JP2002321277A - Highly ductile polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly ductile polyester film capable of being suitably adapted to a use for requiring flexibility and moldability, for example, a use as the substitution of a vinyl chloride sheet other than a use for molding transfer, a molded container, the lamination of a metal or the like. SOLUTION: The highly ductile polyester film is a film not showing thermal adhesiveness at 150 deg.C and a degree of crystallization is not less than 30%, the thickness irregularity in the longitudinal direction of the film is not more than 5%, and the plastic deformation resistance in the maximum refractive index direction of the film is not more than 0.50 MPa/%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly ductile polyester film, and more particularly to applications requiring moldability, for example, for forming and transferring, for forming containers, metal bonding, etc., and various kinds of vinyl chloride. The present invention relates to a highly ductile polyester film suitably used in a sheet replacement use.

[0002]

2. Description of the Related Art Polyester films, especially polyethylene terephthalate films, have high strength, heat resistance,
It has excellent chemical resistance and is widely used in industrial applications such as packaging materials in combination with relatively inexpensive prices. In these applications, moldability is one of the properties required for the polyester film. As an example of a polyester film having good moldability, an unstretched polyethylene terephthalate film may be mentioned, but in the case of unstretched polyethylene terephthalate, it is not easy to reduce the thickness to 200 μm or less, and even when the thickness exceeds 200 μm. When the temperature reaches about 100 ° C. in a humid environment, the gloss of the surface may change.

On the other hand, biaxially oriented polyethylene terephthalate film, which is the most widely used polyester film, hardly causes whitening even in a wet heat environment, and has a strength, an elastic modulus,
Although it has excellent dimensional stability, on the other hand, it does not always have sufficient suitability for applications that require a large deformation of a certain level or more due to too high rigidity, and there is a need for improved moldability.

Therefore, attempts have been made to reduce the draw ratio, or to biaxially align a copolymer of other components such as isophthalic acid to impart moldability and enable large deformation. .

[0005] However, a reduction in the draw ratio not only impairs the uniformity of the thickness and the orientation, but also reduces the productivity, and is not always optimal for industrial mass production. Also,
The method of copolymerizing other components to reduce crystallinity improves the moldability, but also increases the thermal adhesiveness, so that the slipperiness of the metal jig in the film forming process and the film processing process deteriorates. In severe cases, problems such as fusion may occur, and at the same time, there is a problem that the heat resistance decreases due to a decrease in melting point. For this reason, there is a demand for a film which is substantially made of a homopolyester and has a biaxial orientation, and which also has moldability.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyester film which can be suitably used for applications requiring moldability. is there.

[0007]

Means for Solving the Problems As a result of diligent studies, the present inventor has found that if a polyester film is devised to have a specific deformation behavior by devising its physical properties, high moldability can be obtained without impairing productivity. The inventor has obtained the knowledge that it can be obtained, and has completed the present invention.

That is, the gist of the present invention is to provide a non-heat-adhesive film having a crystallinity of 30% at 150 ° C.
As described above, the polyester film has a thickness unevenness in the longitudinal direction of the film of 5% or less and a plastic deformation resistance in the maximum refractive index direction of 0.50 MPa /% or less.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The polyester referred to in the present invention is a polymer obtained by polycondensing a dicarboxylic acid component and a glycol component. Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, azelaic acid, sebacic acid, Examples thereof include aliphatic dicarboxylic acids such as 4-cyclohexyldicarboxylic acid, and examples of glycols include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, and 1,4-cyclohexane. Dimethanol and the like.

[0010] The polyester film of the present invention (hereinafter simply referred to as a film) is non-heat-adhesive at 150 ° C. When the film has thermal adhesiveness at 150 ° C., when various types of film are formed, the slipperiness at a high temperature with respect to metal forming equipment becomes insufficient, and in extreme cases, there is a possibility that fusion may occur.

