JPH11156933A - Polypropylene terephthalate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the distribution of the physical properties of a film in the width direction uniform and eliminate its torsional phenomenon due to thermal treatment or the like after making bags of the film by specifying the difference between the absolute values of boiling water shrinkage factor in two different specified directions of the longitudinal direction at specified positions to the right and the left from the center of the entire width of the film. SOLUTION: The biaxially orientated polypropylene terephthalate film is cut, for example, each in the form of a 21 cm square piece from a position located equivalent to 40% of the entire width to the right/left from the center of the film. Next, a circle with a diameter of 20 cm in the middle of each of the samples as a center, for example, is drawn and further, a straight line which passes through the center of the circle in the directions of 0 deg., 45 deg., 90 deg. and 135 deg. longitudinally is drawn to measure the diameter of each of these directions as lengths before treatment. In addition, these samples are thermally treated in a boiling water, then water sticking to the surfaces of the samples is removed and air-dried, and the diameter in each of the directions is measured as the length after treatment. Further, absolute values of boiling water shrinkage factors in the direction of 45 deg. and in the direction of 135 deg. when the longitudinal direction is set at 0 deg., are sought, so that the difference between these absolute values is 3.5 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polypropylene terephthalate film formed by longitudinal and horizontal sequential biaxial stretching.

[0002]

2. Description of the Related Art Polyester films represented by polyethylene terephthalate have excellent mechanical properties, heat resistance and processability, and are widely used in food packaging, industrial use, magnetic recording, photographic applications, etc. Polyamide-based resin films are used for packaging heavy or water-based products, especially in food applications, because of poor impact resistance. However, since the polyamide resin film changes in size and strength due to moisture absorption, there is a problem of deformation and thermal deterioration of the packaging bag, and a laminate of a polyester film and a polyamide film is used particularly in applications requiring retort treatment. .

[0003]

A polypropylene terephthalate film can be cited as a film which can make up for both disadvantages. Polypropylene terephthalate has a lower elastic modulus and better flexibility than a polyethylene terephthalate film, and has a lower moisture absorption than a polyamide resin film. However, when the film is formed by one-stage vertical and horizontal sequential biaxial stretching, distribution of physical properties tends to occur in the film width direction, and when used as a packaging material, torsion phenomenon occurs due to heat treatment after bag making and serious troubles occur. Had become.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors studied stretching conditions, analyzed the characteristics of the obtained film, and finally solved the above-mentioned problems.
That is, 40% of the full width from the center to the left and right of the full width of the film
The difference (absolute difference in boiling water shrinkage) between the absolute value of the boiling water shrinkage in the 45-degree direction and the absolute value of the boiling water shrinkage in the 135-degree direction when the vertical direction is set to 0 degree at the position of is 3.5 or less. A biaxially oriented polypropylene terephthalate film characterized by the following.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

First, the polypropylene terephthalate used in the present invention contains terephthalic acid as a main acid component,
Polyester containing 1,3-propanediol as a main glycol component, and these acid components and / or glycol components include isophthalic acid, phthalic acid, diphenyl-4,4-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, Naphthalene-2,7-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, diphenoxyethane-4,
4-dicarboxylic acid, diphenylsulfone-4,4-dicarboxylic acid, diphenylether-4,4-dicarboxylic acid, malonic acid, 1,1-dimethylmalonic acid, succinic acid,
Acid components such as glutaric acid, adipic acid, sebacic acid and decamethylene dicarboxylic acid; glycol components such as ethylene glycol, tetramethylene glycol, neopentyl glycol, cyclohexane dimethanol, hydroquinone, and bisphenol A; polyethylene glycol, polypropylene glycol, and polytetraethylene Methylene glycol or copolymers thereof may be copolymerized

As the method for producing the polyester in the present invention, a conventionally known method for directly obtaining a polyester by the reaction of a dicarboxylic acid and a glycol, or a catalyst for transesterifying a lower alkyl ester of a dicarboxylic acid with a glycol, such as sodium, potassium, Heat-reacting using one or more of compounds containing magnesium, calcium, zinc, strontium, titanium, zirconium, manganese, and cobalt to obtain a low-polymerized polyester, and the obtained low-polymerized polyester is then subjected to the presence of a polymerization catalyst. And a method obtained by heating and polymerizing at 200 to 260 ° C. under reduced pressure.

