JP2001114912A - Stretched aromatic polyester film and preparation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an stretched arom. polyester film which is favorably used as a packaging material, etc., has biodegradability, transparency, and heat sealability in impulse sealing, high frequency sealing, ultrasonic sealing, etc., is excellent in elongation properties as well as mechanical properties, and further has a low vapor permeability, a low oxygen permeability and/or a low carbon dioxide gas permeability necessary for a packaging material and to provide a manufacturing method therefor. SOLUTION: This stretched aromatic polyester film essentially consists of an aromatic polyester copolymer wherein the acid components comprise about 50 to about 90 mol% of terephthalic acid, about 0.2 to about 6 mol% of a sulfonic acid metal salt and about 4 to about 49.8 mol% of an aliph. dicarboxylic acid, and the glycol components comprise about 50 to about 99.9 mol% of ethylene glycol and about 0.1 to about 50 mol% diethylene glycol. It has an impulse sealing strength and/or a high frequency sealing strength of >=3 N/15 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biodegradable (biodegradable) stretched aromatic polyester film and a method for producing the same, and more particularly, to a biodegradable (biodegradable) polyester film suitably used for packaging materials and the like. Low moisture permeability, low oxygen permeability, and low carbon dioxide gas permeability with transparency and heat sealability by impulse seal, high frequency seal, ultrasonic seal, etc., and selectively respond to gas barrier properties required for packaging materials The present invention relates to a stretched aromatic polyester film having at least one of the above properties and also having excellent mechanical strength, and a method for producing the same.

[0002]

2. Description of the Related Art Biodegradable resin compositions have been studied in view of social concerns or demands for disposal of resin products such as plastic films. Above all, the development of biodegradable aromatic polyester resin compositions that show degradability under high humidity and high temperature conditions during the composting process of waste has been actively conducted,
Various applications have been proposed. For example, Japanese Patent Publication No. Hei 5-507109, Japanese Patent Publication No. Hei 6-505513.
And JP-A-6-505040 are obtained by polymerizing a glycol component of ethylene glycol and diethylene glycol with an alkali metal salt or alkaline earth metal salt of sulfonic acid and a diacid component of terephthalic acid. Polyesters and fibers, films, sheets, and nonwovens of fibers comprising the polyesters are described.

Further, a biaxially oriented stretched film obtained by forming a film by melt-extruding a polylactic acid-based polymer having biodegradability and then subjecting it to a stretching process, such as a polypropylene stretched film, a polystyrene stretched film, or a polyethylene stretched film. A biodegradable film having properties similar to film properties including strength and transparency, such as a terephthalate stretched film, and a method for producing the same are known (JP-A-6-23836 and JP-A-7-20527).
No. 8).

Furthermore, a biaxially oriented film formed by extruding a polyhydroxy acid composition to form a film and then performing a stretching treatment,
A film having improved strength, rigidity, transparency, and the like is known (Japanese Patent Publication No. 5-508819).

On the other hand, at present, films such as polyolefin resins, polyamide resins, polyester resins, and polyvinyl chloride resins are widely used as packaging materials.

[0006]

However, a film formed from a biodegradable polymer generally has the mechanical strength required for use as a packaging material, for example.
Transparency, gas barrier properties, and the like were insufficient compared to films conventionally used as packaging materials, such as polyolefin resins, polyamide resins, polyester resins, and polyvinyl chloride resins.

A stretched film using a polylactic acid-based resin is
Although the strength and the transparency are improved as described above, there is still a problem that it does not have practically sufficient rigidity, impact resistance, heat sealability and gas barrier properties.

Further, when a film is extruded using polylactic acid, particularly poly L-lactic acid, the melting point is 170 ° C., the glass transition temperature (about 60 ° C.) and the crystallization temperature (about 11 ° C.).
(0 ° C.), there is a problem that the suitable width of the stretching conditions is narrow, that is, the stretchability is poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide biodegradability, transparency, and heat sealability by an impulse seal, a high frequency seal, an ultrasonic seal, and the like. With excellent stretchability, film strength, and mechanical properties such as strength, rigidity and impact resistance inherent in polyethylene terephthalate, and low moisture permeability that selectively responds to gas barrier properties required for packaging materials A method for producing a stretched aromatic polyester film having at least one of low oxygen permeability and low carbon dioxide gas permeability, and a stretched aromatic polyester film having a wide range of suitable stretching conditions and no problem in production. To provide.

