JPH08169964A - Polyester film for lamination molding with metallic sheet - Google Patents

Abstract

PURPOSE: To obtain a film excellent in process stability as well as white light- shielding properties and the most suitable for use where it is fusion-bonded to a metallic sheet and then molded. CONSTITUTION: This film is made of a polyester resin containing 10-30wt.% white pigment and having a void content of 4-20%, a melting peak temperature of 150-245 deg.C, an oligomer content of 3wt.% or below and a degree of orientation of 0.7-4.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a polyester film which has excellent laminating properties with a metal plate and processing properties of a laminated body, and in particular, has a small amount of stains in the film forming and processing steps, and after being heat-sealed to a metal plate. TECHNICAL FIELD The present invention relates to a polyester film for metal plate laminating and forming, which is suitable for molding it.

[0002]

2. Description of the Related Art Conventionally, as a white polyester film, a copolymer component of (A) polymer is added in an amount of 2 to 50 mol% and an inorganic filler is added in an amount of 1 to 20% by weight (for example, JP-A-52-13542). (B), the heat of crystal fusion of the (B) film is suppressed to 6.0 cal / g or less, and 5 to 30% by weight of white inorganic particles are added (for example, JP-A 1-2).
No. 41492), (C) average particle size 0.1 to 25 μm
1 × 10 ⁸ particles / mm ^{3 were} added, melting point 210-
A film having a temperature of 245 ° C. (for example, JP-A-5-170942) is known. However, the above (A) and (B)
The white film (C) has a lot of stains in the film forming step and various processing steps, and it cannot be said that it exhibits practically sufficient characteristics in the application where it is heat fused to a metal and heated after molding. .

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an excellent white light-shielding property and at the same time excellent processability and process stability against stains and the like. Particularly, a metal suitable for forming after heat-sealing on a metal plate. It is intended to provide a polyester film for plate laminating and forming.

[0004]

A polyester film for laminating and molding metal plates of the present invention which meets this object is a polyester film comprising a polyester resin containing a white pigment in an amount of 10 to 30% by weight. ) Void ratio is 4 to 20%, (b) melting peak temperature is 150 to 245.
And (c) the content of (c) -containing oligomer is 3% by weight or less, and (d) the degree of orientation is 0.7 to 4.0.

The polyester resin constituting the polyester film for laminating and molding metal plates of the present invention contains, as acid components, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, adipic acid, Azelaic acid, sebacic acid, decanedicarboxylic acid, aliphatic carboxylic acids such as trimellitic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used, as the alcohol component, ethylene glycol,
Aliphatic diols such as diethylene glycol, butanediol, hexanediol, and alicyclic diols such as cyclohexanedimethanol can be used.

In the film of the present invention, 10 to 30
Various white pigments are added in the range of wt%. Typical white pigments include titanium oxide, barium sulfate, calcium carbonate and the like. Among these white pigments, the average particle size is 0.1 to 1.2 μm, and the loss on drying is 0.8.
% Of titanium oxide particles in an amount of 8 to 20% by weight is preferable because more excellent process stability can be obtained.

As the titanium oxide particles, for example, rutile type, brookite type and anatase type titanium oxide particles can be used. In particular, rutile type titanium oxide particles obtained by silane treatment (treatment with a silane coupling agent) are effective in achieving the loss on drying within the above range.

The average particle size of titanium oxide particles is 0.1 to 1.2 in order to achieve a predetermined whitening while ensuring moldability.
μm is preferred.

Among the titanium oxide particles, those which have been subjected to a hydrophobic treatment are particularly preferable, and the drying loss of the hydrophobic treated particles is measured by a test amount of 2 g based on JIS-K5101 21 (water content). Is preferably 0.8% or less.

In order to reduce the loss on drying to 0.8% or less, it is effective to subject the titanium oxide particles to a surface treatment. For example, it is effective to treat with a silane coupling agent, isopropyl titanate or the like, or to treat with two or more kinds of hydrous oxides, and then further hydrophobize with an organic compound.

The film of the present invention contains 10 to 30% by weight of the above white pigment. 10% by weight
If the amount is less than the above, it is difficult to achieve the desired whitening, and if it exceeds 30% by weight, the whitening is achieved, but the moldability may be deteriorated, and the content of the particles becomes too large and the film itself becomes brittle. May be.

