JPH04221622A - Polyester film - Google Patents

Abstract

PURPOSE:To make the title film rich in flexibility, soft to the touch and applicable to a base of a gold or silver thread or an ointment or an adhesive tape, by a method wherein a film making of specific polyester is performed under a specific condition. CONSTITUTION:A polyester uncrystalloidal and unstretched sheet is stretched 2.0-5.0 times in a longitudinal direction at a temperature of Tg to Tg+50 deg.C and stretched further 2.0-5.0 times in a widthwise direction at the temperature of Tg to Tg+50 deg.C. Heat treatment is performed after stretching, a heat treatment temperature is selected out of a range of the melting point Tm-60 to Tm-1 deg.C and when the same exceeds Tm-1 deg.C, breaks occur frequently through melting of a film and the film is stuck to a holding surface of a clip. When the same is less than Tg-60 deg.C, since it becomes that flexibility of the film is not obtained and dimensional stability is lowered drastically, it is not preferable. A facial degree of orientation DELTAP of the objective film is not exceeding 0.1200, and when the DELTAP exceeds 0.1200, since the tensile modulus of elasticity of the film is high, the film becomes the one having no flexibility.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film that is highly flexible, has low stiffness, and is soft to the touch.

0002

[Prior Art and Problems to be Solved by the Invention] Biaxially stretched polyester films have excellent physical and chemical properties, and are used for magnetic tapes, capacitors, packaging, plate making, and electrical insulation. It is used as a base material in an extremely wide range of industrial fields, and demand for it continues to increase.

[0003] Conventional biaxially oriented polyester films are
It had a strong elasticity and was hard to the touch, so when it was used as a base material for adhesive tape, for example, when it was pasted on a convex surface, the elasticity of the polyester film caused it to gradually peel from the edges. There was a problem with it peeling off. Furthermore, when used as a base material for a patch, the stiffness of the waist prevents movement from moving with the skin, resulting in discomfort for the user. Furthermore, when used as a gold-silver-based film, the poor feel of the polyester film causes discomfort when it comes into contact with the skin, and improvements have been sought in both cases.

0004

[Means for solving the problem] In view of the above-mentioned circumstances, the present inventors have made extensive studies and found that the above-mentioned problem can be solved by forming a film from a certain polyester under certain conditions. The invention was completed.

That is, the gist of the present invention is that after biaxially stretching polyester having a glass transition temperature of 50°C or less, (T
The polyester film has a degree of planar orientation (ΔP) of 0.1200 or less, which is obtained by heat treatment at a temperature of m-60) to (Tm-1)°C (Tm is the melting point of the polyester).

The present invention will be explained in detail below. As the acid component constituting the polyester in the present invention, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and 1,10-decanedicarboxylic acid are preferred, and among them, , adipic acid, and sebacic acid are preferred, and in particular, it is preferable to use adipic acid and/or sebacic acid as the aliphatic dicarboxylic acid in an acid component constituting the polyester in an amount of 5 to 30 mol%, preferably 10 to 25 mol%. good. On the other hand, glycol components include ethylene glycol,
trimethylene glycol, tetramethylene glycol,
Pentamethylene glycol and hexamethylene glycol are preferred.

[0007] Polyester can be obtained by a known method by appropriately combining these components, but an antimony compound is preferably used as a polycondensation catalyst in order to suppress yellowing of the polymer and improve thermal stability during melting. used. Furthermore, the glass transition temperature (hereinafter, T
g) is 50°C or lower, preferably 45°C or lower, more preferably 40°C or lower. When Tg exceeds 50°C, it becomes difficult to develop flexibility after forming into a film.

[0008] Furthermore, the heat of crystal fusion (hereinafter abbreviated as ΔHm) of the polyester used in the present invention is usually 8 to 4 cal.
/g. When ΔHm exceeds 8 cal/g, it is difficult to obtain the desired flexibility of the film;
If it is less than 1/g, the fusion of the polymer chips becomes intense,
This causes various troubles in processes such as drying. In order to improve the workability of the film after processing, it is effective to blend particles into polyester to make the film surface rough and slippery. Known methods such as an additive particle method in which inert fine particles are added during the polyester reaction can be used.

[0009] Furthermore, when adipic acid or sebacic acid is used as part of the acid component constituting the polyester, the intrinsic viscosity [η] decreases when drying and when melted, and coloring is large compared to, for example, polyethylene terephthalate. There is a tendency. To suppress this, it is recommended to add an antioxidant. Examples of antioxidants include hindered phenol-based antioxidants and phosphite-based antioxidants, and hindered phenol-based antioxidants are particularly preferably used.

The obtained polyester is basically formed into a film as follows. That is, after drying, it is melt-extruded into a sheet form from an extruder, and this is rapidly cooled using, for example, an electrostatic cooling method to form an amorphous unoriented sheet. Then, the obtained sheet is heated to Tg~(Tg+50)℃ in the longitudinal direction.
Stretched 2.0 to 5.0 times at a temperature of
Stretch 2.0 to 5.0 times at ~(Tg+50)°C. At this time, a method of stretching in one direction in two or more stages can also be adopted, but even in that case, it is preferable to select a final stretching ratio so that it falls within the above range. Moreover, it is also possible to simultaneously biaxially stretch the amorphous unoriented sheet so that the area magnification becomes 4 to 25 times. After stretching, heat treatment is applied,
The heat treatment temperature is selected from the range of (Tm-60) to (Tm-1)°C, preferably (Tm-40) to (Tm-1)°C, more preferably (Tm-20) to (Tm-1)°C. Re,
The heat treatment time is selected from the range of 1 second to 10 minutes. If the heat treatment temperature exceeds (Tm-1)°C, it is not preferable because the film will frequently break due to melting or the film will stick to the clip gripping surface. On the other hand, if the temperature is less than (Tm-60)°C, not only the flexibility of the film, which is one of the objects of the present invention, cannot be obtained, but also the dimensional stability is significantly reduced, which is not preferable. Such heat treatment may be performed under limited shrinkage or elongation of the film within 20% or at a constant length, and may be performed in two or more stages. Furthermore, if necessary, the degree of plane orientation (hereinafter abbreviated as ΔP) of the film of the present invention, which may be stretched again in the longitudinal direction and/or width direction before or after heat treatment, is 0.1200 or less, preferably 0. .1100 or less, more preferably 0.1000
It is as follows. When ΔP exceeds 0.1200, the tensile modulus of the film is high, resulting in an inflexible film. The tensile modulus E of the polyester film of the present invention is usually 350 kg/mm2 or less, preferably 300 kg
/mm2, more preferably 250 kg/mm2 or less.

