KR20150008872A - Polyester film and method for producing same - Google Patents

Abstract

INDUSTRIAL APPLICABILITY The present invention provides a polyester film which is industrially practicable and has excellent balance of mechanical properties in the MD and TD directions, impact resistance and the like. And a tensile elongation at break of at least 80%, a planar orientation of 0.12 to 0.14, an impact strength of 0.05 J / m or more , And a polyester film having a sticking strength of 0.5 N / 占 퐉 or more.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyester film,

The present invention relates to a polyester film and a process for producing the same. More particularly, the present invention relates to a polyester film excellent in balance of impact resistance, flexural strength and mechanical strength, which is suitable for applications in which conventional nylon films or other flexible films have been used, and a method for producing the same.

Polybutylene terephthalate (PBT) is conventionally used as an engineering plastic because of its excellent mechanical properties and impact resistance. Particularly, it is used as a useful material because of its high crystallization rate and good productivity. However, PBT has been considered to be difficult to biaxially stretch because of its rapid crystallization rate. This is because crystallization occurs due to orientation in the stretching process and stretching becomes difficult. On the other hand, in order to take advantage of the inherent properties of PBT, studies have been conducted over the past 40 years to improve the mechanical properties and impact resistance of the film by increasing the surface orientation by biaxial stretching. However, Is an unstretched cast sheet and a film obtained by the inflation method. Since the orientation of the PBT is insufficient in the film, it is difficult to say that the film has inherently attracted the characteristics of the PBT. Particularly, the PBT film of the inflation method has a problem that the stretching magnification is unlikely to be uniform due to the manufacturing method thereof, the thickness precision is poor, and the sticking strength is low because the surface orientation coefficient is not high . Therefore, a PBT film obtained by biaxial stretching by a tenter has been studied. Hereinafter, some consideration will be given to the examination of past PBT films.

Conventionally, stretching in the TD direction at a draw ratio of 3.5 or less and stretching in the MD direction at a strain rate of 100000% / minute or more yields a biaxially stretched PBT film to produce a film having uniformly stretched thickness unevenness (See, for example, Patent Document 1). However, as is apparent from the results of Examples, such prior art has a problem that the stretching speed is increased only in the MD direction and the elongation is low and the film is not balanced in the MD and TD directions.

Further, based on the result of the experiment, the stretching temperature is calculated from the degree of crystallization at the time of non-stretching, the stretching is performed in the MD (or TD) direction at a temperature lower than the temperature, (For example, refer to Patent Document 2). [0004] In order to solve the above-mentioned problems, there is disclosed a technique for producing a film having excellent thickness resistance and suppression of breakage at the time of film formation. However, this conventional technique is such that the stretching at the second stage is stretching at a very high temperature as seen from the Tg (45 DEG C) of PBT at 120 DEG C, and the state in which the orientation crystallization progresses is rearranged in the second stage direction There is a problem that the balance between the mechanical properties in the MD direction and the TD direction is inferior.

A technique for producing a film excellent in gas barrier property and pinhole property by alternately laminating PBT and a resin other than PBT such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) is known (see, for example, Patent Document 3 Reference). However, since such prior arts have laminated layers containing PET or PEN resin in addition to PBT, stretching at a drawing temperature of PET or PEN, which has a higher Tg than PBT, is carried out at a stretching temperature. From the Tg of PBT, It has been extended. As a result, the characteristics of the original PBT film can not be derived. In addition, since the resin composition in the film is of two kinds, it is difficult to add trimming debris and the like to the raw material at the time of film formation for reuse, .

Japanese Patent Laid-Open Publication No. 51-146572 Japanese Patent Laid-Open Publication No. 51-40904 Japanese Patent No. 4273855

The present invention has been made in the background of the problems of the prior art. In other words, it is an object of the present invention to provide a method of producing a PBT having a high degree of crystallization, in order to suppress breakage caused when a PBT having a high crystallization rate is suppressed, By suppressing nonuniformity and reducing the specific gravity difference in the width direction in the unstretched state of the film, breakage can be greatly suppressed, industrially practicable, and the balance of mechanical properties in the MD / TD direction, Impact resistance and the like, and a process for producing the polyester film.

Means for Solving the Problems The present inventors have intensively studied in order to achieve these objects, and as a result, they have completed the present invention.

