JP2002069276A - Gas barrier polyester film and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film which excels in transparency and gas barrier properties and is used for such as food packaging. SOLUTION: The polyester film is composed of polytrimethylene terephthalate (PTT) and/or polytetramethylene terephthalate (PBT) and poly-m-xylylene diadipamide (MXD6) at a ratio (wt.%) of 60-90 to 40-10. A method for manufacturing a gas barrier polyester film comprises stretching an unstretched film in the lengthwise and crosswise directions by the simultaneous biaxial stretching method in manufacturing this film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas barrier polyester film and a method for producing the same.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Biaxially stretched polyester films, such as polyester and polytrimethylene terephthalate (PTT) and polytetramethylene terephthalate (PBT), have moisture-proof properties, mechanical strength,
It has excellent heat resistance and oil resistance, and is widely used in the food packaging field and the like. Since films used for food packaging are required to have a high gas barrier property to prevent deterioration of the contents, polyvinylidene chloride (PVD)
Although polyester films coated with C) have been suitably used, PVDC has a problem in that dioxin is generated when incinerated at a low temperature.

As a gas barrier resin containing no chlorine, there is an aromatic polyamide resin. Among them, polymethacrylylene adipamide (MXD6) is particularly excellent in gas barrier properties. For example, JP-B-53-33618 discloses MXD6 / PET = 99.5-50 / 0.5-50 (% by weight). It has been disclosed that a polyamide-based biaxially stretched film having the composition of (1) has excellent gas barrier properties and dimensional stability. As described above, the gas barrier property of the film composed of PET and MXD6 is excellent, but the compatibility is not good. Therefore, in order to improve the compatibility between PET and MXD6 and increase the transparency, a compatibilizing agent must be used. It had to be blended (Japanese Patent Publication No. Hei 6-2871). However, when used for applications such as food packaging, there is a problem that the compatibilizer is subject to restrictions on food hygiene, and a polyester resin material that can achieve high transparency without a compatibilizer when used in combination with MXD6. Was required.

[0004]

An object of the present invention is to solve the above-mentioned problems and to provide a polyester film which is excellent in gas barrier properties and transparency and is suitable for food packaging applications.

[0005]

Means for Solving the Problems The present inventors have found that the above problems can be solved by adopting a specific production condition using a polyester resin composition having a specific composition. The invention has been reached.

That is, the gist of the present invention is as follows. (1) 60-90 for PTT and / or PBT and MXD6
/ 40 to 10 (mass%) gas barrier polyester film. (2) 60-90 for PTT and / or PBT and MXD6
A method for producing a gas-barrier polyester film, comprising stretching an unstretched film consisting of / 40 to 10 (% by weight) in the longitudinal and transverse directions by a simultaneous biaxial stretching method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[0008] The polyester resin component constituting the polyester film of the present invention comprises PTT and / or PBT. PTT is a polyester resin composed of a dicarboxylic acid component mainly containing terephthalic acid and a diol component mainly containing 1,3-propanediol, and PBT is a dicarboxylic acid component mainly containing terephthalic acid. And a diol component containing 1,4-propanediol as a main component. As a method of synthesizing these polyester resins, for example, each component including a main component is subjected to an esterification reaction or transesterification to obtain a reaction product having an esterification reaction rate of 92 to 98%.
Next, a polycondensation catalyst is added, and under reduced pressure, 220-26.
A polycondensation reaction is performed at 0 ° C. for 3 to 5 hours, and then, if necessary, a solid phase polymerization is performed.

The above-mentioned PTT and PBT may be used alone as a polyester resin component, or a mixed polyester of both may be used. Further, the mixed polyester may be partially or entirely a block or random copolymer of PTT and PBT.

The PTT and PBT used in the present invention can be copolymerized with other components as long as the effects are not impaired. Isophthalic acid, phthalic acid,
2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, succinic acid, adipic acid, sebacic acid,
Dicarboxylic acids such as dodecane diacid, dimer acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, and cyclohexanedicarboxylic acid;
Oxycarboxylic acids such as 4-hydroxybenzoic acid, ε-caprolactone, and lactic acid; glycols such as 1,6-hexanediol and cyclohexanedimethanol; trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin, and pentane And polyfunctional compounds such as erythritol.