[0010]

Means for Solving the Problems In order to solve such problems, the present inventors have developed terephthalic acid, sulfonate,
It has been found that a stretched aromatic polyester film that solves the above problems can be provided by forming and stretching a film using a polyester copolymer having a repeating unit composed of an aliphatic dicarboxylic acid, ethylene glycol, and diethylene glycol. Was.

That is, the stretched aromatic polyester film of the present invention comprises a repeating unit composed of terephthalic acid, a metal salt of sulfonic acid, an aliphatic dicarboxylic acid, ethylene glycol, and diethylene glycol.
About 50 mol% to about 90 mol% of terephthalic acid, about 0.2 mol% to about 6 mol% of sulfonic acid metal salt, and about 4 mol% to about 49.8 mol% of aliphatic dicarboxylic acid component unit
And ethylene glycol in the glycol component is about 5
0 to about 99.9 mole%, and at least one of impulse seal strength and high frequency seal strength of the film, comprising an aromatic polyester copolymer in which diethylene glycol is about 0.1 to about 50 mole%. Is 3 N / 15 mm or more.

The above-mentioned stretched aromatic polyester film is further characterized in that it can be ultrasonically sealed.

Further, any one of the above films has
Moisture permeability of 0 g / m ² · d or less, 300 cc / g · m ² · d
Oxygen permeability of atm or less, and 1000 cc / g
It is characterized by having a gas barrier property indicated by at least one of carbon dioxide gas permeability of not more than m ² · d · atm.

According to another aspect of the present invention, there is provided a method for producing a stretched aromatic polyester film comprising a repeating unit comprising terephthalic acid, a metal salt of a sulfonic acid, an aliphatic dicarboxylic acid, ethylene glycol, and diethylene glycol. Terephthalic acid in the acid component is about 50
From about 0.2 mol% to about 6 mol%, from about 0.2 mol% to about 6 mol% of the metal sulfonate, and from about 4 mol% to about 49.8 mol% of the aliphatic dicarboxylic acid. About 50 mol% to about 99.9 mol% glycol,
And about 0.1 mol% to about 50
Mole percent aromatic polyester copolymer, molding the aromatic polyester copolymer to form an unstretched film containing the aromatic polyester polymer, and stretching the unstretched film It is characterized by comprising a process.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In this specification, an impulse seal strength refers to a strength measured by an impulse seal method. The strength is as follows. After overlapping the film seals and holding them with a nichrome wire, apply a pulse current to the nichrome wire to instantaneously generate heat and seal, then cut into strips 15 mm in the direction perpendicular to the seal bar. JIS K712 using the test piece prepared
It is obtained by measuring the maximum strength of the seal portion by a tensile test according to No. 7.

The high-frequency seal is a method of sealing a film in which a dielectric loss occurs by placing the film in a high-frequency electromagnetic field and utilizing a heat generation phenomenon generated inside the film. The high frequency seal strength is obtained by superimposing the film seals,
After placing the electrodes between the electrodes to be applied, applying a voltage to generate heat and sealing, a test piece prepared by cutting into a strip of 15 mm in a direction perpendicular to the seal bar is used in accordance with JIS.
It is obtained by measuring the maximum strength of the seal portion by a tensile test according to K7127.

Ultrasonic sealing is a method in which a superposed film is pressed between sound poles for applying ultrasonic vibration, and is sealed by utilizing the energy of reciprocating motion at the interface of the film. Ultrasonic seal strength refers to JIS K
It refers to the maximum strength of the seal portion (length 1 mm) of the sound pole measured by a tensile test according to 7127.

The impulse seal strength, the high-frequency seal strength, and the ultrasonic seal strength are indicators of heat sealability.

The moisture permeability can be obtained by measuring under the conditions of 40 ° C. and 90% RH according to JIS K7129.

The oxygen permeability and the carbon dioxide gas permeability are determined by JI
It can be obtained by measurement under the conditions of 20 ° C. and 60% RH in accordance with SK7126.