That is, the present invention relates to a polyester resin composition comprising a polyester resin containing 60% by mass or more of PBT, wherein the MD elongation is at least 80%, the elongation at break is at least 80%, the plane orientation is from 0.12 to 0.14, Or more, and a sticking strength of 0.5 N / 占 퐉 or more.

According to the present invention, in the polyester film and the production method thereof, in order to suppress the breakage which occurs when the PBT having a high crystallization rate is stretched, the shear rate in discharging the molten resin from the die in the width direction, By suppressing non-uniformity of crystallinity due to the difference in speed and reducing the specific gravity difference in the width direction in the unstretched state of the film, breaking at the time of stretching the film is largely suppressed, And the balance of dynamic characteristics in the TD direction, impact resistance and the like can be improved.

Hereinafter, the present invention will be described in detail.

The polyester resin used in the present invention contains PBT as a main component and preferably has a content of PBT of 60 mass% or more, more preferably 70 mass% or more, particularly preferably 75 mass% or more, 80% by mass or more. If the content is less than 60% by mass, the impact strength and pinhole resistance of the film deteriorate, and the film characteristics become insufficient.

The PBT to be used as a main component is preferably a dicarboxylic acid component having a terephthalic acid content of 90 mol% or more, more preferably 95 mol% or more, still more preferably 98 mol% or more, and most preferably 100 Mol%. Butanediol as a glycol component is preferably 90 mol% or more, more preferably 95 mol% or more, still more preferably 97 mol% or more, and most preferably 1,4-butanediol But not by-products generated by ether linkages.

Examples of the dicarboxylic acid component that may be copolymerized include isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, have. Examples of the glycol component which may be copolymerized include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, cyclohexanediol , Polyethylene glycol, polytetramethylene glycol, polycarbonate diol, and the like.

They need to adjust the copolymerization amounts of the individual monomers within a range that can satisfy the impact strength and stab strength of the film in balance with other polyester resins and the amounts of additives described below.

Other constituent components are not particularly limited, but other polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN) and polypropylene terephthalate (PPT) A polyester-based or polyamide-based elastomer in which at least one of a flexible polyether component, a polycarbonate component and a polyester component is copolymerized can be added to the polyester resin in order to improve the pinhole resistance at the time of bending have.

The lower limit of the addition amount of these additives is 0% by mass, and the upper limit is preferably 20% by mass. If it exceeds 20%, the above effect may be saturated, and transparency of the film may be lowered.

The lower limit of the resin melting temperature is preferably 200 占 폚, and if it is lower than 200 占 폚, the discharge of the molten resin may become unstable. The upper limit of the resin melting temperature is preferably 320 DEG C, and if it exceeds 320 DEG C, deterioration of the resin may occur.

The polyester resin may contain conventionally known additives such as a lubricant, a stabilizer, a colorant, an antioxidant, an antistatic agent, an ultraviolet absorber and the like, if necessary.

As the lubricant species, inorganic lubricants such as an organic lubricant, silica, calcium carbonate and alumina are preferable, and silica and calcium carbonate are more preferable, and calcium carbonate is particularly preferable. By these, transparency and slipperiness of the film can be expressed.

The lower limit of the activator concentration is preferably 100 ppm, and if it is less than 100 ppm, the slipperiness of the film may be lowered. The upper limit of the activator concentration is preferably 20,000 ppm, and if it exceeds 20000 ppm, the transparency of the film may be lowered.

As a point for obtaining the film according to the present invention, it is necessary to reduce the difference in the crystallization degree in the width direction of the unstretched film at the time of casting. As a specific method for this, casting to a cooling roll at a low temperature can be mentioned. It is also possible to increase the cooling efficiency by providing a touch roll for cooling the surface not in contact with the cooling roll.

As another method, the inventors of the present invention have found that the difference in crystallization in the width direction of the unstretched film can be reduced by using the new method to be described later. That is, it has been found that the difference in the crystallization degree in the width direction of the unstretched film can be reduced and the stretched stress distribution at the time of TD stretching can be made uniform by casting the raw materials having the same composition at the time of casting. Conventionally, the degree of crystallization of the unstretched film at the time of casting becomes high at the time of casting, while the crystallinity of the central portion of the unstretched film becomes low. Therefore, the stretching stress in the stretching in the TD direction becomes uneven in the width direction of the unstretched film, TD stretching at a very high temperature has become necessary because it is easy to break. On the other hand, this reason is inferred. However, even when the same resin is laminated, the interface of the layer is present, crystallization is accelerated by the interface thereof, and large crystals exceeding the layer are suppressed. It is considered that the degree of crystallization in the width direction becomes uniform. As a specific method, a general multilayered device (multilayered feed block, static mixer, multi-layered multi-manifold, etc.) can be used. For example, thermoplastic resin sent out from another flow path by using two or more extruders is placed in a field block, static mixer, A multi-layer lamination method using a multi-manifold die or the like can be used. Further, in the case of multi-layering the raw materials having the same composition, it is also possible to achieve the object of the present invention by introducing the above-described multilayering apparatus into the melt line from the extruder to the die using only one extruder.

