JPH11105223A - Flexible polyester film excellent in gas barrier property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film, which is excellent in gas barrier properties and transparent and flexible. SOLUTION: This film is produced by laminating the deposit of an oxide on at least one side of a resin layer mainly made of a polyester having a main repeating unit of a trimethylene terephthalate under the following four conditions are satisfied, a haze value <=5%, a tensile modulus of elasticity <=250 kgf/mm<2> (23 deg.C), a moisture permeability <=20 g/m<2> /24 hr (40 deg.C/90% RH) and an oxygen permeability <=10 cc/m<2> /24 hr/atm (25 deg.C/50% RH).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a polyester film having excellent gas barrier properties and being transparent and flexible, particularly important for packaging films for fresh foods, processed foods, pharmaceuticals, medical equipment, electronic parts and the like. The present invention relates to a transparent and flexible polyester film having excellent gas barrier properties as a characteristic.

[0002]

2. Description of the Related Art Conventionally, polyethylene terephthalate (hereinafter sometimes abbreviated as PET) -based films are excellent in mechanical properties, heat resistance, gas barrier properties, transparency, etc., and are therefore used for magnetic recording, industrial use, and food. Widely used as packaging films. However, in some applications such as industrial and packaging films, these applications have their own limitations due to the lack of flexibility required for shape coverage of protective objects.

[0003] Therefore, a method of imparting flexibility to a PET film has been proposed. For example, a method of copolymerizing polytetramethylene glycol or dimer acid (Japanese Unexamined Patent Publication No.
JP-A-79667) and a method of adding a flexible ionomer (JP-A-52-84244, etc.). However, the target film lacks flexibility and has basic properties such as heat resistance and weather resistance. Was not enough.

A film made of polytrimethylene terephthalate has been proposed in Japanese Patent Application Laid-Open No. 8-325391 as a film showing flexibility, for use in packaging industrial parts. It is the present situation that development to such as is limited.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a transparent and flexible polyester film which is effective as a general packaging material, has excellent gas barrier properties. And

[0006]

In order to achieve the above-mentioned object, a transparent and flexible polyester film of the present invention, which has excellent gas barrier properties, comprises a polyester whose main repeating unit is trimethylene terephthalate as a main component. An oxide deposited layer is laminated on at least one surface of the resin layer, and satisfies the following conditions (1) to (4). (1) to the over haze value ≦ 5% (2) Tensile elastic modulus ^{≦ 250kgf / mm 2 (23 ℃} ) (3) moisture permeability ^{≦ 20g / m 2 / 24hr (} 40 ℃ / 90
% RH) (4) Oxygen permeability ^{≦ 10cc / m 2 / 24hr /} atm
(25 ° C / 50% RH)

The polyester film of the present invention having the above structure has flexibility, transparency, and excellent gas barrier properties.

In a preferred embodiment of the present invention, the thickness of the resin layer mainly composed of polyester is 10 to 250 μm.
And the thickness of the oxide deposition layer can be 10 to 5000 °.

Further, as a preferred embodiment of the present invention,
The oxide can be silicon oxide and / or aluminum oxide.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a transparent and flexible polyester film having excellent gas barrier properties according to the present invention will be described.

The polyester (hereinafter sometimes abbreviated as PTT) whose main repeating unit is trimethylene terephthalate used in the present invention is a polyester composed of a terephthalic acid component and a 1,3-propanediol component. The main objects of the present invention are terephthalic acid and 1,3-propanediol as main components, and isophthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, ethylene glycol, 1,4-butanediol, bisphenol A, etc. May be copolymerized within a range in which a film having the following formula can be obtained.

The polyester used in the present invention wherein the main repeating unit is trimethylene terephthalate usually has an intrinsic viscosity of 0.6 or more. When the intrinsic viscosity is less than 0.6, breakage often occurs during film formation, and it tends to be difficult to obtain a practically usable resin layer.

Further, the polyester may contain a polyester of another repeating unit or another thermoplastic resin as long as the resin layer aimed at by the present invention can be obtained. In addition, known additives can be contained as needed. For example, a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a lightfast agent, an impact resistance improver, and the like may be contained. However, since the polyester film of the present invention needs to be transparent and its contents visible in a state in which the oxide vapor deposition layer is vapor-deposited, the type of additive so as to have high transparency even before the vapor deposition layer is vapor-deposited Need to be considered.

