JPH1052861A - Laminating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for laminating a metal having excellent suitability for heat fusion processing and excellent moldability. SOLUTION: It is made of a polyester resin, and has an intrinsic viscosity (IV), a melting peak temperature (Tm) (° C), a melting shoulder (Ts) (° C), and a particle content (W) (% by weight).
110-100 × IV-W ≦ Tm−Ts ≦ 180-10
0 × IV−W, and the coefficient of thermal expansion is 8 × 10 ⁻⁶
６０60 × 10 ⁻⁶ cm / cm / ° C., and the difference between the coefficient of thermal expansion in the longitudinal direction and the coefficient of thermal expansion in the width direction is 10 × 10 ⁻⁶ cm / cm.
A film for forming a laminate on metal, which is not higher than cm / ° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film suitable for molding after heat-sealing to metal, and more particularly to a transparent or white polyester film excellent in suitability for heat-sealing processing and moldability.

[0002]

2. Description of the Related Art Conventionally, as a polyester film for metal lamination, a copolymer component (A) of a polymer has been used in an amount of 2 to 2.
50% by mole, and 1 to 20% by weight of an inorganic filler (for example, JP-A-52-13542), (B)
The heat of crystal fusion of the film is suppressed to 6.0 cal / g or less,
5 to 30% by weight of white inorganic particles added (for example, JP-A-1-241492), (C) average particle size 0.1
A film having a melting point of 210 to 245 ° C. to which 1 × 10 ⁸ particles / mm ³ of particles having a particle size of
No. 0942), (D) a lubricant having an average particle diameter of 2.3 μm or less, a melting point of 210 to 245 ° C., a thickness direction refractive index of 1.505 to 1.545, and a surface direction refractive index of 1. 61
A film having a DSC (differential scanning calorimeter) subpeak of 150 to 205 ° C.
17427), and (E) a film (for example, JP-A-6-107815) in which protrusions are defined in place of the refractive index in the plane direction described in (D) above.

[0003] However, these films are still insufficient in suitability for lamination to metal and lack in production stability.

[0004]

SUMMARY OF THE INVENTION In view of the above situation, it is an object of the present invention to provide a polyester film suitable for molding after heat-sealing to metal, and particularly excellent in heat-sealing workability and moldability. Another object of the present invention is to provide a film for laminating a metal made of a polyester resin.

[0005]

In order to solve the above-mentioned problems, the film for laminating a metal of the present invention is made of a polyester resin, and has an intrinsic viscosity (IV), a melting peak temperature (Tm) (° C.) , Melting shoulder (Ts)
(° C.), particle content (W) (% by weight): 110-100 × IV-W ≦ Tm−Ts ≦ 180-10
0 × IV−W, and the coefficient of thermal expansion is 8 × 10 ^{−6 to} 60 × 10
^-6 cm / cm / ° C., and a difference in thermal expansion coefficient between the longitudinal direction and the width direction is 10 × 10 ⁻⁶ cm / cm / ° C. or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester resin constituting the polyester film of the present invention contains, as an acid component, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, adipic acid, azelaic acid, and the like. Sebacic acid, aliphatic dicarboxylic acids such as decanedicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used.As the alcohol component,
Aliphatic diols such as ethylene glycol, diethylene glycol, butanediol and hexanediol, and alicyclic diols such as cyclohexanedimethanol can be used.

[0007] A white pigment for forming a white film or particles as a lubricant contained therein as a substantially transparent film are added to a film made of such a polyester resin. The appearance of the film of the present invention is not limited, such as transparent, white, and black.
The film to which various white pigments are added in the range described above is preferable. As typical white pigments, titanium oxide, barium titanate, barium sulfate, calcium carbonate and the like can be used. Further, as a lubricant to be added, for example,
Ring-shaped particles such as synthetic, natural aggregated or spherical silica, clay and mica, heavy and light inorganic particles such as calcium carbonate, alumina and zirconia, or various types such as cross-linked polystyrene, imide, silicone, fluorine and acrylic Organic particles can be used.

In the film according to the present invention, the intrinsic viscosity (IV) of the film and the melting peak temperature (T
m) (° C.), melting shoulder (Ts) (° C.), particle content (W) (% by weight) as the white pigment or lubricant is 110-100 × IV-W ≦ Tm-Ts ≦ 180-10
It is necessary to satisfy the relationship 0 × IV−W. In other words, the difference between the melting peak temperature (Tm) and the melting shoulder (Ts) is within a specific range in relation to the intrinsic viscosity (IV) and the particle content (W). Range). If the ratio is out of this specific range, good suitability for heat fusion processing and moldability cannot be obtained during lamination molding to metal.