When two or more extruders are used, the raw material of the same composition is preferably such that the difference between the maximum mass% and the minimum mass% in the content of each raw material mixed in the thermoplastic resin fed out from each extruder is 10% 5% by mass or less, particularly 2% by mass or less is allowed. When a copolymer is used in the polyester, the content of the copolymerized monomers blended in the thermoplastic resin fed out from each extruder is preferably 5 mol% or less, more preferably 3 mol% or less, Is allowed to be 2 mol% or less. When the weight average molecular weight in terms of styrene by GPC is determined by GPC, the value obtained by dividing the difference in molecular weight by the molecular weight of the larger molecular weight is 30% or less, more preferably 20% or less, particularly 10 % Or less, and if it is within this range, the respective raw material molecular weights are allowed to be different or the same as individual raw materials.

The method of introducing the above-described multilayered device into the melt line from the extruder to the die using only one extruder is a preferable method in view of the simplicity of the device and the management of each raw material.

The lower limit of the die temperature is preferably 200 占 폚, and if it is lower than 200 占 폚, the discharge of the molten resin is not stabilized and the thickness of the film may become uneven. The upper limit of the die temperature is preferably 350 占 폚. When the temperature exceeds 350 占 폚, the thickness of the film becomes non-uniform. Besides, deterioration of the resin occurs and appearance defect may occur due to dripping.

The lower limit of the cooling roll temperature is preferably -10 占 폚, and if it is lower than -10 占 폚, the effect of equalizing the crystallization degree in the width direction of the unstretched film may be saturated. The upper limit of the cooling roll temperature is preferably 80 占 폚, and if it exceeds 80 占 폚, the degree of crystallization of the unstretched film becomes too high and the stretching may become difficult. In order to reduce the difference in crystallinity in the width direction of the unstretched film, it is effective to reduce the crystallinity. In the case where the multilayered method described later is not used, the preferable cooling roll temperature is 10 DEG C or less, to be. In this case, it is preferable to lower the humidity of the environment around the cooling roll due to the prevention of condensation. On the other hand, by using a multilayer method or the like to be described later, it is possible to reduce the difference in crystallinity in the width direction of the unstretched film, and in this case, casting is possible even at a temperature of 15 to 40 캜.

The temperature difference in the width direction of the cooling roll is preferably as small as possible, and the preferable temperature difference is 5 DEG C or less, more preferably 3 DEG C or less. When the temperature difference exceeds 5 占 폚, the difference in the crystallization degree in the width direction of the unstretched film during casting may not be reduced.

In the casting, since the high temperature resin contacts the surface, the temperature of the surface of the cooling roll is increased. Generally, the cooling roll is cooled by flowing cooling water through a piping in the cooling roll. In order to secure a sufficient amount of cooling water, to design an arrangement of piping, to maintain the sludge on the piping, It is necessary to reduce the temperature difference between the two. In particular, care should be taken when cooling at low temperature without using a method such as multilayering.

In the case of a cast in a multilayer structure, it is at least three or more, preferably five or more, more preferably eight or more, particularly preferably 100 or more. When the number of layers is small, the difference in specific gravity in the width direction of the non-stretched film becomes large, and the effect of improving the stretchability is small. When the number of layers is 100 or more, the effect of reducing the specific gravity difference in the width direction of the non-stretched film is stabilized, and the thickness uniformity of each layer is also stabilized and the effect of appearance is improved.

Next, the stretching method will be described. Although the stretching method can be performed in the sequential biaxial stretching even in the simultaneous biaxial stretching, in order to increase the sticking strength of the film, it is necessary to increase the plane orientation coefficient of the film, and in that point, biaxial stretching is preferable.

The lower limit of the MD stretching temperature is preferably 40 占 폚, and more preferably 45 占 폚. If it is less than 40 DEG C, breakage tends to occur easily. The upper limit of the MD stretching temperature is preferably 100 占 폚, and more preferably 95 占 폚. If it exceeds 100 캜, it may be difficult to orient the film and the mechanical properties of the film may be deteriorated.