In the polyester film for laminating and forming metal plates of the present invention thus constructed, the melting peak temperature is controlled to 150 to 245 ° C.
More preferably, it is 215 to 225 ° C. If the melting peak temperature is lower than 150 ° C, heat resistance may be insufficient, and if it is higher than 245 ° C, moldability and adhesiveness may be insufficient. The melting peak temperature of the resin is DSC manufactured by Perkin Elmer Co., Ltd., and the heating rate is 1
It is measured at 0 ° C./min.

In the film of the present invention, the content of oligomers is 3% by weight or less, preferably 1.5% by weight.
It is desirable that the amount be less than 1.0% by weight, more preferably less than 1.0% by weight, in terms of process stability. If the content of the oligomer is more than 3% by weight, the oligomer may be easily deposited on the surface when it is passed through the process for a long time, and when applied to a food can or the like, various troubles such as contamination of contents may occur.

Further, the film of the present invention may be a uniaxially stretched film, but a biaxially stretched film is preferable in terms of strength, durability, strength after molding and the like.

As the transesterification catalyst for the above polyester resin, Ca, Li, Mn, Zn, Ti or the like can be used. Alternatively, terephthalic acid may be directly transesterified. Further, as the polymerization catalyst, S
b ₂ O ₃ , germanium oxide or the like can be used.
Further, the film of the present invention may contain other additives, if necessary, such as optical brighteners, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, etc., to the extent they are usually added. You may add in the range which does not impair the objective and effect of invention.
In particular, it is preferable to add an antioxidant because it has improved resistance to moist heat.

Further, in the film of the present invention, it is necessary that the void rate is within the range of 4 to 20%. A low void ratio is acceptable as far as the void ratio is concerned. However, if the void ratio is lower than the above range, the amount of oligomers deposited on the surface layer of the film increases, which is not preferable. or,
When the void ratio is higher than the above range, the film becomes brittle and it becomes difficult to achieve predetermined physical properties such as strength.

Further, the degree of orientation in the film of the present invention must be in the range of 0.7 to 4.0. If it is lower than 0.7, the bondability will be insufficient, and if it is higher than 4.0, the moldability will be insufficient.

Next, a typical production method of the film of the present invention will be explained, but the production method is not limited to this. The above-described predetermined titanium oxide particles and the polyester resin to which various additives are added are melted, discharged from the die, cooled and formed into a film. In the case of uniaxially or biaxially stretching, the stretching temperature is 60 to 120 ° C. as the longitudinal stretching condition.
A stretching ratio of 2.6 to 5.5 is preferable, and in the case of biaxial stretching, the stretching temperature is 70 to 160 as a condition for transverse stretching.
℃, draw ratio 2.6-5.0 times is preferable, heat setting is 1
It is preferable to carry out at 10 to 240 ° C. and to set the relaxation rate in the range of 0 to 10%.

The titanium oxide particles may be added at the time of polymerization, may be melt-mixed and dispersed at the time of molding into a film, or may be a method of preparing a high-concentration master pellet and diluting it.

The polyester film molded as described above is laminated on a metal plate by heat fusion by a known method to form a metal plate-film laminate.

Typical examples of the metal plate to which the film of the present invention is attached include tin plate, tin-free steel, aluminum and the like. The surface of these metal plates may be subjected to organic or inorganic treatment as appropriate.
The metal-film laminate formed as described above is suitable for use in, for example, food cans and beverage cans.

[Measuring Method] The measuring method of each characteristic used in the description of the present invention and the examples described later will be described below. (1) Light-shielding property A film having a thickness of 15 μm was prepared and the optical density (JIS-K
7605). ◯: Optical density of 0.30 or more ×: Optical density of less than 0.30 It was determined that the sample could be put to practical use.

(2) Amount of oligomer (% by weight) The filtrate obtained by dissolving / re-depositing with hexafluoroisopropanol / acetone was subjected to gel permeation chromatography (WA).
TERS, GPC244), detection wavelength 254n
m, the amount of cyclic trimer was measured using chloroform (1 ml / min) as a solvent, and the amount of oligomer was determined.

(3) Void ratio (%) White pigment addition amount / white pigment specific gravity + [(1-white pigment addition amount) / polyester part specific gravity] = 1 / δ was calculated, and [1-
(Film specific gravity / δ)] × 100 is the void ratio. However, the polyester was all crystallized, and the specific gravity was 1.515.

