JP3328492B2 - Polyester film for decorative metal plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for decorative metal sheets, and more particularly to a polyester film having excellent moldability and excellent solvent resistance, stain resistance, heat resistance, design and surface properties. The present invention relates to a polyester film for a decorative metal sheet useful for a decorative metal sheet for household appliances and the like.

[0002]

2. Description of the Related Art A decorative metal plate in which a metal plate is coated with a resin,
It has been used in the past because of its excellent rust-prevention properties. In particular, decorative steel sheets (coated metal sheets) in which metal sheets such as steel sheets are coated with vinyl chloride resin are used for building materials, household appliances, vehicles, etc. Widely used for applications.

However, with a decorative steel sheet coated with a vinyl chloride resin, the surface of the vinyl chloride resin layer deteriorates due to the influence of ultraviolet rays, heat, moisture, and the like, and the plasticizer in the vinyl chloride resin volatilizes as time passes. As a result, there are disadvantages such as markedly degraded surface characteristics and severe discoloration.

In order to improve this disadvantage, a method of coating an acrylic resin layer on a coated vinyl chloride resin (Japanese Patent Laid-Open No.
JP-A-32834), a method of laminating an acrylic resin film (JP-A-56-162649), or a method of applying a fluororesin paint (JP-A-63-2930).
No. 48) has been proposed.

[0005] A method using a polyolefin resin instead of a vinyl chloride resin (JP-A-63-159028) has also been proposed.

However, the method of applying an acrylic resin layer or the method of laminating an acrylic resin film has a drawback that the solvent resistance of the acrylic resin is inferior. When a fluororesin is used, the properties as a resin are excellent, but the cost is high. And it is not economical. Further, the method using a polyolefin resin has drawbacks such as poor heat resistance of the polyolefin resin.

Therefore, it is conceivable to laminate a biaxially stretched polyethylene terephthalate film having excellent properties such as solvent resistance, stain resistance, heat resistance, economy and surface properties on a metal plate in place of the vinyl chloride resin. . However, this polyethylene terephthalate film has a drawback of being inferior in moldability due to its high rigidity.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of the conventionally used resin for decorative metal sheets,
It is an object of the present invention to provide a polyester film for a decorative metal plate, which satisfies all of the moldability, solvent resistance, stain resistance, heat resistance, design properties and surface properties in a well-balanced manner.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to develop a polyester film for decorative metal sheets free of the above-mentioned disadvantages, and as a result, have reached the present invention.

That is, the present invention has a melting point of 210 to 24.
A polyester film for a decorative metal plate, comprising a copolymerized polyester having an intrinsic viscosity of 0.52 to 0.80 at 5 ° C and a plane orientation of 0.120 to 0.140.

The copolyester in the present invention is a saturated polyester comprising a dicarboxylic acid component and a diol component, and has a melting point in the range of 210 to 245 ° C. Of these, copolymerized aromatic polyesters, particularly copolymerized polyethylene terephthalate, are preferred.

Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid; Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be exemplified. Examples of the diol component include aliphatic diols such as ethylene glycol, 1,4-butanediol, and 1,6-hexanediol, branched glycols such as neopentyl glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol. And alicyclic diols such as cyclohexane dimethanol. These can be used as components of a copolyester having a melting point in the range of 210 to 245 ° C. Among them, a combination of terephthalic acid, ethylene glycol and a copolymer component is particularly preferred.

The melting point of the above copolymerized polyester is 210-210.
It is 245 ° C, preferably 215 to 240 ° C, particularly preferably 220 to 235 ° C. When the melting point of the polymer is less than 210 ° C., the heat resistance is poor. On the other hand, when the melting point of the polymer exceeds 245 ° C., the crystallinity of the polymer is too large and the moldability is impaired.

Here, the melting point of the copolyester was measured by Du Pont Instruments 910.
A method in which a melting peak is determined at a heating rate of 20 ° C./min using DSC. The amount of the sample is about 20 mg.

The copolymerized polyester in the present invention includes:
In order to impart appropriate friction characteristics and workability to the film, the film preferably contains inert particles. Examples of the inert particles include, for example, Periodic Tables IIA, IIB, IVA, IV
Fine particles containing the element B (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.), fine particles made of a polymer having excellent heat resistance such as a crosslinked silicone resin, crosslinked polystyrene, and the like can be given. .

The amount of inert particles in the copolymerized polyester is preferably determined by the winding property in the film production process. Generally, it is preferable to add a small amount of particles having a large particle diameter and a large amount of particles having a small particle diameter. For example, an average particle size of 2.0
0.05% by weight, average particle size 0.3
For μm titanium dioxide, it is preferable to add about 0.3% by weight. By intentionally adjusting the content of the lubricant, the film can be made opaque. For example, by adding 10 to 15% by weight of titanium dioxide,
It can be a white film.

The inert particles can be incorporated into the polyester by a method of adding it during the polycondensation reaction of the copolyester or a method of adding it to the copolyester during the film formation of the film.