The aromatic polyester used in the present invention is prepared by using ethylene glycol and diethylene glycol essentially as glycol components and essentially using terephthalic acid, a metal sulfonic acid salt and an aliphatic dicarboxylic acid as acid components. Produced by a polycondensation method.

Terephthalic acid in the acid component is about 50 mol%
約 90 mol%, preferably 52-83 mol%. The greater the amount of terephthalic acid, the higher the mechanical strength.

The metal salts of sulfonic acid include metal salts of 5-sulfoisophthalic acid, metal salts of 4-sulfoisophthalic acid,
Metal salts of sulfophthalic acid and the like, and metal salts of 5-sulfoisophthalic acid are preferred. The metal ion is preferably an alkali metal such as sodium, potassium and lithium, and an alkaline earth metal such as magnesium. The most preferred metal sulfonic acid salt is the sodium salt of 5-sulfoisophthalic acid.

The metal sulfonic acid salt in the acid component is about 0.2
Mol% to about 6 mol%, preferably about 2 mol% to about 5 mol%. This component is not only relatively expensive,
When used in an excessive amount, it makes the polyester water-soluble and further affects physical properties such as film shrinkage. The metal sulphonates significantly contribute to the degradation properties of the resulting films, even at as low as 0.2 mol%.

The aliphatic dicarboxylic acid has 2 to 18 carbon atoms,
It is preferably an aliphatic dicarboxylic acid having 2 to 10 carbon atoms, specifically, azelanic acid, succinic acid, adipic acid,
Sebacic acid, glutaric acid and the like can be mentioned. Among them, glutaric acid is preferred.

Typical composting by decomposition of a plastic film is performed under high temperature and high humidity conditions. Usually about 7
The glass transition temperature (Tg) of the polyester must be about 70 ° C. or less, and preferably about 65 ° C. or less, since the temperature is lower than 0 ° C. In the present invention, an aliphatic dicarboxylic acid is used to reduce the glass transition temperature to about 70 ° C. or lower. The content of the aliphatic dicarboxylic acid contributes to improving the decomposition characteristics of the film.

[0027] The aliphatic dicarboxylic acid component unit in the acid component is about 4 mol% to about 49.8 mol%, preferably 10 mol% to 45 mol%. If the amount is less than 4 mol%, the glass transition temperature cannot be significantly reduced, while 49.
If it exceeds 8 mol%, the glass transition temperature will be lowered, and the appropriate rigidity will be lost.

Incidentally, an ester-forming derivative such as a dimethyl ester of an acid can be used instead of the dicarboxylic acid.

[0029] Ethylene glycol in the glycol component is from about 50 mol% to about 99.9 mol%, and diethylene glycol is from about 0.1 mol% to about 50 mol%. Preferably, the ethylene glycol is from 80 mol% to 98 mol%
And the amount of diethylene glycol is 2 mol% to 20 mol%. When the amount of diethylene glycol exceeds 50 mol%, mechanical properties such as tensile strength of the film are adversely affected, while when the amount is less than 0.1 mol%, decomposability becomes insufficient.

The glass transition temperature may be further reduced by replacing up to 20 mol% of ethylene glycol with another glycol such as triethylene glycol.

The aromatic polyester polymer used to form the film of the present invention is prepared by a generally well-known polymerization method. For example, a linear polyester in which all of the above monomer components are charged into a polymerization vessel together with antimony or another catalyst and polycondensed under appropriate polycondensation conditions, whereby monomer units are randomly distributed along the molecular chain. Can be manufactured. As another method, there can be mentioned a method in which two or more monomer components are first reacted to prepare a prepolymer, and then the remaining monomer components are added to carry out polymerization.

The aromatic polyester polymer used to form the film of the present invention decomposes under high-humidity and high-temperature conditions, which are typical composting conditions, and most of the monomers and oligomers resulting from the decomposition, that is, terephthalic acid Acids and glycols, and oligomers thereof, are easily digested by microorganisms in solid waste or compost to carbon dioxide and water.

