JP3275465B2 - Barrier flexible polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film having high barrier properties, and more particularly to a flexible polyester film having excellent flexibility.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET) biaxially stretched film, which is a representative example of a polyester film, is an industrial material and a magnetic recording material because of its excellent mechanical strength, thermal properties, humidity properties and many other excellent properties. It is used in a wide range of fields such as packaging materials.

[0003] However, in applications where impact resistance and pinhole resistance are important, nylon biaxially stretched films are often used, and PET films are used as main constituents because of their hardness, which is the reverse of their toughness. Less likely.
For example, among the packaging materials, in particular, applications that require gas barrier properties, moisture resistance, etc., impact resistance and kneading resistance,
Furthermore, their low-temperature properties are required, and nylon biaxially stretched films are often used. These packages are made by laminating a biaxially stretched film with a sealant layer such as polyethylene or polypropylene, and filling the contents. The bags are ruptured when the filled bags are dropped. It is important to take into account the strength of the bag to prevent the contents from leaking due to the opening of the pinhole and the resistance to rubbing to prevent the pinhole from being formed when the bag is rubbed by repeated external forces. Are excellent in these properties.

[0004]

On the other hand, nylon films also have a problem in characteristics. Particularly, the essential properties of nylon polymers such as a high moisture absorption coefficient and a high humidity expansion coefficient are as follows.
When the film is stored in the form of a roll, there are problems in that the flatness is deteriorated, the vapor deposition processing is difficult, and the adhesive strength of the print / laminate layer is reduced when absorbing moisture. On the other hand, the PET film has a very small moisture absorption coefficient and humidity expansion coefficient, has no problem with the humidity characteristics, and is easy to process such as coating. However, when a gas barrier layer is simply coated on a normal PET film, since the film is hard, the impact resistance is low, the coat layer is easily broken, and defects are easily generated in the coat layer.

[0005] The present invention provides a barrier which is not inherent in PET film as described above, and which has characteristics such as impact resistance and pinhole resistance like a biaxially stretched nylon film, and in particular, also has excellent gas barrier properties. It is an object of the present invention to provide a flexible polyester film.

[0006]

According to the object of the present invention, a barrier flexible polyester film according to the present invention has a Young's modulus of 10%.
~250kg / mm ^2, the piercing strength of 10kg / mm or more
Which is mainly composed of polyethylene terephthalate
A biaxially oriented polyester film made of flexible polyester A (hereinafter, sometimes simply referred to as a flexible polyester film) is formed by laminating a gas barrier layer on at least one surface.

[0007] Generally, a biaxially stretched nylon film has a high strength and a superior puncture strength than a PET film. This is because a hydrogen bond formed by an amide bond portion of nylon is formed in the polymer. It is said.
However, since the polyester film does not have such a portion that forms such a hydrogen bond, it is necessary to improve the characteristics based on another principle in order to obtain the same characteristics as nylon.

[0008] As a result of examining the impact resistance and rubbing resistance of a polyester film as in a nylon biaxially stretched film, it was found that the polyester film has a flexibility equal to or less than nylon and a puncture resistance equal to or greater than nylon. I found that I should give it to the film. Specifically, the flexible polyester film of the present invention has a Young's modulus of 1 to 1.
250 kg / mm ² , preferably 50 to 200 kg / m
m ² , and the piercing strength is 10 kg / mm or more, preferably 15 kg / mm or more, and more preferably 20 kg / m.
m or more. Here, if the Young's modulus is too low, it is not preferable because the handleability is poor because the bag does not have rigidity.
A normal PET film has a Young's modulus twice that of a nylon film and a puncture strength of about 1/2, and is considerably different in characteristics from the flexible polyester film of the present invention.

