JP3083705B2 - 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 a decorative metal sheet, and more particularly to a polyester film having excellent moldability and excellent solvent resistance, stain resistance, heat resistance, design and surface properties. useful into a decorative metal plate such as household electric appliances
The present invention relates to a polyester film for a decorative metal plate.

[0002]

2. Description of the Related Art A coated metal plate in which a metal plate is coated with a resin has been conventionally used because of its excellent rust prevention properties. In particular, a metal plate such as a steel plate is coated with a vinyl chloride resin having a printed layer or the like. The decorative steel sheet (decorative metal sheet) is widely used for building materials, home appliances, vehicles and the like.

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. And thus have disadvantages such as markedly degraded surface properties and severe discoloration.

In order to improve such disadvantages, for example, a method of coating an acrylic resin layer on a coated vinyl chloride resin (Japanese Patent Application Laid-Open No. 3-32834) and a method of laminating an acrylic resin film (Japanese Patent Application Laid-Open No. 56-1981). 162649) or a method of applying a fluororesin paint (JP-A-63
-293048) and the like.

[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 disadvantage that the solvent resistance of the acrylic resin is inferior. When a fluororesin is used, the characteristics as a resin are excellent, but economical. There is a disadvantage of not being a target. Further, the method using a polyolefin resin has drawbacks such as poor heat resistance of the polyolefin resin.

In addition, a method of laminating a biaxially stretched polyethylene terephthalate film having excellent properties such as solvent resistance, stain resistance, heat resistance, economy and surface properties in place of a vinyl chloride resin on a metal plate can be considered. . However, this polyethylene terephthalate film has a drawback that molding processability is inferior due to its high rigidity.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems 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 sheet, 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 a decorative metal plate free of the above-mentioned problems, and as a result, have reached the present invention.

That is, the present invention has a melting point of 210 to 245.
5 ° C.
m of a biaxially oriented polyester film having a maximum heat shrinkage stress in the machine direction and the cross direction of 130 mm.
３００300 gf / mm ² and at 150 ° C.
When the film shrinks for 0 minutes,
3.0 to 5.0%, and the lateral heat shrinkage is 0.5 to 5.0%.
It is a polyester film for a decorative metal sheet characterized by being 3.0% .

The copolyester referred to in the present invention is a saturated polyester composed of a dicarboxylic acid component and a diol component, a copolyester having a melting point in the range of 210 to 245 ° C., and a particularly preferable example is copolyethylene terephthalate. It can be mentioned as.

The dicarboxylic acid component includes 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; An alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid can be exemplified. Examples of the diol component include aliphatic diols such as ethylene glycol, butane diol, and hexane diol; branched glycols such as neopentyl glycol; polyoxyalkylene glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol; An alicyclic diol such as methanol can be exemplified. These can be used as components of a copolyester having a melting point in the range of 210 to 245 ° C.

The proportion of the copolymer component depends on the type thereof, but as a result, the melting point of the polymer is from 210 to 245 ° C., preferably from 215 to 240 ° C., more preferably from 220 to 235 ° C.
It is the ratio in the range of ° 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 polyester is measured by Du.
Pont Instruments 910 DSC
And determining a melting peak at a heating rate of 20 ° C./min. The amount of the sample is about 20 mg.

[0015] The copolymerized polyester in the present invention is not limited by the production method. For example, in order to produce a copolymerized polyester having ethylene terephthalate as a main component, terephthalic acid, ethylene glycol and a copolymerized component are subjected to an esterification reaction, and the resulting reaction product is subjected to a polycondensation reaction to form a copolymerized polyester. Alternatively, a method in which dimethyl terephthalate, ethylene glycol and a copolymer component are subjected to a transesterification reaction, and then the resulting reaction product is subjected to a polycondensation reaction to obtain a copolymerized polyester is preferably used.

In the production of the copolymerized polyester, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber and an antistatic agent can be added as required. 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 copolyester in the present invention preferably contains a lubricant such as inert particles in order to improve the workability during film formation or handling of the laminate. Is, for example, Periodic Table IIA,
Inorganic fine particles containing elements IIB, IVA, IVB (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.) or organic fine particles made of a polymer having good heat resistance such as silicone resin, cross-linked polystyrene, etc. And the like.