[0011] MXD6 used in the present invention is obtained by a polycondensation reaction between methacrylylenediamine and adipic acid.
Moreover, what contained the paraxylylene adipamide component at 5 mass% or less may be sufficient.

[0012] The polyester film of the present invention comprises PTT
And / or PBT and MXD6 are 60 to 90/40 to 10
(% By mass), preferably 70 to 85/30 to 15 (% by mass). MXD
If 6 is less than 10% by mass, the effect of gas barrier properties will be insufficient, and if it exceeds 40% by mass, excellent mechanical properties, dimensional stability and transparency of PTT or PBT will be reduced, and extrusion will not occur. Occasionally, a phenomenon in which the film pulsates (a so-called ballast phenomenon) tends to occur.

The haze of the polyester film of the present invention is 20% or less, and has excellent transparency.

Further, the polyester film of the present invention comprises:
The oxygen permeability is 300 ml / m ² · day · MPa (converted to a thickness of 12 µm) or less. Oxygen permeability is 300ml /
If it is larger than m ² · day · MPa, the gas barrier properties for use in food packaging and the like are insufficient.

[0015] The polyester film of the present invention comprises a uniaxial stretching in the longitudinal or transverse direction, a sequential biaxial stretching in the longitudinal and transverse directions,
It can be manufactured by simultaneous biaxial stretching in the vertical and horizontal directions or by an inflation method. Above all, a tenter-type simultaneous biaxial stretching method is most preferable.

That is, PTT and / or PBT and MX
D6 is charged into an extruder, and is heated and melted at 220 to 280 ° C., extruded into a sheet from an extruder equipped with a T-die, and placed on a cooling drum whose temperature is adjusted to 25 ° C. or less by an electrostatic application casting method or the like. Closely contacted and quenched, the end of the obtained unstretched sheet having the desired thickness is gripped by clips of a tenter-type simultaneous biaxial stretching machine, heated to 40 to 100 ° C., and lengthwise and widthwise 2 to 4 times. It is simultaneously biaxially stretched about twice. Thereafter, the film is heat-treated at a temperature lower than the melting point for several seconds at a relaxation rate of 0 to 7%, cooled to room temperature, and wound at a speed of 20 to 300 m / min to obtain a film having a desired thickness. At the time of stretching, the unstretched sheet may be preliminarily stretched by about 1 to 1.2 times in the longitudinal and / or transverse directions as necessary, and then simultaneously biaxially stretched.

Heat treatment after stretching is a necessary step for reducing the thermal shrinkage of the film. For the heat treatment, a known method such as a method of blowing hot air, a method of irradiating infrared rays, or a method of irradiating microwaves can be used.
Above all, a method of blowing hot air is preferable because uniform and accurate heating can be achieved.

For the purpose of imparting specific performance to the present invention, various processings such as irradiation of ultraviolet rays, α rays, β rays, γ rays or electron beams, corona treatment, plasma irradiation, flame treatment, or polyamide, Various known methods such as application of a resin such as polyolefin, lamination, vapor deposition of a metal such as aluminum oxide and silicon oxide, and coating of a photocatalytic resin such as titanium oxide can be applied.

The film of the present invention is formed by adding a necessary amount of an inorganic lubricant such as silica, alumina, kaolin or the like in order to further improve the passability during the production and the process, thereby imparting a slip property to the film surface. Can be. In order to further improve the printability of the film, for example, an antistatic agent can be contained.

[0020]

Next, the present invention will be described more specifically with reference to examples. The method for measuring characteristic values in the evaluation of the examples and comparative examples is as follows. (1) Haze Measurement was performed using a haze meter TC-HIIIDPK manufactured by Toyo Denshoku Co., Ltd. in accordance with ASTM-D-1003-61. (2) Oxygen permeability MOCON gas permeability measuring device OX-TRAN2 /
Using No. 20, the measurement was performed under the conditions of a temperature of 20 ° C. and a humidity of 65%.