[0011]

[Examples] The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. The measurement methods and definitions of various physical properties and characteristics are as follows. Note that "parts" in Examples and Comparative Examples indicate "parts by weight."

(1) Melting point (Tm), glass transition temperature (T
g), heat of crystal fusion (ΔHm) Differential calorimeter SSC580DS manufactured by Seiko Electronic Industries, Ltd.
Measurement was performed using C20 type. After melting and holding 10 mg of a sample at 300°C for 5 minutes under a N2 stream, the resulting sample was set in a DSC device and the temperature was raised from -30°C at a heating rate of 10°C/min. The glass transition temperature (Tg) is sensed when the DSC curve bends due to a change in specific heat, and the baseline shifts in parallel. The intersection of the point with the maximum value and the tangent line was taken as the starting point of bending, and this temperature was taken as the glass transition temperature (Tg). The endothermic peak temperature due to crystal melting was defined as the melting point (Tm). Furthermore, the heat of crystal fusion (ΔHm) of the polyester was calculated from the endothermic peak area.

(2) Refractive index of the film Using an Abbe refractometer manufactured by Atago Optical Co., Ltd., measure the maximum value nγ of the refractive index within the film plane, the refractive index nβ in the direction perpendicular to it, and the refractive index nα in the film thickness direction. The average refractive index and degree of plane orientation ΔP were calculated from the following equations. Note that the refractive index was measured at 23° C. using sodium D line.

[0014]

[Math 1]

(3) Evaluation of flexibility Tensile modulus E was used as an index of flexibility. That is, the lower the tensile modulus E, the more flexible the material is. Using a tensile testing machine Intesco Model 2001 manufactured by Intesco Co., Ltd., a sample film of 300 mm in length and 20 mm in width was tested in a room controlled at a temperature of 23°C and a humidity of 50% RH.
Tensile at a strain rate of 0%/min, calculated by the following equation using the initial linear portion of the tensile stress-strain curve.

E=Δσ/Δε E=tensile modulus (kg/mm2) Δσ=stress difference Δ due to original average cross-sectional area between two points on a straight line
ε = Strain difference between the same two points Example 1 84 parts of dimethyl terephthalate, 1 part of dimethyl sebacate
9 parts of ethylene glycol, 60 parts of ethylene glycol, and 0.09 part of magnesium acetate tetrahydrate were heated to raise the temperature and a transesterification reaction was carried out while distilling off methanol. After the reaction started, the temperature was raised to 230° C. over about 5 hours to substantially complete the transesterification reaction. Next, an ethylene glycol slurry of wet silica particles having an average particle diameter of 0.82 μm as measured by centrifugal sedimentation was added so that the silica content was 0.02% by weight based on the polyester. Furthermore, after adding 0.04 parts of ethyl acid phosphate and 0.04 parts of antimony trioxide, the temperature was gradually increased to 280°C, and the pressure was gradually reduced from normal pressure to 1 mmHg. The pressure was reduced. The reaction was stopped 5 hours after the start of the polycondensation reaction, and a polyester having a melting point of 222°C and a glass transition point of 36°C was obtained.

The obtained polyester was extruded into a sheet from an extruder at 280°C, and the thickness was reduced to 3 by using an electrostatic cooling method.
A 10 μm amorphous unoriented sheet was obtained. The obtained sheet was then stretched 3.5 times in the longitudinal direction at 38°C and further 3.5 times in the width direction at 55°C, and heat treated at 220°C for 7 seconds to obtain a biaxially stretched film with a thickness of 25 μm. . The average refractive index of the obtained film was 1.5811, and the degree of plane orientation ΔP was 0.
．． 0934, and the tensile modulus E is 210 kg/mm2
A film that is highly flexible and soft to the touch was obtained.

Example 2 A biaxially stretched film with a thickness of 25 μm having an average refractive index and ΔP shown in Table 2 was prepared by changing the acid component and glycol component of polyester as shown in Table 1, and changing the film forming recipe as appropriate. I got it. The obtained film was highly flexible and soft to the touch.

Comparative Examples 1 and 2 The acid component and glycol component of the polyester were changed as shown in Table 1, and the film forming recipe was appropriately changed to form a biaxial film having a thickness of 25 μm and having the average refractive index and ΔP shown in Table 2. A stretched film was obtained. All of them had poor flexibility and were hard to the touch.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Effects of the Invention] Since the film of the present invention is highly flexible and soft to the touch, it can be applied to a wide range of uses such as gold and silver threads, base materials for adhesive patches, and base materials for adhesive tapes, and its industrial value is high.

Claims (1)

[Claims] Claim 1: After biaxially stretching polyester having a glass transition temperature of 50°C or less, (Tm-60) to (Tm-1)
)°C (Tm is the melting point of polyester), and has a degree of plane orientation (ΔP) of 0.1200 or less.