The lower limit of the MD stretching magnification is preferably 2.5 times. When the MD stretching magnification is lower than 2.5, the orientation is difficult to be aligned, and therefore the mechanical properties and thickness unevenness of the film may be deteriorated. The upper limit of the MD stretching magnification is preferably 5 times, and if the MD stretching magnification exceeds 5 times, the effect of improving mechanical strength and thickness irregularity of the film may be saturated.

The lower limit of the TD stretching temperature is preferably 40 占 폚, and if it is lower than 40 占 폚, breakage of the film tends to occur easily. The upper limit of the TD stretching temperature is preferably 100 占 폚, and if it exceeds 100 占 폚, the orientation is difficult to be aligned, and therefore the mechanical properties of the film may be lowered.

The lower limit of the TD stretching magnification is preferably 2.5 times, and if it is less than 2.5 times, the orientation is difficult to be aligned, so that the mechanical properties and thickness unevenness may be deteriorated. The upper limit of the TD stretching magnification is preferably 5 times, and when it exceeds 5 times, the effect of improving the mechanical strength and thickness variation of the film may be saturated.

The lower limit of the TD heat fixing temperature is preferably 150 占 폚, and if it is lower than 150 占 폚, the heat shrinkage ratio of the film becomes large, and deviation or erroneous shrinkage may occur during processing. The upper limit of the TD heat fixing temperature is preferably 250 占 폚. If the temperature exceeds 250 占 폚, the film may melt away even if it does not dissolve.

The lower limit of the TD relax rate is preferably 0.5%. If the TD relax rate is less than 0.5%, the film tends to be broken at the time of heat fixation. The upper limit of the TD relax rate is preferably 10%, and if the TD relax ratio exceeds 10%, the film may be loosened or the like, resulting in thickness irregularity.

In the biaxially stretched film of the present invention, the lower limit of the film thickness is preferably 3 탆, more preferably 5 탆, and still more preferably 8 탆. If it is less than 3 탆, the strength as a film may be insufficient. The upper limit of the film thickness is preferably 100 占 퐉, more preferably 75 占 퐉, and still more preferably 50 占 퐉. If the thickness exceeds 100 탆, the film becomes too thick, which makes it difficult to carry out processing for the purpose of the present invention.

It is preferable that the difference between the maximum thickness and the minimum thickness in the entire width is in the range of 0 to 25%, more preferably in the range of 0 to 20% with respect to the average thickness with respect to the thickness unevenness in the entire roll width desirable. If it is more than 25%, the appearance of the roll may be reduced or distortion may occur in secondary processing, which is not preferable. In order to reduce the difference between the maximum thickness and the minimum thickness in the entire width, it is necessary that the stretching ratio in the width direction is uniform, but for that, it is necessary to make the degree of crystallization at the time of non-stretching uniform.

The lower limit of the specific gravity of the central portion of the undrawn film of the present invention is preferably 1.25 g / cm 3, and when it is less than 1.25 g / cm 3, the effect of improving the stretchability of the unstretched film may be saturated. The upper limit of the specific gravity of the central portion is preferably 1.3 g / cm 3, and if the specific gravity exceeds 1.3 g / cm 3, the degree of crystallization becomes too high and the drawing may become difficult.

The upper limit of the difference in specific gravity in the transverse direction of the present invention is preferably 0.03 g / cm 3, and when it exceeds 0.03 g / cm 3, the stretching stress becomes nonuniform in the transverse direction to cause breakage of the film, May cause unevenness in thickness and unevenness in physical properties.

The lower limit of the MD elastic modulus of the film of the present invention is preferably 1 GPa, and if it is less than 1 GPa, the film tends to elongate, and pitch shift may occur during processing such as printing or lamination. The upper limit of the MD elastic modulus is preferably 2 GPa, and if it exceeds 2 GPa, the film may be disadvantageous from the viewpoint of workability such as drawing after bonding with various sealants and the like.

The lower limit of the TD elastic modulus of the film of the present invention is preferably 1 GPa, and if it is less than 1 GPa, the film tends to elongate, and problems may arise during processing. The upper limit of the TD elastic modulus is preferably 2 GPa, and if it exceeds 2 GPa, the film may be disadvantageous from the viewpoint of workability such as drawing processing after bonding the film with various sealants and the like. Further, the TD elastic modulus can be set within a range by the heat fixing temperature.