The copolymerized polyester in the present invention is not limited by the production method. For example, in order to produce a copolymerized polyethylene terephthalate having ethylene terephthalate as a main component, terephthalic acid, ethylene glycol and a copolymerization component are subjected to an esterification reaction, and then the obtained reaction product is subjected to a polycondensation reaction to obtain a copolymerized polyester. Or a method of subjecting dimethyl terephthalate, ethylene glycol and a copolymer component to a transesterification reaction, and then subjecting the resulting reaction product to a polycondensation reaction to obtain a copolymerized polyethylene terephthalate.

In the production of the copolymerized polyester, if necessary, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent and the like can be added. Such antioxidants include, for example, hindered phenol compounds, hindered amine compounds, sulfur atom-containing ester compounds, and the like, and ultraviolet absorbers include, for example, benzophenone compounds, benzotriazole compounds,
Sasylate compounds and the like can be mentioned.

The polyester film of the present invention is obtained by melting the above-mentioned copolymerized polyester, discharging it from a die, forming it into a film, and further biaxially stretching and heat setting.

The film has a plane orientation of 0.1.
It is in the range of 120 to 0.140. This plane orientation is 0.
If it is less than 120, the heat resistance becomes insufficient, the heat shrinkage of the film due to heat at the time of bonding the metal plates becomes too large, the shrinkage becomes a wrinkle (wrinkle) pattern, and the surface becomes dull and dull. Good products cannot be obtained. On the other hand, when the plane orientation exceeds 0.140, the moldability deteriorates.

Here, the plane orientation was measured in an atmosphere of 25 ° C. using an Abbe refractometer, monochromatic sodium D line as a light source, and methylene iodide as a mounting liquid. is there. It is determined by subtracting the refractive index in the thickness direction from １ ／ of the sum of the refractive indices in the film surface direction (vertical and horizontal directions).

In the present invention, the intrinsic viscosity of the copolymerized polyester constituting the film is in the range of 0.52 to 0.80, preferably in the range of 0.54 to 0.70.

When the intrinsic viscosity is less than 0.52, other physical properties are suitable, and even if the lamination to the metal plate is performed well, the material is liable to be broken during or after forming. Become. On the other hand, those having an intrinsic viscosity of more than 0.80 are not economical because they are excessive in quality and the productivity of the raw material polymer is lowered.

In order to obtain the film characteristics in the present invention,
In the biaxial stretching process, particularly in the sequential stretching process, the longitudinal stretching ratio is found in the range of 2.5 to 3.6 times, the transverse stretching ratio is found in the range of 2.7 to 4.0 times, and the heat setting temperature is found in the range of 150 to 230 ° C. Heat treatment is preferred.

As described above, the film of the present invention can be manufactured by using a conventionally known film forming method. For example, the copolyester is melt-extruded into a sheet, quenched to produce an unstretched film, heated by roll heating, infrared heating, or the like, and stretched in the machine direction to form a stretched film. This stretching is preferably performed by utilizing the peripheral speed difference between two or more rolls. The stretching temperature is a temperature higher than the glass transition point (Tg) of the copolyester,
The temperature is preferably 20 to 40 ° C. higher. This magnification depends on the physical properties of the final film, but is preferably 2.5 times or more. It is preferable that the magnification is further 3.6 times or less.

The longitudinally stretched film is subsequently stretched in the transverse direction,
A biaxially oriented film is formed by sequentially performing heat setting and heat relaxation processes, and these processes are performed while the film is running.
The transverse stretching treatment is performed at the glass transition point (T
g) Start at a temperature 20 ° C. above. Then, the heating is performed while the temperature is raised to a temperature lower by (120 to 30) ° C. than the melting point (Tm) of the polyester. The stretching start temperature is (Tg + 40)
C. or lower, for example, isophthalic acid 12
73% in the case of mol% copolymerized polyethylene terephthalate
Preferably it is in the temperature range of 113 ° C. The maximum stretching temperature is preferably a temperature (100 to 40) C lower than Tm.

The temperature rise in the transverse stretching process may be continuous or stepwise (sequential). Usually the temperature is raised sequentially. For example,
The transverse stretching zone of the stenter is divided into a plurality of sections along the film running direction, and the temperature is raised by flowing a heating medium at a predetermined temperature in each zone. If the transverse stretching start temperature is too low, the film breaks, which is not preferable. On the other hand, if the maximum stretching temperature is lower than (Tm-120) ° C., the heat yield of the film increases, and the uniformity of physical properties in the width direction is unfavorably reduced. On the other hand, if the maximum stretching temperature is higher than (Tm-30) ° C., the film becomes soft and breaks due to disturbance or the like, which is not preferable.

The magnification of the transverse stretching depends on the physical properties of the final film, but is preferably at least 2.7 times, more preferably at least 3.0 times. This magnification is further preferably set to 4.0 times or less.

