JP2001158073A - White laminated polyester film for laminating metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white laminated polyester film for laminating a metal plate having excellent moldability, light shielding properties, cutting resistance and excellent printing ink color developability. SOLUTION: In the white laminated polyester film for laminating a metal plate obtained by laminating a copolymer polyester layer (layer A) containing a rutile type titanium oxide having a mean particle size of 0.2 to 0.35 μm of 0.5 to 15 wt.% and a melting point of 210 to 245 deg.C on one surface of a copolymer polyester layer (layer B) containing a rutile type titanium oxide having a mean particle size of 0.2 to 0.35 μm of 10 to 50 wt.% and a melting point of 210 to 245 deg.C and an intrinsic viscosity of a polymer part of 0.46 to 0.66, and laminating a copolymer polyester layer (layer C) having a melting point of 210 to 245 deg.C on the other surface of the layer B, the absolute value (|ηa-ηc|) of the difference of the viscosities <=a, <=c of the polymer parts of the layer A from the layer C is less than 0.15, the intensity ratio of the spectral reflectivity of the films of the laminated film having wavelengths of 440 nm and 700 nm is 1.25 or less, and the layer C is an adhesive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white laminated polyester film for laminating a metal plate, and more particularly to a laminating metal plate useful for forming the outer surface of a container after laminating to a metal plate. The present invention relates to a white laminated polyester film for processing.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion of the inner and outer surfaces. Recently, coating with a thermoplastic resin film has been attempted as a method for imparting rust prevention without using an organic solvent for the purpose of simplifying the process, improving hygiene, and preventing pollution. That is, tin, tin-free steel,
Studies have been made on a method of laminating a thermoplastic resin film on a metal plate of aluminum or the like and then making the can by drawing or the like. Polyolefin films and polyamide films have been tried as this thermoplastic resin film, but they do not satisfy all of moldability, heat resistance and fragrance retention.

Therefore, attention has been paid to polyester films, especially polyethylene terephthalate films, as having balanced properties, and several proposals based on these have been made. That is, (A) a biaxially oriented polyethylene terephthalate film is laminated on a metal plate and used as a material for can production (JP-A-56-10451, JP-A-1-192546). (B) An amorphous or extremely low-crystalline aromatic polyester film is laminated on a metal plate and used as a material for can production (Japanese Patent Application Laid-Open No. 1-192545, Japanese Patent Application Laid-Open No. 2-573).
No. 39). (C) A biaxially oriented polyethylene terephthalate film having a low orientation and thermally fixed is laminated on a metal plate and used as a can-making material (JP-A-64-22530).

[0004] However, the present inventors' studies have revealed that no satisfactory characteristics can be obtained in any case, and that each has the following problems. Regarding (A), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance and fragrance retention, but has insufficient molding workability. In such cases, breakage occurs. About (B), since it is an amorphous or extremely low-crystalline aromatic polyester film, the moldability is good, but the fragrance retention is inferior, and post-processing such as printing after can-making, retort sterilization, Furthermore, there is a possibility that the film may be easily embrittled by long-term storage and be easily broken by an impact from the outside of the can. As for (C), the effect is not exerted in the intermediate region between the above (A) and (B), but it has not yet reached the low orientation applicable to can processing.

[0005] In general, printing is performed on the outer surface of the metal container. When printing, a white paint is primed in advance for the purpose of shading and then printed. By making the thermoplastic resin film to be laminated on the metal plate a light-shielding film, it is possible to omit the undercoating of the white paint, but in the above methods (A), (B) and (C), In a white film produced by addition,
The respective disadvantages are not eliminated, and the purpose of the outer surface of the can is not achieved.

As a film which can solve the above-mentioned problems, a laminated polyester film comprising a copolymerized polyester having a specific melting point range containing rutile type titanium oxide is disclosed (JP-A-10-226032). Such a film achieves a low orientation applicable to can making and is excellent in light-shielding properties.

However, the above-mentioned film containing rutile-type titanium oxide has a bluish color and does not show a printed pattern, so that it may be necessary to further apply paint on a thermoplastic resin film to be laminated on a metal plate. there were.

Further, a white film containing titanium oxide at a high concentration for improving the light-shielding property has a problem that a transport roll is damaged and scraped during a film forming process.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a white laminated polyester film which is excellent in moldability, light-shielding properties and abrasion resistance, and which is excellent in coloration of a printing ink for metal plate lamination. It is in.

[0010]

Means for Solving the Problems The present inventors have made intensive studies to develop a white polyester film for can processing without these problems, and as a result, have reached the present invention.