It is preferable that the content of such a lubricant is such that the film winding property in the film manufacturing process is good or the workability in handling the laminate is good. Generally, it is preferable to add a small amount of a lubricant having a large particle size and a large amount of a lubricant having a small particle size. For example, in the case of silica having an average particle size of 2.0 μm, about 0.05% by weight,
0.3% by weight for titanium dioxide with an average particle size of 0.3 μm
It is preferable to add to a certain extent. Further, 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, a white film having good light-shielding properties can be obtained.

The above-mentioned additives such as a lubricant can be added to the polyester film by a method of adding the same during the polycondensation reaction of the copolyester or a method of adding the copolyester during the film formation of the film.

The polyester film of the present invention has a maximum heat shrinkage stress in the longitudinal and transverse directions of the film of 130.
３００300 gf / mm ² , preferably 150
３００300 gf / mm ² .

This heat shrinkage stress was applied to a metal plate.
Affects film surface properties. That is, in the vertical direction,
The heat shrinkage stress is 130 gf / in any one of the horizontal directions.
mm ^TwoIf less, heat the film and attach it to a metal plate
When joining, it is not enough to shrink the film
Adhesion is incomplete, and the flat and good surface
It cannot be stuck as an ilum. As a result,
Irregularities appear on the surface of the combined film, so-called Yuzu
It becomes a surface with irregularities like yuzu skin called skin, and the surface
Good products cannot be obtained.

On the other hand, when the heat shrinkage stress in one of the longitudinal direction and the transverse direction of the film exceeds 300 gf / mm ² , the film is heated and bonded to a metal plate (hereinafter sometimes referred to as “heat lamination”). ), The heat shrinkage of the film becomes too large, and the surface of the laminated film shrinks, causing wrinkles called wrinkle patterns,
Further, since the surface becomes dull and dull, a good product cannot be obtained.

Further, the polyester film of the present invention comprises:
The temperature indicating the maximum value of the heat shrinkage stress in the longitudinal direction and the transverse direction (hereinafter sometimes referred to as “peak temperature”) is 150 to 2
The temperature is preferably in the range of 05 ° C, more preferably
The temperature is preferably 00 ° C, particularly preferably 160 to 195 ° C.

This peak temperature may affect the surface properties of a film laminated on a metal plate by heating. That is, the heat laminating is usually performed by setting the film heating temperature to 1
Perform at a temperature higher than 50 ° C, but with a peak temperature of 150
If the temperature is lower than 0 ° C., it is difficult to obtain an appropriate heat shrinkage stress at a normal heating temperature, and a good film cannot be obtained.
Further, in order to make the shrinkage stress of the film appropriate, the film heating temperature at the time of heat lamination may be set to a temperature lower than 150 ° C. Adhesive strength is insufficient and sufficient lamination cannot be performed.

When the peak temperature exceeds 205 ° C., in order to obtain an appropriate heat shrinkage stress, the film heating temperature at the time of heat lamination is set to a temperature exceeding 205 ° C. However, at such a temperature, the film is easily broken. If the film heating temperature during the heat lamination is lower than 205 ° C., the heat shrinkage stress of the film due to the heating during the lamination does not reach the maximum, and a good film surface can be obtained. Can not.

The heat shrinkage stress and peak temperature of the film were measured by SINKU-RIKO ™ manufactured by Vacuum Riko Co., Ltd.
-3000 type THERMO-MECHANICAL
Using ANALYZER, the polyester film can be obtained by heating the polyester film from room temperature to a temperature just before the polyester is melted at a heating rate of 10 ° C./min, and then measuring. The size of the film used for measurement is 15mm
× 5 mm.

Further, the polyester film of the present invention comprises:
The heat shrinkage of the film when treated at 150 ° C. for 30 minutes is 3.0 to 5.0% in the longitudinal direction, particularly 3.0 to 4.5%.
Is preferably 0.5 to 3.0%, particularly preferably 0.7 to 2.5% in the horizontal direction. If the heat shrinkage in the vertical direction is too small, it is difficult to utilize the heat shrinkage of the film when bonding the film to the metal plate, and it is difficult to bond the film as a flat film having good surface properties. As a result, the surface of the film is likely to be in the form of citron texture, and it is difficult to obtain a good product. If the heat shrinkage in the longitudinal direction is too large, the heat shrinkage of the film becomes too large when the film is bonded to a metal plate, so that the film tends to have a wrinkled pattern or a dull surface without luster, and it is difficult to obtain a good product.