Preferred polymerization catalysts include antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds and titanium compounds.

Examples of the titanium compound include tetraalkyl titanates, tetraaryl titanates, titanyl oxalates, titanyl oxalate, chelate compounds containing titanium, tetracarboxylates of titanium, and the like. Specific examples include tetraethyl titanate and tetrapropyl titanate. , Tetraphenyl titanate or partial hydrolysates thereof, titanyl ammonium oxalate, potassium titanyl oxalate, titanium triacetylacetonate and the like.

The polyester film of the present invention may contain inorganic particles, organic salt particles and crosslinked polymer particles.

The inorganic particles include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, and fluorine oxide. Lithium oxide and the like.

Examples of the organic salt particles include calcium oxalate, terephthalate such as calcium, barium, zinc, manganese and magnesium.

Examples of the crosslinked polymer particles include homopolymers or copolymers of vinyl monomers such as divinylbenzene, styrene, acrylic acid, methacrylic acid, acrylic acid or methacrylic acid. In addition, organic particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin may be used.

[0014] The polyester film of the present invention may comprise a nucleating agent, an antioxidant, a coloring inhibitor, a pigment,
You may mix | blend a dye, an ultraviolet absorber, a mold release agent, a lubricant, a flame retardant, and an antistatic agent.

Next, the method for producing the film of the present invention will be described, but is not necessarily limited thereto. As described above, polypropylene terephthalate is polymerized by a known method, then chipped, and
Alternatively, after blending with other polymers and additives as required, the mixture is extruded into a sheet from an extruder equipped with a T-die, and while being applied with an electrostatic charge, the sheet is closely contacted with a cooled casting drum and solidified by cooling. Let it. This unstretched film is stretched by a roll-type longitudinal stretching machine, then guided into a tenter, and horizontally stretched.
Heat treatment at ℃. If necessary, heat treatment may be performed while relaxing in the width direction.

In order to obtain the film of the present invention, the longitudinal stretching is divided into two stages of a former stage and a latter stage at a temperature of not less than a glass transition temperature (Tg) + 20 ° C. and not more than a low temperature crystallization temperature (Tc) + 20 ° C. The longitudinal stretching is preferably performed at a magnification of 3.0 or more and 4.5 or less, and preferably without cooling the space between the former stage and the latter stage to Tg or less. Thereby, it became possible to form a polypropylene terephthalate film having uniform physical properties in the width direction.

[0017]

Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Evaluation Method (1) Boiling Water Shrinkage Ratio and Boiling Water Shrinkage Ratio Oblique Difference A biaxially oriented polypropylene terephthalate film was placed 21 cm square from the center of the full width and 40% of the full width to the left and right from the center (end). Cut out samples. 20c diameter centered on the center of each sample
Draw a circle with a vertical direction of 0 °, 45 °, 90 ° and 13
A straight line passing through the center of the circle is drawn in the direction of 5 °, and the diameter in each direction is measured, which is defined as the length before processing. The sample is heat-treated in boiling water for 30 minutes, taken out, and the water adhering to the surface is removed and air-dried. After air drying, measure the diameter of each area,
Length after processing. The boiling water shrinkage is calculated using the following equation. Boiling water shrinkage = (length before treatment−length after treatment) / length before treatment × 100 (%) For each sample, 4 when the vertical direction is 0 °
The absolute value of the boiling water shrinkage in the 5 ° direction and the absolute value of the boiling water shrinkage in the 135 ° direction are obtained, and the difference between the absolute value of the boiling water shrinkage in the 45 ° direction and the absolute value of the 135 ° direction is calculated. Ask. The average value of the difference between the samples at both ends was defined as the oblique difference in boiling water shrinkage.