(4) Orientation degree measuring device: FTS-15E / D (FT-IR manufactured by Bio Rad Digilab) Light source: Special ceramics detector: MCT auxiliary device: micro-ATR measuring auxiliary device (WILKS)
Incident angle: 45 ° IRE: KRS-5, using polarizer Measurement conditions: Decomposition ability = 4 cm ⁻¹ Cumulative number of times = 500 times As the degree of orientation, the absorption ratio of (νC—O trans band) and benzene ring (970 cm ⁻¹ / 790 cm ⁻¹ ) was obtained and used as the degree of orientation.

(5) Laminating property Melting peak temperature (if two or more peaks appear, arithmetical average in melting energy ratio) + 8 ° C. After bonding with tin-free steel to a thickness of 0.3 mm, it is rapidly cooled to 210 ° C. After drying for 5 minutes, a 250g weight was dropped from a height of 6cm to give an impact, and then 6V under 1% NaCl water.
A voltage of 0.2 mA or less is applied as a good “◯”, and other than that is a bad “x”.

(6) Formability After laminating in the same manner as in the above (4), 1.37 times draw forming was performed, and then drying treatment was performed at 210 ° C. for 10 minutes. The case where the metal film and the film were floated, the case where the film was whitened, and the case where the end portion was significantly shrunk were evaluated as bad "x", and the others were evaluated as good "○".

(7) Processability (process stability) After laminating in the same manner as in (4), the temperature is 160 ° C. for 2 hours (when the melting peak temperature is 170 ° C. or less, the melting peak temperature-
A drying process is carried out (at a temperature of 10 ° C.). The surface of the sample is washed with isopropyl alcohol to quantify the amount of oligomers deposited on the surface. A case where 1/3 or more or 2% by weight or more of the contained oligomer amount was precipitated was judged as poor "x", and other cases were judged as good "○".

[0029]

EXAMPLES Hereinafter, examples will be described. Examples 1 to 3 and Comparative Examples 1 to 5 To the polyester resin of the acid component and the alcohol component shown in Table 1, the rutile type titanium oxide particles subjected to the treatment shown in Table 1 were added in the amounts shown in Table 1, and the extruder was used. Was melt-extruded at 280 ° C., discharged from a die into a sheet and cast.
This unstretched sheet is stretched at a temperature of 102 ° C. and a stretch ratio of 3.0.
After longitudinally stretching at a doubling rate, using a tenter, stretching temperature 110 ° C,
The film was transversely stretched at a draw ratio of 3.1 times and heat-treated at 190 ° C. at a transverse relaxation rate of 1.0% to form a 15 μm-thick biaxially stretched metal sheet polyester film for laminating and forming. Table 1 shows the evaluation results of this film.

However, in Comparative Example 2, the film was longitudinally stretched 3.0 times at 95 ° C. In Comparative Example 3, the film was longitudinally stretched 3.8 times at 102 ° C., then laterally stretched 4.3 times at 110 ° C., and heat-treated at 180 ° C. In Comparative Example 5, an unstretched sheet was used. In Example 3, longitudinal stretching was performed at 80 ° C. for 3.0 times, and then at 93 ° C. for 3.
It was transversely stretched 1 time and heat-treated at 140 ° C. at a relaxation rate of 1.0.

[0031]

[Table 1]

[0032]

As described above, in the case of the polyester film for metal plate laminating and shaping of the present invention, the addition amount of the white pigment contained is specified, and the void ratio, the melting peak temperature, the contained oligomer amount, Since the degree of orientation is specified, it is possible to obtain a film which has excellent white light-shielding properties and, at the same time, excellent process stability and which is suitable for use in forming after heat fusion with a metal plate.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location C08L 67/00 KJR (72) Inventor Wataru Oe 1-1-1, Sonoyama, Otsu, Shiga Prefecture Toray Co., Ltd. Ceremony company Shiga business site

Claims (3)

[Claims] 1. A polyester film comprising a polyester resin containing a white pigment in an amount of 10 to 30% by weight, wherein (a) the void ratio is 4 to 20%, (b) the melting peak temperature is 150 to 245 ° C., and (C) A polyester film for metal sheet laminating and forming, characterized in that the content of the contained oligomer is 3% by weight or less and (d) the degree of orientation is 0.7 to 4.0. 2. The polyester film for metal sheet laminating and forming according to claim 1, wherein the white pigment is titanium oxide, and the titanium oxide is subjected to a hydrophobic treatment. 3. A metal plate-film laminate obtained by bonding the metal film laminating / forming polyester film according to claim 1 and a metal plate.