JPH07117118A - Oriented polyester film - Google Patents

Abstract

PURPOSE:To provide an oriented polyester film which is consisting of a polyether ester block copolymer, is drawn at least in one direction, has an excellent softness and bettered thickness spots. CONSTITUTION:An oriented polyester film is made of a polyether ester block copolymer which contains a terephthalic acid, a tetramethylene glycol and a polytetramethylene glycol as principal components with a content of the polytetramethylene glycol of 50-80wt.%. The oriented polyester film is drawn at least in one direction and a break elongation ratio in longitudinal and lateral directions (where a smaller break elongation is a denominator) is 1.2 or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretched polyester film, and more specifically, it comprises a polyetherester block copolymer containing terephthalic acid, tetramethylene glycol and polytetramethylene glycol as main components and is stretched in at least one direction. , Flexible,
The present invention relates to a stretched polyester film having improved thickness unevenness.

[0002]

2. Description of the Related Art Thermoplastic polyester elastomers are
It is well known that the amount of use has increased in recent years due to its good moldability, and that it is used in various applications by taking advantage of features such as heat resistance and cold resistance.

As a method for producing an unstretched film, for example, a method for producing an unstretched film (cast film) of a thermoplastic polyester elastomer by water coating casting (Japanese Patent Laid-Open No. 4-33829).
It has been known.

[0004]

However, the film obtained by the conventional method has a high unevenness in thickness because it is unstretched, and the cost is high due to poor productivity such that a wide film cannot be obtained. It was a problem.

[0005]

Means for Solving the Problems The inventors of the present invention have made earnest studies to improve the above-mentioned problems, and as a result, have excellent flexibility, a remarkable elastic recovery rate, productivity improvement, cost reduction, and stretching with good thickness variation. The inventors have found that a polyester film can be obtained and have reached the present invention.

That is, according to the present invention, a polyether ester block copolymer containing terephthalic acid, tetramethylene glycol and polytetramethylene glycol as main components and having a polytetramethylene glycol component content of 50 to 80% by weight is used. And a stretching elongation ratio in the machine direction and the transverse direction (where the smaller breaking elongation is the denominator) is 1.2 or more. Is.

The polyether ester block copolymer in the present invention is a polyether ester block copolymer containing terephthalic acid, tetramethylene glycol and polytetramethylene glycol as main components. This copolymer is a block copolymer having tetramethylene terephthalate as a main hard segment and polytetramethylene glycol as a main soft segment, and has rubber elastic properties, and is a kind of thermoplastic polyester elastomer.

In the polyether ester block copolymer, the content of the polytetramethylene glycol component should be 50 to 80% by weight, and the molecular weight of the polytetramethylene glycol component should be 400 to 4%.
000, and particularly preferably 600 to 3500.
If this content exceeds 80% by weight, a film having excellent flexible and elastic performance can be obtained, but the melting point of the block copolymer becomes too low, so that the elastic performance during dry heat treatment and wet heat treatment decreases sharply. And a flexible elastic film with poor durability, on the other hand, if it is less than 50% by weight, the permanent set is large,
The film is inferior in elastic properties, which is not preferable.

If the molecular weight is less than 400, the block property of the obtained polyetherester block copolymer is deteriorated, so that the elastic performance is deteriorated, and the melting point of the polymer is lowered, which causes a problem in durability against drying treatment and wet heat treatment. It is not preferable because it will occur. On the other hand, when the molecular weight is more than 4000, polytetramethylene glycol is difficult to phase-separate into a block copolymer during the production of the polymer, and the rubber elastic performance is not exhibited, which is not preferable.

The polyether ester block copolymer will be described in more detail. An acid component in which 80 mol% or more, preferably 90 mol% or more of the dicarboxylic acid component is terephthalic acid or its ester-forming derivative,
80 mol% or more of the short-chain glycol component, preferably 90
80% by weight or more, preferably 90% by weight or more of the short-chain (low molecular weight) glycol component in which mol% or more is tetramethylene glycol or its ester-forming derivative, and the long-chain glycol component have a molecular weight of 400 to 4000, preferably 600. A copolymer obtained by a polycondensation reaction with a long-chain glycol component, which is ˜3500 polytetramethylene glycol, is preferably used.