The lower limit of the TD breaking strength of the film of the present invention is preferably 100 MPa, and if it is less than 100 MPa, breakage may occur during processing of the film. The upper limit of the TD breaking strength is preferably 500 MPa, and when it exceeds 500 MPa, the effect of improving the breaking strength of the film may be saturated.

The lower limit of the elongation at break of the MD of the present invention film is preferably 80%, and more preferably 90%. If it is less than 80%, the film may be disadvantageous in terms of processability such as drawing processing after being bonded to various sealants and the like. The upper limit of the MD elongation at break is not particularly limited, but is preferably 200%. The MD elongation at break can be set within the range depending on the MD magnification and the heat fixing temperature.

The lower limit of the TD breaking elongation of the film of the present invention is preferably 80%, and more preferably 90%. If it is less than 80%, the film may be disadvantageous in terms of processability such as drawing processing after being bonded to various sealants and the like. The upper limit of the TD breaking elongation is not particularly limited, but is preferably 500%. The TD breaking elongation can be made within the range by the TD magnification and the heat fixing temperature.

The lower limit of the plane orientation coefficient of the film of the present invention is preferably 0.12, and if it is less than 0.12, the sticking strength, the impact strength and the like may be lowered. The upper limit of the plane orientation coefficient is preferably 0.14, and if it exceeds 0.14, the film productivity may be lowered, and the flexibility may be lowered. The plane orientation coefficient can be set within the range by the MD magnification and the heat fixing temperature. In addition, as the stretching method, sequential biaxial stretching is more preferable than simultaneous biaxial stretching, particularly sequential biaxial stretching in which stretching in the MD direction and stretching in the TD direction is more preferable.

The variation of the planar orientation coefficient of the film after stretching according to the present invention is such that the difference between the maximum value and the minimum value of the planar orientation coefficient measured by dividing the entire width of the film by 10 is 0.02 or less, And preferably 0.01 or less. If it is more than 0.02, unevenness in the thickness of the film is large in addition to the deviation of the mechanical properties, which is not preferable. In order to reduce the variation of the plane orientation coefficient, the specific gravity difference (difference in crystallinity) in the width direction of the unstretched film is reduced.

It is preferable that the orientation axis angle of the stretched film of the present invention is in the range of 0 to 40 degrees. In the present invention, orientation balance is made in the MD direction and the TD direction, but if it exceeds 40 degrees, distortion or the like of the film occurs after heating, which is not preferable. As a specific method for this purpose, a method of reducing the shrinkage in the MD direction when thermally fixing after TD stretching can be employed, similar to a general method for reducing bowing, By reducing the difference in crystallinity between the center portion and the end portion, the film end bowing after stretching can be reduced, which is advantageous.

The lower limit of the stiction strength of the film of the present invention is preferably 0.5 N / m, and more preferably 0.9 N / m. If it is less than 0.5 N / 탆, the strength at the time of processing the film or when the film is made into a bag may be insufficient. The upper limit of the stiction intensity is preferably 1.5 N / m, and when it exceeds 1.5 N / m, the improvement effect becomes saturated. The stab intensity can be set within the range by the MD magnification and the heat fixing temperature.

The lower limit of the impact strength (impact resistance) of the film of the present invention is preferably 0.05 J / m, and more preferably 0.06 J / m. If it is less than 0.05 J / m, the strength may be insufficient when used as a bag. The upper limit of the impact strength (impact resistance) is preferably 0.2 J / m, and when it exceeds 0.2 J / m, the improvement effect becomes saturated.

The lower limit of the moisture absorptive rate of the film of the present invention is preferably 0.1%, and when it is less than 0.1%, the improvement effect is saturated. The upper limit of the moisture absorption rate is preferably 1%, and when it exceeds 1%, a change in the moisture absorption dimension may easily occur.

The lower limit of the MD heat shrinkage percentage of the film of the present invention is preferably 0.1%. If the MD shrinkage percentage is less than 0.1%, the improvement effect may be saturated, and the MD shrinkage may dynamically disappear. The upper limit of the MD heat shrinkage rate is preferably 4%. If the MD thermal shrinkage ratio exceeds 4%, a pitch shift may occur depending on the dimensional change during processing such as printing.