In the flexible polyester A mainly comprising the flexible polyester film of the present invention, the dicarboxylic acid component constituting the polyester includes aromatic dicarboxylic acid, alicyclic dicarboxylic acid, aliphatic dicarboxylic acid, polyfunctional acid and the like. Is mentioned. Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenic acid, and derivatives thereof, and alicyclic dicarboxylic acids include 1,4-
There are cyclohexanedicarboxylic acid and its derivatives, and the like, and as the aliphatic dicarboxylic acid, there are adipic acid, sebacic acid, dodecandioic acid, eicoic acid, dimer acid and derivatives thereof, and as the polyfunctional acids, trimellitic acid, Melitic acid and its derivatives are representative. Representative examples of the alcohol component include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, bisphenol, and derivatives thereof. It is something. Further, the flexible polyester A used in the present invention is a block of a polyester ether obtained by copolymerizing a polyether such as polyethylene glycol or polytetramethylene glycol, or a polyester amide obtained by copolymerizing a polyamide, or an aliphatic polyester such as polycaprolactone. It also includes a copolymer and the like.

[0010] Among these polyesters, the present invention
The film formability, such as biaxial stretching properties, humidity properties, heat resistance, chemical resistance, low cost and other viewpoint et al, polyethylene terephthalate (PET) as a main component, preferably the acid component and alcohol component of the polyester 50 each
A polyester whose mole% or more is terephthalic acid, ethylene glycol or a derivative thereof is used as the flexible polyester A of the flexible polyester film of the present invention. Further, from the viewpoint of imparting flexibility, it is desirable that the glass transition temperature of the flexible polyester A is 60 ° C. or lower, preferably 55 ° C. or lower, particularly preferably 50 ° C. or lower.

Further, in order to impart flexibility to the film, it is effective to copolymerize an aliphatic dicarboxylic acid, a polyether, an aliphatic polyester or the like with a polyester mainly composed of PET, for example. 8 or more,
It is preferable to copolymerize a long-chain aliphatic dicarboxylic acid having preferably 20 or more alkylene groups in view of weather resistance and quality stability. Examples of the long-chain aliphatic dicarboxylic acid include dodecandioic acid, eicoic acid, dimer acid and derivatives thereof, and in particular, in the present invention, among these, a branched aliphatic dicarboxylic acid having a branched structure may be used. From the viewpoint of improving the impact resistance, it is preferable to use a dimer acid from the viewpoint of improving heat resistance and transparency.

The term "dimer acid" as used herein is a generic term for a mixture of a linear branched structure and a cyclic branched structure obtained by dimerizing and hydrogenating an unsaturated aliphatic dicarboxylic acid such as methyl oleate. Has 20 to 80 carbon atoms,
Preferably it is 30-60. Moreover, although the unsaturated bond usually remains, the bromine value measured by ASTM-D-1159 is 0.05 to 10 (g / 100 g), preferably 0.1 to 5 (g / 100 g). Is heat resistant,
It is preferable because of its excellent flexibility. The copolymerization amount of the dimer acid is from 1 to 40 mol%, preferably from 5 to 20 mol%, based on the acid component.

The flexible polyester A mainly comprising the flexible polyester film of the present invention is, for example, PET.
In the case of a copolymerized polyester with an aliphatic dicarboxylic acid or the like for imparting flexibility, the melting point, the glass transition point, and the crystallinity are reduced, and the biaxially stretched film manufacturing process involves cooling during extrusion casting. Adhesion to a drum, adhesion to a stretching roll, and adhesion to a clip in a tenter is likely to occur, which may reduce productivity. Further, when the copolymerization increases, the biaxial stretching property of the polyester A alone deteriorates, and the relationship between the stretching and the stress is 1%.
The one-to-one correspondence is lost, resulting in so-called necking stretching, which leads to deterioration of the thickness section. This poor biaxial stretching property is particularly attributable to polybutylene terephthalate (PBT).
This is particularly remarkable in a flexible polyester containing as a main component, for example, it is very difficult to obtain a smooth biaxially stretched film using a copolymerized PBT obtained by copolymerizing 15 mol% of dimer acid.

In view of the above, flexible polyester A
Laminating polyester B having a glass transition point of 45 ° C. or higher, preferably 55 ° C. or higher on at least one surface of the polyester resin in order to prevent sticking to rolls and clips in light of the preferable stretching temperature of polyester A Is preferred.

