JPH03169529A - Biaxially oriented polyester film for molding - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented white polyester film which has high degree of consealment and low gloss and is superior in moldability, by a method wherein polyester is formed by adding other polymer into the polyester. CONSTITUTION:The title film is of a biaxially oriented polyester film for molding having distictive features where apparent specific gravity is 0.4-1.3, a degree of consealment is at least 2.0 and film strength F100 at the time of 100% stretching under an atmosphere of 150 deg.C is 0.5-5.0kg/mm<2>. It is preferable that since 4-12C preerably 6-12C aliphatic dicarboxylic acid ingredient can improve the foregoing moldability, heat resistance and mottled thickness as the aliphatic dicalboxylic acid ingredient contained in the polyester constituting a film. In addition, it is preferable that the film is in structure having a fine closed cell in its surface and inside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a biaxially stretched white polyester film for use in military forms, which has a high degree of hiding, low gloss, and excellent shapeability.

[Conventional technology and issues to be solved]

Conventionally, biaxially stretched 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, stretch, cold, injection, in-mold, embossing, etc. is being considered, and the uses of processed polyester film include for transcription of precepts, molding, etc. for containers,
Applications for electrical outages, packaging, decoration, etc. are being considered.

As such a film, for example, JP-A-64-11
As shown in JP-A No. 820, JP-A-64-16650, JP-A-64-22530, JP-A-64-40400, JP-A-64-45699, etc.
BACKGROUND ART Biaxially stretched and heat-set films are known that are copolymerized with a combination of isophthalic acid, sebacic acid, diethylene glycol, neobentyl glycol, 1,4-cyclohexanedimethanol, and the like. In addition, in order to improve formability, we reduced the vertical and horizontal orientation during biaxial stretching,
Known methods include a method of lowering the planar orientation coefficient of the film, a method of lowering the heat-setting temperature, a method of relaxing the film in the longitudinal and lateral directions, and the like, in appropriate combinations.

However, in order to meet the expanding range of uses, there is a demand for molding films with even higher added value.

[Means to solve the problem]

As a result of intensive studies in view of the above request, the present inventors discovered that by incorporating other polymers into polyester and foaming it, it is possible to further improve the appearance and obtain a film with a luxurious feel. has been completed.

That is, the gist of the present invention is that the apparent specific gravity is 0.4 to 1.3.
and the degree of concealment is 0. 2 or more, and the film strength F100 at 100% elongation in an atmosphere of 150 ° C.
0.5 to 5.0 kg/w''.

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, 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, etc. 5 Also, as a diol component, ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol , triethylene glycol, polyalkylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, and other known diol components.

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, glycerin, pentaerythritol, etc. Multifunctional compounds can also be used to the extent that the product retains substantially linear macromolecules.

In the polyester constituting the film 11 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.

As the acid component of the polyester constituting the film of the present invention, an aliphatic dicarboxylic acid component is added in an amount of 1 to 20 mo in the total acid component.
It is preferably contained in an amount of 1%, and more preferably contained in an amount of 1 to 1 Q mol%. A film in which the content of the aliphatic dicarboxylic acid component in the total acid component exceeds 20 mo1% is not preferable because it shows a decrease in heat resistance and worsening of thickness unevenness.

Further, if the content is less than 1 mol%, no improvement in the above characteristics is 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 it can improve the shapeability, heat resistance, and thickness unevenness.

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 oxide, titanium oxide, calcium phosphate, lithium fluoride, and carbon black, and melted polyester resin. Examples include internal particles formed inside the polymer during polyester production by insoluble high-melting point organic compounds during film formation, crosslinked polymers, and metal compound catalysts used during polyester synthesis, such as alkali metal compounds and alkaline earth metal compounds. The content of fine particles contained in the film is usually 0.00
It ranges from 2 to 0.9% by weight, and the average particle size is o. oo
It is preferable that it is in the range of i 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,
It is undesirable because sufficient strength and restraint cannot be obtained.

In the film of the present invention, the film strength F100 at 100% elongation in an atmosphere of 150°C is 0.5 to 5.
It must be in the range of kg / * m 2. F in the present invention. . is the average value of the longitudinal and transverse strength of the film at 100% elongation at 150°C. FIG. The value preferably ranges from 0.5 to 3 kg/mu2.