The lower limit of the TD heat shrinkage percentage of the film of the present invention is preferably 0.1%. When the TD heat shrinkage percentage is less than 0.1%, the improvement effect is saturated, and the film may dynamically back out. The upper limit of the TD heat shrinkage rate is preferably 3%. If the TD heat shrinkage ratio is more than 3%, there is a case where the film is wrinkled in the width direction due to dimensional changes during processing such as printing.

The lower limit of the haze of the film of the present invention is preferably 0%. The upper limit of the haze is preferably 50%, more preferably 30%, still more preferably 20%. If the contents are not visible, this does not apply. If the haze is more than 30%, the content may become difficult to be seen when used as a bag.

The lower limit of the number of pin-holes generated in the gelbo-flex test of the laminate obtained by laminating the film and the sealant of the present invention by the dry lamination method is preferably zero. The upper limit of the number of pin-holes is preferably 10, more preferably 5. If it exceeds 10, the film may be easily punctured when used as a bag. A method of measuring the pin-odd number will be described later.

This application claims the benefit of priority based on Japanese Patent Application No. 2012-110536 filed on May 14, The entire contents of the specification of Japanese Patent Application No. 2012-110536 filed on May 14, 2012 are incorporated herein by reference.

<Examples>

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. The evaluation of the film was carried out by the following measurement method.

[Specific gravity of unstretched film]

The specific gravity of each sample at 23 占 폚 was measured according to JIS Z8807 8 (liquid weighing method) using SGM-300P, a specific gravity measuring device of Shimadzu Corporation.

The difference in the specific gravity in the width direction was obtained by dividing the value obtained by subtracting the minimum value from the maximum value of the obtained results by the minimum value, collecting 10 samples in the width direction from the obtained unstretched film, measuring the specific gravity by the above method.

[Mechanical properties (breaking strength, elongation at break)]

Complies with JIS K7113. A sample having a width of 10 mm and a length of 100 mm was cut out from the film using a razor. The cut samples were allowed to stand in an atmosphere at 23 DEG C and 35% RH for 12 hours, and then subjected to measurements under the conditions of a temperature of 23 DEG C and a humidity of 35% RH at a chuck distance of 40 mm and a tensile rate of 200 mm / The average value of the measurement results was used. As the measuring apparatus, Autograph AG5000A manufactured by Shimadzu Corporation was used.

[Face orientation]

A 10-point sample was taken from the roll sample in the width direction. The refractive index (nx) in the film longitudinal direction, the refractive index (ny) in the width direction, and the refractive index (nz) in the thickness direction of the sample were measured by an Abbe refractometer using a sodium D line as a light source according to JIS K7142-1996 5.1 And the planar orientation coefficient? P was calculated by the following formula. The average value of the obtained plane orientation coefficients was determined as the plane orientation coefficient.

DELTA P = (nx + ny) / 2-nz

The difference in planar orientation coefficient in the width direction is defined as the difference between the maximum value and the minimum value of the above-mentioned 10 points of sample.

[Angle of orientation axis]

Using an MOA-6004 type molecular alignment system manufactured by Oji Chemical Co., Ltd., the orientation angle (?) Of the molecular chain orientation principal axis of the film edge was determined.

[Impact strength]

Using Impact Tester manufactured by Toyo Seiki Seisakusho Co., Ltd., the strength against impact punching of the film under an atmosphere of 23 占 폚 was measured. The impact spherical surface having a diameter of 1/2 inch was used. The unit is J / m.

[Sting intensity]

(2) of the "Standard for Food, Additives, etc., Standard 3: Instrument and Container Packaging" (1982 Ministry of Health and Welfare Notice No. 20) Strength Test Method &quot;. A needle having a tip diameter of 0.7 mm was stuck to the film at a sticking speed of 50 mm / min, and the strength of the needle at the time of penetration through the film was measured to determine the sticking strength. The measurement is carried out at room temperature (23 캜), and the unit is N.

[Pinhole property]

33.6 parts by mass of a polyester polyol (TM-509, manufactured by Toyo Moton Co., Ltd.), 20 parts by mass of a polyisocyanate (manufactured by Toyo Moton Co., Ltd., CAT -10 L), and 62.4 parts by mass of ethyl acetate were mixed and dry laminated using the obtained urethane-based adhesive to prepare a laminate.