Example 1 A reactor was charged with 30.4 kg of 1,3-propanediol and 33.2 kg of terephthalic acid, and subjected to an esterification reaction at a temperature of 240 ° C. for 4 hours while stirring under a pressure of 3000 hPa. A 96% esterification reaction product was obtained.
40 kg of the obtained esterification reaction product was transferred to a polymerization reactor, and 2 mol of tetrabutyl titanate was added to 1 mol of the acid component.
× 10 ^-4 mol, and the resulting polyester 10
Hindered phenolic antioxidant (Irganox 1010 manufactured by CIBA-GEIGY) based on 0 parts by mass
Was added under a reduced pressure of 2.7 hPa, and 225
After conducting a polycondensation reaction at 3 ° C. for 3 hours, the mixture was pelletized and polytrimethylene terephthalate (PT) having an intrinsic viscosity of 0.89 was prepared.
T) was obtained. Polymethaxylylene adipamide (MXD
6) MX Nylon 6001 manufactured by Mitsubishi Gas Chemical Company
(Relative viscosity 2.1) was used. PTT / MXD6 = 8
The mixture mixed at 0/20 (% by mass) was put into a 150 mmφ extruder equipped with a T die, melt-extruded into a sheet at a resin temperature of 270 ° C., and an applied voltage was applied to a cooling drum having a surface temperature of 15 ° C. By cooling while contacting, an unstretched sheet having a thickness of 150 μm was obtained. Next, the unstretched sheet was heated to 75 ° C. using a tenter-type simultaneous biaxial stretching machine.
After stretching at 3.5 ° C. and 3.5 times at 30 ° C.,
After heat treatment at 00 ° C. to make the relaxation rate in the transverse direction 3%, the film was cooled to room temperature to obtain a 12 μm-thick biaxially stretched film. Table 1 shows the results of measuring the haze and oxygen permeability of the obtained film.

Example 2 As polytetramethylene terephthalate (PBT),
NOVADU manufactured by Mitsubishi Engineering-Plastics Corporation
R-5010 (intrinsic viscosity 1.1) was used. As the meta-xylylene adipamide (MXD6), MX nylon 6001 (relative viscosity 2.1) manufactured by Mitsubishi Gas Chemical Company was used. A mixture of PBT / MXD6 = 80/20 (% by mass) was formed into a sheet and stretched in the same manner as in Example 1 to obtain a biaxially stretched film having a thickness of 12 μm. Table 1 shows the results of measuring the haze and oxygen permeability of the obtained film.

Examples 3 to 5 and Comparative Examples 1 to 4 Biaxially stretched films were obtained in the same manner as in Example 1 except that the mixing ratio of PTT, PBT and MXD6 was changed as shown in Table 1. Table 1 shows the results of measuring the haze and oxygen permeability of the obtained film.

[0024]

[Table 1]

In Examples 1 to 5, films having excellent transparency and gas barrier properties could be obtained.
In No. 2, since the mixing ratio of MXD6 was low, oxygen permeability was high, and sufficient gas barrier properties could not be obtained. Furthermore, in Comparative Examples 3 and 4, since the mixing ratio of MXD6 was high, sufficient compatibility with the polyester resin was not obtained, and a film having high haze and poor transparency was obtained.

[0026]

According to the present invention, a polyester film having excellent gas barrier properties and transparency is provided, and can be suitably used for applications such as food packaging.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) B29K 67:00 B29K 67:00 77:00 77:00 B29L 7:00 B29L 7:00 F term (reference) 4F071 AA45 AA54 AH04 BA01 BB06 BB08 BC01 BC10 BC17 4F210 AA24 AA29 AG01 QC07 QG01 QG18 4J002 CF05W CF07W CF07X CL012 CL013 GG02

Claims (4)

[Claims] 1. A polytrimethylene terephthalate (P) comprising terephthalic acid and 1,3-propanediol as main components.
(TT) and / or 60 to 90% by mass of a polyester resin component composed of polytetramethylene terephthalate (PBT) containing terephthalic acid and 1,4-butanediol as main components, and 40 to 10% by mass of polymethaxylylene adipamide
Gas barrier polyester film consisting of 2. Oxygen permeability when converted to a thickness of 12 μm is 3
2. The gas barrier polyester film according to claim 1, wherein the content is not more than 00 ml / m ² · day · MPa. 3. The gas barrier polyester film according to claim 1, wherein the haze is 20% or less. 4. An unstretched film comprising 60 to 90% by mass of a polyester resin component comprising polytrimethylene terephthalate and / or polytetramethylene terephthalate and 40 to 10% by mass of polymethaxylylene adipamide is vertically and horizontally oriented. A method for producing a gas-barrier polyester film, comprising stretching by a simultaneous biaxial stretching method.