JP2002179892A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester film suitably usable in applications requiring flexibility or moldability, e.g. applications of vinyl chloride sheet substitutes, molding transfer, molded containers or metal lamination. SOLUTION: This polyester film is characterized in that the film is composed of plural polyesters different in melting point and has 20-95 mol% compositional ratio of a high-melting polyester having respective at least one crystal melting peak appearing in a temperature region of 235-275 deg.C and a temperature region of 180-230 deg.C and exhibiting the crystal melting peak at the highest temperature within the range of 235-275 deg.C and 80-5 mol% compositional ratio of a low- melting polyester exhibiting the maximum crystal melting enthalpy within the range of 180-230 deg.C and >=1.3 ratio of crystal amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polyester film used for applications requiring flexibility and moldability, for example, as a substitute for vinyl chloride sheets, for molding transfer, for molding containers, and for metal bonding.

[0002]

2. Description of the Related Art A biaxially oriented polyester film, especially a polyethylene terephthalate film, has excellent strength, heat resistance, chemical resistance, etc., and has been widely used in industrial applications such as packaging materials, because of its relatively low price. ing.

However, generally used biaxially oriented polyethylene terephthalate films are excellent in strength, elastic modulus, and dimensional stability, but are required to have flexibility or plastic deformation of a certain level or more due to excessively high rigidity. However, they do not always have sufficient suitability, and improvements in flexibility and moldability have been demanded.

Therefore, it is possible to reduce the stretching ratio of the film,
After copolymerizing other components such as isophthalic acid, or bonding to a metal plate for metal bonding applications,
Attempts have been made to impart formability by a heat treatment at a temperature slightly lower than the melting point of the film to partially melt the higher-order structure, and to make large deformation possible.

However, the reduction of 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.

In the method of reducing the crystallinity by copolymerizing other components, the moldability is improved, but the thermal adhesiveness is also increased. May worsen or, if severe, cause troubles such as fusing.
There were problems such as a decrease in heat resistance due to a decrease in melting point.

Further, the method of partially melting the higher-order structure by performing a high-temperature heat treatment near the melting point of the film requires controlling the temperature at the 0.1 ° C. level in order to make the amount of the remaining higher-order structure uniform. It is necessary and unsuitable for mass production at low cost, and has a limitation that it can be used only in a laminate application using a heat-resistant material such as a metal plate as a base material.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has a problem to be solved. It is an object of the present invention to provide a polyester film which can be suitably used for molding containers, metal bonding and the like.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have obtained a film having high flexibility and moldability without impairing productivity by adopting a specific structure. And found that the present invention was completed.

That is, the gist of the present invention is a film composed of a plurality of polyesters having different melting points,
In the DSC measurement, the temperature range of 235 to 275 ° C. and 18
At least one crystal melting peak appears in the temperature range of 0 to 230 ° C., and the composition ratio of the high melting point polyester showing the highest crystal melting peak in the range of 235 to 275 ° C. is 20 to 95 mol%, 180 to 230 mol%. The polyester film is characterized in that the composition ratio of the low-melting polyester exhibiting the maximum crystal melting enthalpy in the range of ° C is 80 to 5 mol% and the crystal ratio is 1.3 or more.

[0011]

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 in which a dicarboxylic acid component and a glycol component are polycondensed. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid. Acid, aromatic dicarboxylic acids such as 4,4'-diphenyldicarboxylic acid, or aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and 1,4-cyclohexyldicarboxylic acid; examples of glycols include Examples include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and the like.

The term "ethylene terephthalate" or "butylene terephthalate" as used herein means a repeating ester unit obtained by condensing terephthalic acid and ethylene glycol, or terephthalic acid and 1,4-butanediol, respectively. A polyester in which 80 mol% or more of all polyester units are ethylene terephthalate means a polyester mainly composed of ethylene terephthalate, and a polyester in which 80 mol% or more of all polyester units is butylene terephthalate is a polyester mainly composed of butylene terephthalate. .

The film of the present invention has a melting point of 235 to 27.
5 ° C. polyester (hereinafter referred to as high melting point polyester) and polyester having a melting point of 180 to 230 ° C. (hereinafter, referred to as “high melting point polyester”)
Low-melting polyester). Then, after stretching, the low-melting polyester is subjected to a heat treatment at a temperature lower than the melting point of the high-melting polyester but higher than the melting point of the low-melting polyester, thereby maintaining the molecular orientation and crystal structure of the high-melting polyester phase. The molecular orientation and crystal orientation of the phase are reduced to achieve flexibility and moldability.

