JPH0367629A - Biaxially oriented polyester film for molding - Google Patents

Abstract

PURPOSE:To improve moldability, heat resistance and unevenness of film thickness, by a method wherein the title film is comprised of copolymer polyester containing aliphatic dicarboxylic acid in a specific ratio on the basis of the whole acid ingredient and strength and uneven thickness of the film at the time of extension are limited. CONSTITUTION:Content of an aliphatic dicarboxylic acid in the whole acid ingredient of copolymer polyester is made so as to fall within a range of 1-20 mol%, preferably a range of 1-10 mol%. Film strength F100 at the time of extension of 100% under atmosphere at 150 deg.C is made so as to fall within a range of 0.5-5 kg/mm<2> in a film. The F100 is a mean value of strength of a longitudinal and lateral directions at the time of extension of 100% at the 150 deg.C. It is preferably a range of 0.5-3 kg/mm<2>. Unevenness of film thickness should be 40% or less, preferably 30% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a biaxially oriented polyester film for molding which has excellent moldability, heat resistance and uneven thickness.

[Prior Art and Problems to be Solved by the Invention] Conventionally, biaxially oriented polyester films have excellent strength and heat resistance, and have been widely applied to various industrial applications. for example,
The use of polyester film as a raw material or auxiliary material for vacuum, compressed air, stretching, cold processing, injection, in-mold, embossing, etc. is being considered, and the applications of the processed polyester film include molding transfer, molding containers, Applications for electrical outages, packaging, decoration, etc. are being considered.

However, biaxially oriented polyester films have poor moldability compared to vinyl chloride resins, so it has been difficult to use them in these applications. In particular, improvements in moldability have been sought as base films for mold transfer and molded containers.

However, when the moldability is improved, the thickness unevenness of the film is greatly worsened, causing various problems during processing. For example, if the molding transfer film has uneven thickness, the film will stretch unevenly during molding transfer, resulting in irregularities in the transferred design. Furthermore, if the film for a molded container has uneven thickness, the moldability will be non-uniform, and there is a tendency for the film to break or for partial delamination to occur during lamination processing.

Therefore, there has been a demand for a polyester film for molding that is excellent in both moldability and film thickness unevenness.

[Means to solve the problem]

In view of the above-mentioned problems, the present inventors have conducted extensive studies and found that a film containing a specific amount of a specific acid component in polyester and having specific physical properties has excellent moldability and thickness unevenness. They discovered this and completed the present invention.

That is, the gist of the present invention is that the film is made of a copolyester containing an aliphatic dicarboxylic acid component in an amount of 1 to 20 mol% based on the total acid component, and has a film strength F1° when stretched 100% in an atmosphere of 150°C. of 0.5 to 5 kg/mm'', and the film has a thickness unevenness of 40% or less.

The present invention will be explained in detail below.

The polyester used in the present invention contains terephthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid,
Consists of one or more known dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl ether dicarboxylic acid, aliphatic dicarboxylic acid, etc. Also, as a diol component, ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, hexane It is a polyester consisting of one or more known diol components such as methylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, 1,4-cyclohexanedimethanol, and neopentyl glycol.

In the polyester of the present invention, copolymerization components include, for example, oxycarboxylic acids such as p-oxybenzoic acid, benzoic acid, benzoylbenzoic acid, monofunctional compounds such as methoxypolyalkylene glycol, and polyfunctional compounds such as glycerin and pentaerythritol. Functional compounds can also be used to the extent that the product retains a substantially linear polymer.

In the polyester constituting the film of the present invention, the proportion of polyethylene terephthalate is preferably 50 mol% or more, more preferably 70 mol% or more. If the polyethylene terephthalate content is less than 50 mol%, the strength and heat resistance of the film will decrease, which is not preferable.

In the polyester constituting the film of the present invention, the aliphatic dicarboxylic acid component content in the total M component is 1 to 20+
It is in the range of soJ%, preferably in the range of 1 to 10 mol%. The reason why it is possible to simultaneously improve the formability and heat resistance of the film and reduce thickness unevenness by meeting these requirements is that by adding an aliphatic dicarboxylic acid component, the molecular chains of polyester have flexibility and crystallinity. It is presumed that this is because it became possible to simultaneously impart the above characteristics, thereby achieving the above characteristics.

In the polyester constituting the film of the present invention, the content of aliphatic dicarboxylic acid components in the total acid components is 2011I
A film with an o content of more than 1% is not preferable because it actually shows a decrease in heat resistance and worsens thickness unevenness. Further, in a film in which the content is less than 1 moj 2%, no improvement in the above characteristics is observed, which is not preferable.