Acid components other than terephthalic acid used in an amount of less than 20 mol% include, for example, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, bis (4-carboxyl). Phenyl)
Aromatic dicarboxylic acids such as methane and 4,4′-diphenyl ether dicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid and dodecanedioic acid, and aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and These ester-forming derivatives are mentioned.

Examples of the low-molecular-weight glycol component other than tetramethylene glycol used in an amount of less than 20 mol% include ethylene glycol, 1,3-propanediol, 1,5-pentadiol and 1,6-hexane. Examples thereof include diol, diethylene glycol and 1,4-cyclohexanedimethanol.

The long-chain glycol component other than polytetramethylene glycol used in an amount of less than 20% by weight is, for example, poly (oxyethylene) glycol,
Examples thereof include poly (oxypropylene) glycol.
The long-chain glycol including polytetramethylene glycol is a homopolymer, or a random copolymer or a block copolymer in which two or more kinds of repeating units constituting the homopolymer are copolymerized in a random or block form,
Alternatively, it can be used as a mixed polymer in which two or more kinds of the above homopolymers or copolymers are mixed.

The above-mentioned polyetherester block copolymer usually has a melting point of 180 to 250 ° C. and is a polymer capable of being melt-cast into a film. And it is excellent in flexibility, alkali resistance, chlorine resistance, moist heat resistance, heat resistance and the like.

In order to further improve durability such as ultraviolet resistance and heat resistance, it is preferable to add an antioxidant, an ultraviolet absorber, etc. to the polyether ester block copolymer. Examples of such antioxidants include hindered phenol compounds, hindered amine compounds, sulfur atom-containing ester compounds and the like, and examples of ultraviolet absorbers include benzophenone compounds, benzotriazole compounds, sacylate compounds and the like. .

The stretched polyester film of the present invention comprises:
In order to provide appropriate friction and workability, it is preferable to contain inert particles, and examples of the inert particles include fine particles containing the elements of IIA, IIB, IVA, IVB of the periodic table (for example, , Kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.), silicone resin,
Examples thereof include fine particles made of a polymer having high heat resistance such as crosslinked polystyrene.

In the stretched polyester film of the present invention, the polyetherester block copolymer is melted, extruded from a die and rapidly cooled to obtain an unstretched film, and then the unstretched film is stretched in at least uniaxial direction, preferably in transverse uniaxial direction. It can be manufactured by a method of stretching and then heat setting. As a quenching method for producing the unstretched film, a method of introducing it into a water tank, a method of quenching and solidifying on a casting drum, or the like can be used. Especially in the latter case, it is preferable to apply water on the casting drum. As a stretching method, stretching with a clip is preferable. This is because the polyether ester block copolymer has a low glass transition temperature (Tg), so that the film sticks to the roll during stretching with a roll, and the stretching point of the film during stretching is on the stretching roll. It is difficult to obtain a film having few stretch spots and no scratches because it goes back to the above. The stretching temperature is preferably (Tg) to (Tg + 70) ° C., and the heat setting temperature is preferably higher than the stretching temperature and lower than the melting point of the polymer. The stretching ratio is a ratio that satisfies the breaking elongation ratio.

In the present invention, the stretched polyester film has a breaking elongation ratio in the machine direction and the transverse direction (however, when the breaking elongations in the two directions are different, the smaller breaking elongation is used as the denominator).
Must be 1.2 or more. When this ratio is less than 1.2, the thickness unevenness is large, which is not preferable. This breaking elongation tends to decrease as the stretching ratio increases.

The stretched polyester film preferably has a compressive elastic modulus in the range of 0.10 to 0.35 gf / μm. When this value is taken, a stretched film which is excellent in flexibility, has a remarkable elastic recovery rate, and is excellent in touch can be obtained. If the compressive elastic modulus is less than 0.10 gf / μm, the film has a firmness rather than the characteristic of flexibility, resulting in poor handleability and wrinkles, which is not preferable. On the other hand, when it exceeds 0.35 gf / μm, flexibility and elastic recovery properties do not appear.