According to our study results, the strength F100 value is deeply related to the film's formability, and FIG. is 5 kg/l1
A film exceeding 2 is undesirable because its moldability deteriorates. Also, F.I.O. is 0. If the weight of the film is less than 5 kg/vnr2, the film will be deformed non-uniformly during ritual formation, and for example, in the case of a transfer film, the pattern to be transferred will be distorted, which is not preferable. Further, the difference in strength between the longitudinal and transverse directions of the film when stretched at 150° C. and 100% is usually 3 kg/mm 2 or less, preferably 2 kg/mm 2 or less, and more preferably 1 kg/w” or less.

If this difference exceeds 3 kg/mm, the anisotropy increases and the shapeability deteriorates.

Further, in the present invention, the heat of fusion of the film is preferably 1
~3caji! /g, more preferably 1 to 6 cal/g
is within the range of Heat of fusion is 3cajl! A film with a weight exceeding 1/g is undesirable because its shapeability deteriorates.

On the other hand, for films with a heat of fusion of less than 1 cal/g, especially when recycling edges etc., crystallization is extremely difficult in the raw material drying process during film formation, and complicated processes such as vacuum drying are required. This is undesirable and also worsens the thickness unevenness of the film.

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.

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 with a transverse shrinkage rate of more than 0% is undesirable because, when used for pattern transfer, the film shrinks in the drying process after the printing layer is formed.

On the other hand, the film of the present invention preferably has a structure having fine closed cells on its surface and inside, and the apparent specific gravity of the film of the present invention is 0. It needs to be in the range of 4 to 1.3, preferably 0. 6-1
．． 3, more preferably 0. It is in the range of 8 to 1.2.

Apparent specific gravity is 0. If it is less than 4, the mechanical strength of the film will be insufficient, which is not preferable.

Further, the hiding degree of the film of the present invention is 0. It needs to be 2 or more, preferably 0. It is 3 or more. If the hiding degree is less than 0.2, the diameter of the closed cells present in the film will increase, which will not only reduce the mechanical strength, but also necessitate the addition of a large amount of pigment when used as a white film. Undesirable.

Although it is necessary for the film of the present invention to have the above-mentioned properties, there are no particular limitations on the manufacturing method as long as such properties and requirements are not impaired.

For example, one method for obtaining the polyester film for military commandments of the present invention is to blend a specific polypropylene into polyester, extrude it into a sheet shape, and then biaxially stretch the sheet to form a film. be. For details, please refer to melt flow index (hereinafter referred to as M.F.) for polyester.
Abbreviated as I) 3 to 20-t% of crystalline polypropylene homopolymer having a molecular weight of 0.2 to 120 is blended, melt-extruded to form a substantially amorphous sheet, and then the sheet is biaxially divided by area magnification. This is a method of forming a film by stretching the polyester film by a factor of 4 times or more, and forming a polyester film containing numerous fine closed cells on the surface and inside of the film.

By employing such a method, it is possible to easily obtain a biaxially stretched film having an apparent specific gravity of 0.4 to 1.3, a degree of hiding of 0.2 or more, and a biaxially stretched film. Moreover, the thickness of the film of the present invention, which can be produced under normal stretched polyester film production conditions without modification of conventional film production equipment, is not particularly limited, but may be any thickness preferably used as a film for certain shape transfers. Saha 5~5
00 μm, more preferably 5 to 300 μm.

〔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.

(Film strength FI0 at 100% elongation in 11150°C atmosphere. (kg / 2) ■ Intesco tensile tester with constant temperature chamber Intesco 2001 type constant temperature chamber 15
Set the temperature to 0℃, and place a film with a width of 150mm between the chucks at a temperature of 50mm.
After leaving it for 2 minutes, the tensile speed was set to 20.
The strength at 100% elongation was measured at 0 mu/min.

Measurements were made in the vertical and horizontal directions of the film, and the average value was taken as F100. Note that for films that break before 100% stretching, the conversion was performed according to the following formula.

Strength at 100% elongation (kg/am2) = (2) Thickness of the film A continuous film thickness measuring device (using an electronic micrometer) manufactured by Madarasu Ritsu Electric Co., Ltd. was used to measure the thickness of the film at a length of 5 m along the longitudinal direction of the film. The thickness unevenness was calculated using the following formula.

Film average thickness XIOO (%) (3) Film average refractive index (n), plane orientation degree (Δ
P), Birefringence (Δn) The refractive index of the film was measured using an Ambe refractometer manufactured by Atago Co., Ltd. and a sodium lamp as a light source.