As for the polyester B, a crystalline polyester represented by PET is preferable from the viewpoint of preventing sticking, but is not limited thereto. Further, it is preferable that the melting point and the glass transition point are higher than those of the polyester A because the thermal dimensional stability of the whole film is improved.
Further, it is preferable to select a polyester having higher breaking strength and Young's modulus than polyester A after biaxial stretching, since it is possible to improve the breaking strength and the like while keeping the stiffness of the film soft. Therefore, the lamination of polyester B is more than simply improving the film forming property, the disadvantages of flexible polyester A are thermal stability,
The effect of compensating the strength in the pulling direction and the like can be provided.

The dicarboxylic acid component, alcohol component, and copolymerization components such as polyether, polyamide and aliphatic polyester constituting the polyester B are the same as the polyester A. In addition to the glass transition point, the polyester B further includes: Flexible polyester A with poor biaxial stretchability
It is preferable that the polyester has good stretching characteristics in order to assist the stretching characteristics of the polyester. Specifically, a polyester mainly composed of PET, a polyester mainly composed of a polymer composed of 1,4-cyclohexanedimethanol and terephthalic acid, and the like are preferable. PET, copolymerized PET with isophthalic acid, adipic acid, sebacin Number of oxygen such as acid 4
And copolymerized PET with an aliphatic dicarboxylic acid having an alkylene group of from 8 to 8. In the case of a copolymer, the amount of the copolymer component is 1 to 40 mol%, preferably 5 to 20 mol%.

The polyester B is laminated on at least one side of the flexible polyester A, and the thickness ratio thereof is 1 in the ratio of the total thickness of the polyester A layer to the total thickness of the polyester B layer. : 1 to 50: 1, preferably 2: 1 to 25: 1 (total of A layer: total of B layer). B
When the proportion of the layer is too small, the effect of improving the biaxial stretchability is reduced, which is not preferable. When the proportion of the B layer is large, the flexibility and impact resistance of the film are unfavorably deteriorated.

The lamination of the polyester B is preferably carried out on both sides of the flexible polyester A, in which case it is easier to avoid sticking problems during the production of the film, and is more likely to occur in the case of a two-layer film. The problem of curling is also easy to avoid. The polyester B laminated on both sides of the flexible polyester A may have a slightly different composition or the like from each other within the scope of the present invention. In order to improve the adhesiveness between layers in the laminated film, for example, two kinds of polymers A1, A2,
And B / A1 / A2 / A1 / using polyester B
Five layers may be laminated as in B, or two types of polymer A1,
A2 may be mixed to give B / (A1 + A2) / B.

In the present invention, B comprising polyester B
The addition of inert particles to the layer is effective in improving slipperiness. Here, examples of the inert particles include inorganic compounds such as silicon oxide, aluminum oxide, zirconium oxide, calcium carbonate, and magnesium carbonate, and insoluble organic compounds such as crosslinked polystyrene, crosslinked divinylbenzene, benzoguanamine, and silicone. In particular, colloidal silica, pulverized silica, crosslinked polystyrene, silicone and the like are preferable in terms of transparency. There are no particular restrictions on the particle size and the amount of the particles, but in terms of slipperiness and transparency, the average particle size is 0.01 to 10 μm, preferably 0.1 to 5 μm, and the addition amount is 0.001 to 10 %, Preferably 0.05 to 1% by weight. Further, the polyester A may contain particles as long as the properties are not impaired. Further, the laminated film may be manufactured by mixing polyester A and polyester B in terms of raw material recovery in the laminated film.

In the flexible polyester film of the present invention, additives such as an antistatic agent, a heat stabilizer, an antioxidant, a crystal nucleating agent, a weathering agent, an ultraviolet absorber, a pigment and a dye impair the object of the present invention. Can be used to a lesser extent.
In addition, surface irregularities such as embossing and sand matting, or surface treatments such as corona discharge treatment, plasma treatment, and alkali treatment may be performed as necessary. Further, the flexible polyester film of the present invention may have an easy-adhesion treatment agent, an antistatic agent, a water vapor / gas barrier agent (such as polyvinylidene chloride), a release agent, an adhesive, an adhesive, a flame retardant, an ultraviolet absorber, and a matting agent. May be coated or printed with pigments, dyes, etc., and vacuum-deposited metals such as aluminum, aluminum oxide, silicon oxide, palladium and their compounds for the purpose of shading, water vapor / gas barrier, surface conductivity, infrared reflection, etc. The purpose and method are not limited to the above.