At the same time, the film has a coefficient of thermal expansion of 8
In the range of × 10 ^{−6 to} 60 × 10 ⁻⁶ cm / cm / ° C.
Further, the difference between the coefficient of thermal expansion in the longitudinal direction and the coefficient of thermal expansion in the width direction of the film must be 10 × 10 ⁻⁶ cm / cm / ° C. or less.
If the coefficient of thermal expansion is out of the above range, the difference in the amount of thermal expansion between the metal to be laminated and the metal to be laminated becomes too large, so that good heat-fusibility cannot be obtained. When the difference between the thermal expansion coefficient in the longitudinal direction and the thermal expansion coefficient in the width direction exceeds the above value, wrinkles and undesired shrinkage in the width direction may be generated during lamination molding.

In particular, in the film of the present invention, titanium oxide particles having an average particle diameter of 0.1 to 1.2 μm and a loss on drying of 0.8% or less are added to a film of the polyester resin as described above in an amount of 25 to 40% by weight. %, The effect of the present invention is remarkable and more preferable.

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 that have been subjected to an organic treatment such as a silane treatment (a silane coupling agent treatment) or a polyhydric alcohol treatment are effective in achieving the above-mentioned range of loss on drying.

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

The loss on drying of the particles is determined according to JIS-K51.
It was measured with a trial weight of 2 g based on 21 (water) of 01. The loss on drying is preferably 0.8% or less. If it is more than 0.8%, heat resistance and wet heat resistance are undesirably deteriorated.

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 hydrated oxides, and further hydrophobize with an organic compound.

In the film of the present invention, as described above,
It is preferable that the white pigment is contained in an amount of 10 to 45% by weight. If the amount is less than 10% by weight, it is difficult to achieve the desired whitening. If the amount exceeds 45% by weight, the whitening is achieved, but the moldability may be deteriorated, and the particle content becomes too large. There is a risk that it will become brittle.

The film of the present invention thus constituted,
Particularly, the white polyester film preferably has a melting peak temperature of 150 to 255 ° C.
The temperature is more preferably from 15 to 235 ° C. If the melting peak temperature is lower than 150 ° C, heat resistance may be insufficient, and if it is higher than 255 ° C, moldability and adhesiveness may be insufficient. Here, the melting peak temperature of the resin was measured at a heating rate of 10 ° C./min using a DSC manufactured by Seiko Denshi Co., Ltd.

In the film of the present invention, 3% by weight of a component having a molecular weight of 2000 or less (that is, an oligomer component) is used.
It is preferable to set the following. It is more preferably 1.5% by weight or less, particularly preferably 1% by weight or less, from the viewpoint of process stability. If the content of the oligomer is more than 3% by weight, when the oligomer is passed through the process for a long time, the oligomer is deposited on the surface and easily stained, and when applied to food cans and the like, various troubles such as contamination of contents may occur.

As the transesterification catalyst for the polyester resin, Ca, Li, Mn, Zn, Ti and the like can be used. Alternatively, terephthalic acid may be directly transesterified. 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 a fluorescent whitening agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent, etc. You may add in the range which does not impair the objective and effect of this invention. In particular, the antioxidant is preferably added because the moisture-heat resistance is improved.

Further, when the polyester film of the present invention is a white film, the surface gloss is 20 to 70%, and the optical density at a thickness of 20 μm is 0.2 to 0.6.
Particularly, it is preferable from the viewpoint of printing appearance and the like in laminating a metal. Here, the optical density represents the degree of opacity of the film, and represents the ratio of the intensity I ₀ of the incident light to the intensity I of the transmitted light as log (I ₀ / I). .

Further, it is preferable to cover the surface opposite to the laminate with a film layer containing a small amount of oligomer, since troubles caused by oligomer deposition in each step are prevented.

The film of the present invention can be a uniaxially stretched film, but is preferably a biaxially stretched film in view of strength, durability, strength after molding and the like.
In the case of a two-layer structure, a film layer (A layer), (B layer)
Is not particularly limited, but the thickness ratio of layer A / layer B is preferably in the range of 1/100 to 100/1. When laminating a low oligomer layer, the thickness of the layer is 1 to 10
Setting it to μm is effective in achieving the effect of suppressing oligomer precipitation in the above-described process. In this case, of course, three or more layers may be used.

Next, a typical production method of the film of the present invention will be described, but the present invention is not limited thereto. The polyester resin to which the predetermined lubricant particles, white pigment, and various additives are added is melted, discharged from a die, cooled and formed into a film. When a two-layer laminated film is produced, each is melted by two extruders, laminated by a polymer tube, a feed block for lamination, and a lamination die, discharged into a sheet from the die, cooled and molded. In the case of uniaxial or biaxial stretching, the stretching temperature is 60 to 12 as the condition of longitudinal stretching.
0 ° C. and a draw ratio of 2.6 to 5.5 times are preferred. When stretching biaxially or more, the stretching conditions are as follows: stretching temperature 70 to 1
60 ° C., a draw ratio of 2.6 to 5 times is preferable, and heat setting is 1
It is performed at 10 to 240 ° C., and the relaxation rate is preferably in the range of 0 to 10%. In order to achieve the coefficient of thermal expansion of the present invention, it is preferable to cool once after stretching or heat setting and then cool after heating.