The aliphatic dicarboxylic acid component to be contained in the polyester used in the film of the present invention is an aliphatic dicarboxylic acid component having 4 to 12 carbon atoms, preferably 6 to 12 carbon atoms.
It is preferable because the moldability, heat resistance, and thickness unevenness can be improved.

Furthermore, in order to improve the slipperiness of the film, it is also preferable to contain fine particles such as an organic lubricant or an inorganic lubricant.
If necessary, additives such as stabilizers, colorants, antioxidants, antifoaming agents, and antistatic agents may be contained. Fine particles that impart slipperiness include kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate,
Known inert external particles such as aluminum oxide, titanium oxide, calcium phosphate, lithium fluoride, carbon black, high melting point organic compounds that are insoluble during melt film formation of polyester resin, metal compound catalysts used during crosslinked polymer and polyester synthesis, e.g. alkali metal compounds,
Examples include internal particles formed inside the polymer during polyester production due to alkaline earth metal compounds and the like.

The content of fine particles contained in the film is usually 0.00
The range is from 2 to 0.9% by weight, and the average particle size is 0.00
It is preferably in the range of 1 to 3.5 μm.

The intrinsic viscosity of the polyester of the present invention in the film is preferably 0.50 or more, more preferably 0.60 or more. If the intrinsic viscosity of the film is less than 0.50,
This is not preferred because sufficient strength and moldability cannot be obtained.

In the film of the present invention, film strength Fl at 100% elongation in a 150°C atmosphere. . is 0.5~5
It needs to be in the range of kg/mm2. F in the present invention
l (10 is the average value of the longitudinal and transverse strength of the film at 100% elongation at 150°C. Fl. The value preferably ranges from 0.5 to 3 kg/nun2.

According to our study results, the strength FIG. The value is closely related to the formability of the film, and Fl. . is 5 kg/mm
A film with a flow of more than 0.5 kg/mn+2 is undesirable because it reduces moldability.Furthermore, a film with a floo of less than 0.5 kg/mn+2 will deform the molding film unevenly, and for example, in a transfer film, the pattern to be transferred will be distorted. Distortion may occur, which is undesirable.
The difference in film strength at % elongation is usually 3 kg/in" or less, preferably 2 kg/mm2 or less, more preferably 1 kg/mm2 or less. Such a difference is 3 kg/mm2 or less.
If it exceeds 2, the anisotropy will increase and the moldability will deteriorate.

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 elongation of the film during molding will become uneven, resulting in distortion of the design during molding transfer, and rupture or delamination when used for molded containers. This is not desirable in terms of processing suitability.

The film of the present invention is F. . It is essential that the film of the present invention has a degree of plane orientation ΔP of 0.040 to 0.140, more preferably 0.050 to 0.140. The range is 0.120. A film with a degree of plane orientation ΔP exceeding 0.140 is undesirable because of insufficient moldability. Further, a film having a plane orientation degree ΔP of less than 0.040 is not preferable because the strength of the film decreases and flatness deteriorates.

Furthermore, the average refractive index of the film of the present invention is preferably 1.
．． It is in the range of 560 to 1.598. A film in which n exceeds 1°598 is undesirable because the crystallinity of the film increases. On the other hand, a film with -n- of less than 1.560 is not preferable because the crystallization of the film is insufficient and the heat resistance is poor.

In the present invention, the density of the film is preferably 1.34
5 to 1.390, more preferably 1.355 to 1.38
It is in the range of 0. If the density of the film is less than 1.345, the heat resistance will be poor and unsatisfactory, while if the density exceeds 1.390, the moldability will be insufficient, which is not preferred.

Further, in the present invention, the heat of fusion of the film is preferably 1
~3caA/g, more preferably 1 to 6ca(1/g
is within the range of A film having a heat of fusion of more than 8 caA/g is undesirable because of poor moldability.

Since crystallization is extremely difficult in the drying process, a complicated process such as vacuum drying is required, which is undesirable, and it also worsens uneven thickness of the film, which is also undesirable.

Regarding the shrinkage properties of the film of the present invention, at 150°C
It is preferable that the shrinkage percentage in both the longitudinal and transverse directions after the minute treatment is 10% or less, more preferably 5% or less.

For a film having a shrinkage rate of more than 10% in the vertical or horizontal direction, it is preferable that the shrinkage rate of the film is 0% or less in the heating section during the processing step (if the film expands, the shrinkage rate is negative).

A film having a shrinkage rate in the transverse direction of more than 0% is undesirable because, when used for mold transfer, the film shrinks in the drying process after forming the printed layer.

Regarding the mechanical strength of the film of the present invention, the Young's modulus of the film in the longitudinal and transverse directions is preferably 300 k
g/mm" or more, more preferably 350 kg/mm" or more. A film having a Young's modulus of less than 300 kg/mm'' is undesirable because it tends to elongate during the molding process.