The thickness of the flexible polyester film of the present invention is not particularly limited, but is 1 to 100 μm, preferably 5 to 100 μm.
Effectively used at 〜500 μm.

The thin-film laminated flexible polyester film of the present invention is obtained by laminating a gas barrier layer on at least one surface of the above-mentioned flexible polyester film.

This gas barrier layer is formed from a resin coating layer or an inorganic thin film layer made of a metal or a metal compound. The resin coating layer is, for example, a layer made of polyvinylidene chloride or an ethylene-vinyl alcohol copolymer, and the inorganic thin film layer is a layer made of any of aluminum, aluminum oxide, and silicon oxide. In particular, it is preferable to provide a resin coating layer or the like in terms of compatibility between transparency and high barrier properties. An anchor layer may be provided between the gas barrier layer and the polyester film.

When the biaxially oriented polyester film has a Young's modulus at room temperature of 50 kg / mm ² or more, the adhesion strength of the thin film at the time of vapor deposition can be further improved, in addition to the improvement in bag dropping strength and resistance to rubbing. Furthermore, prevention of heat loss on the can can be achieved. In addition, it is possible to prevent cracks in the vapor-deposited film and the coating film when using a product composed of a thin-film laminated flexible polyester film.

Next, a method for producing the barrier flexible polyester film of the present invention will be described, but the present invention is not limited thereto. Polyester A and polyester B are melt-extruded by separate extruders, and two types of polymers are composite-extruded into a sheet shape using a feed block or a manifold composite die and quenched and cast. The resulting cast sheet is produced by a usual sequential biaxial stretching film forming process in which longitudinal stretching, transverse stretching, and heat treatment are performed. In addition, a simultaneous biaxial stretching process, a tubular process, or the like can also be employed.

In the above-mentioned sequential biaxial stretching process, simultaneous biaxial stretching process and the like, in order to achieve the physical properties of the flexible polyester film of the present invention, the stretching ratio and the heat treatment temperature are important. As a result of repeated experiments, in particular, the piercing strength is affected by the stretching ratio and the heat treatment temperature, and the stretching ratio (longitudinal stretching ratio × lateral stretching ratio) is 4 to 25 times, preferably 6 to 20 times.
The heat treatment temperature is preferably 150 to 250 ° C. The piercing strength sharply decreases when the stretching ratio is low or high, and the piercing strength is low when the heat treatment temperature is low, and the Young's modulus or the like decreases when the heat treatment temperature is high.

On at least one side of the biaxially oriented flexible polyester film obtained as described above, a resin coating layer or a vapor-deposited thin film of a metal or a metal compound is laminated by coating or vapor deposition. The coating method and the vapor deposition method are not particularly limited, and known methods can be employed.

The thin film laminated flexible polyester film of the present invention is suitably used in applications where a biaxially stretched nylon film having flexibility is conventionally used, and is particularly suitable for applications requiring gas barrier properties. . In particular, when applied to packaging materials, it is excellent in impact resistance, rubbing resistance, low-temperature properties, and also has excellent gas barrier properties, and cannot be obtained with conventional nylon biaxially stretched films or ordinary PET films. Excellent characteristics are obtained.

[Methods for measuring and evaluating physical properties and characteristics]
Methods for measuring and evaluating various physical properties and characteristics used in the description of the present invention or the examples described later will be described. (1) Melting point (Tm), glass transition temperature (Tg) Measured using a differential scanning calorimeter DSC2 (manufactured by PerkinElmer). Sump 10 mg under nitrogen flow 280
C. for 5 minutes, and then quenched with liquid nitrogen. In the process of raising the temperature of the obtained sample at a rate of 10 ° C./min, a specific heat change based on a transition from a glassy state to a rubbery state is read, and this temperature is defined as a glass transition temperature (Tg). The melting point (Tm) was used.

