JP2611415B2 - Biaxially oriented polyester film for molding, film for molding transfer, and film for molding container - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film for molding, excellent in moldability, flatness and heat resistance, a film for transfer, and a film for molded containers.

[Problems to be solved by conventional technology and invention]

Hitherto, biaxially stretched polyester films have excellent strength and heat resistance and have been widely applied to various industrial uses. For example, vacuum, compressed air, overhang, cold, injection, in-mold,
Considering the use of polyester film as a raw material or auxiliary material for embossing, etc., and considering the application of the processed polyester film to molding transfer, molding containers, electrification, packaging, decoration, etc. Have been.

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. In particular, improvement of moldability has been demanded as a base film for molding transfer and molding containers.

[Means for solving the problem] In view of the above problems, the present inventor has conducted intensive studies and found that a biaxially stretched polyester film having a specific value of film strength under high-temperature stretching conditions has excellent moldability. As a result, the present invention has been completed.

That is, the gist of the present invention is to provide a biaxially stretched polyester film for molding, a film for molding transfer, and a film, wherein the film strength F ₁₀₀ at 100% elongation under an atmosphere at 150 ° C. is 0.5 to 7 kg / mm ^2. Exists in container film.

 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, etc. And one or more dicarboxylic acids of the formula (I), and as a diol component, ethylene glycol, propylene glycol, trimethylene glycol, tetramethyl glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, 1,4-cyclohexane It is a polyester comprising one or more known diol components such as dimethanol and neopetyl glycol.

In the polyester of the present invention, as a copolymerization component, for example, oxycarboxylic acid such as p-oxybenzoic acid, benzoic acid, benzoylbenzoic acid, monofunctional compound such as methoxypolyalkylene glycol, glycerin, pentaerythritol, trimethylenepropane Polyfunctional compounds such as can be used as long as the product can retain a substantially linear polymer.

In the polyester of the present invention, the proportion of polyethylene terephthalate is preferably at least 50 mol%, more preferably at least 70 mol%. If the polyethylene terephthalate content is less than 50 mol%, the strength and heat resistance of the film are undesirably reduced.

In the polyester of the present invention, adipic acid, sebacic acid, and an aliphatic dicarboxylic acid component such as 1,10-decanedicarboxylic acid are contained as one of the copolymer components, so that 100 % Elongation strength can be reduced, which is preferable. The content of the aliphatic dicarboxylic acid component in the polyester of the present invention is preferably 1 to 25 mol%, more preferably 1 to 20 mol%.
% Range. If the content exceeds 25 mol%, the strength is sufficiently reduced, but the heat resistance is undesirably reduced.

Further, 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, and, if necessary, a stabilizer, a coloring agent, an antioxidant, an antifoaming agent, and an antistatic agent. And the like. 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
The range is 0.005 to 0.9% by weight, and the average particle size is 0.001 to
Preferably it is in the range of 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, it is not preferable because sufficient strength and moldability cannot be obtained.

In the film of the present invention, it is necessary at 100% elongation of the film strength F ₁₀₀ under an atmosphere of 0.99 ° C. is in the range of 0.5~7kg / mm ^2. F _{100 in the} present invention is ₁₀₀ at 150 ° C.
It is the average value of the strength in the vertical and horizontal directions of the film at the time of% elongation. F ₁₀₀ value is preferably in the range 0.5 to 5 kg / mm ^2, more preferably of 0.5~3kg / mm ^2.

According to our study results, the intensity F ₁₀₀ value is deeply related to the formability of the film, the film F ₁₀₀ Kos to 7 kg / mm ^2, the moldability decreases, unfavorably. Also, F ₁₀₀
When the film is less than 0.5 kg / mm ^2, the film is deformed non-uniformly at the time of molding. For example, in the case of a transfer film, the transferred pattern is undesirably deformed. Also vertical and horizontal 15
The difference in film strength at 0 ° C. and 100% elongation is usually 3 kg / mm ² or less, preferably 2 kg / mm ² or less. The difference is 3
If it exceeds kg / mm ² , the anisotropy increases and the formability deteriorates.

The reason why this way have a moldability is good correlation with F ₁₀₀ is unknown, we result of observation of the film behavior in vacuum forming as an example, be inferred as follows this behavior.
In other words, vacuum forming of polyester film is usually 10
After heating at a temperature of 0 to 200 ° C, average opening diameter: depth = 10: 1 to 1:
Although the film is formed by the mold 1, it is considered that the film is locally forced to stretch by 100% or more near the corner of the mold. Wherein in the F ₁₀₀ is high the film, in such a locally extended portion, partially very high stress is generated, easily lead to rupture of the film by the stress concentration, it is considered that the moldability decreases. On the other hand, F ₁₀₀ is 0.
In the film having a very low value of less than 5 kg / mm ^2,
Although the moldability is good, it may be that only a very weak tension is generated in the uniformly stretched portion such as the plane portion of the mold, and as a result, the film may not be stretched uniformly in the portion. Conceivable.

