JP2692284B2 - Biaxially oriented polyester film for molding - Google Patents

Description

The present invention relates to a biaxially stretched polyester film for molding which has excellent moldability, heat resistance and thickness unevenness.

[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.

However, when the moldability is improved, the unevenness of the film thickness is greatly deteriorated, and various problems occur during processing. For example, if the film for molding transfer has uneven thickness, the elongation of the film becomes non-uniform during molding transfer, resulting in disorder of the transferred pattern. In addition, if the film for a molding container has uneven thickness, the moldability becomes non-uniform, so that there is a tendency that the film is broken or a partial delamination occurs during the laminating process.

Therefore, there has been a demand for a polyester film having excellent moldability and film thickness variation.

[Means for solving the problem]

In view of the above problems, the inventors of the present invention have made extensive studies, and are a film containing a specific amount of a specific acid component in polyester, and a film having specific physical properties is a moldability,
They have found that they are extremely excellent in thickness unevenness, and have completed the present invention.

That is, the gist of the present invention consists of a copolymerized polyester containing 1 to 20 mol% of an aliphatic dicarboxylic acid component with respect to the total acid component, under an atmosphere of 150 ° C., a film strength F ₁₀₀ at 100% elongation of 0.5 to 5 kg / The biaxially stretched polyester film for molding is characterized in that it has a thickness of mm ² and a thickness variation of the film is 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, etc., consisting of one or more known dicarboxylic acids, and as the diol component, ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, It is a polyester comprising one or more known diol components such as 1,4-cyclohexanedimethanol and neopentyl glycol.

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 polyethylene terephthalate content 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 aliphatic dicarboxylic acid component in all acid components is 1 to 20mo
It is in the range of 1%, preferably in the range of 1 to 10 mol%. By satisfying such requirements, the moldability of the film, the improvement of heat resistance and the improvement of thickness unevenness can be achieved at the same time, by adding an aliphatic dicarboxylic acid component, the flexibility and crystallinity of the molecular chain of the polyester It is presumed that this is because the above properties can be achieved at the same time.

In the polyester constituting the film of the present invention, the content of fatty acid dicarboxylic acid component in the total acid component is 20 mol%
If the film exceeds the range, the heat resistance is rather lowered and the unevenness in thickness is rather deteriorated, which is not preferable. In addition, the content is 1 mol%
Films of less than 1 are not preferable because the above properties are not improved.

As the aliphatic dicarboxylic acid component to be contained in the polyester constituting the film of the present invention, the 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 is preferable because it can be improved.

Further, in order to improve the slipperiness of the film, it is also preferable to contain fine particles such as an organic lubricant and an inorganic lubricant, and if necessary, a stabilizer, a colorant, an antioxidant, an antifoaming agent, an antistatic agent. It may contain additives such as agents. 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 fine particles contained in the film is usually 0.
002 to 0.9% by weight, the average particle size is 0.001 to 3.5
It is preferably in the range of 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. When 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, the film strength F ₁₀₀ at 100% elongation in an atmosphere of 150 ° C. needs to be in the range of 0.5 to 5 kg / 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. The F ₁₀₀ value is preferably in the range 0.5 to 3 kg / mm ² .

According to the results of our study, the strength F ₁₀₀ value is closely related to the formability of the film, and a film having an F ₁₀₀ of more than 5 kg / mm ² is not preferable because the formability is lowered. 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, and more preferably 1 kg.
/ mm ² or less. If the difference exceeds 3 kg / mm ² , the anisotropy becomes large and the formability deteriorates.

In the film of the present invention, the thickness unevenness of the film is 40%
It is below, preferably below 30%. If the thickness unevenness of the film exceeds 40%, the moldability and the elongation of the film during molding become non-uniform, and distortion of the pattern occurs during transfer of molding, or breakage or delamination occurs when used as a molding container. It is not preferable in terms of processability.

