KR100439624B1 - Biaxially oriented polyster film, manufacturing method thereof, and laminated film comprising the same - Google Patents

Abstract

In the present invention, a polybutylene terephthalate and a soft polybutylene terephthalate (a) comprising a polytetramethylene glycol (a) and poly (ethylene terephthalate-co-ethylene naphthalate) (b), wherein (a) and A biaxially stretched polyester film is provided, characterized in that the mixing weight ratio of (b) is from 50:50 to 5:95, which is not only excellent in durability, moisture resistance, mechanical properties, heat resistance and oil resistance, but also at least in the longitudinal direction. Excellent tearing linearity. Therefore, the biaxially stretched polyester film and the laminated film including at least one layer of the film according to the present invention can be usefully used as a packaging material for food, medicine, daily necessities, cosmetics and the like.

Description

Biaxially oriented polyester film, its manufacturing method and laminated film comprising the same {Biaxially oriented polyster film, manufacturing method, and laminated film comprising the same}

The present invention relates to a biaxially stretched polyester film, and more particularly, not only has excellent mechanical strength, heat resistance, and dimensional stability, but also has excellent tearing linearity (linear tearing property when pulled) in the longitudinal direction of the film. The present invention relates to a biaxially stretched polyester film useful as a packaging material for food, pharmaceuticals, daily necessities, cosmetics, and the like, a method for producing the same, and a laminated film including the biaxially stretched polyester film.

As the industrial sectors are diversified, various properties and functionality are required for packaging materials. Accordingly, packaging materials using plastic films manufactured from various polymer resins in addition to paper have been used.

Currently, the most widely used packaging materials are polyesters represented as polyethylene terephthalate. Polyester is chemically and physically stable, has high mechanical strength, and is excellent in heat resistance, durability, chemical resistance, electrical insulation, and the like, and is widely used as a raw material for food, medical, and various industrial packaging materials.

The polyester may be produced as a biaxially oriented film or a film laminated in a two-layer or three-layer structure according to a conventional film manufacturing process, wherein the biaxially oriented polyester film is a tubular method, a tenter type It can be manufactured by simultaneous biaxial stretching method, tenter type biaxial stretching method and the like, and has excellent durability, moisture resistance, mechanical strength, heat resistance and oil resistance, and is widely used as various packaging materials, especially food packaging materials.

By the way, the packaging material using a biaxially-stretched polyester film has a problem that tear openability is bad. As a method for improving openability, a method of forming a notch has been suggested. However, when the tear is pulled from the notch, a phenomenon that does not rip linearly occurs frequently, and the contents are not only scattered when opened, but are easily broken, and when the contents are liquid, the contents may be splashed to pollute the user's clothes.

In order to overcome this problem, various methods have been proposed. For example, a film obtained by laminating a uniaxially stretched polyolefin film as an intermediate layer as a material having excellent linearity when tearing a film, for example, a "biaxially stretched polyester film / uniaxially" Laminated film of the three-layered structure like the "stretched polyolefin film / unstretched polyolefin film." However, the film having such a structure not only has a troublesome process in that the intermediate layer is to be manufactured separately, but the manufacturing cost may increase due to this, and its use is limited.

As another method for imparting tear linearity to a biaxially stretched polyester film, Japanese Patent Application Laid-Open No. Hei 8-169962 discloses a thermoplastic polyester resin A having an acid component mainly of terephthalic acid or naphthalenedicarboxylic acid, and the resin A Disclosed is a biaxially stretched polyester film mainly composed of a mixture of thermoplastic polyester resins B which can be phase separated from each other. In the above document, polyethylene terephthalate (hereinafter referred to as PET) is used as resin A, and a block copolymer of poly (tetramethylene glycol) (hereinafter referred to as PTMG) and polybutylene terephthalate (hereinafter referred to as PBT) is used as resin B. In the case of large-scale production using an extruder of 200mmΦ or more, there is a problem that the film thickness unevenness is not suitable as a packaging material.

The technical problem to be achieved by the present invention is a biaxially stretched polyester film that is excellent in tear linearity and easy to mass production while maintaining dimensional stability under low hygroscopicity, mechanical properties, transparency, steering, heat resistance, oil resistance and dry heat or wet heat environment To provide.

Another technical problem to be achieved by the present invention is to provide a method for producing a biaxially stretched polyester film as described above.

Another technical problem to be achieved by the present invention is to provide a laminated film comprising the biaxially stretched polyester film as described above.

1 is a cross-sectional view of a film sample used for tear linearity evaluation of a biaxially stretched polyester film prepared according to Examples and Comparative Examples of the present invention.

2A is a cross-sectional view of a biaxially drawn polyester film sample having excellent tear linearity.