The film of the present invention has a crystallinity of 30% or more, preferably 40% or more, more preferably 50% or more. If the degree of crystallinity is less than 30%, whitening easily occurs in a moist heat environment. The upper limit of crystallinity is usually 100
%. In addition, in the application of the film, the complete crystal density determined from the crystal lattice constant, the measured density of the amorphous,
It is common to calculate the degree of crystallinity by the so-called density method of calculating the degree of crystallinity from the measured density of the sample. Is not necessarily appropriate as an index of the whitening characteristic in the above. Therefore, in the present invention, the crystal ratio calculated by X-ray diffraction is used as an index.

The film of the present invention has a thickness unevenness of 5
% Or less. If the thickness unevenness exceeds 5%, the molding process becomes uneven. The lower limit of thickness unevenness in the vertical direction is usually 0.5%
It is.

The film of the present invention has a plastic deformation resistance after yielding in a tensile test of 0.50 MPa /% or less, preferably 0.30 MPa /% or less, more preferably 0.20 MPa /% or less.
MPa /% or less. If the plastic deformation resistance exceeds 0.50, the formability will be insufficient. The lower limit of the above plastic deformation resistance is usually 0 MPa /%.

As an example of a method for reducing the plastic deformation resistance while satisfying other requirements, there is a method such as polyethylene terephthalate and polybutylene terephthalate which have different melting points and are individually compatible with each other while being compatible with each other in the amorphous phase. After mixing polyesters which can be made into each other and subjecting them to biaxial stretching according to a conventional method, a method of performing heat fixing at a temperature equal to or higher than the melting point of one polyester and lower than the other melting point may be used.

The film of the present invention may be made of a general biaxially oriented polyethylene terephthalate from the viewpoint of easy adhesion of printing ink, easy adhesion of metal plate, easy adhesion of metal deposition, antistatic, imparting of slipperiness and prevention of scratching, if necessary. According to the film,
A filler or the like may be appropriately contained, or various coatings may be applied.

In applications where the film of the present invention is used after being laminated on multiple materials, a composite film may be formed by providing an adhesive layer on one surface of the film of the present invention. The adhesive layer may be an adhesive coating layer or an adhesive surface layer formed by a coextrusion method or the like. In this case, the non-thermal adhesive property at 150 ° C., which is one of the requirements of the film of the present invention, only needs to satisfy the surface on the side opposite to the adhesive layer.

The film of the present invention can be produced, for example, as follows. First, polyethylene terephthalate pellets and polybutylene terephthalate pellets are mixed in equal weight and sufficient, and are melted while being degassed and dehydrated by a vented twin-screw extruder. The obtained melt is extruded into a sheet shape from a T-die and rapidly cooled to a temperature of less than 30 ° C. immediately on a cooling drum to obtain a substantially amorphous sheet. Next, the obtained amorphous sheet was stretched 3.3 times in the longitudinal direction at 55 ° C. and 4.0 times in the transverse direction, and then heat-fixed at 245 ° C. for 3 seconds while keeping the film width fixed. A 100 micron thick biaxially stretched film is obtained.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the following examples, “parts” means parts by weight. The evaluation method is as follows.

(1) Crystallinity (%): Measured with an X-ray diffractometer “RINT2000” manufactured by Rigaku Corporation. That is, the diffraction of the crystal lattice plane arranged in parallel to the film plane was measured by reflection method 2θ / θ scanning. The X-ray used was a Kα ray of Cu, and the output was 40 kV and 30 mA. With respect to the obtained diffraction profile, the amorphous halo appearing at 2θ ≒ 21 ° and the other diffraction peaks were separated into peaks, and the respective peak areas were obtained. The former was A, the latter was C, and the sum was C. The crystallinity was determined according to the equation. In the peak separation, the peak was assumed to be a linear sum of a Gaussian function and a Lorentz function.