The polyester film constituting the present invention, which comprises a resin layer containing a polyester whose main repeating unit is trimethylene terephthalate as a main component, can be obtained by forming and stretching by a known method. It is preferable that the film is heat-set after stretching. For example, when a resin layer containing a polyester whose main repeating unit is trimethylene terephthalate as a main component used in the present invention is produced by extrusion, a known T-die method, inflation method, or the like can be applied. With this, an unstretched film can be obtained. The extrusion temperature is determined from the melting temperature (Tm) of the polymer used to Tm + 70.
° C, more preferably Tm + 20 to Tm + 50 ° C
Range. If the extrusion temperature is too low, it is difficult to obtain extrusion stability, and it is easy to overload. On the other hand, if it is too high, the decomposition of the polymer becomes severe, which is not preferable. The die of the extruder used in the present invention may have an annular or linear slit. The temperature of the die may be as high as the extrusion temperature range. The draw ratio (ratio of T-die lip interval / film thickness) when extruding with a T-die is preferably 5 or more and 130 or less.

The biaxial stretching of an unstretched film composed of a resin containing a polyester whose main repeating unit is trimethylene terephthalate as a main component can be performed simultaneously with the uniaxial stretching and the second axial stretching. Is also good. The stretching temperature is determined from the glass transition temperature (Tg) of the polymer used.
The range of g + 50 ° C. is preferred. More preferably, Tg +
The range is 10 to Tg + 40 ° C. If the stretching temperature is lower than Tg, stretching is difficult, and if it exceeds Tg + 50 ° C., the thickness uniformity and the mechanical strength of the obtained film are undesirably reduced.

The stretching in the vertical and horizontal directions may be performed in one stage or in other stages, but it is ultimately at least three times, more preferably 3.5 times or more in each stretching direction. Stretching at a transverse area magnification of 9 times or more, more preferably 12 times or more, is a general condition in terms of thickness uniformity and mechanical properties. If the longitudinal and transverse stretching ratios are each 3 times or less and the area magnification is 9 times or less, it tends to be difficult to obtain a film having good thickness uniformity, and the improvement in physical properties such as mechanical strength is also poor. The thickness of the resin layer containing polyester whose main repeating unit is trimethylene terephthalate as a main component is usually about 10 to 250 μm, preferably 12 to 250 μm.
It is about 250 μ.

The resin layer used in the present invention may be multi-layered by a co-extrusion method or a coating method in the production process. The resin layer used in the present invention may be subjected to a corona treatment, a coating treatment or a flame treatment in order to improve adhesion and wettability depending on the use. In particular, the above treatment may be performed before the deposition of the oxide layer on the film in order to increase the adhesion between the film and the deposition layer of the oxide.

The deposited layer of the oxide constituting the present invention may be a deposited layer of an oxide exhibiting transparency and gas barrier properties satisfying the above conditions (1) to (4). Although metal oxides are widely used, a vapor deposition layer containing silicon oxide and / or aluminum oxide as a main component is particularly preferable.

The thickness of the oxide deposited layer is usually from 10 to 50.
00 °, more preferably in the range of 50-2000 °. If the film thickness is less than 10 mm, it is difficult to obtain sufficient gas barrier properties. Even if the film thickness is excessively larger than 5000 mm, the effect of improving gas barrier properties is saturated, and the bending resistance becomes poor or the production cost is reduced. Is not practical.

For the formation of the above-mentioned oxide vapor deposition layer, a physical vapor deposition method such as a vacuum vapor deposition method, a sputtering method, an ion plate method, or a chemical vapor deposition method such as a CVD method is appropriately used.
As the heating method employed at this time, resistance heating, induction heating, electron beam heating, or the like can be applied. Oxygen, nitrogen, hydrogen, argon, carbon gas, water vapor, or the like may be introduced as a reaction gas, or a reactive deposition method using a method such as ozone addition or ion assist may be employed, and a bias may be applied to the substrate. It is also possible to change the film forming conditions such as heating and cooling of the substrate. Such deposition materials, reaction gas, substrate bias, and heating / cooling conditions can be similarly changed when employing a sputtering method or a CVD method. Before or during the deposition of the oxide, the surface of the substrate to be deposited is subjected to corona treatment, flame treatment, low-temperature plasma treatment, glow discharge treatment,
It is also effective to further increase the adhesion strength of the oxide by performing a reverse sputtering treatment, a roughening treatment, or the like.

In the present invention, the resin layer mainly composed of polyester whose main repeating unit is trimethylene terephthalate, on which the deposited layer of oxide is laminated, must be colorless and transparent, and the packaged contents must be visible. The haze (haze value) of the laminated film needs to be 5% or less. It should be noted that the formation of another layer is not adversely affected as long as the object of the present invention is not impaired.

