxially oriented polyester film can be laminated after preparation or laminated during film formation.

The biaxially oriented polyester film of the present invention can be used as a packaging material, for example, by providing an inorganic deposition layer on the biaxially oriented polyester film of the present invention, and further forming a heat sealable resin layer called a sealant. The formation of the heat sealable resin layer is usually carried out by an extrusion laminating method or a dry laminating method. As a thermoplastic polymer which forms a heat sealable resin layer, polyethylene resins, such as HDPE, LDPE, LLDPE, and polypropylene resin should just be sufficient to express sealant adhesiveness. Ethylene-vinyl acetate copolymer, ethylene-α-olefin random copolymer, ionomer resin and the like can be used.

The sealant layer may be a single layer film or a multilayer film, and may be selected according to the required function. For example, in terms of imparting moisture resistance, a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer or polymethylpentene is interposed can be used. Further, the sealant layer may be blended with various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.
The thickness of the sealant layer is preferably 10 to 100 μm, and more preferably 20 to 60 μm.

The biaxially oriented polyester film of the present invention can be used as a base film of a laminate for a packaging material. The layer configuration of the laminate includes, for example, a base layer / gas barrier layer / protective layer, a base layer / gas barrier layer / protective layer / sealant layer, a base layer / gas barrier layer / BR> ^ protective layer / resin layer / sealant Layer, substrate layer / resin layer / gas barrier layer / protective layer / sealant layer, substrate layer / gas barrier layer / protective layer / printed layer / sealant layer, substrate layer / printed layer / gas barrier layer / protective layer / sealant layer, Base material layer / gas barrier layer / protective layer / resin layer / printing layer / sealing layer, base material layer / resin layer / printing layer / gas barrier layer / protective layer / sealant layer, base material layer / printing layer / gas barrier layer / protective layer / Resin layer / sealant layer, base material layer / printing layer / resin layer / gas barrier layer / protective layer / sealant layer, base material layer / resin layer / gas barrier layer / protective layer / printing layer / sealant layer, and the like.

The laminate using the biaxially oriented polyester film of the present invention can be suitably used for applications such as packaged products, various label materials, lid materials, sheet molded articles, laminate tubes and the like. In particular, it is used for packaging bags (for example, pouches, such as a pillow bag, a standing pouch, and a 4-way pouch). The thickness of the laminate can be appropriately determined depending on the application. For example, it is used in the form of a film or sheet having a thickness of about 5 to 500 μm, preferably about 10 to 300 μm.

EXAMPLES The present invention will next be described in more detail by way of examples, which should not be construed as limiting the invention thereto. In addition, evaluation of the film was performed by the following measuring method.
[Dimensional change at 120 ° C]
The temperature was raised from room temperature to 200 ° C. and measured using TMA (thermal mechanical analyzer) manufactured by Shimadzu Corporation. However, the temperature rising rate was 10 ° C./min, the width of the measurement sample was 4 mm, the length of the measurement sample was 10 mm, and the initial tension was 400 mN.
The dimensional change (%) at 120 ° C. of the obtained temperature change curve was read.

[Thickness of film]
It measured using a dial gauge according to JIS K7130-1999 A method.

[Thickness accuracy]
A film piece is cut out in the width direction of the obtained film roll, and the maximum thickness when measured using a dial gauge at 5 cm pitch is Tmax, the minimum thickness is Tmin, and the average thickness is Tave. I asked for accuracy.
Thickness accuracy (%) = {(Tmax-Tmin) / Tave} x 100% (1)

[Degree of plane orientation of film ΔP]
Measure the refractive index (Nx) in the film longitudinal direction, the refractive index (Ny) in the width direction, and the refractive index (Nz) in the thickness direction according to JIS K 7142-1996 A method using a sodium D line as a light source Then, ΔP was calculated by the equation (2).
Orientation coefficient (ΔP) = (Nx + Ny) / 2-Nz (2)

Thermal contraction rate
The thermal shrinkage of the polyester film was measured by the dimensional change test method described in JIS-C-2151-2006.21 except that the test temperature was 150 ° C. and the heating time was 15 minutes. The test pieces were used as described in 21.1 (a).

[Steel strength]
The puncture strength of the polyester film was measured by the test method described in JIS-Z1707.

[Preparation of gas barrier layer]
Aluminum oxide was vapor-deposited on the substrate layers shown in Examples and Comparative Examples described later. The film is set on the unwinding side of a continuous vacuum deposition machine and is run through a cooling metal drum to wind up the film. At this time, the pressure in the continuous vacuum deposition machine is reduced to 10 ^-4 Torr or less, metal aluminum of 99.99% purity is loaded into the alumina crucible from the lower part of the cooling drum, metal aluminum is heated and vapor-deposited, The film was deposited and deposited on the film while supplying oxygen for oxidation reaction to form an aluminum oxide film having a thickness of 30 nm.