In order to adjust the film forming processability or the mechanical properties of the aromatic polyester polymer as long as the mechanical properties, decomposability or other properties of the polyester are not changed, a plasticizer, a lubricant, The film may be formed using an aromatic polyester composition to which conventional additives such as an inorganic filler, an antioxidant, and a weather stabilizer have been added.

The polyester copolymer forming the film of the present invention typically has an intrinsic viscosity in the range of 0.1 to 1.5, preferably in the range of 0.3 to 1.2.

First, an unstretched film is formed using the above-mentioned aromatic polyester polymer or its composition.
The method of forming the unstretched film is such that the flakes containing the aromatic polyester polymer are supplied to an extruder, melted, extruded through a film die, and quenched with a chill roll, so that the thickness ranges from about 5 μm to about 300 μm. The unstretched film is formed and collected on a take-up roll.

Then, the obtained unstretched film is monoaxially stretched with a certain width, sequentially biaxially stretched, or simultaneously biaxially stretched within a temperature range not lower than the glass transition temperature and not higher than the crystallization temperature. A stretched aromatic polyester film having one of the impulse seal strength and the high-frequency seal strength of 3 N / 15 mm or more is obtained. When a film is used as a packaging material, both the impulse seal strength and the high frequency seal strength are 3N / 15m.
m or more.

Such a film exhibits an ultrasonic sealing strength required as a packaging material and further has a strength of 150 g / m 2.
Moisture permeability of ² · d or less, 300cc / g · m ² · d · atm
The following oxygen permeability, and 1000 cc / g · m ² · d
-It has gas barrier properties indicated by at least one of the carbon dioxide gas transmission rates of atm or less.

In the present invention, by stretching the formed film, insufficient film strength of the unstretched film can be improved, and good film strength and transparency can be obtained.

The stretching is carried out by appropriately selecting stretching conditions. Usually, the stretching temperature is in the range of 40 ° C. to 100 ° C., preferably 60 ° C. to 80 ° C., and the stretching ratio is 1.5%.
It is carried out within a range of up to 6.0 times, preferably 2.5 to 6.0 times. Choosing an appropriate stretching ratio is very important for increasing the film strength, which is one of the objects of the present invention. If the stretching ratio is 1.5 or less, the strength becomes insufficient, and if it is 6 times or more, the uniformity of the film is lost.

Further, the dimensions may be stabilized by performing a heat treatment (heat set) after the stretching. By performing the heat treatment, a stretched film having good heat sealing properties can be obtained.

In the specific stretching step, a nip roll composed of a combination of a metal roll and a rubber roll capable of providing a gripping force necessary for regulating the traveling speed and / or a rotary roll using a vacuum suction type suction roll are used. The quenched film after forming is passed through a rotating roll while regulating the running speed, thereby the running direction (MD)
Stretch. The film stretched in the running direction is introduced into a tenter device, and both ends in the width direction are gripped by a tenter grip, and stretched in the width direction (TD) while running with the tenter grip. Then, it is heat-treated at a temperature of 120C to 160C to obtain a biaxially stretched polyester film. The stretching in the running direction and the width direction of the polyester film may be performed in this order, sequentially in the reverse order, or simultaneously, but generally, the stretching is first performed in the running direction and then in the width direction. It is preferred to stretch in the direction.

The stretched aromatic polyester film of the present invention includes, for example, agricultural and horticultural products such as multi-films for agricultural and horticultural use, seed tapes, pesticide bags, garbage bags for compost, garbage bags, draining bags, and supermarket shopping. Household goods such as bags, paper cups, paper plates, etc., coated paper for paper resource recovery, office supplies such as print laminating, card covers, window frame envelopes, cover films for printed paper, disposable diaper pack sheets, sanitary products, disposable gloves, laundry It can be preferably used for general packaging applications including hygiene articles such as bags, bottles, shrink films for miscellaneous goods, films and wrap films for food packaging.