The film of the present invention requires that F ₁₀₀ be within the above range, but the degree of plane orientation ΔP of the film of the present invention is 0.1.
It is preferably in the range of 040 to 0.140, and more preferably in the range of 0.050 to 0.120. A film having a degree of plane orientation ΔP of more than 0.140 is not preferable because the moldability is insufficient. 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.

Further, the average refractive index of the film of the present invention is preferably
It is in the range of 1.580 to 1.598. Is more than 1.598, the crystallinity of the film is undesirably high.
On the other hand, when the film has a molecular weight of less than 1.580, on the contrary, the crystallization of the film is not sufficient, and the heat resistance is poor, which is not preferable.

In the present invention, the heat of dissolution 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 dissolution of more than 8 cal / g are not preferred because moldability decreases. On the other hand, films with a heat of dissolution of less than 1 cal / g
Since crystallization is extremely difficult in the raw material drying step during film formation, complicated steps such as vacuum drying are required, which is not preferable.

Regarding the shrinkage properties of the film of the present invention,
The shrinkage in the longitudinal and transverse directions after the minute treatment is preferably 10% or less, more preferably 5% or less.

A film having a shrinkage ratio 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, in the use of a transfer film, 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 longitudinal and transverse directions of the film is preferably 300 kg / mm
^{It is 2} or more, more preferably 350 kg / mm 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.

Furthermore, in the film of the present invention, the birefringence of the film is preferably 0.025 or less, more preferably 0.020 or less. If the birefringence of the film exceeds 0.025, the anisotropy of the film becomes large, and the moldability decreases, which is not preferable.

Although the thickness of the film of the present invention is not particularly limited, the thickness preferably used as a film for molding transfer is 5 to 5.
It is 200 μm, more preferably 5 to 150 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 or vacuum dryer such as a hopper dryer, a paddle dryer, and an oven, 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 9 times or more to obtain a biaxially oriented film, and if necessary, the film is stretched vertically and / or After re-stretching in the transverse direction, 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, the transverse direction and / or the temperature at the highest temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet.
Alternatively, performing a relaxation of 0.1 to 30% in the longitudinal direction is also a preferred embodiment in the present invention. 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, etc. to the film, a coating layer may be formed on one or both sides of the film, or a corona discharge treatment may be performed. Absent.

As described above, according to the present invention, it is possible to obtain a polyester film which is excellent in moldability, flatness and heat resistance, and has very few coarse substances, and is extremely suitable as a film for molding, molding transfer and molding container. .

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples.
The present invention is not limited to these examples unless it exceeds the gist.

 In addition, the evaluation method of a film is shown below.

(1) Film strength at 100% elongation in a 150 ° C atmosphere F ₁₀₀ (kg / mm ² ) Intesco 20 tensile testing machine with a thermostatic chamber manufactured by Intesco Corporation
A 01-type thermostat was set at 150 ° C., a film having a width of 15 mm was set so that the distance between the chucks was 50 mm, and the film was allowed to stand for 2 minutes. Then, the strength at 100% elongation at a tensile speed of 200 mm / min was measured. Measurements performed on longitudinal and transverse directions of the film, and the average value was defined as the F _100. In addition, about the film which fracture | ruptures before 100% elongation, it converted according to the following formula.

(2) Average refractive index (), plane orientation (Δ
P), birefringence (Δn) 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.

(3) Heat of dissolution of film (cal / g) Using a differential scanning calorimeter DSC-1B manufactured by PerkinElmer, the peak area accompanying the melting of the crystal of the sample measured at a heating rate of 16 ° C./min was determined. It was calculated according to the following equation.

A: Heat of fusion per unit area on the chart when measuring indium under the same conditions (cal / cm ² ) S: Area of the melting peak of the sample (cm ² ) m: Weight of the sample (g) (4) Intrinsic viscosity (η) 200mg sample is phenol / tetrachloroethane = 50/50
After heating for 30 minutes at about 110 ° C, add
(5) Heat shrinkage rate of film (%) During film guard open at a temperature of 150 ± 2 ° C, the film is heat shrunk for 3 minutes with no load, and the heat shrinkage rate in the vertical and horizontal directions is calculated by the following formula. And asked for it.