That is, according to the present invention, the average particle size is from 0.2 to
0.35 μm of rutile type titanium oxide is 10 to 50% by weight
The average particle diameter is 0.2 to 0.35 on one surface of a copolymerized polyester layer (B layer) having a melting point of 210 to 245 ° C. and an intrinsic viscosity of a polymer part of 0.46 to 0.66.
A copolyester layer (layer A) containing 0.5 to 15% by weight of rutile type titanium oxide having a melting point of 210 to 245 ° C. is laminated, and a melting point of 210 is formed on the other surface of layer B. To 245 ° C (C)
), Wherein the absolute value (|) of the difference between the intrinsic viscosities (ηa, ηc) of the polymer portions of the A layer and the C layer is
ηa−ηc |) is less than 0.15, and the intensity ratio of the spectral reflectance of the film at a wavelength of 440 nm to 700 nm of the laminated film is 1.25 or less,
It is a white laminated polyester film for a metal plate laminating process using a layer C as an adhesive layer.

As the copolymerized polyester used for the film of the present invention, copolymerized polyethylene terephthalate is representatively mentioned. This copolymer component may be an acid component or an alcohol component. Examples of the acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid.Also, examples of the alcohol component include butanediol and hexanediol. And alicyclic diols such as cyclohexanedimethanol. These can be used alone or 2
More than one species can be used. Of these, isophthalic acid is preferred. The proportion of the copolymer component depends on the type thereof, and as a result, the polymer melting point is in the range of 210 to 245 ° C, preferably 215 to 235 ° C. When the melting point of the polymer is less than 210 ° C., the heat resistance is inferior. 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. The copolymerized polyesters in the A to C layers may have different types of copolymerization components and different copolymerization ratios, or may be the same.

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

In the present invention, the rutile type titanium oxide contained in the copolymerized polyester has an average particle size of 0.2 to 0.1.
35 μm rutile-type titanium oxide. This average particle size is preferably between 0.22 and 0.30 μm. When the average particle size is within the above range, a film having excellent printing ink coloring properties can be obtained. If the average particle size is less than 0.2 μm,
It is difficult to disperse uniformly in the copolymerized polyester, and the light-shielding properties also become poor. Average particle size 0.35μ
Rutile-type titanium oxide having a particle size larger than m has many coarse particles, and is liable to break during film formation.

The rutile type titanium oxide has a purity of 95.
% Or more is preferable. If it is less than 95%, when added at a high concentration, the dispersibility is poor and the molecular weight of the polyester is remarkably reduced.

In the present invention, the content of rutile type titanium oxide in the layer B is 10 to 50% by weight, preferably 15 to 50% by weight.
４０40% by weight. If the content is less than 10% by weight, the light-shielding property of the film is not sufficient, while 50% by weight
The light-shielding property is saturated when it exceeds, further improvement of the effect is not seen, rather the film breakage at the time of film stretching increases, and after laminating the obtained film to a metal plate,
When molded into a container, it tends to break. On the other hand, the content of the layer A is 0.5 to 15% by weight, preferably 0.5 to 1% by weight.
0% by weight. When this content exceeds 15% by weight,
The transfer roll is scratched and scraped during film formation.

In the present invention, rutile type titanium oxide can be added to the C layer, and the average particle size and the amount of addition are preferably the same as those of the A layer.

Before the rutile type titanium oxide in the present invention is contained in the copolymerized polyester, it is preferable to adjust the particle size and remove coarse particles by using a purification process.
As an industrial means of the purification process, a pulverizing means includes, for example, a dry or wet centrifuge. Of course, these means may be used in combination of two or more, and may be purified stepwise. Various methods can be used to make the copolymerized polyester contain rutile-type titanium oxide. A typical method is as follows. (A) A method of adding before the end of transesterification or esterification reaction at the time of synthesizing the copolyester, or adding before starting the polycondensation reaction. (A) A method of adding to the copolymerized polyester and melt-kneading. (C) In the above methods (a) and (b), a method in which a master pellet containing a large amount of titanium oxide is produced, kneaded with a copolyester containing no particles, and a predetermined amount of rutile-type titanium oxide is contained. .

When the method (a) of adding rutile-type titanium oxide at the time of polyester synthesis is used, it is preferable to add the rutile-type titanium oxide to a reaction system as a slurry in which glycol is dispersed in glycol.

In the present invention, other particles such as alumina, calcium carbonate, silica, barium sulfate, anatase type titanium oxide and the like can be used together with the rutile type titanium oxide.

[0021] The copolymerized polyester film in the present invention is not limited by its production method. For example, a method of subjecting terephthalic acid, ethylene glycol and a copolymer component to an esterification reaction, and then subjecting the resulting reaction product to a polycondensation reaction to form a copolymerized polyester, or a transesterification reaction of dimethyl terephthalate, ethylene glycol and a copolymer component. And then subjecting the resulting reaction product to a polycondensation reaction to form a copolymerized polyester. In the production of the copolymerized polyester, other additives such as a fluorescent whitening agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent and the like can be added as necessary. In particular, when the whiteness is to be improved, the addition of a fluorescent whitening agent is effective.