■ n=- (n, +n, +n7) 3 1 ΔP-- (ny +n,) 2 n α Δn=n7 - n, In the above formula, n7, n, and nct are each the maximum refractive index in the film plane , represents the refractive index in the direction orthogonal thereto and the refractive index in the thickness direction.

(4) Heat of fusion of film (caA/g) Determine the area of the peak associated with melting of the crystals of the sample measured using Birkin Elmer's differential scanning calorimeter DSC-1B at a heating rate of 16°C/min. Calculated according to the following formula.

■ Heat of fusion of film = A-S・-(caβ/g) m A: Heat of fusion per unit area on the chart when measuring indium under the same conditions (Caj!/CI+! S: Melting peak of the sample Area (co!) m: Weight of sample (g) (5) Intrinsic viscosity (η) 200 mg of sample was mixed with phenol-tetrachloroethane = 5
In addition to 20 mε of a 0/50 mixed solvent, 30
After heating for a minute, measurements were taken at 30°C.

(6) Heat shrinkage rate of film (%) The film was heat-shrinked for 3 minutes under no load while the guard was open at a temperature of 150 ± 2°C, and the heat shrinkage rate in the vertical and horizontal directions was determined according to the following formula. Ta.

However, l0: Original length 10cm l: Length after contraction (7) Shapeability as a transfer film Length 10cm, Width 10CII+, Maximum depth 2, O Cl
Using a mold No. 11, the film was preliminarily formed inside the mold using vacuum and pressure, and then heated resin was injected to form the film. The formability of the film was evaluated as follows based on the frequency of film breakage during forming.

○: 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 film for molded containers A 16 μm polyester film was laminated with a 70 μm unstretched polypropylene film via an adhesive, preheated, and then a mold with an opening diameter of 10 cm and a depth of 3 am was formed. A plastic tray was made using vacuum pressure and air pressure. Those in which peeling occurred between the eyebrows or frequent breakage between the polyester film and polypropylene film during shaping were rated ×, and those that could be shaped without particular problems were rated ○.

(9) Cut out a 10 cm x 10 cm sample from any part of the apparent specific gravity film, measure the average thickness at 9 arbitrary points with a micrometer to determine the volume, and then weigh the sample, The weight per unit was determined. The number of measurements was performed on five samples, and the average value was taken as the apparent specific gravity.

QO) The density of transmitted light under the G filter was measured using an obscurity Macbeth densitometer TD-904 type. The larger this value is, the higher the hiding power is. Measurements were made at three points, and the average value was taken as the degree of concealment.

Qll Melt Flow Index (M.F.I) (
g/10min) Measured according to the method of JIS K-6758-1981. The lower this value is, the higher the melt viscosity is.

(Auto) Glossiness (%) Measured using a gloss meter model VG-107 manufactured by Nippon Denshoku ■ in accordance with the method of JIS Z-874. Using a black standard plate as a reference, values at an incident angle and a reflection angle of 60' were measured. The number of measurements was n=3, and the average value was taken as the glossiness.

Example dicarboxylic acid: terephthalic acid unit 80mol1%
, isophthalic acid units 16 mo1%, sebacic acid units 4
It consists of 98 mo1% of ethylene glycol units and 2 diethylene glycol units as diol part.
After pre-crystallizing a copolymerized polyester chip containing 500 ppm of amorphous silica particles with an average particle size of 1.4 μm, the chip was coated with a crystalline polyester of Melt Flow Index (M.F.I) 5. 10 wt % of propylene homobolymarcant was added and uniformly blended.

The mixed polymer was 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 9 times in the transverse direction.
Stretched 3.4 times at 5°C with 12% lateral relaxation and 0.
Heat treatment was carried out at 175° C. with 3% longitudinal relaxation. The average thickness of the obtained film was 38 μm, and the intrinsic viscosity was 0.63.

The physical properties and characteristics of the obtained film are shown in Table 1 below.

Table 1 [Effects of the Invention] The film of the present invention is a white film with a high degree of concealment and a low gloss, and is useful as a film for precepts that give a sense of luxury, and its industrial value is high.

Claims (1)

[Claims] (1) Apparent specific gravity is 0.4 to 1.3 and concealment degree is 0
．． 2 or more, and the film strength F_1_0_0 at 100% elongation in an atmosphere of 150°C is 0.5 to 5.0.
A biaxially oriented polyester film for molding, characterized in that the film is kg/mm^2.