JPH03159727A - Biaxially oriented polyester film for forming - Google Patents

Abstract

PURPOSE:To obtain the polyester film excellent in formability, heat resistance and thickness unevenness by a method in which a polyester film is the film containing the plasticizer of 0.01-5wt.%, and the strength and the fusion heat of the film are specified. CONSTITUTION:A polyester film is the film containing the plasticizer of 0.01-5wt.% and has the film strength F100 of 0.5-5kg/mm<2> at the elongation of 100% in the atmosphere of 150 deg.C and the fusion heat of 1-8cal/g of said film. In the case of the film whose content of plasticizer exceeds 5%, the bleed out of the plasticizer to the surface of the film becomes remarkable, and the peeling property of the mold releasing layer and the printing layer provided on the surface of the film becomes too high unpreferably. In the case of the film whose content of the plasticizer is less than 0.01wt.%, its formability is not improved. When the fusion heat Hm of the film exceeds 8cal/g, the sufficient accuracy of forming is not obtained, and in the case of the content less than 1cal/g, the thickness uneveness of the film is deteriorated. In the case of the film whose strength F100 exceeding 5kg/mm<2>, its formability is lowered, and in the case of the film whose strength is less than 0.5kg/mm<2>, the film deforms ununiformly in forming, whereby the distortion, etc., of the pattern to be transferred is unpreferably generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a biaxially stretched polyester film for shaping, which is excellent in shapeability, heat resistance, and thickness unevenness.

[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, since biaxially oriented polyester films have inferior shapeability compared to vinyl chloride resins, it has been difficult to apply them to these applications. In particular, there has been a demand for improvement in the formability of the film for use as a base film for copying forms and containers.

In response to the above requirements, the present inventors have proposed a two-wheel stretched polyester film with improved shapeability in various ways.

However, in such films, formability,
It has been difficult to simultaneously satisfy high levels of heat resistance and thickness unevenness.

Particularly in the field of mold transfer, the film is required to have extremely deep drawability in some areas, and at the same time, it is also required to transfer highly accurate patterns. Defects such as uneven thickness of the film, which could cause problems, were not tolerated.

[Means to solve problems]

In view of the above-mentioned problems, the inventors of the present invention have made the polyester that forms the film contain a specific amount of plasticizer as a result of intensive studies.
It was discovered that by imparting specific physical properties, a polyester film having excellent shapeability, heat resistance, and thickness unevenness could be obtained, and the present invention was completed.

That is, the gist of the present invention is that the plasticizer is contained in an amount of 0.01 to 5 wt%.
It is a film containing 100% in an atmosphere of 150℃
Film strength F1 during stretching. . is 0.5~5kg/mm
”, and the heat of fusion of the film is 1 to 8 cal!/
g.

The present invention will be explained in detail below.

The polyester used in the present invention includes dicarboxylic acids such as terephthalic acid, oxalic acid, malonic acid, succinic acid, adivic 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, etc., and diols such as ethylene glycol, brobylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, It is a polyester consisting of one or more kinds of known diols such as diethylene glycol, triethylene glycol, polyalkylene glycol, 1,4-cyclohexanedimethanol, and neopentyl glycol.

In the polyester of the present invention, copolymerization ingredients include, for example, oxycarboxylic acids such as p-oxybenzoic acid, benzoic acid, benzoylbenzoic acid, monofunctional compounds such as methoxypolyalkylene glycol, glycerin, and pentaerythritol. Polyfunctional compounds can also be used to the extent that the material can maintain 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 forming the film of the present invention, the acid component preferably contains 1 to 2 aliphatic dicarboxylic acids.
0moj! %, more preferably 1 to 10 mo 1%, it becomes possible to improve the moldability, heat resistance, and thickness unevenness of the film.

In the polyester constituting the film of the present invention, the content of aliphatic dicarboxylic acid in the total acid component is 20 moJ.
%, it is not preferable because it causes a decrease in heat resistance and worsens thickness unevenness. In addition, this content is Lmol
If it is less than %, no improvement in the above characteristics will be observed, which is not preferable.

The aliphatic dicarboxylic acid component to be contained in the polyester constituting 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 further improved.

In addition, in order to improve the slipperiness of the film, organic lubricants,
It is also preferable to contain fine particles such as an inorganic lubricant, and if necessary, additives such as stabilizers, colorants, antioxidants, antifoaming agents, and antistatic agents may be contained. Fine particles that impart slipperiness include known inert external particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum ξium oxide, titanium oxide, calcium phosphate, lithium fluoride, and carbon black, and polyester resin. During the melt film formation of polyester, internal particles formed inside the polymer during polyester production are removed by insoluble high-melting point organic compounds, crosslinked polymers, and metal compound catalysts used during polyester synthesis, such as alkali metal compounds and alkaline earth metal compounds. Can be mentioned. The content of fine particles contained in the film is usually 0.00
The range is from 2 to 5.0% by weight, and the average particle size is 0.00% by weight.
It is preferably in the range of 1 to 10.0 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 0350,
It is undesirable because sufficient strength and restraint cannot be obtained.