Here, l ₀ : original length 10 cm l: length after shrinkage (6) Formability as transfer film Using a mold (1) shown in Fig. 1 having a length of 10 cm, a width of 10 cm, and a maximum depth of 1.5 cm, Was preformed in a mold under vacuum and pressure, and then 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.

(7) Suitability as transfer film As shown in FIG. 1, after forming a layer (4) composed of a release layer, a printing layer and an adhesive layer on the film (3), it is actually formed by the method of (6) above. Transfer was performed continuously. 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 ×.

(8) Suitability as Film for Molding Container A 16 μm polyester film was laminated with a 70 μm unstretched polypropylene film via an adhesive, and then heated and vacuum molded to prepare a plastic tray.
When the laminated film was insufficiently molded at the time of molding, it was evaluated as x, and when it could be molded sufficiently until it came into close contact with the mold, it was evaluated as ○.

Example 1 80 mol% of terephthalic acid units as a dicarboxylic acid component,
100 ppm of amorphous silica particles having an average particle size of 1.0 μm, comprising 15 mol% of phthalic acid units and 5 mol% of sebacic acid units and ethylene glycol units as a diol component.
Pre-crystallize the copolyester containing
The mixture was extruded from an extruder having a T-die at ℃ and quenched and solidified to obtain an amorphous sheet having an intrinsic viscosity of 0.66. After stretching the obtained sheet 3.3 times in the longitudinal direction at 85 ° C., then in the transverse direction at 100 ° C.
The film was stretched 3.5 times, and heat-treated at 185 ° C. while performing 10% relaxation in the width direction and 0.5% relaxation in the longitudinal direction. The average thickness of the obtained film was 50 μm.

Example 2 A copolyester comprising 94 mol% of terephthalic acid and 6 mol% of adipic acid units as a dicarboxylic acid component, 70 mol% of ethylene glycol units and 30 mol% of 1,4-cyclohexane dimethanol units as a diol component, and an average particle diameter of 1.1 Polyethylene terephthalate containing 2000 ppm of kaolin (μm) was mixed at a ratio of 70/30 (wt%), and then dried, extruded and formed into a film exactly as in Example 1 to obtain a film having an average thickness of 38 μm. The ultimate grain size of the film was 0.70.

Comparative Example 1 Implemented using a copolymerized polyester containing 97 ppm of terephthalic acid units and 3 mol% of isophthalic acid units as dicarboxylic acid components and 100 ppm of amorphous silica particles having an average particle size of 1.0 μm and consisting of ethylene glycol as a diol component. Drying and extrusion were carried out in the same manner as in Example 1 to obtain an amorphous sheet having an intrinsic viscosity of 0.62. The obtained amorphous sheet was stretched and heat-treated at 200 ° C. under tension and fixing in the same manner as in Example 1 to obtain a film having an average thickness of about 50 μm.

Table 1 summarizes the physical properties of the films of Examples 1 and 2 and Comparative Example 1 and the suitability for moldability as a transfer film. Film of Comparative Example 1 as a transfer film poor in large moldability F _100, was inadequate.

Examples 3 and 4 and Comparative Example 2 Extrusion and extrusion were performed in exactly the same manner as in Examples 1 and 2 and Comparative Example 1 except that the longitudinal stretching ratio was 3.5 times in Examples 1 and 2 and Comparative Example 1.
Films were formed to form films having an average thickness of 16 μm, which were used as Examples 3 and 4 and Comparative Example 2, respectively.

Table 2 summarizes the physical properties of the films obtained in Examples 3 and 4 and Comparative Example 2 and their suitability as films for molded containers. Film of Comparative Example 2 has a large F _100, inferior vacuum moldability was unsuitable as molded container film.

[Effect of the Invention] The film of the present invention has excellent moldability, flatness and heat resistance, is suitable as a base film for molding, molding transfer and molding containers, and has high industrial value.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of 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 (3)

(57) [Claims] 1. A biaxially stretched polyester film for molding, wherein the film strength F ₁₀₀ at 100% elongation in an atmosphere at 150 ° C. is 0.5 to 7 kg / mm ² . 2. A film for forming and transferring, wherein a film strength F ₁₀₀ at 100% elongation in an atmosphere at 150 ° C. is 0.5 to 7 kg / mm ² . 3. A film for a molded container, wherein the film strength F ₁₀₀ at 100% elongation in an atmosphere at 150 ° C. is 0.5 to 7 kg / mm ² .