The film of the present invention is required to have F ₁₀₀ and thickness unevenness within the above range, and further, the plane orientation degree Δ of the film of the present invention is
P is preferably in the range of 0.040 to 0.140, more preferably 0.050 to 0.120. The degree of plane orientation ΔP is 0.
Films exceeding 140 are not preferable because the moldability is insufficient. In the case of a film having a degree of plane orientation ΔP of less than 0.040,
It is not preferable because the strength of the film is lowered 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 1.560 to 1.598. Is more than 1.598, the crystallinity of the film is undesirably high.
On the other hand, in the case of a film having a ratio of less than 1.560, on the contrary, the crystallization of the film is insufficient and the heat resistance is poor, which is not preferable.

In the present invention, the density of the film is preferably 1.345.
The range is from 1.390 to 1.390, more preferably from 1.355 to 1.380.
If the density of the film is less than 1.345, the heat resistance is poor and it is not sufficient. On the other hand, if the density of the film exceeds 1.390, the moldability is 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 moldability decreases. On the other hand, in the case of a film having a heat of fusion of less than 1 cal / g, especially when recycling the ears and the like, crystallization is extremely difficult in the raw material drying step during film formation, and thus a complicated step such as vacuum drying is required, It is not preferable, and unevenness in the thickness of the film is deteriorated, 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, it is preferable that the shrinkage in the lateral direction under the above conditions is 0% or less (when the film expands, the shrinkage is negative). 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.

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. 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 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 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 machine direction and the transverse direction at least at an area ratio of 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. According to the above, the film is re-stretched in the machine direction and / or the transverse direction, and then heat-treated at a temperature preferably 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 particular, it is preferable to perform 5 to 30% relaxation in the horizontal direction. 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, releasability, etc. to the film, a coating layer is formed on one side or both sides of the film, corona discharge treatment or the like is performed. It doesn't matter.

〔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 atmosphere of 150 ° C F ₁₀₀ (kg / mm ² ) Intesco 20
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) Thickness unevenness of the film was measured with a continuous film thickness measuring instrument (using an electronic micrometer) manufactured by Anritsu Electric Co., Ltd. at a length of 5 m along the longitudinal direction of the film, and the thickness unevenness was produced by the following formula. .

(3) Average refractive index of film (), degree of 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.

(4) Heat of fusion of film (cal / g) The differential scanning calorimeter DSC-B manufactured by Perkin Elmer Co., Ltd. was used to determine the area of the peak associated with the melting of the crystals of the sample measured at a heating rate of 16 ° C./min. It was calculated according to the following formula.

A: Heat of fusion per unit area (cal / cm ² ) on the chart when indium was measured under the same conditions S: Area of melting peak of sample (cm ² ) m: Weight of sample (g) (5) Intrinsic viscosity (η) 200 mg sample is phenol / tetrachloroethane = 50/50
After heating for 30 minutes at about 110 ° C, add
Was measured.

(6) Heat shrinkage rate of film (%) The film is heat-shrinked for 3 minutes in a Gard oven at a temperature of 150 ± 2 ° C. in an unloaded state, and the heat shrinkage rate in the longitudinal and transverse directions is calculated according to the following formula. It was

However, l _o : Original length 10 cm l: Length after shrinkage (7) Formability as a transfer film Using a mold (1) with a length of 10 cm, a width of 10 cm, and a maximum depth of 2.0 cm shown in Fig. 1, a film is formed. Was pre-molded in a mold with vacuum and air, and then heated resin was injected to mold. The formability of the film was evaluated as follows based on the frequency of film breakage during molding.

：: No break in the film.

Δ: Film breakage sometimes occurs at one or two places, which causes trouble during continuous operation.

×: The film is frequently broken and cannot be used.

(8) Suitability as a transfer film As shown in FIG. 1, after forming a layer (4) consisting of a release layer, a printing layer and an adhesive layer on the film (3), it is actually molded 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 ×.