For this reason, the film of the present invention has a high melting point polyester composition ratio of 20 mol% or more, preferably 40 mol% or more.
Mol% or more, more preferably 65% or more. If the composition ratio of the high melting point polyester is less than 20 mol%, the moldability is excellent, but the strength becomes insufficient, which is not preferable. Or the composition ratio of low melting polyester is 5 mol%
Or more, preferably 15% or more, more preferably 25%
That is all. If the composition ratio of the low melting point polyester is less than 5 mol%, the moldability becomes insufficient, which is not preferable. Since the other polyester composition has a lower limit, the high-melting polyester and the low-melting polyester have respective upper limits. The upper limit of the former is 95 mol%, and the upper limit of the latter is 80 mol%.
It is.

Further, in order for the high-melting polyester to achieve practical strength and the low-melting polyester to achieve moldability, it is necessary to form individual crystal structures and to melt them individually. For this reason, diffraction peaks must be individually detected in X-ray diffraction measurement of a crystal lattice plane parallel to the film plane, and in DSC measurement,
Individually, the crystal melting endothermic peak must be detected.

The film of the present invention has a crystal ratio of 1.3 or more, preferably 1.5 times or more, and more preferably 2.0 times or more.
More than double. The crystal ratio is the value obtained by dividing the maximum diffraction intensity of the peaks derived from the high melting point polyester by the maximum diffraction intensity among the peaks derived from the low melting point polyester in the X-ray diffraction of the crystal lattice plane parallel to the film plane. Say. If the crystal ratio is less than 1.3, the moldability is insufficient because the orientation and crystals of the low-melting polyester phase mostly remain.

As a combination of a high-melting polyester and a low-melting polyester used in the film of the present invention, those which are suitable from the viewpoint of characteristics and suitability for industrial mass production include a polyester mainly composed of ethylene terephthalate and butylene terephthalate. It is a combination of polyester as the main component. This is because it is compatible to the extent that the glass transition is fused, but is excellent in characteristics in that a separate crystal structure is formed and separate crystal melting occurs, and it is industrially mass-produced. It is relatively inexpensive because it is a polyester. In particular, a combination of polyethylene terephthalate and polybutylene terephthalate, each of which is a combination of homopolymers from the viewpoint of cost, is suitable.From the viewpoint of moldability characteristics, each of the other components is copolymerized in a small amount. Combinations of copolymerized polybutylene terephthalate are suitable. As the latter copolymerization component, isophthalic acid, 1,4-cyclohexanedimethanol,
Suitable are 2,6-naphthalenedicarboxylic acid, polytetramethylene glycol, and the like.

In the film of the present invention, it is required that the high-melting polyester and the low-melting polyester individually cause crystal melting. However, by giving excessive shearing and melting time, the high-melting polyester and the low-melting polyester can be separated. Attention must be paid to the possibility that the fine particles are finely dispersed, so that partial melting of the higher-order structure becomes difficult to occur, and the whole system may be melted all at once.

The film of the present invention may be 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. A filler or the like may be appropriately contained according to the film, or various coatings may be applied.

The production method of the polyester film of the present invention is not limited as long as its properties are satisfied, but an example is shown for reference. First, a mixture obtained by sufficiently stirring and mixing polyethylene terephthalate and polybutylene terephthalate at room temperature is kept at 150 ° C. for 6 hours under a nitrogen gas stream and dried. The dried mixed polyester is extruded at 280 ° C. using a screw extruder. The extruded melt sheet is immediately quenched on a cooling drum to less than 30 ° C. and becomes substantially amorphous. The obtained amorphous sheet is 3.4 times longer in the longitudinal direction and 4.times. In the transverse direction at a temperature equal to or higher than the glass transition temperature.
It is stretched 0 times and then kept at 230 ° C for 3
Heat fix for 2 seconds.

[0022]

EXAMPLES (1) Polyester composition A sample film was dissolved in a deuterium trifluoroacetate solvent, ¹ H-NMR was measured, and the molar ratio of each polyester was determined from an integral curve.

(2) An aluminum pan containing 10 mg of DSC sample film
What was heated to 0 ° C. was rapidly cooled with liquid nitrogen to produce an amorphous sample. The amorphous sample was measured at a temperature rising rate of 20 ° C./min in the range of 0 to 300 ° C. using a DSC 2920 manufactured by TA Instruments to determine the glass transition temperature and the crystal melting temperature.