(2) Mechanical properties Regarding the tensile Young's modulus, ASTM-D-882-8
It measured according to 1 (Method A).

(3) Piercing Strength A film having a diameter of 30 mm is stretched without loosening, and a sapphire needle having a tip angle of 60 degrees and a tip R of 0.1 mm is used to pierce the center of the circle at a speed of 50 mm / min. The force when the needle penetrated was converted into a film thickness of 1 mm, which was defined as the piercing strength.

(4) Oxygen permeability According to ASTM-D-3985, an oxygen permeability measuring device (OX-TRAN100 manufactured by Modern Controls)
Was measured under the conditions of 20 ° C. and 0% RH. Further, Fed. Shown in MIL-B-131F. Test
MethodStd. Method20 of No101C
According to No. 17, the so-called gel botester (manufactured by Tester Sangyo Co., Ltd.) was used to set the ambient temperature to 25 ° C., and the oxygen permeability was measured for the sample which was bent 100 times in the same manner as described above.

(5) Dropping test A 50 μm crystallized polypropylene film was laminated on the four sides with an impeller using a laminated sita film to prepare 10 80 mm × 180 mm bags containing 200 cc of water. Was dropped from a height of 1 m in an atmosphere of 25 ° C., and the number of ruptured or water leaked bags was compared among 10 samples.

[0034]

The present invention will be described below by way of examples. Example 1 Copolyester A having an intrinsic viscosity of 0.72 by a known method using 85 mol% of terephthalic acid as a dicarboxylic acid component, 15 mol% of hydrogenated dimer acid having 36 carbon atoms, and 100 mol% of ethylene glycol as a diol component. (Tm22
2 ° C., Tg 17 ° C.). On the other hand, 90 mol% of terephthalic acid and 10 mol% of sebacic acid as dicarboxylic acid components,
Copolymer Polyester B (Tm 233 ° C., Tg 55 ° C.) having an intrinsic viscosity of 0.66 was obtained by a known method using ethylene glycol 100 mol% as a diol component.

After drying these two types of copolyesters with a known vacuum dryer, polyester A is fed to a 90 mmφ extruder, polyester B is fed to a 40 mmφ extruder, polyester A is 275 ° C., polyester B is 27 mm
Melt extrusion at 0 ° C, polyester B / polyester A /
After laminating into three layers so that polyester B (lamination thickness ratio 1: 10: 1) was obtained, it was expanded in the width direction in a die and discharged in a sheet form from a 1.0 mm slit. The sheet was tightly cooled and solidified while applying an electrostatic charge to a casting drum kept at 25 ° C., and then 3.3 mm at 70 ° C. with a stretching roll.
-Fold longitudinal stretching, 3.3-fold transverse stretching at 80 ° C in a tenter,
Heat treatment was performed at 200 ° C. for 5 seconds to obtain a biaxially stretched flexible polyester film having a thickness of 15 μm. Table 1 summarizes the characteristic values.

The surface of the obtained film was subjected to a corona treatment, and a polyvinylidene chloride (PVDC) solution was applied using a bar coater. After application, 1 in hot air oven
It was dried at 00 ° C. for 1 minute and heat-treated at 150 ° C. for another 1 minute. The thickness of the coat layer is 5 μm. This polyvinylidene chloride-coated film has an oxygen permeability of 2.3 (cc / m2).
² * day) and a high gas barrier property, and when this coated film was rubbed 100 times with a gelbo tester, the oxygen permeability was reduced to only 2.6 (cc / m ² * day). It was found that defects were hardly generated in the coat layer.