(2) Curl height A uniaxially stretched polypropylene film of 40 μm is laminated on a biaxially oriented polypropylene terephthalate film by a dry laminating method, and then heat-sealed in three directions to form a rectangular filled bag of 21 cm long × 14.6 cm wide. Produced. Next, 100 bags were stacked on each other for 24 hours in an atmosphere with a humidity of 50% RH. Leave to stand, the curl height of the corner of the bag (m
m) was measured. (See Fig. 1)

Example 1 94 parts by weight of dimethyl terephthalate, 74 parts by weight of 1,3-propanediol and 0.0 part of tetrabutyl titanate
35 parts by weight were charged into a reaction vessel, and the temperature inside the vessel was gradually raised from 150 ° C. to 230 ° C., and methanol distilled off was removed from the system, thereby substantially terminating the esterification reaction. next,
The pressure was gradually reduced from 230 ° C. and the temperature was raised.
C. and 1.0 mmHg or less, and the polymerization reaction was carried out for 2 hours. The intrinsic viscosity of the obtained polymer was 0.83.

The propylene terephthalate polymer was vacuum-dried at 160 ° C. for 2 hours by a conventional method, extruded from a T-die, and brought into close contact with a casting drum by electrostatic charge to obtain a cast film. The Tg of the cast film was 50 ° C. and the Tc was 70 ° C. After stretching the cast film in the first step at a stretching temperature of 85 ° C. in the longitudinal direction at 1.5 times, the second step stretching at 75 ° C. while maintaining the temperature at 70 ° C. so that the total magnification becomes 3.0 times. Was done. Subsequently, the film was stretched 3.5 times in the width direction at 65 ° C. in a tenter, and heat-treated at 200 ° C. while relaxing 5% in the width direction to obtain a biaxially stretched polypropylene terephthalate film having a thickness of 12 μm. Table 1 shows the oblique difference in the shrinkage ratio of boiling water and the curl height of the obtained film.

Example 2 A biaxially oriented polypropylene terephthalate film having a film thickness of 12 μm was obtained in the same manner as in Example 1 except that the temperature of the MD stretching in the first stage was 75 ° C.
Table 1 shows the oblique difference in the shrinkage ratio of boiling water and the curl height of the obtained film.

Comparative Example 1 The polypropylene terephthalate polymer of Example 1 was vacuum dried at 160 ° C. for 2 hours by a conventional method, extruded from a T-die, and adhered to a casting drum by electrostatic charge to obtain a cast film. The cast film was heated on a roll heated to 60 ° C., stretched 2.5 times in the longitudinal direction after stretching in a tenter, and stretched 3 times in the width direction at 65 ° C. in a tenter.
Heat treatment was performed at 0 ° C. while relaxing 5% in the width direction to obtain a biaxially oriented polypropylene terephthalate film having a film thickness of 12 μm. Table 1 shows the oblique difference in the shrinkage ratio of boiling water and the curl height of the obtained film.

Comparative Example 2 The polypropylene terephthalate polymer of Example 1 was vacuum-dried at 160 ° C. for 2 hours by a conventional method, extruded from a T-die, and brought into close contact with a casting drum by electrostatic charge to obtain a cast film. After stretching the cast film in the first stage at a stretching temperature of 60 ° C. in the longitudinal direction at 1.5 times, the second stage stretching is performed while maintaining the temperature at 50 ° C. so that the total magnification becomes 3.0 times at the stretching temperature of 60 ° C. Was done. Subsequently, the film was stretched in the transverse direction in the same manner as in Example 1 to reduce the film thickness to 12
A μm biaxially oriented polypropylene terephthalate film was obtained. Table 1 shows the oblique difference in the shrinkage ratio of boiling water and the curl height of the obtained film.

[0025]

[Table 1]

[0026]

According to the biaxially oriented polypropylene terephthalate film of the present invention, the oblique difference in the boiling water shrinkage is small and the twisting phenomenon does not occur even in the heat treatment after bag making.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method for measuring a curl height.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 7:00

Claims (1)

[Claims] 1. A film having a width of 4 from the center of the film to the left and right.
At the position of 0%, the difference between the absolute value of the boiling water shrinkage in the 45-degree direction and the absolute value of the boiling water shrinkage in the 135-degree direction (oblique difference in the boiling water shrinkage) when the vertical direction is 0 degree is 3.5. A biaxially oriented polypropylene terephthalate film characterized by the following.