According to the present invention, an oxide deposited layer is laminated.
The resin layer whose main repeating unit is trimethylene terephthalate has a tensile modulus of elasticity of 25 when measured at 23 ° C.
0 kgf / mm ² or less.
If it exceeds 0 kgf / mm ² , the characteristics as a flexible film cannot be utilized.

[0023]

EXAMPLES Hereinafter, the contents and effects of the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the following examples unless departing from the gist thereof. The methods for evaluating physical properties in the following examples and comparative examples are as follows.

(Haze value of film) A haze value was measured using a haze meter manufactured by Nippon Denshoku Co., Ltd. according to JIS-K6714.

(Gas barrier property) The amount of oxygen permeation is measured by an oxygen permeability measuring device (“OX-TRAN 10 / 50A”) Mod.
The measured value was 0% humidity, 25 ° C. temperature, and purged for 2 days. In addition, the water vapor transmission rate can be measured by a water vapor transmission rate (moisture permeability) measuring device (“PERMAT”).
RAN "(manufactured by Modern Controls) at a temperature of 40 ° C., a humidity of 90% and a 2-day purge.

(Tensile Modulus) ASTM D-882-8
It measured according to 1 (Method A). (Measurement temperature 23 ° C)

(Intrinsic viscosity) Measurement was carried out at 20 ° C. using a phenol: tetrachloroethane = 1: 1 (weight ratio) mixed solvent as a solvent.

(Example 1) A polytrimethylene terephthalate having an [η] of 0.83 (amorphous silica: psiloid SY-350 containing 2000 PPM as a lubricant) was used as a raw material, and a 30 mm extruder with a T-die was used. Extruded at a resin temperature of 260 ° C., cooled with a chill roll,
Immediately after obtaining an unstretched film of 00 μm, the film is stretched 3.2 times in the longitudinal direction at 70 ° C. by a roll-type stretching machine, and further stretched 4 times in a transverse direction at 80 ° C. by a tenter-type stretching machine. After heat setting at 200 ° C, a corona treatment
A 5 μm stretched film was obtained. The obtained corona-treated biaxially stretched film was subjected to electron beam heating-type vacuum evaporation using silicon dioxide and aluminum oxide as evaporation materials, with a film thickness of 200 ° and an aluminum oxide content of 40% by weight.
Were deposited. Table 1 shows the physical properties.

(Comparative Example 1) Polyethylene terephthalate having an [η] of 0.62 (amorphous silica: 2000 PPM of thyroid SY-350 as a lubricant) was used as a raw material.
Using a die extruder with a diameter of 30 mm, the resin temperature is 29.
Extruded at 0 ° C, cooled with a chill roll, about 300μ thick
Immediately after obtaining an unstretched film having a length of m, the film is stretched 3.2 times in the machine direction at 90 ° C. by a roll-type stretching machine, and further stretched 4 times in a transverse direction at 110 ° C. by a tenter-type stretching machine. After heat-setting at 230 ° C, corona treatment is performed to a thickness of 2
A 5 μm stretched film was obtained. The obtained biaxially stretched film having been subjected to corona treatment was laminated with a 200-mm-thick vapor-deposited layer having an aluminum oxide content of 40% by weight using silicon dioxide and aluminum oxide as a vapor-depositing material using an electron beam heating type vacuum vapor-deposition apparatus. Table 1 shows the physical properties.

[0030]

[Table 1]

[0031]

According to the flexible polyester film of the present invention having excellent gas barrier properties, it has flexibility, is transparent,
And it has excellent gas barrier properties.

Claims (3)

[Claims] 1. An oxide deposited layer is laminated on at least one surface of a resin layer mainly composed of polyester whose main repeating unit is trimethylene terephthalate, and the following conditions (1) to (4) are satisfied. Flexible polyester film with excellent gas barrier properties characterized by satisfying (1) to the over haze value ≦ 5% (2) Tensile elastic modulus ^{≦ 250kgf / mm 2 (23 ℃} ) (3) moisture permeability ^{≦ 20g / m 2 / 24hr (} 40 ℃ / 90
% RH) (4) Oxygen permeability ^{≦ 10cc / m 2 / 24hr /} atm
(25 ° C / 50% RH) 2. The gas barrier property according to claim 1, wherein the thickness of the resin layer containing polyester as a main component is 10 to 250 μm, and the thickness of the deposited layer of the oxide is 10 to 5000 °. Excellent flexible polyester film. 3. The flexible polyester film excellent in gas barrier properties according to claim 1, wherein the oxide is silicon oxide and / or aluminum oxide.