[0043]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Measurement method and evaluation used in this example
The titration method is as follows.Biaxial stretch formability When making biaxially stretched film by performing biaxial stretch molding
After the longitudinal stretching, the film is stretched in the transverse direction using a tenter device.
When performing the process, observe the phenomenon of film film cracking (vertical tearing).
The judgment was made based on the following criteria. Good: always stable without film film cracking (vertical tearing)
Lateral stretching was achieved. Defective… Film film cracking (vertical tearing) occurs and becomes stable
Lacked lateral stretchability. Tensile modulus It was measured according to JIS K7127.Break stress It was measured according to JIS K7127.Elongation at break It was measured according to JIS K7127.Impact strength Piercing impact test for thin packaging materials, puncture
-According to the mechanism principle of the test (JIS P8134). Stretched horizontally
The center of a circular sample with a fixed area
A sample is broken by hitting a hemispherical weight with a diameter of 1.0 inch from below.
The force at the time of doing was read with a discarding needle.Tear strength It was measured according to JIS K7128.Haze It was measured according to JIS K6714.Trance It was measured according to JIS K6714.Impulse seal strength Lay the seals on the film together,
Apply a pulse current to this nichrome wire while holding it
Then, it was instantaneously heated and sealed. Apply this to the seal bar
And cut into 15 mm strips at right angles
And the maximum strength of the seal was measured by a tensile test.
Was.High frequency seal strength Laminate the seal part of the film and place between the applied electrodes.
Then, voltage was applied to invent and seal. This is a seal bar
A 15 mm strip cut at right angles to the
The maximum strength of the seal was measured by a tensile test.
Specified.Ultrasonic seal strength Laminate the seal part of the film and give ultrasonic vibration
Press between the sound poles, and reciprocate at the film interface.
Sealing was performed using the energy of motion. Sound pole seal
(Length 1mm) measured by tensile test
Was.Moisture permeability It was measured according to JIS K7129 (40 ° C, 90
% RH).Gas permeability (oxygen and carbon dioxide gas permeability) It was measured in accordance with JIS K7126 (20 ° C., 60
% RH).Soil degradability A test piece of a predetermined size was left in the soil for 5 months.
After a lapse of time, the test piece was visually observed.

Example 1 Terephthalic acid was about 50 mol%
About 90 mol%, about 0.2 mol% to about 6 mol% of sodium 5-sulfoisophthalate, and about 4 mol% of glutaric acid.
From about 50 mol% to about 99.9 mol% ethylene glycol and from about 0.1 mol% to about 50 mol% diethylene glycol. Aromatic polyester copolymer having a repeating unit (density: 1.35 g / cm ³ ; melting point: 2)
A flake (small particle) having a melt index of 25 g / 10 minutes under a condition of 00 ° C; 220 ° C under a load of 2160 g) is preliminarily dried in an oven, and then melted at a cylinder set temperature of 200 to 220 ° C by a 60 mm diameter extruder. After extruding the T-die, quenching (30 ° C) with cast roll, thickness 20
A 0 μm film was formed. The film was stretched 3.0 times at 60 ° C. and 4.5 times at 70 ° C. by using a sequential biaxial stretching apparatus, and then heat-treated at 150 ° C. for 20 seconds to obtain a biaxially stretched fragrance having a thickness of 20 μm. An aromatic polyester film was obtained.

The obtained film was evaluated and measured. Table 1 shows the results.

Comparative Example 1 Polylactic acid resin (trade name LACEA H-100E manufactured by Mitsui Chemicals, Inc., density 1.28 g /
cm ^3; mp 160 ° C.; 190 ° C., after predrying melt index 10 g / 10 min) of the flakes (small particles) in an oven under the conditions under 2160g load by 60mm径押extruder, melted at a cylinder temperature of 200 ° C. Then, after extruding the T-die, it was rapidly cooled (30 ° C.) with a cast roll to form a film having a thickness of 200 μm. The film was stretched 3.0 times at 65 ° C.
After laterally stretching at 4.5 ° C 4.5 times, heat treatment was performed at 140 ° C for 20 seconds to obtain a biaxially stretched polylactic acid-based film having a thickness of 20 µm.

The obtained film was evaluated and measured. Table 1 shows the results.