On the other hand, if the heat shrinkage in the lateral direction is too small, it is difficult to utilize the heat shrinkage of the film when bonding the film to the metal plate, and it is difficult to bond the film as a flat film having good surface properties. As a result, the surface of the film is likely to be in the form of citron texture, and it is difficult to obtain a good product. If the heat shrinkage in the transverse direction is too large, the heat shrinkage of the film becomes too large when the film is bonded to a metal plate, and the film shrinks and has a wrinkle-like surface, making it difficult to obtain a good product. Further, the shrinkage of the film in the horizontal direction becomes too large, and the film cannot be bonded to the edge portion of the metal plate satisfactorily.

The heat shrinkage in the longitudinal direction of the film is preferably larger than that in the transverse direction. The reason for this is the process of laminating the film on a metal plate by heating and laminating the film in the vertical direction with a roll to take out and wind it up, while the film passes through the process in a free state in the horizontal direction. Therefore, it is suitable to use films having different heat shrinkage rates in order to obtain a decorative metal plate having good surface properties.

The biaxially stretched 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 form an unstretched film, heated by roll heating, infrared heating, or the like, and stretched in the machine direction to obtain a vertically stretched film. The stretching in the longitudinal direction is preferably performed by utilizing the peripheral speed difference between two or more rolls. The stretching temperature is preferably a temperature higher than the glass transition point (hereinafter sometimes referred to as “Tg”) of the copolymerized polyester, and more preferably 20 to 40 ° C. higher than Tg. The stretching ratio in the machine direction is preferably 2.5 times or more and 3.6 times or less, although it depends on the physical properties of the target film. When the stretching ratio is in this range, the thickness unevenness of the film becomes favorable, and it is difficult to break the film during film formation, which is preferable.

The longitudinally stretched film is preferably stretched in the transverse direction, and then subjected to heat setting and heat relaxation processes in order to obtain a biaxially stretched film. Can be. The stretching in the transverse direction is preferably started at a temperature 20 ° C. higher than the glass transition point of the copolymerized polyester, and the melting point of the polyester (hereinafter referred to as “T
m ") in some cases while raising the temperature to a temperature lower by 120 to 30 ° C. The stretching start temperature is preferably (Tg + 40) ° C. or lower. For example, in the case of polyethylene terephthalate obtained by copolymerizing 12% by mole of isophthalic acid, the temperature is preferably in the temperature range of 73 to 113 ° C. The maximum stretching temperature is 100 to 100
Preferably, the temperature is 40 ° C. lower.

The temperature in the stretching process in the transverse direction may be continuous or stepwise (sequential), and 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 stretching start temperature in the transverse direction 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 shrinkage of the film increases, and the uniformity of physical properties in the width direction is unfavorably reduced. On the other hand, when the maximum stretching temperature is (Tm−
If the temperature is higher than 30 ° C., the film becomes soft, and the film is broken by disturbance or the like, which is not preferable.

The stretching ratio in the transverse direction depends on the physical properties of the target film, but is preferably at least 2.7 times, more preferably at least 3.0 times, and preferably at most 4.0 times. . When the stretching ratio in the transverse direction is in this range, the thickness unevenness of the film becomes good, and it is difficult to break the film during film formation, which is preferable.

In order to obtain a polyester film having the above-mentioned heat shrinkage in the longitudinal direction and the transverse direction, it is necessary to carry out the biaxial stretching in the longitudinal direction and the transverse direction, especially when performing the biaxial stretching successively. , The stretching ratio in the longitudinal direction is 2.5 to 3.6 times,
It is preferable that the stretching ratio in the transverse direction is 2.7 to 4.0 times and the heat setting temperature is 150 to 230 ° C.

The polyester film of the present invention has a thickness of 5 to 100 μm, preferably 7 to 75 μm, more preferably 10 to 50 μm. If the thickness is less than 5 μm, breakage or the like is likely to occur during processing, while
Above is not only unnecessary for the purposes of the present invention, but also uneconomical.

As the metal plate to which the polyester film of the present invention is bonded, steel, iron, aluminum, tinplate,
It is a plate generally called a metal plate such as 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 having a printed layer on at least one side. This printing layer is preferably provided on the surface of the polyester film laminated with the metal plate.

Further, the decorative metal plate of the present invention has a printed layer provided on one side of the polyester film of the present invention, and a polyvinyl chloride film is laminated on the printed layer side.
More preferably, the decorative metal plate is obtained by further laminating a metal plate on the polyvinyl chloride film.