The laminate was cut into a size of 20.3 cm (8 inches) x 27.9 cm (11 inches), and the rectangular test film after the cut was left to stand for 24 hours or more under conditions of a temperature of 23 DEG C and a relative humidity of 50% . Then, the rectangular test film was rolled up into a cylindrical shape having a length of 20.32 cm (8 inches). One end of the cylindrical film was fixed to the outer periphery of a disk-shaped fixing head of a gelboplex tester (manufactured by Rikagou Co., Ltd., model N0.901) (conforming to the standard of MIL-B-131C) The other end was fixed to the outer periphery of the disk-shaped movable head of the tester opposed to the fixed head at a distance of 17.8 cm (7 inches). Then, the movable head was rotated 440 degrees in the direction of the fixed head, while approaching 7.6 cm (3 inches) along the axes of both heads parallel to each other in parallel, and then straightened to 6.4 cm (2.5 inches) A one-cycle bending test in which the operation was performed in the reverse direction to return the movable head to the initial position was repeated 1000 times in succession at a speed of 40 cycles per minute. The experiment was carried out at 5 占 폚. Thereafter, the number of pinholes occurred in a portion within 17.8 cm (7 inches) x 27.9 cm (11 inches) excluding the fixed head of the tested film and the portion fixed to the outer periphery of the movable head was measured (i.e., 497 cm 2 ) Were measured.

[Intrinsic viscosity of polyester]

0.1 g of polyester was dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane (volume ratio: 3/2), and intrinsic viscosity of the polyester was measured at 30 캜 using an Ostwald viscometer.

[Melting point of polyester]

The sample amount was measured using a differential scanning calorimeter (DSC), manufactured by SII, with a sample amount of 10 mg and a temperature raising rate of 20 캜 / min. The melting endothermic peak temperature detected here is defined as the melting point of the polyester.

[thickness]

The thickness of the film was measured by the method according to JIS-Z-1702.

[Heat shrinkage rate]

The heat shrinkage was measured by the dimensional change test method described in JIS-C-2318, except that the test temperature was set to 150 캜 and the heating time was set to 10 minutes.

[Hayes]

The haze value of the sample was measured with respect to three different sites using a haze meter (NDH2000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) in accordance with JIS-K-7105.

[Thickness uniformity (Tv (%))]

Film pieces were cut in the longitudinal direction from the center portion of the obtained film roll, and the thickness of the film was measured using a dial gauge at a pitch of 5 cm. The thickness uniformity was calculated from the results.

[Peel strength]

33.6 parts by mass of a polyester polyol (TM-509, manufactured by Toyo Moton Co., Ltd.), 20 parts by mass of a polyisocyanate (manufactured by TOYOTO MOTOR CO., LTD., CAT- 10 L), and 62.4 parts by mass of ethyl acetate were mixed and dry laminated using the urethane-based adhesive thus obtained to prepare a laminate.

The laminate was cut into a test piece having a width of 15 mm and a length of 200 mm and a test piece of a polyester film "Tensilon UMT-II-500" manufactured by Toyo Baldwin Co., Ltd. under the conditions of a temperature of 23 캜 and a relative humidity of 65% And the peel strength on the bonded surface between the untreated surface and the polyolefin resin layer was measured. The tensile speed was 10 cm / min and the peeling angle was 180 degrees.

[Absorption rate]

The film according to the present invention was cut into a square of 50 mm on one side and the film was immersed in water held at a temperature of 23 占 폚 占 2 占 폚 in accordance with JIS-K-7209-7.2.1 (Method A) Were measured. The moisture absorption rate was calculated by the following formula (1).

Moisture absorption rate (%) = 100 x [M2] - [M1] / [M1]

In the above formula (1), [M1] is the weight of the film before immersion in water, and [M2] is the weight of the film after immersion in water.

[Example 1]

A master batch containing PBT resin (Nova Duran 5020, melting point 220 ° C, manufactured by Mitsubishi Engineering Plastic Co., Ltd., melting point 220 ° C) and calcium carbonate as a lubricant was added using a two-axis vent type extruder and melted at 270 ° C , Cast from T-Dice at 270 占 폚 and adhered to a cooling roll at 0 占 폚 by electrostatic adhesion to obtain an unstretched film. The surface temperature of the cooling roll was measured (thermocouple) at intervals of 10 cm in the width direction, and the deviation was 3 DEG C or less. Subsequently, the film was stretched 3.2 times in the longitudinal direction at 60 占 폚, passed through a tenter, stretched 3 times in the transverse direction at 80 占 폚, subjected to a stretching heat treatment at 200 占 폚 for 3 seconds and a relaxation treatment for 1 second , And both ends were cut off to obtain a PBT film having a thickness of 12 탆. Table 1 shows the film forming conditions, physical properties and evaluation results of the obtained film. The orientation axis angle at the end of the film was 35 degrees, and the deformation of the sample after the measurement of the heat shrinkage rate was slight.