(3) Crystal Amount Ratio The X-ray diffraction of the sample film was measured with an X-ray diffractometer RINT2000 manufactured by Rigaku Corporation. In other words, the sample film is stuck on the aluminum folder for powder sample measurement,
Diffraction of the crystal lattice plane arranged parallel to the film plane
The measurement was performed by θ / θ scanning. X-rays used Cu Kα rays, and the output was 40 kV and 30 mA. In the obtained diffraction profile, the value obtained by dividing the diffraction intensity of the maximum peak among the diffractions of the high melting point polyester obtained by the NMR and DSC measurement results by the diffraction intensity of the maximum peak among the diffractions of the low melting point polyester was obtained. The crystal ratio was determined.

(4) Formability and Practical Strength A tensile test was carried out using an Autograph AG-I manufactured by Shimadzu Corporation at 23 ° C. under the conditions of a sample width of 15 mm, a chuck gap of 50 mm, and a tensile speed of 200 mm / min. Done, stress-
Obtain the strain curve. The stress-strain curve (SS curve) in the region from 5% to fracture is regressed by a linear function, and its slope, that is, the coefficient of the primary term is used as a formability index.
Those having Pa /% or less were regarded as having good moldability. The stress at break was used as a practical strength index, and those having a stress of 50 MPa or more were considered to have sufficient practical strength.

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

[Polymerization of Polyester] Polyester (a) 100 parts of dimethyl terephthalate, ethylene glycol 6
0 parts and 0.1 part of calcium acetate-water salt were placed in a reactor and transesterified. That is, the reaction start temperature is set to 1
The temperature was raised to 70 ° C., and the reaction temperature was gradually raised with the distillation of methanol. After 4 hours, the temperature was raised to 230 ° C. to substantially end the transesterification reaction. Then average particle size 1.5μ
After adding ethylene glycol slurry containing 0.04 parts of phosphoric acid and 0.04 parts of antimony trioxide, polycondensation reaction was performed. That is,
The temperature was gradually increased and the pressure was gradually decreased. After 2 hours, the temperature was set to 280 ° C., the pressure was set to 0.3 mmHg, and the reaction was continued. When the intrinsic viscosity became 0.70 dl / g, the reaction was stopped. A polyester (a) containing 0.1 part of silica was obtained.

Polyester (b) Polyester (b) was obtained in the same manner as polyester a, except that dimethyl terephthalate was changed to 100 parts and dimethyl terephthalate was changed to 92 parts and dimethyl isophthalate was changed to 8 parts. The intrinsic viscosity was 0.70 dl / g.

Polyester (c) Novadour 5010 manufactured by Mitsubishi Engineering-Plastics Corporation was used 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. in a vented twin screw extruder, and extruded from a T-die. Immediately quenching to a temperature below 30 ° C. yielded a substantially amorphous film. The obtained amorphous film is stretched 3.4 times in the machine direction at 68 ° C. by a roll stretching machine and 4.0 times in the transverse direction at 80 ° C. by a tenter stretching machine. Heat fix for 1 second, then add 16 more
A 5% width relaxation was performed at 0 ° C. to obtain a 25 μm-thick polyester film.

Example 2 A polyester film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that polyester (b) was used instead of polyester (a).

Comparative Example 1 100 parts of the polyester (a) was extruded in the same manner as in Example 1, then stretched 3.4 times at 80 ° C. and 4.0 times at 100 ° C. To obtain a polyester film having a thickness of 25 μm.

Comparative Example 2 A polyester film having a thickness of 25 μm was obtained in the same manner as in Example 2, except that polyester (b) was replaced with 50 parts and 18 parts, and polyester (c) was replaced with 50 parts and 82 parts. .

Comparative Example 3 A polyester film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the heat setting temperature was changed to 200 ° C. instead of 240 ° C.

The results obtained are summarized in Table 1 below.

[0036]

[Table 1]

In the above Table 1, ET means ethylene terephthalate, and BT means butylene terephthalate.

[0038]

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

Claims (2)

[Claims] 1. A film comprising a plurality of polyesters having different melting points, wherein the film has a
At least one crystal melting peak appears in each of a temperature range of 5 to 275 ° C and a temperature range of 180 to 230 ° C.
The composition ratio of the high melting point polyester exhibiting the highest temperature crystal melting peak in the range of 5 to 275 ° C is 20 to 95 mol%,
A polyester film, wherein the composition ratio of the low-melting polyester exhibiting the maximum crystal melting enthalpy in the range of 0 to 230 ° C is 80 to 5 mol%, and the crystal ratio is 1.3 or more. 2. The polyester film according to claim 1, wherein the high melting point polyester is a polyester mainly composed of ethylene terephthalate, and the low melting point polyester is a polyester mainly composed of butylene terephthalate.