Furthermore, in the film of the present invention, the birefringence of the film is preferably 0.025 or less, more preferably 0.02.
It is less than or equal to 0. If the birefringence index of the film exceeds 0.025, the anisotropy of the film will increase, resulting in a decrease in moldability, which is undesirable.

The thickness of the film of the present invention is not particularly limited, but the thickness preferably used as a film for molding transfer is 5 to 5.
00 μm, more preferably 5 to 300 μm.

Next, the method for manufacturing the film of the present invention will be specifically explained.
As long as the constituent requirements of the present invention are satisfied, the invention is not particularly limited to the following examples.

The polyester of the present invention containing an appropriate amount of inorganic particles as a slip agent, if necessary, is dried using a commonly used dryer such as a hopper dryer, a paddle dryer, an open dryer, or a vacuum dryer, and then dried at 200 to 320°C. Extrude with For extrusion, T-die method, tubular method, etc.
Any existing method may be used.

After extrusion, an amorphous sheet is obtained by quenching. It is preferable to use an electrostatic application method during the quenching, since this improves the thickness unevenness of the amorphous sheet.

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, and more preferably 8 times or more and 16 times or less, to obtain a biaxially oriented film, and as necessary. After re-stretching the film in the longitudinal and/or transverse directions depending on the
A desired film is obtained by heat treatment at a temperature in the range of 0°C.

In the heat treatment step, it is also a preferred embodiment of the present invention to perform relaxation of 0.1 to 30% in the transverse and/or longitudinal directions in the highest temperature zone of the heat treatment and/or the cooling zone at the exit of the heat treatment. It is one of the Particularly in the transverse method, it is preferable to carry out a relaxation of 5 to 30%. Further, in the heat treatment step, two-stage heat treatment may be performed.

During or after the above-mentioned stretching process, a coating layer is applied to one or both sides of the film in order to impart adhesion, antistatic properties, slipperiness, mold release properties, etc. to the film. I don't mind if you do something like that.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples unless it exceeds the spirit thereof.

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

(11 Film strength at 100% elongation in 150°C atmosphere F +oo (kg/ml11”) Intesco tensile tester with constant temperature chamber Intesco 2001 type constant temperature chamber was set at 150℃, and a 15 mm wide film was placed between the chucks. After setting it so that it is 50mm and leaving it for 2 minutes,
The strength at 100% elongation was measured at a tensile speed of 200 mm/min.

Measurements were made in the vertical and horizontal directions of the film, and the average value was Fl. . And so. Note that for films that break before 100% elongation, the conversion was performed according to the following formula.

Strength at 100% elongation (kg/mm") = Strength at break (kg/nun") The film was measured at a length of 5 m along the longitudinal direction using a meter (using a meter), and the thickness unevenness was calculated using the following formula.

xlOO (%) (3) Average refractive index (n) of film, degree of plane orientation (ΔP)
, Birefringence (Δn) The refractive index of the film was measured using an Asobe refractometer manufactured by Atago Co., Ltd. and a sodium lamp as a light source.

n- (n, +n, +nγ) △P=　　　　　(na+n,)-n.

△n=nγ = n.

In addition, in the above formula, n7. n and n represent the maximum refractive index within the film plane, the refractive index in the direction perpendicular to the maximum refractive index, and the refractive index in the thickness direction, respectively.

(4) Heat of fusion of film (caA/g) Temperature increase rate 1 using PerkinElmer differential scanning calorimeter DSC-IB
The area of the peak associated with the melting of the crystal of the sample measured at 6° C./min was determined and calculated according to the following formula.

Heat of fusion of film - A-3 (caj2/g) A: Heat of fusion per unit area on the chart when measuring indium under the same conditions (ca (!/crA)) S: Area of the melting peak of the sample (cut) m: Weight of sample (g) (5) Intrinsic viscosity (η) Sample 200nw is phenol/tetrachloroethane = 5
0150 mixed solvent at about 110°C.
After heating for 0 minutes, measured at 30°C (6) Heat shrinkage rate of film (%) The film was heat-shrinked for 3 minutes with no load in a guarded oven at a temperature of 150 ± 2°C, and The heat shrinkage rate was determined according to the following formula.

i.

However, 10: Original length IQ cm Shiny: Length after shrinkage (7) Formability as a transfer film As shown in Figure 1, length 10 cm, width 1 OCT 11, maximum depth 2
, Oc! ff mold (1), the film was preformed inside the mold in vacuum and pressure, and then heated resin was injected to perform molding. The moldability of the film was evaluated as follows based on the frequency of film breakage during molding.

