JP2692284C - - Google Patents

Description

The present invention relates to a biaxially oriented polyester film for molding having excellent moldability, heat resistance and uneven thickness. [Problems to be Solved by Conventional Techniques and Inventions] Conventionally, biaxially stretched polyester films have excellent strength and heat resistance, and have been widely applied to various industrial uses. For example, the use of a polyester film as a raw material or auxiliary material such as vacuum, compressed air, overhang, cold, injection, in-mold, embossing, etc. has been studied. Application for electric discharge, electric discharge, packaging, decoration, etc. are being studied. However, the biaxially stretched polyester film is inferior in moldability as compared with the vinyl chloride resin, and thus has been difficult to apply in these applications. Especially for molding transfer,
Improvements in moldability have been demanded as base films for molded containers. However, when the moldability is improved, unevenness in the thickness of the film is greatly deteriorated, and various problems occur during processing. For example, if the thickness of the film for forming and transferring is uneven, the stretch of the film becomes uneven during the forming and transferring, so that the transferred design is disturbed. Further, if the film for a molded container has uneven thickness, the moldability becomes non-uniform, so that there is a tendency that the film is broken or partial delamination occurs during lamination. Accordingly, there has been a demand for a polyester film having excellent moldability and uneven thickness of the film. [Means for Solving the Problems] In view of the above problems, the present inventors have conducted intensive studies, and as a result, a film containing a specific acid component in a polyester in a specific amount, and a film having specific physical properties, The present inventors have found that the properties and the thickness unevenness are extremely excellent, and have completed the present invention. That is, the gist of the present invention is that the aliphatic dicarboxylic acid component is added in an amount of 1 to 20 with respect to the total acid component.
mol% containing copolyester, 100%
A decompression time of film strength F ₁₀₀ is 0.5~ 3 kg / mm ^2, and the thickness unevenness of the film lies in molding the biaxially oriented polyester film, characterized in that 40% or less. Hereinafter, the present invention will be described in detail. Polyester used in the present invention, as a dicarboxylic acid component, terephthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, aliphatic Dicarboxylic acid and the like, consisting of one or more known dicarboxylic acids, and ethylene glycol, propylene glycol as a diol component,
It is a polyester comprising one or more known diol components such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like. In the polyester of the present invention, copolymerizable components include, for example, oxycarboxylic acids such as p-oxybenzoic acid, monofunctional compounds such as benzoic acid, benzoylbenzoic acid, and methoxypolyalkylene glycol; and polyfunctional compounds such as glycerin and pentaerythritol. Functional compounds can also be used to the extent that the product can retain a substantially linear polymer. In the polyester constituting the film of the present invention, the proportion of polyethylene terephthalate is preferably at least 50 mol%, more preferably at least 70 mol%. If the content of polyethylene terephthalate is less than 50 mol%, the strength and heat resistance of the film are undesirably reduced. In the polyester constituting the film of the present invention, the content of the aliphatic dicarboxylic acid component in the total acid component is in the range of 1 to 20 mol%, preferably in the range of 1 to 10 mol%. By satisfying such requirements, the film moldability, the improvement of heat resistance and the improvement of thickness unevenness can be achieved at the same time because the addition of the aliphatic dicarboxylic acid component makes the polyester molecular chain flexible and crystalline. At the same time, it is presumed that the above characteristics could be achieved. In the polyester constituting the film of the present invention, a film in which the content of the aliphatic dicarboxylic acid component in all the acid components exceeds 20 mol% is not preferred because the heat resistance is rather deteriorated and the thickness unevenness is deteriorated. On the other hand, if the content is less than 1 mol%, the above characteristics are not improved, which is not preferable. As the aliphatic dicarboxylic acid component to be contained in the polyester constituting the film of the present invention, an aliphatic dicarboxylic acid component having 4 to 12 carbon atoms, preferably 6 to 12 carbon atoms, has the above-mentioned moldability, heat resistance, and uneven thickness. It can be improved and is preferable. In addition, in order to improve the lubricity of the film, it is also preferable to include fine particles such as an organic lubricant and an inorganic lubricant. If necessary, a stabilizer, a coloring agent, an antioxidant, an antifoaming agent, and an antistatic agent are used. It may contain an additive such as an agent. As the fine particles imparting lubricating properties, known inert external particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, lithium fluoride, carbon black, and melting of polyester resin Internal particles formed inside the polymer during polyester production by a high melting point organic compound which is insoluble during film formation, a crosslinked polymer, and a metal compound catalyst used during polyester synthesis, such as an alkali metal compound or an alkaline earth metal compound. The content of the fine particles contained in the film is usually in the range of 0.002 to 0.9% by weight, and the average particle size is preferably in the range of 0.001 to 3.5 μm. The polyester of the present invention has an intrinsic viscosity in the film of preferably 0.50 or more, more preferably 0.60 or more. If the intrinsic viscosity of the film is less than 0.50, sufficient strength and moldability cannot be obtained, which is not preferable. In the film of the present invention, 0.99 ° C. atmosphere at 100% elongation of the film strength F ₁₀₀ under should be in the range of 0.5~ 3 kg / mm ^2. The F ₁₀₀ in the present invention is vertical and the average value of the lateral strength of the film at 100% elongation at 0.99 ° C.. According to our study results, the strength F ₁₀₀ value is deeply related to the formability of the film, and if the F ₁₀₀ exceeds 3 kg / mm ² , the formability decreases, which is not preferable. Also, the F ₁₀₀ is less than 0.5 kg / mm ² films, molded during the film unevenly deformed, for example, in the transfer film, undesirable distortion of the pattern to be transferred is generated. The difference in film strength between the longitudinal and transverse directions at 150 ° C. and 100% elongation is usually 3 kg / mm ² or less, preferably 2 kg / mm ² or less, more preferably 1 kg / mm ² or less.