The white pigment (for example, titanium oxide particles) may be added at the time of polymerization.
It may be melt-mixed and dispersed, or a method of preparing a high-concentration master pellet and diluting it.

The white or substantially transparent polyester film formed as described above is, for example, heat-sealed to a metal plate by various methods to form a metal laminate.

As the metal plate to which the film of the present invention is bonded, tinplate, tin-free steel, aluminum and the like can be mentioned as typical examples. These metal plates may be appropriately subjected to an organic or inorganic treatment on the surface.

[Measurement Method and Evaluation Method] Hereinafter, a method for measuring characteristics used in the description of the present invention and a method for evaluating effects according to the present invention will be described. (1) Intrinsic viscosity IV 8g / 100m in o-chlorophenol at 25 ° C
The viscosity ratio ηr between the polymer solution and the solvent is determined as follows: 0.0246 × ηr + 0.2677 = Intrinsic viscosity.

(2) Melting peak temperature Tm (° C.), dissolving shoulder Ts (° C.) Using DSC manufactured by Seiko Denshi Co., Ltd., heating rate 10 ° C.
/ Min, the partial melting peak temperature when the temperature was raised at a sample amount of 8 mg was determined as a melting shoulder, and the peak temperature was determined as a melting peak temperature.

(3) Coefficient of thermal expansion Determined from the average coefficient of thermal expansion when the temperature was raised from 25 ° C to 65 ° C.

(4) Laminate strength The sample film was heated to 230 ° C. and had a thickness of 0.25.
4 kg / 15 m for a sample that was laminated and quenched while pressing with a nip roll at 120 ° C.
When a 180 ° peeling force of at least m was obtained, the lamination strength was rated as “」 ”, and the other values were rated as“ x ”.

(5) Laminating Wrinkles When a film having a width of 1500 mm is laminated at a running speed of 250 m / min. Under a condition of 13 m under the conditions of the above item (4), three or more wrinkles are evaluated as “×”, and the others are evaluated as “X”. ○ ”.

(6) Width Shrinking When laminating under the conditions of the above item (5), one having a width shrunk by 5 mm or more on one side was marked as "x", and the others were marked as "o".

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Examples 1 to 4 and Comparative Examples 1 to 3 A polyethylene terephthalate / isophthalate copolymer of 12 mol% of isophthalate (however, Example 4 has a polyethylene terephthalate of 0 mol% of isophthalate)
Except for Example 2, a raw material containing 0.3% by weight of colloidal silica having an average particle diameter of 0.8 μm was used. In Example 2, a raw material containing 20% by weight of rutile type titanium oxide particles having an average particle diameter of 0.35 μm was used. Was. After the raw material pellets are sufficiently dried, they are supplied to an extruder and melt-extruded at 280 ° C., cast from a slit die into a sheet, cast on a cooling drum whose surface temperature is controlled at 30 ° C. Was adhered to the drum surface while being cooled and solidified to obtain an unstretched sheet. The unstretched sheet was stretched under the stretching conditions and heat treatment conditions shown in Table 1 to obtain a biaxially stretched polyester film having a thickness of 20 μm. However, in the examples, after the heat treatment shown in Table 1, the temperature was cooled to 90 ° C. or less while maintaining the temperature at an interval of 30 ° C. for 2 seconds.
After the heat treatment, it was rapidly cooled to 90 ° C. or less.

[0033]

[Table 1]

Table 2 shows the properties of the obtained film and the properties when laminated on a metal. Films satisfying the conditions specified in the present invention (Examples 1 to 4) all exhibited good laminating properties.

[0035]

[Table 2]

[0036]

As described above, when the film for lamination molding of the present invention is used, excellent suitability for heat fusion processing and moldability can be obtained when lamination molding is performed on metal.

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Claims (2)

[Claims] 1. A polyester resin having an intrinsic viscosity (IV), a melting peak temperature (Tm) (° C.), a melting shoulder (Ts) (° C.), and a particle content (W) (% by weight) of 110-. 100 × IV-W ≦ Tm−Ts ≦ 180-10
0 × IV−W, and the coefficient of thermal expansion is 8 × 10 ^{−6 to} 60 × 10
^-6 cm / cm / ° C., and a difference in thermal expansion coefficient between the longitudinal direction and the width direction is 10 × 10 ⁻⁶ cm / cm / ° C. or less, lamination molding to metal. For film. 2. The film for lamination molding on metal according to claim 1, wherein the particles contain a white pigment, and the content of the white pigment is in a range of 10 to 45% by weight.