2B is a cross-sectional view of a biaxially stretched polyester film sample having poor tear linearity.

The technical problem of the present invention includes a soft polybutylene terephthalate (a) and a poly (ethylene terephthalate-co-ethylene naphthalate) (b) comprising a polybutylene terephthalate and polytetramethylene glycol, (b) It can be made by a biaxially stretched polyester film characterized in that the mixed weight ratio of a) and (b) is 50:50 to 5:95.

Another technical problem of the present invention is to prepare a soft polybutylene terephthalate comprising (a) polybutylene terephthalate and polytetramethylene glycol; (b) coextruding the flexible polybutylene terephthalate and poly (ethylene terephthalate-co-ethylenenaphthalate) at a mixing ratio of 50:50 to 5:95 to prepare an unstretched sheet; And (c) biaxially stretching the unstretched sheet 3 to 5 times in the longitudinal and transverse directions at 90 to 140 ° C., respectively.

Another technical problem of the present invention is a substrate layer; And soft polybutylene terephthalate (a) and poly (ethylene terephthalate-co-ethylene naphthalate) (b), which are formed on at least one surface of the base layer and include polybutylene terephthalate and polytetramethylene glycol. It can be made by a laminated film characterized in that the biaxially stretched polyester film contained in a weight ratio of 50:50 to 5:95.

In the present invention, the poly (tetramethylene glycol) has a molecular weight of 500 to 10,000, the content is preferably 5 to 30% by weight based on the total amount of the soft polybutylene terephthalate.

In addition, the polyethylene terephthalate-co-ethylene naphthalate is a transesterification reaction of ethylene glycol with an acid component containing 70 to 95% by weight of dimethyl terephthalate and 5 to 30% by weight of dimethyl-2,6-naphthalate, The oligomer is prepared by directly ester-reacting ethylene glycol with an acid component including 70 to 95 wt% terephthalic acid and 5 to 30 wt% 2.6-naphthalenedicarboxylic acid, followed by melt polymerization or solid phase polymerization. Can be. That is, in the biaxially stretched polyester film according to the present invention, the poly (ethylene terephthalate-co-ethylene naphthalate) has a mixed weight ratio of ethylene terephthalate and ethylene naphthalate of 70:30 to 95: 5, preferably 80 It is a copolymer of: 20-90: 10.

Biaxially stretched polyester film according to the present invention can be prepared according to the following production method.

First, during the polymerization of PBT, the PTMG content is 5 to 30% by weight, preferably 10 to 20% by weight, more preferably, by adding and condensation-polymerizing PTMG having a molecular weight of 500 to 10,000, preferably 1,000 to 3,000. Preferably 10-15% by weight of flexible PBT. In this case, PBT and PTMG may be melted and mixed with an extruder as a simpler method.

At this time, when the molecular weight of the PTMG is less than 500, the tearing linearity effect is not obtained, whereas when the molecular weight of the PTMG is more than 10,000, mechanical properties such as mechanical strength, dimensional stability, and haze are deteriorated, and stable tearing linearity of the film does not appear. In addition, when the PTMG content is less than 5% by weight, the tearing linearity of the obtained film does not appear, whereas when it exceeds 30% by weight, the film may pulsate at the time of extrusion, making it difficult to mass-produce and increasing the film thickness nonuniformity. May cause problems.

Subsequently, another component constituting the biaxially stretched polyester film according to the present invention is poly (ethylene terephthalate-co-ethylene naphthalate), and as an acid component, dimethyl terephthalate and dimethyl-2,6-naphthalate, Alternatively, an oligomer may be prepared by transesterification using terephthalic acid and 2,6-naphthalenedicarboxylic acid using ethylene glycol as the diol component or by direct esterification, followed by melt polymerization or solid phase polymerization. .

The resulting soft PBT and PETN were mixed in a mixing weight ratio of 50:50 to 5:95, preferably 70:30 to 10:90, more preferably 80:20 to 10:90, and then introduced into an extruder and heated. After melting, it is passed through a T-die to prepare an unstretched sheet. At this time, if the mixed weight ratio of the flexible PBT is less than 5% by weight, the tearing linearity is not obtained, whereas when it exceeds 50% by weight, the film thickness nonuniformity becomes large or satisfactory tearing linearity is not obtained. Since physical properties, such as strength, dimensional stability, and haze, fall, there arises a problem of lack of practicality.

Subsequently, the obtained unstretched sheet was brought into close contact with a cooling drum by an electrostatically applied casting method or the like, and then cooled, and then stretched 3 to 5 times in the longitudinal and transverse directions at a temperature of 90 to 140 ° C., and again at a temperature of 210 to 240 ° C. Heat treatment to prepare a biaxially stretched film. At this time, if the stretching temperature is less than 90 ℃ uniform stretch film can not be obtained, if it exceeds 140 ℃, the crystallization of the PET is promoted, the transparency may be worsened. In addition, if the draw ratio is less than 3 times, the strength of the resulting film is lowered, and if it exceeds 5 times, there is a problem that it is difficult to perform the stretching process.