kg / mm ² or less. If the difference exceeds 3 kg / mm ² , the anisotropy increases and the moldability deteriorates. In the film of the present invention, the thickness unevenness of the film is 40% or less, preferably 30% or less. If the thickness unevenness of the film exceeds 40%, the moldability and the elongation of the film at the time of molding become non-uniform, and the pattern is distorted at the time of molding transfer, or breakage or delamination occurs when used as a molding container. It is not preferable from the viewpoint of workability. Film of the present invention is F ₁₀₀ and thickness unevenness is essential to be in the above range is preferably further range of planar orientation ΔP is from 0.040 to 0.140 of the film of the present invention, further Preferably it is in the range of 0.050 to 0.120. Plane orientation Δ
Films having a P of more than 0.140 are not preferred because of insufficient moldability. Further, a film having a degree of plane orientation ΔP of less than 0.040 is not preferable because the strength of the film is reduced and the flatness is deteriorated. Is not sufficiently crystallized, and the heat resistance is poor. In the present invention, the density of the film is preferably in the range of 1.345 to 1.390, and more preferably in the range of 1.355 to 1.380. 1.345 film density
If it is less than 1, heat resistance is inferior and is not sufficient. On the other hand, if the film exceeds 1.390, the moldability becomes insufficient, which is not preferable. In the present invention, the heat of fusion of the film is preferably in the range of 1 to 8 cal / g, more preferably 1 to 6 cal / g. Films having a heat of fusion of more than 8 cal / g are not preferred because the moldability decreases. On the other hand, a film having a heat of fusion of less than 1 cal / g is particularly difficult to crystallize in a raw material drying step at the time of film formation, especially when recycling ears, and requires a complicated step such as vacuum drying. This is not preferable, and the thickness unevenness of the film worsens, which is not preferable. Regarding the shrinkage characteristics of the film of the present invention, both the shrinkage in the longitudinal and transverse directions after treatment at 150 ° C. for 3 minutes are preferably 10% or less, more preferably 5% or less. A film having a shrinkage factor of more than 10% in the vertical or horizontal direction is not preferable because the film shrinks greatly in a heating section during the processing step. In particular, when the film is used for transfer, the shrinkage in the horizontal direction under the above conditions is preferably 0% or less (when the film expands, the shrinkage is set to minus). In the case of a film having a lateral shrinkage of more than 0%, when used for forming and transferring, the film shrinks in the drying step after the formation of the print layer, which is not preferable. Regarding the mechanical strength of the film of the present invention, the Young's modulus in the machine direction and the transverse direction of the film is preferably 300 kg / mm ² or more, more preferably 350 kg / m 2.