[Preparation of protective layer]
A solution of 60% by weight water, 30% by weight isopropanol and 10% by weight urethane resin is applied onto the inorganic vapor deposited thin film layer of the gas barrier layer deposited and formed as described above by a wire bar coating method, for 30 seconds at 150 ° C. It dried and obtained the protective layer. The applied amount after drying was 0.190 g / m ² (as solid content).
Urethane resin: A dispersion of a commercially available metaxylylene group-containing urethane resin ("Takelac (registered trademark) WPB 341"; solid content: 30%, manufactured by Mitsui Chemicals, Inc.) was prepared as the urethane resin. The oxidation of this urethane resin was 25 mg KOH / g, and the glass transition temperature measured by DSC was 130 ° C. Further, the ratio of aromatic or araliphatic diisocyanate to the entire polyisocyanate component measured by ¹ H-NMR was 85 mol%.

[Production of laminated laminate for evaluation]
A urethane-based two-component curable adhesive (Takelac (registered trademark) A525S manufactured by Mitsui Chemicals, Inc.) and Takenate (registered trademark) on the protective layer of the laminated film provided with the gas barrier layer / protective layer on the aforementioned base film A) A50 "is blended at a ratio of 13.5: 1 (weight ratio) by a dry laminating method to obtain a 70 μm thick non-stretched polypropylene film (" P1147 "manufactured by Toyobo Co., Ltd.) as a heat sealable resin layer By laminating and aging at 40 ° C. for 4 days, a laminate gas barrier laminate for evaluation was obtained. In addition, the thickness after drying of the adhesive bond layer formed with urethane type 2 liquid curing adhesive agent was about 4 micrometers in all.

[Battery resistance after retort treatment]
The above laminate is cut into a size of 15 cm square, two sheets are stacked so that the sealant is on the inside, and the three sides are heat sealed at a seal temperature of 160 ° C. and a seal width of 1.0 cm. I got a 3-way sealed bag of 13 cm in size.
The resulting three-way sealed bag was filled with 250 mL of water, and then the fourth hole was closed by heat sealing to prepare a water-filled four-way sealed bag.
The obtained four-way sealed bag was subjected to wet heat treatment held in hot water at 130 ° C. for 30 minutes, and then room temperature 5 ° C., humidity 35% R.H. H. Under the circumstances, the sample was dropped from a position 100 cm high onto the concrete plate, and the number of drops was counted until tears and pin holes occurred.

[Gas barrier properties of laminate: oxygen permeability (OTR)]
Using the oxygen permeability measuring apparatus ("OX-TRAN 2/20" manufactured by MOCON), according to the electrolytic sensor method (Appendix A) of JIS-K7126-2 with respect to the above-mentioned laminated laminate, the temperature 23 The oxygen permeability in the normal state was measured under an atmosphere of 65 ° C. and a relative humidity of 65%. The oxygen permeability was measured in the direction in which oxygen permeates from the base film side to the sealant side.

[Gas barrier properties of laminate: water vapor permeability (WVTR)]
Using the water vapor transmission rate measuring apparatus ("PERMATRAN-WIA" manufactured by MOCON) according to JIS-K7129-1992 B method with respect to the above-mentioned laminated laminate, under an atmosphere of temperature 40 degrees and relative humidity 90% The water vapor permeability in normal condition was measured. The water vapor transmission rate was measured in the direction in which water vapor permeates from the base layer film side to the sealant side.

Example 1
Intrinsic viscosity consisting of PBT resin (1100-211XG (CHANG CHUN PLASTICS CO., LTD., Intrinsic viscosity 1.28 dl / g) and terephthalic acid // ethylene glycol = 100 // 100 (mol%) using a single screw extruder A melt of 0.22 dl / g of PET resin, silica particles with an average particle diameter of 2.4 μm as inert particles blended at 0.16% by weight as silica concentration is melted at 290 ° C and then the melt line is 12 The melt was divided and laminated to obtain a multilayer melt made of the same raw material, cast from a T-die at 270 ° C., and electrostatically applied to a 15 ° C. cooling roll. The sheets were brought into close contact by the adhesion method to obtain an unstretched sheet.
Then, the film is stretched 2.9 times in the longitudinal direction (MD) at 60 ° C., then stretched 4.3 times in the width direction (TD) at 85 ° C. through a tenter, and tension heat treatment at 200 ° C. for 3 seconds After carrying out a relaxation treatment of 9% for 1 second, the grip portions at both ends were cut and removed by 10% to obtain a mill roll of a film having a thickness of 15 μm. The film forming conditions, physical properties and evaluation results of the obtained film are shown in Table 1.