In addition, in this invention, you may employ | adopt any method, such as a tenter simultaneous biaxial stretching method, a tenter type biaxial stretching method, or the tubular biaxial stretching method.

The tensile strength of the biaxially stretched polyester film according to the present invention thus obtained is preferably 20 to 35 kgf / mm 2, but if the tensile strength is less than the above range, there is a problem that the practical strength is insufficient. There is a problem that it is uneconomical because the workability at the time of film production becomes poor.

In addition, the dry heat shrinkage rate of the biaxially stretched polyester film according to the present invention is preferably in the range of 3% or less (average value in the length direction and the width direction) when treated at 160 ° C. for 15 minutes. It is not desirable because it falls.

In addition, the haze of the biaxially stretched polyester film according to the present invention is preferably 10% or less, but if the haze exceeds 10%, there is a problem that the transparency of the film is lowered and the commodity value is lowered.

The biaxially stretched polyester film according to the present invention may be surface treated by corona discharge treatment, surface hardening treatment, plating treatment, coloring treatment or various coating treatments, and at least one surface of the film may be coated with another film, fabric, nonwoven fabric, paper, By laminating a metal or the like, the effect of the present invention can be further enhanced.

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to this.

First, the physical properties of the biaxially stretched polyester film obtained according to the following Examples and Comparative Examples are evaluated as follows.

(1) Relative viscosity: It measured in the solvent (concentration: 0.5 g / Pa, temperature: 20 degreeC) which mixed the same amount of phenol and tetrachloroethane.

(2) Tear-Linearity: The biaxially stretched polyester film was cut to 205 mm in the longitudinal direction (MD direction) and 40 mm in the width direction (TD direction) as shown in FIG. Ten samples in which grooves of 5 mm length were formed were produced. Then, the tensile straightness was tested by tearing in the groove in the MD direction. On the other hand, the tear linearity of the TD direction was evaluated in the same manner as described above except that the film sample was 40 mm in the MD direction and 205 mm in the TD direction. The evaluation of the tensile linearity in the MD and TD directions was performed for each of the left end, the center and the right end of the film wound up after the stretching heat treatment. As a result of the evaluation, the number of samples reaching the opposite side from the grooved side as shown in FIG. 2A and the other side other than the opposite side from the grooved side as shown in FIG. 2B are shown. By counting the number of samples that have reached the side, it is determined that the tensile linearity is excellent when eight or more cases as in FIG. 2A are obtained.

(3) Haze: Haze was evaluated according to ASTM D103-61 using a film having a thickness of 12 µm.

(4) Tensile strength: The film was evaluated according to ASTM D882 using a film having a width of 10 mm and a length of 100 mm.

(5) Thickness nonuniformity: The thickness of 20 points | pieces was measured with 10 micrometers pitch of the thickness direction center part width direction of a film using the micrometer, and thickness nonuniformity (%) was computed according to the following formula.

[(Thickness maximum-thickness minimum) / thickness average] * 100

Example 1

194 kg of dimethyl terephthalate, 108 kg of 1,4-butanediol and 80 ppm of tetrabutyl titanate were added to the reaction vessel, and the ester exchange reaction was performed for 2.5 hours while heating and heating at 150 ° C to 210 ° C. 90 kg of the reaction product was transferred to a polymerization reactor, 40 ppm of tetrabutyl titanate was added thereto, and then 10 kg of PTMG having a molecular weight of 1,100 was added thereto. Subsequently, when the final pressure reached 10 mmHg and the final pressure reached 10 mmHg, the temperature was increased from 210 ° C and finally melt-polymerized at a temperature of 245 ° C for 2 hours to give a flexible polybutylene terephthalate (PBT) having a relative viscosity of 1.60. Obtained.

Next, an oligomer is formed by transesterifying an acid component consisting of 90% by weight of dimethyl terephthalate and 10% by weight of dimethyl-2,6-naphthalate with ethylene glycol, followed by melt polymerization to obtain poly (ethyleneterephthalate-co Ethylenenaphthalate) (PETN) was obtained.

The resulting flexible PBT and PETN were mixed at a mixing weight ratio of 15:85, and then quenched tightly by applying an applied voltage to a cast roll using a 200 mm Φ extruder equipped with a T-die to obtain an unstretched sheet having a thickness of about 190 μm. Obtained. The unstretched sheet was stretched 3.5 times at 90 ° C. using a longitudinal longitudinal drawing machine and 4.5 times at 120 ° C. with a tenter transverse stretching machine, and then subjected to a heat treatment at 230 ° C. at 3% in the transverse direction, and slowly cooled to room temperature. To obtain a biaxially stretched film having a thickness of 12 µm. The physical properties of the obtained biaxially stretched film were evaluated and shown in Table 1.