[0020]

## EQU1 ## Crystallinity = C / (C + A) × 100

(2) Non-thermal adhesiveness: Two rectangular sample films each having a width of 15 mm were stacked, and a "heat seal tester" manufactured by Tester Sangyo Co., Ltd. was used. Heat sealing was performed so as to be parallel to the width direction. When one of the non-pressurized portions was fixed, and a weight of 100 g was attached to the other end, and was vertically dropped, the following two classifications were performed based on the peeling state at the seal portion.

[0022]

[Table 1] ○: Non-thermal adhesion (peeling occurred at the seal part) ×: Thermal adhesion (peeling did not occur at the seal part)

(3) Thickness unevenness (%): Using a film thickness measuring device manufactured by Anritsu Electric Co., the thickness along the longitudinal direction of the sample film is measured, and the thickness unevenness is calculated from the following equation. did.

[0024]

## EQU2 ## Thickness unevenness = maximum film thickness−minimum film thickness) / average film thickness × 100

(4) Plastic deformation resistance (MPa /%): Two polarizing plates are arranged so that their polarization planes are perpendicular to each other, and a sample film is sandwiched between them. Then, the film is appropriately rotated while the position of the polarizing plate is fixed, and two directions in which light is completely extinguished are specified. The refractive index in the specified direction is measured with an Abbe refractometer, and the direction having the larger value is defined as the maximum refractive index direction.

Cut out a rectangular sample film having a length of 100 mm or more and a width of 15 mm in the direction of the maximum refractive index, and having
A tensile test was performed at a speed of 200 mm / min with a “Shimadzu Autograph AG-I” manufactured by Shimadzu Corporation. From the obtained stress-strain curve, the maximum stress after yield (σb), the minimum stress from yield to reaching the maximum stress (σy),
The values of strain (εb) at σb and strain (εy) at σy were determined, and the plastic deformation resistance was determined according to the following equation. In the case where no clear yield was observed, 0.2% proof stress was assigned to σy. The unit of stress was MPa and the unit of strain was%.

[0027]

## EQU3 ## Plastic deformation resistance = (σb−σy) / (εb−εy)

(5) Formability: A laminate obtained by bonding a sample film to a steel sheet having a thickness of 0.25 mm using an epoxy adhesive was subjected to a DuPont impact test. That is, tip R3 / 16 inch, falling weight 500g, falling distance 3
Dents were formed under the condition of 0 cm. The enamel value on the convex side of the obtained dentz was measured, and the following two classifications were performed.

[0029]

[Table 2] ○: good moldability (0.5 mA or less) ×: poor moldability (more than 0.5 mA)

(6) Heat resistance: 121 ° C.2 on the sample film
The retort treatment was performed for 30 minutes under atmospheric pressure conditions. The treated film was air-dried after washing with water, and classified into the following three stages by visual observation.

[0031]

○: No white spots are observed. Δ: Some white spots are observed but not noticeable. X: Vitiligo was observed and the appearance was significantly impaired.

The polyester used in the examples and comparative examples was produced by the following method.

(1) Polyester A: 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.1 part of calcium acetate-water salt were placed in a reactor and transesterified. That is, the reaction start temperature was set to 170 ° C., the reaction temperature was gradually increased with the distillation of methanol, and after 4 hours, the temperature was raised to 230 ° C. to substantially end the transesterification reaction. Next, an ethylene glycol slurry containing amorphous silica having an average particle size of 1.5 μm and phosphoric acid 0.1 wt.
After adding 04 parts, 0.04 part of antimony trioxide was added, and a polycondensation reaction was performed. That is, the temperature is gradually increased and the pressure is gradually decreased.
The pressure was set to 0.3 mmHg and the reaction was continued. When the intrinsic viscosity reached 0.70 dl / g, the reaction was stopped to obtain a polyester A containing 0.1 part of silica.

(2) Polyester B: 85 parts of dimethyl terephthalate instead of 100 parts of dimethyl terephthalate
Polyester B was obtained in the same manner as polyester A, except that 15 parts of dimethyl isophthalate were used. The intrinsic viscosity was 0.70 dl / g.