As an important component of the present invention, it is necessary to contain a plasticizer in the film in an amount of 0.01 to 5 wt%, preferably 0.05 to 2 wt%.

Plasticizers used in the present invention include dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, di-n-hexyl phthalate, di-n-heptyl phthalate, di-2-ethylhexyl phthalate, and di-n-hexyl phthalate. Di-n-octyl, di-n-nonyl phthalate, diethyl isophthalate, di-n-butyl isophthalate, di-2-ethylhexyl isophthalate,
Aromatic dicarboxylic acid esters such as diethyl terephthalate, di-n-butyl terephthalate, and di-2-ethylhexyl terephthalate; phosphate esters such as triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, and cresyl phosphate ; dimethyl sebacate, diethyl sebacate,
Sebacic acid esters such as di-n-butyl sebacate, diamyl sebacate, and hexyl adipate; adipic acid esters, butyl phthalyl butyl glycolate, polyethylene glycol, glycols such as tributyl citrate, glycolose, and oleic acid. Examples include fatty acid ester type plasticizers such as tetrahydrofurfuryl and methylacetyl ricileate, but are not limited to these plasticizers.

Among the plasticizers used in the film of the present invention, aromatic dicarboxylic acid ester plasticizers are preferred because they have excellent heat resistance and are less likely to cause sublimate or bleed-out problems during film formation.

In particular, phthalate ester plasticizers are preferred because they have excellent heat resistance and improve the shapeability of the film. In the present invention, the melting point of the plasticizer contained in the film at normal pressure is preferably 300°C or higher, more preferably <3
The temperature is 50°C or higher. A film in which the melting point of the plasticizer is less than 300° C. is undesirable because the heat resistance of the plasticizer is insufficient, resulting in severe thermal deterioration during the film extrusion process and generation of a large amount of sublimate.

Moreover, the solubility parameter of the plasticizer used in the present invention is preferably 6.5 to 1). 0 [(ca1/c m-
3) l/2), more preferably 7. 0 ~
1 0. 0( (cal /cIl-s) l/t
) is within the range. Solubility parameter of plasticizer is 6.5
Less than or 1). If the plasticizer exceeds 0, the polyester of the present invention will not be able to sufficiently swell, and will not be uniformly impregnated into the film, making it impossible to improve the moldability of the film, which is undesirable.

The content of the plasticizer in the film of the present invention is 0.01 to 5 wt%, preferably 0.05 to 5 wt% based on the film weight.
21) In the range of t%. A film with a plasticizer content of more than 5 wt% is not preferred because the plasticizer bleeds out to the surface of the film and the releasability of the release layer, printed layer, etc. provided on the surface of the film becomes too high.

In addition, an ungrooved film with a plasticizer content of 0.01 wt% cannot be expected to improve its shapeability.

In the film of the present invention, the second important structural requirement is that the heat of fusion ΔHIII of the film is 1 to 8 ca 1/
g, preferably in the range of 2 to 6 c
It is in the range of al/g. ΔHI1 of the film is 3caj
! If it exceeds /g, the crystallinity of the film is high and it becomes difficult to effectively impregnate the plasticizer into the polyester, making it impossible to obtain sufficient moldability, which is not preferable.

In addition, when the Δlm of the film is less than lcal/g, orientational crystallization hardly progresses during stretching of the film, and the rise of stress accompanying stretching is low, resulting in poor thickness unevenness of the film, which is also undesirable.

In the film of the present invention, the melting point of the film is preferably 250°C or lower, more preferably 240°C or lower. If the melting point of the film exceeds 250°C, extremely high temperatures must be used when blending the plasticizer into the film, which is undesirable because thermal deterioration of the plasticizer is likely to occur.

Furthermore, the film of the present invention has a temperature of 1 in an atmosphere of 150°C.
Film strength FIOO at 00% stretching is 0.5-5kg
FII as used in the present invention
IQ is the average value of the strength in the longitudinal and transverse directions of the film during IQQ9A stretching at 150°C. FIG. The value is preferably 0. It is in the range of 5 to 3 kg/mm''.

According to our study results, the strength is F1. . The value is deeply related to the formality of the film, and is FIO. A film in which the weight exceeds 5 kg/m is undesirable because of its poor formability.

Also, F.I.O. If the film is less than 0.5 kg/mm", the film will deform unevenly during the formation, and for example, in the case of a transfer film, the pattern to be transferred will be distorted, which is undesirable. The difference in film strength at 100% stretching is usually 3 kg/mm" or less, preferably 2k+r/mm2 or less, more preferably lkg/mm" or less.
mm" or less. If the difference exceeds 3 kg/mm", the anisotropy increases and the shapeability deteriorates.