Example 2 Polyester A had a limiting viscosity of 0.70 and a dimer acid copolymerization amount of 10 mol% (terephthalic acid 90 mol%) (Tm = 2
Polyester B was converted to a polyethylene terephthalate having an intrinsic viscosity of 0.65 obtained by a known method from 100 mol% of terephthalic acid as a dicarboxylic acid component and 100 mol% of ethylene glycol as a diol component. Extrusion temperature 280 ° C,
15 μm in thickness in the same manner as in Example 1 except that the laminated thickness ratio of polyester B / polyester A / polyester B is 1: 30: 1, the longitudinal stretching ratio is 3.7 times, and the lateral stretching ratio is 3.6 times. Flexible polyester film was obtained. Table 1 summarizes the physical properties. When the obtained film was treated in the same manner as in Example 1 and coated with polyvinylidene chloride, the oxygen permeability was 2.5 (cc / mm ² · day), indicating a good gas barrier property. Also in the gelbot tester 1
The oxygen permeability after rubbing 00 times is 3.6 (cc / mm ² ·
day), it was found to maintain the barrier to a considerable extent.

Example 3 As a polyester A, a copolymer polyester B (T) having an intrinsic viscosity of 0.69 was obtained by a known method using 80 mol% of terephthalic acid and 20 mol% of sebacic acid as dicarboxylic acid components.
m211 ° C., Tg 32 ° C.), and as the polyethylene terephthalate used in Example 2 as polyester B,
A flexible polyester film having a thickness of 15 μm was obtained in the same manner as in Example 1. Table 1 shows the physical property values. The obtained film was treated in the same manner as in Example 1, and coated with polyvinylidene chloride.

Example 4 The film obtained in Example 2 and an ethylene vinyl alcohol copolymer (EVOH) film (12 μm) were dry-laminated using a urethane-based adhesive. The resulting film has an oxygen permeability of 0.9 (cc / mm ² · day).
And good gas barrier properties.

Comparative Example 1 A polyethylene terephthalate (PET) biaxially stretched film was used as a base film in the same manner as in Example 1.
Polyvinylidene chloride resin coating was performed. The oxygen permeability of the prepared PVDC-coated PET film was 2.2.
(Cc / m ² · day) and almost the same barrier properties as in Example 1, but the oxygen permeability after 100 times of rubbing with a gelbo tester was 15.7 (cc / m ² · day), which was very low. It turned out that many coat layer defects occurred.

[0041]

[Table 1]

[0042]

As described above, according to the barrier flexible polyester film of the present invention, the Young's modulus is 1
Since a gas barrier layer is laminated on at least one surface of a biaxially oriented polyester film having excellent flexibility of 0 to 250 kg / mm ² and piercing strength of 10 kg / mm or more, it has excellent impact resistance, pinhole resistance, etc. The film can be a film having a barrier layer on which a gas barrier property is unlikely to be formed. In particular, a film suitable for use in packaging materials requiring gas barrier properties can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // B29K 67:00 B29K 67:00 B29L 9:00 B29L 9:00 (56) References JP-A-5-131601 (JP, A) JP-A-2-219832 (JP, A) JP-A-3-164249 (JP, A) JP-A-4-77531 (JP, A) JP-A-5-43726 (JP, A) JP-A-4 -8745 (JP, A) JP-A-3-231929 (JP, A) JP-A-52-151365 (JP, A) JP-A-6-79776 (JP, A) JP-A-6-190969 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 7/04

Claims (5)

(57) [Claims] Claims: 1. A Young's modulus of 10 to 250 kg / mm ² ,
The piercing strength is 10 kg / mm or more and polyethylene
Flexible polyester A based on terephthalate
A flexible polyester film having a barrier property, wherein a gas barrier layer is laminated on at least one surface of the biaxially oriented polyester film. 2. The flexible polyester film having barrier properties according to claim 1, wherein said gas barrier layer is laminated by resin coating. 3. The flexible polyester film according to claim 2, wherein the resin coating layer is made of polyvinylidene chloride or an ethylene-vinyl alcohol copolymer. 4. The flexible polyester A has 8 carbon atoms.
Long-chain aliphatic dicarboxylic acid having the above alkylene group
4. The barrier flexible polyester film according to claim 1, which contains 1 to 40 mol% . 5. The polyester film according to claim 1, wherein
Glass transition point on at least one side of flexible polyester A
Is a laminate of polyester B having a temperature of 45 ° C. or higher.
5. The flexible polyester film having barrier properties according to any one of items 1 to 4.