m ² or more. A film having a Young's modulus of less than 300 kg / mm ² is not preferred because the film tends to elongate in the forming step. Further, in the film of the present invention, the birefringence of the film is preferably 0.025 or less, more preferably 0.020 or less. The birefringence of the film is 0.02
If it exceeds 5, the anisotropy of the film becomes large, so that the moldability decreases, which is not preferable. The thickness of the film of the present invention is not particularly limited, but the thickness preferably used as a film for forming and transferring is 5 to 500 μm, more preferably 5 to 300 μm. Next, the production method of the film of the present invention will be specifically described, but is not particularly limited to the following examples as long as the constitutional requirements of the present invention are satisfied. The polyester of the present invention containing an appropriate amount of inorganic particles and the like as a slipping agent, if necessary, is dried using a commonly used dryer such as a hopper dryer, a paddle dryer, or an oven or a vacuum dryer, and then heated to 200 to 320 ° C. And extrude. At the time of extrusion, any existing method such as a T-die method and a tubular method may be employed. After the extrusion, the amorphous sheet is quenched to obtain an amorphous sheet. However, it is preferable to use an electrostatic application method during the quenching because unevenness in the thickness of the amorphous sheet is improved. Next, the obtained amorphous sheet is stretched in the longitudinal and transverse directions so that the area magnification is at least 6 times or more, preferably 8 times or more, more preferably 8 times or more and 16 times or less to obtain a biaxially oriented film. After re-stretching the film in the longitudinal and / or transverse directions according to the above, heat treatment is preferably performed at a temperature in the range of 150 to 220 ° C. to obtain a desired film. In the heat treatment step, it is also a preferable embodiment in the present invention to perform the relaxation of 0.1 to 30% in the transverse direction and / or the longitudinal direction in the zone of the highest temperature of the heat treatment and / or the cooling zone at the outlet of the heat treatment. is there. 5-30 especially in the horizontal direction
It is preferred to perform a% relaxation. In the heat treatment step, a two-step heat treatment may be performed. During or after the stretching step, in order to impart adhesiveness, antistatic property, slipperiness, mold release property, etc. to the film, a coating layer is formed on one or both surfaces of the film, or a corona discharge treatment or the like is performed. It does not matter. [Examples] Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples as long as the gist is not exceeded. In addition, the evaluation method of a film is shown below. (1) Film strength at 100% elongation in an atmosphere of 150 ° C. F ₁₀₀ (kg
/ Mm ² ) A 15 cm thermostat of Intesco 2001 type tensile tester with a thermostat manufactured by Intesco Co., Ltd.
The film was set at 0 ° C., a film having a width of 15 mm was set so that the distance between the chucks was 50 mm, and allowed to stand for 2 minutes. Then, the strength at 100% elongation at a tensile speed of 200 mm / min was measured. The measurement was performed in the vertical and horizontal directions of the film, and the average value was calculated as F ₁₀₀
And In addition, about the film which fracture | ruptures before 100% extension, it converted according to the following formula. (2) Unevenness of film thickness Using a continuous film thickness measuring device manufactured by Anritsu Electric Co. (using electronic micrometer),
The thickness was measured at a length of 5 m along the longitudinal direction of the film, and the thickness unevenness was calculated by the following equation. The refractive index of the film was measured using an Abbe refractometer manufactured by Atago Co., and using a sodium lamp as a light source. Δn = _n γ -n β Note that represents the maximum refractive index, the refractive index and the thickness direction of the refractive index in the direction perpendicular to that of the above formula n _gamma, n _beta and n _alpha Each film plane. (4) Heat of fusion of the film (cal / g) Using a differential scanning calorimeter DSC-1B manufactured by PerkinElmer, the temperature was raised at a rate of 16 ° C. /
The area of the peak accompanying the melting of the crystal of the sample measured in min was determined and calculated according to the following equation. A: Heat of fusion per unit area on a chart when indium was measured under the same conditions (cal / cm ² ) S: Area of melting peak of sample (cm ² ) m: Weight of sample (g) (5) Intrinsic viscosity (η) 200 mg sample was mixed with phenol / tetrachloroethane = 50/50 mixed solvent 2
In addition to 0 ml, heat at about 110 ° C for 30 minutes and measure at 30 ° C. (6) Heat shrinkage of film (%) Heat the film in a gard oven at a temperature of 150 ± 2 ° C for 3 minutes without load. After contraction, the heat shrinkage in the vertical and horizontal directions was determined according to the following equation. Where l _o : original length 10 cm l: length after shrinkage (7) Formability as transfer film Using a mold (I) having a length of 10 cm, a width of 10 cm and a maximum depth of 2.0 cm shown in FIG. After preliminarily molding the film inside the mold with vacuum and pressure, the heated resin was injected to perform molding. The formability of the film was evaluated as follows based on the frequency of film breakage during molding. ：: No break in the film. Δ: Occasionally, film breakage occurs at one or two places, which hinders continuous operation. ×: The film is frequently broken and cannot be used. (8) Suitability as a transfer film As shown in FIG. 1, a film (3) has a layer comprising a release layer, a printing layer, and an adhesive layer (
After the formation of 4), the molding transfer was actually performed continuously by the method of the above (6). When the film could be operated continuously without breakage of the film at the time of molding, and there was no pattern distortion or missing print in printing on the molded product, it was evaluated as ○, and when it was not, it was evaluated as ×. (9) Suitability as a film for a molded container After laminating a 16 μm polyester film with a 70 μm unstretched polypropylene film via an adhesive, preheating, and then applying vacuum air using a mold having an opening diameter of 10 cm and a depth of 3 cm. A plastic tray was made by molding. A sample that caused delamination or frequent breakage between the polyester film and the polypropylene film during molding was evaluated as x, and a film that could be molded without any problem was evaluated as ○. Example 1 80 mol% of terephthalic acid unit and 1 of isophthalic acid unit as a dicarboxylic acid component
After pre-crystallizing a copolyester comprising 500 ppm of amorphous silica fine particles having an average particle diameter of 1.4 μm, comprising 6 mol%, 4 mol% of sebacic acid units, and 98 mol% of ethylene glycol units and 2 mol% of diethylene glycol units as diol components. This was dried, extruded at 280 ° C. using an extruder having a T-die, and quenched and solidified to obtain an amorphous sheet. The obtained sheet was stretched 3.0 times at 75 ° C. in the longitudinal direction between a heating roll and a cooling roll, and subsequently stretched at 95 ° C. in the transverse direction.