Examples 2-6 and Comparative Examples 1-8

Biaxially oriented film in the same manner as in Example 1, except that the molecular weight of PTMG, the content of PTMG in flexible PBT, the content of ethylene naphthalate in PETN and the mixed weight ratio of PETN and flexible PBT were changed as shown in Table 1. To prepare, and to evaluate the physical properties of the prepared biaxially stretched film are shown in Table 1,2.

As can be seen from the results of Tables 1 and 2, the biaxially stretched polyester films of Examples 1 to 6 were found to have excellent transparency thickness degree and mechanical strength as well as good tear linearity.

On the contrary, in the case of Comparative Example 1, the film formation itself was impossible because the content of PTMG in the flexible PBT was too high. In Comparative Example 2, the content of PTMG in the flexible PBT was too small as in Comparative Example 1, resulting in poor tear linearity. appear. In Comparative Example 3, the molecular weight of PTMG in the flexible PBT was too small to obtain good tear linearity. In Comparative Example 4, the molecular weight of PTMG was so large that the thickness nonuniformity was large and the tearing linearity was inferior. In the case of Comparative Example 5, the content of ethylene naphthalate in PETN was too high to obtain sufficient tearing linearity. In Comparative Example 6, since the ethylenetaphthalate unit was not included at all, tensile strength was lowered and tearing straightness was also obtained. It was poor. In the case of Comparative Example 7, the content of the soft PBT was too high, the thickness nonuniformity increased and the tear linearity was poor. In Comparative Example 8, the content of the soft PBT was too small, tearing straightness was not obtained.

The biaxially stretched polyester film according to the present invention is not only excellent in durability, moisture resistance, mechanical properties, heat resistance and oil resistance, but also at least in a tear linearity in the longitudinal direction. Therefore, the biaxially stretched polyester film and the laminated film including at least one layer of the film according to the present invention can be usefully used as a packaging material for food, medicine, daily necessities, cosmetics and the like.

Claims (9)

Soft polybutylene terephthalate (a) and poly (ethylene terephthalate-co-ethylenenaphthalate) (b) comprising polybutylene terephthalate and polytetramethylene glycol, The mixed weight ratio of said (a) and (b) is 50: 50-5: 95, The biaxially-stretched polyester film characterized by the above-mentioned. The biaxially oriented polyester film according to claim 1, wherein the poly (tetramethylene glycol) has a molecular weight of 500 to 10,000 and a content of 5 to 30% by weight based on the total amount of the flexible polybutylene terephthalate. The biaxially stretched polyester film according to claim 1, wherein a mixed weight ratio of ethylene terephthalate and ethylene naphthalate in poly (ethylene terephthalate-co-ethylene naphthalate) is 70:30 to 95: 5. (a) preparing a soft polybutylene terephthalate comprising polybutylene terephthalate and polytetramethylene glycol; (b) mixing the soft polybutylene terephthalate and poly (ethylene terephthalate-co-ethylenenaphthalate) in a weight ratio of 50:50 to 5:95, and then coextrusion to prepare an unstretched sheet; And (c) biaxially stretching the unstretched sheet three to five times in the longitudinal and transverse directions at 90 to 140 ° C., respectively. The method for producing a biaxially stretched polyester film according to claim 4, wherein the poly (tetramethylene glycol) has a molecular weight of 500 to 10,000 and a content of 5 to 30% by weight based on the total amount of the flexible polybutylene terephthalate. . The method for producing a biaxially stretched polyester film according to claim 4, wherein the mixed weight ratio of ethylene terephthalate and ethylene naphthalate in poly (ethylene terephthalate-co-ethylene naphthalate) is 70:30 to 95: 5. . Base layer; And It is formed on at least one side of the base layer, the soft polybutylene terephthalate (a) and poly (ethylene terephthalate-co-ethylene naphthalate) (b) containing polybutylene terephthalate and polytetramethylene glycol is 50 A laminated film comprising a biaxially stretched polyester film contained in a weight ratio of: 50 to 5:95. The laminated film according to claim 7, wherein the poly (tetramethylene glycol) has a molecular weight of 500 to 10,000 and a content of 5 to 30% by weight based on the total amount of the soft polybutylene terephthalate. 8. The laminated film according to claim 7, wherein the mixed weight ratio of ethylene terephthalate and ethylene naphthalate in poly (ethylene terephthalate-co-ethylene naphthalate) is 70:30 to 95: 5.