Comparative Example 2 Polyethylene terephthalate (density: 1.38 g / cm ³ ; melting point: 260 ° C .; 265 ° C.)
Under a load of 2160 g, the melt index is 39 g /
10 minutes) after pre-drying the flakes (small particles) in an oven, and setting the cylinder temperature to 27 using an extruder having a diameter of 60 mm.
After melting at 0 to 300 ° C and extruding a T-die, it was rapidly cooled (30 ° C) with a cast roll to form a 200 µm thick film. This film is successively stretched using a biaxial stretching device.
After stretching 3.0 times at 80 ° C. and stretching 4.5 times at 90 ° C., heat-treat it at 150 ° C. for 20 seconds to obtain a 2 μm-thick 2 μm.
An axially stretched aromatic polyester film was obtained.

The obtained film was evaluated and measured. Table 1 shows the results.

[0051]

[Table 1]

A comparison between Example 1 and Comparative Example 1 relating to a polylactic acid-based film shows that all of them are biodegradable and have excellent strength. It can be seen that the heat sealability by the sonic seal has also been improved, and the moisture permeability, oxygen permeability, and carbon dioxide gas permeability have been significantly improved. Furthermore, it is understood that the film of the present invention has good stretchability, and thus can be manufactured under a wide range of stretch conditions.

When Example 1 is compared with Comparative Example 2 relating to a polyethylene terephthalate film having excellent stretchability, gas barrier properties, film strength, strength, rigidity, and impact resistance, the tensile properties and optical properties of the film of the present invention are compared. , Impact strength, moisture permeability, oxygen permeability, and carbon dioxide gas permeability are maintained to such an extent that practically there is no hindrance. Furthermore, the film of the present invention has soil degradability, impulse seal strength, high frequency seal strength. Is remarkably improved.

[0054]

The stretched aromatic polyester film of the present invention has biodegradability, transparency, and heat sealability by impulse seal, high frequency seal, ultrasonic seal, etc., and has strength, rigidity and impact resistance. It has excellent mechanical properties and has one of low moisture permeability, low oxygen permeability, and low carbon dioxide gas permeability that selectively responds to the gas barrier properties required for packaging materials. Such a film is particularly suitably used as a packaging material.

In the method for producing a film of the present invention, since a polyester film having excellent stretchability is stretched, it is possible to produce a stretched aromatic polyester film under a wider range of stretching conditions than conventional biodegradable films. To

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Claims (4)

[Claims] 1. A stretched aromatic polyester film, wherein the film comprises a repeating unit consisting of terephthalic acid, a metal salt of sulfonic acid, an aliphatic dicarboxylic acid, ethylene glycol, and diethylene glycol, wherein terephthalic acid is contained in the acid component. From about 50 mol% to about 90 mol%, from about 0.2 mol% to about 6 mol% of the metal sulfonic acid salt, and from about 4 mol% to about 49.8 mol% of the aliphatic dicarboxylic acid; An aromatic polyester copolymer wherein ethylene glycol is from about 50 mol% to about 99.9 mol%, and diethylene glycol is from about 0.1 mol% to about 50 mol%; A stretched aromatic polyester film, wherein at least one of the strengths is 3 N / 15 mm or more. 2. The stretched aromatic polyester film according to claim 1, which is capable of being ultrasonically sealed. 3. The film has a moisture permeability of 150 g / m ² · d or less, an oxygen permeability of 300 cc / g · m ² · d · atm or less, and a water permeability of 1000 cc / g · m ² · d · at.
at least one of the carbon dioxide gas permeability of not more than m
The stretched aromatic polyester film according to claim 1 or 2, having a gas barrier property indicated by the following. 4. The method for producing a stretched aromatic polyester film according to claim 1, wherein the terephthalic acid, a metal salt of a sulfonic acid, an aliphatic dicarboxylic acid, ethylene glycol, and diethylene glycol are used. About 50 mol% to about 90 mol% of the terephthalic acid, about 0.2 mol% to about 6 mol% of the sulfonic acid metal salt, and about 4 mol% of the aliphatic dicarboxylic acid in the acid component. About 49.8 mol%, and ethylene glycol in the glycol component is about 50 mol% to about 99.9 mol%.
Mole%, and about 0.1 mole% of diethylene glycol
Forming an aromatic polyester copolymer of about 50 mol% to about 50 mol%, forming the aromatic polyester copolymer to form an unstretched film containing the aromatic polyester polymer, and the unstretched film And a method for producing a stretched aromatic polyester film.