In the film of the present invention, the elongation at break in the longitudinal and transverse directions in an atmosphere of 150°C is preferably 200% or more, more preferably 300% or more, and by satisfying this property, the deformability of the film can be improved. It can be further improved.

In the film of the present invention, the thickness unevenness of the film is usually 40% or less, preferably 30% or less, particularly preferably 15% or less. If the thickness unevenness exceeds 40%, the formability and elongation of the film during molding will be uneven, resulting in distortion of the design when transferring the prefecture, and may cause breakage or delamination when used for prefecture containers. live, etc.
Unfavorable in terms of processing suitability.

The film of the present invention is F1. . is in the above range, and furthermore, the degree of plane orientation ΔP of the film of the present invention is 0. 0 5 0~0. It is preferably in the range of 140, more preferably in the range of 0.060 to 0.120. Planar orientation degree ΔP is 0. A film with a molecular weight exceeding 140 is not preferable because it has insufficient deformability. Further, the plane orientation degree ΔP is o. A film having a hardness of less than o s o is not preferable because the strength of the film decreases and flatness deteriorates.

Furthermore, the average refractive index T of the film of the present invention is preferably 1
．． 550-1.590, more preferably 1.560-1
．． The range is 580. ? A film with a value exceeding 1.590 is not preferred because the swelling of the film by the plasticizer is insufficient and the shapeability is poor. On the other hand, a film with a T of less than 1.550 is undesirable because the swelling of the film progresses too much 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. 3 5 5~1
．． The range is 380. The density of the film is 1. 34
If the density of the film is less than 5, the heat resistance will be poor and unsatisfactory. On the other hand, if the density of the film exceeds 1.390, the shapeability will be insufficient, which is not preferable.

Regarding the shrinkage properties of the film of the present invention, at 150°C
Shrinkage rate in both vertical and horizontal directions after processing for 10% or less
It is preferably 5% or less, and more preferably 5% or less.

A film having a shrinkage rate of more than 10% in the vertical or horizontal direction is undesirable because the film will shrink significantly in the heating section during the processing process. In particular, when used as a transfer film, it is preferable that the shrinkage rate in the lateral direction under the above conditions is 0% or less (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 molding and transfer, the film will shrink in the printing layer formation or subsequent drying process.

Regarding the mechanical strength of the film of the present invention at room temperature, the Young's modulus of the film in the longitudinal and transverse directions is preferably 300 kg/rn or more, more preferably 350
kg/mm" or more. Young's modulus is 300 kg
A film having a diameter of less than 2 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 0. It is preferably 0.25 or less, more preferably 0.020 or less. The birefringence of the film is 0. 0
If it exceeds 2.5, the anisotropy of the film increases, resulting in poor moldability, 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 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.
The invention is not particularly limited to the following examples as long as it satisfies the structural requirements of the present invention.

After drying the polyester of the present invention containing an appropriate amount of inorganic particles as a plasticizer and, if necessary, a slip agent, using a commonly used dryer such as a hopper dryer, paddle dryer, oven, etc. or a vacuum dryer, ~3
Extrude at 20°C. For extrusion, any existing method such as the T-die method or the tubular method may be used. It is also possible to add a plasticizer during extrusion.

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 to an area magnification of at least 6 times or more, preferably 8 times or more, and more preferably 8 times or more and 25 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
The desired film is obtained by heat treatment at a temperature in the range of .

In the heat treatment process, the highest temperature zone of heat treatment and/or
or in the cooling zone at the heat treatment outlet in the transverse and/or longitudinal direction. Relaxation of 1 to 30% is also one of the preferred embodiments of the present invention. Particularly in the transverse direction, it is preferred to achieve a relaxation of 5 to 30%. Further, in the heat treatment step, two-stage heat treatment may be performed.

During or after the above stretching process, a coating layer is formed on one or both sides of the film, or a corona discharge treatment is applied to the film in order to impart adhesiveness, antistatic properties, slipperiness, mold releasability, etc. to the film. It doesn't matter if you do it.

As described above, according to the present invention, it is possible to obtain a polyester film which is excellent in shapeability and heat resistance and is extremely suitable as a molding film with small thickness unevenness.

[Examples] 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 the scope thereof is exceeded.

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

(1) Film strength at 100% elongation in an atmosphere of 150°C F Ioo (kg/mm”') Intesco tensile tester with constant temperature oven Set the constant temperature oven of Intesco 2001 model to 150°C, and test the film with a width of 15 mm. was set so that the distance between the chucks was 50n+m and left for 2 minutes, and then the strength at 100% elongation was measured at a tensile speed of 200mm/IIIin.Measurements were made in the vertical and horizontal directions of the film, and the average value was FIG. Note that for films that break before 100% stretching, the conversion was performed according to the following formula.