[Example 2]

A master batch containing PBT resin (Nova Duran 5020, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) and calcium carbonate as a lubricant was added using a twin-screw vented extruder and melted at 270 占 폚 at a lubricant concentration of 2000 ppm, Line was introduced into a static mixer (STMX) of 12 elements. Thus, the PBT molten material was divided and laminated to obtain a multi-layered molten material containing the same raw material. Thereafter, the film was introduced into a T-die at 270 占 폚, cast, and tightly adhered to a cooling roll at 15 占 폚 by electrostatic adhesion to obtain an unstretched film. The surface temperature of the cooling roll was measured (thermocouple) at intervals of 10 cm in the width direction, and the deviation was 3 DEG C or less. Subsequently, the film was stretched 3.8 times in the longitudinal direction at 60 占 폚, passed through a tenter, stretched 3 times in the transverse direction at 65 占 폚, subjected to a stretching heat treatment at 200 占 폚 for 3 seconds and a relaxation treatment for 1 second , And both ends were cut off to obtain a PBT film having a thickness of 12 탆. Table 1 shows the film forming conditions, physical properties and evaluation results of the obtained film. Further, the orientation axis angle at the end of the film was 25 degrees, and the deformation of the sample after the measurement of the heat shrinkage ratio was slight.

[Examples 3 to 4]

The film was obtained under the conditions shown in Table 1. Table 1 shows the film forming conditions, physical properties and evaluation results of the obtained film. As the Ecoflex (registered trademark), a polybutylene adipate butylene terephthalate copolymer (PBAT) manufactured by BASF was used.

[Comparative Example 1]

The filming was examined by the method described in Example 1 except that the cooling roll temperature at the time of casting was changed to 15 캜. Table 2 shows the film forming conditions. The MD was stretched in the MD stretching of the unstretched film, and a film could not be obtained.

[Comparative Example 2]

A film was obtained under the conditions described in Table 2. Table 2 shows the film forming conditions, physical properties and evaluation results of the obtained film.

[Comparative Example 3]

An unoriented film obtained under the conditions described in Table 2 was used as a sample. The film was formed by adjusting the winding speed so that the thickness was 20 mu m. Further, the orientation axis angle at the end of the film was 5 degrees or less, and no deformation of the sample was observed after the measurement of the heat shrinkage percentage.

[Comparative Example 4]

Toyobo Ester (registered trademark) film E5100 (thickness 12 占 퐉) manufactured by Toyobo Co., Ltd. was used.

[Referential Example 1]

As a typical PBT film, a commercially available PBT film manufactured by Kansai Chemical Co., Ltd. was used. The orientation axis angle at the end of the film was 5 degrees or less and no deformation of the sample was observed after the measurement of the heat shrinkage rate.

The polyester film of the present invention has a crystallization degree due to a difference in shear rate during casting of the molten resin from the die and a cooling rate during casting in order to suppress breakage which occurs when the PBT having a high crystallization rate is stretched. By suppressing non-uniformity and reducing the specific gravity difference in the width direction in the unstretched state, breakage at the time of stretching is largely suppressed. INDUSTRIAL APPLICABILITY The present invention is industrially practicable and can improve the balance of mechanical properties in MD and TD directions, impact resistance and the like.

Claims (5)

And a tensile elongation at break of at least 80%, a planar orientation of 0.12 to 0.14, an impact strength of 0.05 J / m or more , And a sticking strength of 0.5 N / 占 퐉 or more. The polyester film according to claim 1, wherein the difference between the maximum value and the minimum value of the plane orientation coefficient measured by dividing the total film width of the stretched film by 10 is 0.02 or less. The polyester film according to claim 1 or 2, wherein the difference between the maximum value and the minimum value of the thickness of the entire film after stretching is 0 to 25% with respect to the average thickness. The method for producing a polyester film according to any one of claims 1 to 3, wherein the difference in the degree of crystallization in the width direction during casting on the cooling roll is made small. The production method according to claim 4, wherein a method of reducing the difference in crystallinity in the width direction is performed by casting the cooling roll at a low temperature and / or multi-layering the raw materials having the same composition.