The thickness of the stretched polyester film is
It should be set according to the application, but normally 15-
It is in the range of 250 μm.

[0021]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the examples, "parts" means parts by weight. Further, various physical property values and characteristic values in the present invention were measured by the following methods.

(1) Breaking elongation The film is cut into a sample having a width of 10 mm and a length of 150 mm, the chuck distance is 100 mm, and the film is pulled at an instron type universal tensile testing device at a pulling speed of 10 mm / min and a chart speed of 500 mm / min. . It is calculated by the following formula from the elongation of the film at the time when the film is broken.

[0023]

[Equation 1]

(2) Compressive elastic modulus film is cut into a sample having a width of 10 mm and a length of 150 mm,
Using a micro compression tester manufactured by Shimadzu Corporation, a load is applied in the thickness direction of the film. As an indenter, 50
It is measured using a plane indenter of μmφ. As measurement conditions, maximum load 10.00gf, load speed 3mg
f / sec, and press the indenter against the film surface. The compressive elastic modulus is calculated from the tangent line of the rising portion of the obtained load-strain curve.

Example 1 A block copolymer having polytetramethylene terephthalate as a hard segment and polytetramethylene glycol as a soft segment, the content of the soft segment being 60% by weight,
A polyether ester block copolymer containing 0.2 part of a hindered amine antioxidant and 0.2 part of a benzotriazole ultraviolet absorber was used per 100 parts of the block copolymer.

The polyetherester block copolymer is dried, then melted at 200 ° C., extruded from a die at 220 ° C. onto a casting drum coated with water and rapidly cooled to obtain an unstretched film, and then the unstretched film. Was transversely stretched 2.0 times at a temperature of 40 ° C., and further heat treated at 80 ° C. to obtain a lateral uniaxially stretched film. The thickness of this film was 25 μm.

The stretched film was evaluated for elongation at break, compressive elastic modulus and uneven thickness. The results are shown in Table 1.
Shown in.

As a result, the thickness unevenness was good, the breaking elongation in the longitudinal direction was 900%, the breaking elongation in the lateral direction was 600%, and a film having a compressive elastic modulus of 0.30 gf / μm could be obtained.

Comparative Example 1 The same polymer as in Example 1 was used, melted at 200 ° C., extruded at a die temperature of 220 ° C., and rapidly cooled on a water-coated casting drum to obtain an unstretched film. The thickness of this unstretched film was 25 μm. The characteristics of this film are shown in Table 1. The film had flexibility but had poor thickness unevenness.

Comparative Example 2 Polyethylene terephthalate (PET) was melted at 280 ° C., extruded from a die and rapidly cooled to obtain an unstretched film, which was then stretched 2.0 times in the transverse direction at a preheating temperature of 100 ° C. and further 220 ° C. Was heat treated to obtain a horizontally uniaxially stretched film having a thickness of 25 μm. This film had good thickness unevenness, but had a compression elastic modulus of 50 gf / μm and lacked flexibility. The results are shown in Table 1.

[0031]

[Table 1]

[0032]

EFFECTS OF THE INVENTION According to the present invention, a stretched polyester which is composed of a polyether ester block copolymer, has good thickness unevenness, is excellent in flexibility and elastic recovery rate, and is stretched in at least uniaxial direction, preferably in transverse uniaxial direction. A film can be provided.

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Claims (2)

[Claims] 1. A polyether ester block copolymer comprising terephthalic acid, tetramethylene glycol and polytetramethylene glycol as main components and having a polytetramethylene glycol component content of 50 to 80% by weight, and at least A stretched polyester film which is stretched in one direction and has a breaking elongation ratio in the longitudinal direction and the transverse direction (however, the smaller breaking elongation is the denominator) of 1.2 or more. 2. The film has a compressive elastic modulus of 0.10 to 0.
The stretched polyester film according to claim 1, which has a thickness of 35 gf / μm.