Printing is performed on one side of the polyester film of the present invention, and the laminate is laminated by using an adhesive to the polyvinyl chloride film as a base material, and the adhesive is applied to the polyvinyl chloride film surface of the laminate by using an adhesive. A decorative metal plate obtained by bonding to a metal plate is particularly preferable because it has excellent durability.

The polyvinyl chloride in the present invention includes:
Polyvinyl chloride conventionally used for decorative metal plates can be used. For example, polyvinyl chloride or another monomer copolymerizable with vinyl chloride (for example, vinyl acetate, acrylate ester, etc.) and vinyl chloride are used. Can be exemplified.

The resin used for the printing ink of the decorative metal plate of the present invention includes an acrylic resin, a rubber resin, an epoxy resin having an adhesive property to the polyester film.
It is preferable that the resin contains one or more of urethane resin, amino resin and polyester resin. 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 of the present invention include thermosetting resins such as polyurethane, phenol, furan, urea, melamine, polyester, epoxy, and silicone, and acetic acid. Vinyl, ethylene-vinyl acetate copolymer, and a partial hydrolyzate thereof,
One or two of thermoplastic resin such as ethylene-acrylic acid copolymer, acrylic resin, polyamide, etc., butadiene-acrylonitrile rubber, neoprene, other rubber derivatives, other glue, casein, natural resin, gum arabic, etc.
Adhesives containing more than one kind as a main component can be used.

[0043]

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 4 and Comparative Examples 1 to 5] 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 extruded at the temperature shown in Table 1 and quenched and solidified to obtain an unstretched film.

The unstretched film was stretched in the machine direction under the conditions shown in Table 1, then stretched in the transverse direction, and then heat-set, then relaxed in the transverse direction by 4.5%, and then biaxially with a thickness of 25 μm. A stretched film was obtained.

[0046]

[Table 1]

A total of nine kinds of films obtained in the above Examples 1 to 4 and Comparative Examples 1 to 5 were prepared by using an ester-based adhesive.
A laminated film is formed by laminating a film having a thickness of 0.5 mm heated to about 200 ° C. with an epoxy-based adhesive, followed by mirror embossing with a mirror-finished roll. After cooling, a decorative metal plate was obtained. The obtained decorative metal plate was observed and evaluated according to the following criteria. The workability was also evaluated by the following method. Table 2 shows the results of each evaluation.

(1) Gloss ○: The film surface after lamination has gloss. Δ: The surface of the film after bonding is slightly glossy. ×: The film surface after lamination is not glossy.

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

(3) Yuzu skin ○: Yuzu skin is not seen on the film surface after lamination. Δ: A little yuzu skin is seen on the film surface after lamination. ×: Yuzu skin is observed on the film surface after bonding.

(4) Workability The Erichsen value was evaluated by the breaking distance method based on JIS K-5400. That is, using an Erichsen tester, extruding steel balls from the metal plate side of the film-coated decorative metal plate,
The extruding distance was measured until the film was cracked and peeled when the test piece was deformed.

[0052]

[Table 2]

From the results shown in Table 2, it can be seen that the decorative metal sheet using the film of the present invention is excellent in formability and surface properties.

[0054]

The polyester film for a decorative metal sheet of the present invention is excellent in the formability and surface properties of a decorative metal sheet obtained by being bonded to a metal sheet, and is extremely useful as a polyester film for a decorative metal sheet. It is.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 67:02 (56) References JP-A-5-269920 (JP, A) JP-A-6-71747 (JP, A) 63-13828 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 15/08 B29C 55/12 C08J 5/18 CFD

Claims (4)

(57) [Claims] 1. A biaxially stretched polyester film comprising a copolymerized polyester having a melting point of 210 to 245 ° C. and a thickness of 5 to 100 μm, wherein the maximum value of the heat shrinkage stress in the longitudinal and transverse directions of the film is 130. ~ 300gf / mm
² and heat shrink at 150 ° C. for 30 minutes.
The heat shrinkage in the longitudinal direction of the film is 3.0 to 5.0%.
A polyester film for a decorative metal sheet, wherein the heat shrinkage in the transverse direction is 0.5 to 3.0% . 2. The temperature at which the maximum value of the heat shrinkage stress in the longitudinal direction and the transverse direction is in the range of 150 to 205 ° C.
The polyester film for a decorative metal plate as described in the above. 3. A metal sheet one surface to claim 1 or 2 decorative metal plate was allowed laminated polyester film according to. 4. The decorative metal plate according to claim 3 , wherein a polyvinyl chloride film is laminated between the metal plate and the polyester film.