Strength at 100% elongation (kg/mm”) = (2). Film thickness A length of 5 m along the longitudinal direction of the film was measured using a continuous film thickness measuring device (using an electronic micrometer) manufactured by Madarasu Ritsu Electric Co., Ltd. The thickness unevenness was calculated using the following formula.

Thickness irregularity = Film flatness 35JJ thickness (3) Average refractive index (n) of film, degree of plane orientation (ΔP)
, Birefringence (Δn) The refractive index of the film was measured using an A-7be refractometer manufactured by Atago Co., Ltd. and a sodium lamp as a light source.

1 n= (net+n,+nγ)3 1 ΔP= (na+nJ) n. 2 Δn=nγ−nβ In the above formula, na, n5, and n4 each 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.

(4) Heat of fusion ΔHm (caJ/g) of the film, measured by Birkin Elmer's differential scanning calorimeter DSC-IB.
The area of the peak associated with melting of the crystal of the sample measured at a heating rate of 16° C./mtn was determined and calculated according to the following formula.

1 ΔHm=A-S ・(caj2/g) m A: Heat of fusion per unit area on the chart when measuring indium under the same conditions (ca It/cn+”) S: Area of the melting peak of the sample ( C1) m: Weight of sample! (g) (5) Intrinsic viscosity (η) 200 mg of sample was mixed with phenol/tetrachloroethane = 5
In addition to 0/50 mixed solvent 20III1, about 1) Heated at 0°C for 30 minutes and then measured at 30°C. It was heat-shrinked for 3 minutes under no load, and the heat-shrinkage percentages in the vertical and horizontal directions were determined according to the following formula.

However, β. : Original length 10 cm l : Length after shrinkage (7) Shapeability as a transfer film Height 10 cm, * l Ocm, maximum depth 2. Using mold 1 with a step at the bottom of 0cII+, the film was preformed inside the mold in vacuum and compressed air, 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 shaping.

O: 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 breaks frequently and cannot be used.

(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 applied using the method described in (7) above. Molding transfer was performed continuously. It can be operated continuously without breaking the film during molding, and there is almost no distortion of the design when printing complex designs on the products.
The evaluation was rated as ◯ if there was no missing print or the like, and × as otherwise.

Examples 1 to 4 Terephthalic acid unit as dicarboxylic acid component 83mail
%, isophthalic acid units 14 mo1%, sebacic acid units 3
No. 12%, with 98 moj of ethylene glycol units as the diol component. A copolymerized polyester (A) consisting of 2 mol % of diethylene glycol units and 500 ppm of amorphous silica fine particles with an average particle size of 1.4 μm was polymerized according to a conventional method. After drying the obtained copolymerized polyester (A), it was extruded using a two-wheeled extruder. The content of various plasticizers shown in 1 in polyester is 2.0w.
The mixture was kneaded at 250° C. to obtain various masterbatch copolymerized polyesters.

The plasticizer content of the copolymerized polyester (A) and various master bunch copolyesters is shown below. After blending in the proportions shown in 1, the mixture was crystallized and dried, extruded at 270° C. using an extruder equipped with a T-die, and rapidly solidified to obtain an amorphous sheet.

The obtained sheet was stretched 3.5 times in the machine direction at 77°C between a heating roll and a cooling roll, and then stretched at 95°C in the transverse direction.
Stretched 3.6 times at 15% lateral relaxation and 0.35°C. 5
The heat treatment was carried out at 185° C. with a longitudinal relaxation of %.

The average thickness of the obtained film was 50 μm, and the intrinsic viscosity was 0.65.

Comparative Example 1 Using the copolymerized polyester (A) of Example 1, extrusion film formation was carried out in exactly the same manner as in Example 1, and the average thickness was 50 μm.
, a biaxially stretched heat-set film with an intrinsic viscosity of 0.66 was obtained.

The following table summarizes the type and amount of plasticizer, physical properties of the film, and suitability as a prescriptive film for Examples 1 to 4 and Comparative Example. Shown in 1.

〔Effect of the invention〕

The film of the present invention has excellent shapeability, heat resistance, and thickness unevenness, and is suitable for use in shape printing, especially deep-drawing shape transfer that requires precise transfer, and its industrial value is expensive.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an outline of the bogata transcription method, which performs transcription at the same time as the precept. In the figure, l represents a mold, 2 represents an injection machine, 3 represents a base film, and 4 represents a layer including a printing layer.

Claims (1)

[Claims] (1) It is a film containing 0.01 to 5 wt% of a plasticizer, and the film strength F_1_0_0 at 100% elongation in an atmosphere of 150°C is 0.5 to 5 kg/mm^2,
A biaxially stretched polyester film for molding, characterized in that the film has a heat of fusion of 1 to 8 cal/g.