The polyester film of the present invention preferably has a thickness in the range of 5 to 100 μm. More preferably, it is 10 to 50 μm. If the thickness is less than 5 μm, breakage or the like is likely to occur during processing, while if it exceeds 100 μm, not only is it unnecessary but also uneconomical in terms of its use.

The metal plate to which the polyester film of the present invention is bonded is, for example, a plate generally called a metal plate such as steel, iron, aluminum, tinplate, and stainless steel.

The decorative metal plate in the present invention is a decorative metal plate obtained by laminating the polyester film of the present invention on a metal plate, and it is preferable to use a polyester film provided with a printing layer on at least one surface. This printing layer is preferably provided on the surface of the polyester film laminated with the metal plate.

Further, one side of the polyester film of the present invention is printed, and the laminate is laminated by using an polyvinyl chloride film as a base material with an adhesive, and the adhesive is applied to the polyvinyl chloride film surface of the laminate. The decorative metal plate obtained by bonding to a metal plate is particularly preferable because of its excellent durability.

In the present invention, polyvinyl chloride includes
Polyvinyl chloride conventionally used for decorative metal plates can be used. For example, polyvinyl chloride, or other monomers copolymerizable therewith (for example, polyvinyl chloride)
(Vinyl acetate, acrylic acid ester, etc.).

The resin used for the printing ink for the decorative metal plate includes acrylic resin, rubber resin, epoxy resin, urethane resin, amino resin or polyester resin having good adhesiveness to the polyester film. It is preferable to include one or two or more types. As the pigment to be added to the printing ink, one or more of inorganic pigments, organic pigments, and metal powders which are usually used as ink pigments can be used.

Examples of the adhesive for the decorative metal plate include thermosetting resins such as polyurethane, phenol, furan, urea, melamine, polyester, epoxy, and silicone, vinyl acetate, and ethylene. -Vinyl acetate copolymer and its partial hydrolyzate, ethylene-
Acrylic acid copolymer, acrylic resin, thermoplastic resin such as polyamide, butadiene-acrylonitrile rubber, neoprene, other rubber derivatives, other glue, casein, natural resin, gum arabic, etc. Adhesives to be used.

[0037]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 5 and Comparative Examples 1 to 3 Copolymerized polyethylene terephthalate obtained by adding 0.1% by weight of spherical monodispersed silica having an average particle size of 1.5 μm and copolymerizing the components shown in Table 1. Was melt-extruded at the temperatures shown in the same table, and cooled and solidified to obtain an unstretched film.

Next, this unstretched film was stretched longitudinally and transversely under the conditions shown in the same table, and then heat-set.
The film was relaxed by 4.5% in the lateral direction to obtain a biaxially oriented film having a thickness of 25 μm.

[0040]

[Table 1]

A total of nine types of films obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were prepared by using an ester-based adhesive.
A two-layer laminated film was laminated with a 00 μm vinyl chloride resin film, and then laminated to one side of a 0.5 mm-thick galvanized steel sheet heated to about 200 ° C. using an epoxy-based adhesive, followed by a mirror-finished roll. Mirror embossing treatment was performed, followed by cooling to obtain a decorative metal plate.

The following observations were made on this decorative metal plate, and each was evaluated according to the following criteria.

(1) Shrinking wrinkles ；: No wrinkles are observed on the film surface after bonding. Δ: Some wrinkles are observed on the film surface after lamination. X: Wrinkles are seen on the film surface after lamination.

The workability was evaluated by the following method.

(2) Workability The Erichsen value was evaluated by the breaking distance method based on JIS K-5400. Using an Erichsen tester, a steel ball was extruded from the metal plate side of the film-coated decorative metal plate, and the extruded distance until the film was cracked and peeled when the test piece was deformed was measured.

(3) Processability Appearance ；: The film was processed without any abnormality, and no whitening or breakage was observed in the film. X: The film was processed without any abnormality, and whitening and breakage of the film were observed. Table 2 shows the evaluation results.

[0047]

[Table 2]

From the results shown in Table 2, it can be seen that the films of Examples are excellent in molding workability and surface properties.

[0049]

The polyester film for a decorative metal plate of the present invention is excellent in workability and surface properties when molded after laminating to a metal plate, and is extremely useful as a polyester film for a decorative metal plate. is there.

────────────────────────────────────────────────── ─── Continued on the front page (56) References JP-A-8-311213 (JP, A) JP-A-8-309924 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 5/18 C08L 67/00-67/02

Claims (3)

(57) [Claims] 1. A polyester film for a decorative metal sheet comprising a copolymerized polyester having a melting point of 210 to 245 ° C., an intrinsic viscosity of 0.52 to 0.80, and a plane orientation of 0.120 to 0.140. 2. A decorative metal plate in which the polyester film according to claim 1 is laminated on one surface of the metal plate. 3. The decorative metal plate according to claim 2, wherein a polyvinyl chloride film is laminated between the metal plate and the polyester film.