(3) Polyester C: "Novaduran 5010" manufactured by Mitsubishi Engineering-Plastics Corporation
Was designated as polyester C.

Example 1 A mixture of 50 parts of polyester A and 50 parts of polyester C sufficiently stirred and mixed at room temperature was melted at 280 ° C. by a vented twin screw extruder, extruded from a T-die, and immediately on a cooling drum. By quenching to a temperature below 30 ° C., a substantially amorphous film was obtained. The obtained amorphous film is stretched 3.3 times in the machine direction at 55 ° C. by a roll stretching machine and 4.0 times in the transverse direction at 80 ° C. by a tenter stretching machine. The film was heat-fixed for 2 seconds, relaxed at 160 ° C. by 5%, cooled to room temperature, and wound up to obtain a film having a thickness of 50 μm. Table 4 shows the evaluation results of the films.

Example 2 Mixed polyester I and polyester B in which 50 parts of polyester A and 50 parts of polyester C were mixed were melted at 280 ° C. in separate vented twin screw extruders, and the mixed polyester I was discharged to polyester B. Coextrusion from a T-die at a quantitative ratio of 5
Quenching to a temperature of less than resulted in a substantially amorphous film. The obtained amorphous film is rolled with a roll stretching machine.
The film is stretched 3.3 times in the longitudinal direction at 5 ° C. and 4.0 times in the transverse direction at 80 ° C. in the tenter stretching machine, and subsequently heat-set at 240 ° C. for 1 second in the tenter stretching machine. %
After cooling to room temperature, the film was wound up to obtain a film having a thickness of 12 μm. Table 4 shows the evaluation results of the film.
Shown in

COMPARATIVE EXAMPLE 1 Polyester A was melted at 280 ° C. in a vented twin-screw extruder, extruded from a T-die, and immediately cooled on a cooling drum to a temperature of less than 30 ° C. to be substantially amorphous. Was obtained. The thickness of the obtained film was 200 μm. Table 4 shows the evaluation results of the films.

Comparative Example 2 Polyester A was melted at 280 ° C. in a vented twin-screw extruder, immediately extruded from a T-die, and immediately cooled on a cooling drum to a temperature of less than 30 ° C. to be substantially amorphous. Was obtained. The obtained amorphous film was longitudinally 3.3 times at 80 ° C. by a roll stretching machine and 1 × by a tenter stretching machine.
The film is stretched 4.0 times in the transverse direction at 00 ° C., and then heat-set at 240 ° C. for 1 second in a tenter stretching machine.
The film was relaxed by 5% at 5 ° C., cooled to room temperature, and wound up to obtain a film having a thickness of 50 μm. Table 4 shows the evaluation results of the films.

Comparative Example 3 A film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the heat setting temperature after the transverse stretching was changed to 180 ° C. instead of 240 ° C. Table 4 shows the evaluation results of the films.

Comparative Example 4 Polyester B was used in place of Polyester A, and the longitudinal stretch ratio was changed to 3.3 times instead of 2.8 times, and the transverse stretch ratio was changed to 3.3 times.
A film having a thickness of 50 μm was obtained in the same manner as in Comparative Example 3 except that the magnification was changed to 4.0 instead of 1. Table 4 shows the evaluation results of the films.

[0042]

[Table 4]

[0043]

The polyester film of the present invention described above has excellent flexibility and moldability, is suitable for molding applications such as molding transfer, and has an extremely large industrial value.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA43 AF11Y AF14Y AG29 AH04 BB06 BB08 BC01 BC12 BC17 4F210 AA24 AG01 AH81 QC06 QG01 QG18

Claims (1)

[Claims] 1. A non-heat-adhesive film at 150 ° C., having a crystallinity of 30% or more, a thickness unevenness in a longitudinal direction of the film of 5% or less, and a plastic deformation resistance in the maximum refractive index direction of 0.1%.
A polyester film having a pressure of 50 MPa /% or less.