[Examples 2 to 6]
Example 1 was carried out in the same manner as Example 1 except that the raw material composition and the film forming conditions were changed to the biaxially stretched film described in Table 1.

[Comparative Examples 1 to 8]
The film was obtained according to the conditions described in Table 2 using a single screw extruder. Film forming conditions, physical properties and evaluation results of the obtained film are shown in Table 2.

(Comparative example 1)
It implemented by the method similar to Example 1 except having changed the heat setting temperature into the value of Table 2. Although the pinhole resistance of the obtained film was good, the puncture strength was 6.5 N and the tear resistance was poor at 60%. Moreover, since the dimensional change rate was as large as 4.10%, the gas barrier properties were poor. The results are shown in Table 2.

(Comparative example 2)
It implemented by the method similar to Example 1 except having changed the heat setting temperature into the value of Table 2. Although the pinhole resistance and tear resistance of the obtained film were good, the gas shrinkage was poor because the thermal contraction rate was 5.5% and the dimensional change rate was -2.20%. The

(Comparative example 3)
It implemented by the method similar to Example 1 except having changed the polyester resin composition into the value of Table 2. The gas barrier properties of the obtained film were good, but because the content of PBT was small, the puncture strength of the obtained film was 7.2 N, and the resistance to puncture and the resistance to puncture were poor. .

(Comparative example 4)
It carried out by the method described in Table 2. The puncture strength of the obtained film was 8.9 N, and the pinhole resistance and the tear resistance were good, but the dimensional change rate was as large as 4.30%, so the gas barrier properties were poor.

(Comparative example 5)
It carried out by the method described in Table 2. Although the pinhole resistance and tear resistance of the obtained film were good, the gas barrier properties were poor because the dimensional change rate was as large as 4.10%.

(Comparative example 6)
It carried out by the method described in Table 2. The puncture strength of the obtained film was 7.3 N, and the resistance to breakage and pinholes was poor. Moreover, since the dimensional change rate was as large as 4.40%, the gas barrier properties were poor.

(Comparative example 7)
It carried out by the method described in Table 2. The puncture strength of the obtained film was 7.5 N, and the resistance to breakage and pinholes was poor. Moreover, since the dimensional change rate was as large as 4.10%, the gas barrier properties were poor.

(Comparative example 8)
It carried out by the method described in Table 2. The puncture strength of the obtained film was 7.3 N, and the resistance to breakage and pinholes was poor. Moreover, since the heat shrinkage rate is small at 0.8% and the dimensional change rate is high at 4.10%, the gas barrier properties were poor.

(Reference Example 1)
In Example 1, others were similarly film-formed, without introduce | transducing a static mixer into a melt line. During film formation, breakage of the film occurred frequently and no film was obtained with a length of 50 m or more. The thickness accuracy of the obtained film was 30% or more.

(Reference Example 2)
The thickness accuracy was measured for a biaxially oriented film (total thickness 15 μm, width 840 mm) mainly composed of PBT produced by a commercially available inflation method. The thickness accuracy was 28%, which was inferior to the film of the present invention.

According to the present invention, it is possible to obtain a laminated polyester film which is excellent in pinhole resistance, bag-proof resistance after boiling treatment and retorting treatment, and which is excellent in gas barrier properties with less cracking of the gas barrier layer in the protective layer forming step. It can be expected to greatly contribute to the industry because it can be widely applied as food packaging and pharmaceutical packaging materials.

Claims

A polyester resin composition comprising 60 to 100% by weight of polybutylene terephthalate resin (A) and 0 to 40% by weight of polyester resin (B) other than polybutylene terephthalate resin (A), (a) and (b) A biaxially oriented polyester film that simultaneously satisfies
(A) The dimensional change at 120 ° C. with respect to the film original length of the temperature dimensional change curve measured using TMA (thermal mechanical analyzer) is −2.0% to 4.0% in the longitudinal direction of the film.
(B) The thermal shrinkage at 150 ° C. in the longitudinal direction of the film is 1.0% to 5.0%.
The biaxially oriented polyester film according to claim 1, wherein a value of piercing strength measured by a piercing strength test according to JIS-Z1707 is 8.0 N or more.
The biaxially oriented polyester film according to claim 1 or 2, wherein the thickness accuracy in the full width of the film is 1 to 20%.