(9) Suitability as a film for molding container After laminating a 16 μm polyester film and a 70 μm unstretched polypropylene film via an adhesive, preheating, and then vacuum pressure using a mold with an opening diameter of 10 cm and a depth of 3 cm. A plastic tray was created by molding. When the delamination occurred between the polyester film and the polypropylene film at the time of molding, or where breakage occurred frequently, x was given, and those that could be molded without any particular problems were given as o.

Example 1 80 mol% of terephthalic acid units as a dicarboxylic acid component,
Consists of 16 mol% of isophthalic acid unit and 4 mol% of sebacic acid unit. As diol component, ethylene glycol unit 98
After pre-crystallizing a copolyester containing 500 ppm of amorphous silica fine particles having an average particle size of 1.4 μm and consisting of mol% and 2 mol% of diethylene glycol unit, this is main dried and extruded at 280 ° C. using an extruder having a T die, It was rapidly cooled and solidified to obtain an amorphous sheet. The obtained sheet was stretched 3.0 times at 75 ° C in the longitudinal direction between the heating roll and the cooling roll, and then stretched 3.6 times at 95 ° C in the transverse direction, with 15% relaxation in the transverse direction and in the longitudinal direction. Heat treatment was performed at 175 ° C. while performing relaxation of 0.5%. The obtained film had an average thickness of 38 μm and an intrinsic viscosity of 0.66.

Example 2 80 mol% of terephthalic acid unit as a dicarboxylic acid component,
Consists of 17 mol% of isophthalic acid unit and 3 mol% of 1,10-decanedicarboxylic acid unit. 98 mol% of ethylene glycol unit and 2 mol of diethylene glycol unit as diol components.
%, And using the copolyester 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 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 unit as a dicarboxylic acid component,
Copolyester (A) consisting of 16 mol% of adipic acid unit and ethylene glycol as diol component
And a copolyester (B) containing 200 ppm of calcium carbonate particles having an average particle size of 0.9 μm, which comprises terephthalic acid as a dicarboxylic acid component, 80 mol% of ethylene glycol and 20 mol% of neopentyl glycol as a diol component, and 1: After blending in a weight ratio of 1, the mixture was dried, extruded at 270 ° C., and rapidly solidified to obtain an amorphous sheet. The resulting sheet was stretched 2.8 times at 70 ° C and then 90 ° C in the transverse direction.
Was stretched 3.8 times at 180 ° C., heat treated at 180 ° C., and then relaxed at 170 ° C. in the transverse direction by 10%. The average thickness of the obtained film is 25μ
m and the intrinsic viscosity was 0.70.

Example 4 86 mol% of terephthalic acid unit as a dicarboxylic acid component,
After blending the copolymerized polyester consisting of suberic acid units of 14 mol% and ethylene glycol as a diol component with the copolymerized polyester (B) of Example 3 in a weight ratio of 1: 1, the mixture was dried in exactly the same manner as in Example 3, Film formation,
A film having an average thickness of 25 μm was obtained. The intrinsic viscosity of the obtained film was 0.72.

Comparative Example 1 82 mol% terephthalic acid unit as a dicarboxylic acid component,
A copolymerized polyester containing 18 mol% of isophthalic acid units and ethylene glycol as a diol component and containing the same particles as in Example 1 was used, and the longitudinal stretching temperature was 85.
Drying and film formation were carried out in the same manner as in Example 1 except that the temperature was changed to 0 ° C. to obtain a film having an average thickness of 38 μm.

 The intrinsic viscosity of the obtained film was 0.65.

Table 1 collectively shows the physical properties of the films of Examples 1 to 4 and Comparative Example 1 and various suitability as a molding film.

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

[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 (1)

(57) [Claims] 1. A copolymerized polyester containing an aliphatic dicarboxylic acid component in an amount of 1 to 20 mol% with respect to the total acid component.
Film strength at 100% elongation F ₁₀₀ is 0.5-
A biaxially oriented polyester film for molding, which has a thickness variation of 5 kg / mm ² and a thickness unevenness of the film of 40% or less.