While stretching 6 times, while relaxing 15% in the horizontal direction and 0.5% in the vertical direction,
Heat treatment was performed at 175 ° C. The average thickness of the obtained film was 38 μm, and the intrinsic viscosity was 0.66. Example 2 80 mol% of terephthalic acid units and 1 of isophthalic acid units as dicarboxylic acid components
7% by mole, 3% by mole of 1,10-decanedicarboxylic acid unit, 98% by mole of ethylene glycol unit and 2% by mole of diethylene glycol unit as a diol component, using a copolymer polyester containing the same particles as in Example 1. Drying and extrusion were performed in the same manner as in Example 1 to obtain an amorphous sheet. The obtained amorphous sheet was formed into a film in exactly the same manner as in Example 1 to obtain a film having an average thickness of 38 μm. The intrinsic viscosity of the obtained film was 0.66. Example 3 84 mol% of terephthalic acid units and 16 adipic acid units as dicarboxylic acid components
mol%, a copolymerized polyester (A) composed of ethylene glycol as a diol component, terephthalic acid as a dicarboxylic acid component, 80 mol% of ethylene glycol as a diol component and 20 mol% of neopentyl glycol. After blending with a copolymerized polyester (B) containing 2000 ppm of 9 μm calcium carbonate particles at a weight ratio of 1: 1 and drying,
It was extruded at 270 ° C. and quenched and solidified to obtain an amorphous sheet. 70 sheets obtained
The film was stretched 2.8 times at 90 ° C., stretched 3.8 times at 90 ° C. in the transverse direction, heat-treated at 180 ° C., and relaxed 10% at 170 ° C. in the transverse direction. The average thickness of the obtained film is 25μ.
m and the intrinsic viscosity was 0.70. Example 4 86 mol% of terephthalic acid units and 14 suberic acid units as dicarboxylic acid components
mol%, and a copolymerized polyester made of ethylene glycol as a diol component and the copolymerized polyester (B) of Example 3 were blended at a weight ratio of 1: 1. Then, drying and film formation were performed in the same manner as in Example 3. Performed to obtain a film having an average thickness of 25 μm. The intrinsic viscosity of the obtained film was 0.72. Comparative Example 1 82 mol% of terephthalic acid units and 1 of isophthalic acid units as dicarboxylic acid components
Drying and film formation in exactly the same manner as in Example 1 except that a copolymer polyester containing 8 mol% and containing ethylene glycol as the diol component and containing the same particles as in Example 1 was used, and the longitudinal stretching temperature was 85 ° C. Was carried out to obtain a film having an average thickness of 38 μm. The intrinsic viscosity of the obtained film was 0.65. Table 1 summarizes the physical properties of the films of Examples 1 to 4 and Comparative Example 1 and various suitability as a film for molding. [Effects of the Invention] The film of the present invention has excellent moldability, heat resistance, and thickness unevenness, and is suitable for molding, especially for molding transfer and as a base film for molding containers. high.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view schematically showing a molding transfer method in which transfer is performed simultaneously with molding. In the figure, 1 denotes a mold, 2 denotes an injection machine, 3 denotes a base film, and 4 denotes a layer including a printing layer.

Claims (1)

All Claims (1) consists of copolyester containing 1 to 20 mol% of the total acid component aliphatic dicarboxylic acid component, an atmosphere of 0.99 ° C., 100% elongation at the film strength F ₁₀₀ is 0. A biaxially stretched polyester film for molding, which has a thickness of 5 to 3 kg / mm ² and a thickness unevenness of the film of 40% or less.