○: No breakage of the film at all.

Δ: Occasionally, the film was torn in one or two places, which caused problems during continuous operation.

×: Film failure occurs frequently and is unusable.

(8) Suitability as a transfer film After forming a layer (4) consisting of a release layer, a printing layer and an adhesive layer on the film (3) as shown in Figure 1, it is actually molded using the method described in (6) above. Transfer was performed continuously.

It can be operated continuously without film breakage during molding, and
When printing on a molded article, the molded product was evaluated as ○ if there was no distortion of the pattern or missing prints, etc., and otherwise it was evaluated as ×.

(9) Suitability as a film for molded containers After laminating a 16 μm polyester film with a 70 μm unstretched polypropylene film via an adhesive, and preheating, vacuum molding was performed using a mold with an opening diameter of 1Q cm and a depth of 3 cm. A plastic tray was created by pressure molding. 9 Example 1 Terephthalic acid unit 8Q mo as dicarboxylic acid component.
42%, isophthalic acid units: 16 mo/%, sebacic acid units: 4 mo/1%, and as diol components, ethylene glycol units: 98 mo/%, diethylene glycol units: 2 mo! ! %, average particle size 1.4μm
A copolymerized polyester containing 500 ppm of amorphous silica fine particles was pre-crystallized, then main-dried, extruded at 280° C. using an extruder equipped with a T-die, and rapidly solidified to obtain an amorphous sheet. The obtained sheet was stretched 3.0 times in the machine direction at 75°C between a heating roll and a cooling roll, and then stretched 3.6 times in the transverse direction at 95°C to achieve a relaxation of 15% in the transverse direction. Heat treatment was performed at 175° C. while relaxing 0.5% in the longitudinal direction. The average thickness of the obtained film was 38
In μm, the intrinsic viscosity was 0.66.

Example 2 Terephthalic acid unit 80 neo as dicarboxylic acid component
12%, isophthalic acid units 17 mol%, 1°10-
Consisting of 3 no A'% decanedicarboxylic acid units, and 98 mol of ethylene glycol units as diol component.
%, diethylene glycol unit 2mai1%,
Using a 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 subjected to one film in exactly the same manner as in Example 1, and a film having an average thickness of 38 μm was formed for 1 hour. The intrinsic viscosity of the obtained film was 0.66.

Example 3 Terephthalic acid unit 84 mo as dicarboxylic acid component
1%, adipic acid unit 16 mo/%, copolymerized polyester (A) consisting of ethylene glycol as the diol component, dicarboxylic acid component consisting of terephthalic acid, and 80 moI of ethylene glycol as the diol component.
1%, neopentyl glycol 20mof%,
2000pp of calcium carbonate particles with an average particle size of 0.9μm
The mixture was blended with a copolymerized polyester (B) containing m at a weight ratio of 1:1, dried, extruded at 270°C, and rapidly solidified to obtain an amorphous sheet. The obtained sheet was stretched 2.8 times at 70°C, then stretched 3.8 times in the transverse direction at 90°C, heat treated at 180°C, and then relaxed by 10% in the transverse direction at 170°C. The average thickness of the obtained film was 2
5 μm, and the intrinsic viscosity was 0.70.

Example 4 Terephthalic acid units as dicarboxylic acid component 86 mo
1%, 14 moI of supernic acid units! % and ethylene glycol as the diol component. After that, drying and film formation were carried out in exactly the same manner as in Example 3 to obtain a film with 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 as dicarboxylic acid component!
%, isophthalic acid units 18 neo l % YoJ)
Drying and film formation were carried out in exactly the same manner as in Example 1, except that a copolymerized polyester containing particles similar to those in Example 1 and consisting of ethylene glycol as a diol component was used, and the longitudinal stretching temperature was 85°C. A film with an average thickness of 38 μm was obtained.

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 their suitability as molding phase films.

〔Effect of the invention〕

The film of the present invention has excellent moldability, heat resistance, and uneven thickness, and is suitable for molding, particularly as a base film for mold transfer and molded containers, and has high industrial value.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a molding transfer method in which molding and transfer are performed at the same time. In the figure, 1 represents a mold, 2 an injection machine, 3 a base film, and 4 a layer including a printing layer. Applicant Diafoil Co., Ltd.

Claims (1)

[Claims] (1) 1 to 2 aliphatic dicarboxylic acid components to total acid components
Consisting of copolymerized polyester containing 0 mol%, 15
Film strength F_1 at 100% elongation in 0℃ atmosphere
A biaxially stretched polyester film for molding, characterized in that _0_0 is 0.5 to 5 kg/mm^2 and the thickness unevenness of the film is 40% or less.