In the present invention, the intrinsic viscosity of the polymer portion of the layer B is 0.46 to 0.66, preferably 0.48 to 0.68.
０．６0.64. When the intrinsic viscosity is less than 0.46, film breakage during film stretching increases, and when the obtained film is bonded to a metal plate and then molded into a container, the film tends to break. Further, those exceeding 0.66 are excessive quality, and the productivity of the raw material polymer is lowered, which is uneconomical.

The intrinsic viscosities (ηa, ηc) of the polymer portions of the A layer and the C layer are determined by the absolute value of the difference between them (| ηa−ηc).
|) Is less than 0.15, preferably less than 0.12. If the absolute value of the difference is 0.15 or more, a large orientation difference occurs on the front and back of the film, making it difficult to handle at the time of laminating the film, and further causing lamination wrinkles and the like. Here, the intrinsic viscosity of the polymer portion of the film is measured by dissolving in o-chlorophenol, removing a filler such as titanium oxide by a centrifugal separator, and using a 35 ° C. solution.

The film of the present invention has a wavelength of 440n.
m and the intensity ratio of the spectral reflectance at 700 nm is 1.25.
It must be: It is preferably at most 1.20, particularly preferably at most 1.18. When the intensity ratio exceeds 1.25, a film excellent in printing ink coloring property cannot be obtained because the color tone of the film becomes bluish.
In order to set the intensity ratio of the spectral reflectance to the above range, the average particle size and the content of the rutile type titanium oxide contained in the A to C layers may be selected from the above range. In addition, the intensity ratio of the spectral reflectance was 440 nm when the reflectance was measured by a spectrophotometer with a black plate placed on the back of the film.
It is expressed by a value obtained by dividing the reflectance at m by the reflectance at a wavelength of 700 nm.

The film of the present invention can be produced by a known method for producing a laminated film. As an example, a method by biaxial stretching, in particular, sequential biaxial stretching will be described below. In the laminated film of the present invention, the polyesters constituting the A, B, and C layers are separately melted and co-extruded from a die, laminated and fused before solidification, and immediately quenched to obtain a substantially amorphous copolymer. Obtain a polyester sheet. Next, this sheet is heated by roll heating, infrared heating or the like and stretched in the longitudinal direction. At this time, the stretching temperature is preferably 20 to 40 ° C. higher than the glass transition point (Tg) of the copolymerized polyester, and the stretching ratio is preferably 2.7 to 3.6 times. The stretching in the transverse direction is preferably started at a temperature 20 ° C. or more higher than Tg, and is performed while increasing the temperature to 100 to 130 ° C. lower than the melting point (Tm) of the copolymer. The transverse stretching magnification is 2.8 to 3.7.
Preferably, it is doubled. The heat setting temperature is 150
It is selected to adjust the film quality according to the melting point of the copolymerized polyester polymer in the range of from ℃ to 205 ℃. Further, each polyester may be separately melted, extruded to form a film, stretched in an unstretched state or stretched by the stretching method, and then laminated and fused.

The laminated film of the present invention preferably has a total thickness of 6 to 75 μm. Further, it is preferably from 10 to 75 μm, particularly preferably from 15 to 50 μm. If the thickness is less than 6 μm, cracks and the like are likely to occur during processing, while
Anything over is excessive quality and uneconomical.

In the present invention, the thickness (Xa) of the layer A and the thickness B
The ratio (Xa / Xb) of the thickness of the layer (Xb) and the ratio (Xc / Xb) of the thickness (Xc) of the layer C and the thickness (Xb) of the layer B
Is preferably 0.05 to 1.0, and more preferably 0.1 to 1.0.
-0.7 is preferred.

A metal plate on which the film of the present invention is laminated;
In particular, as a metal plate for can making, a plate of tin, tin-free steel, aluminum or the like is suitable. The bonding of the polyester film to the metal plate can be performed, for example, by the following method. The metal plate is heated to a temperature equal to or higher than the melting point of the film, the film is laminated, and then cooled. The surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. An adhesive layer is primer-coated on the film in advance, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive such as an epoxy-based adhesive, epoxy-
Ester-based adhesives, alkyd-based adhesives, and the like can be used.

In the film of the present invention, it is preferable that the layer C is adhered to a metal plate and adhered thereto. Further, it is preferable that the film of the present invention is bonded to a metal plate so as to be an outer surface of a formed container or can.

[0030]

The present invention will be further described below with reference to examples.

Examples 1 to 7, Comparative Examples 1 to 5 Rutile-type titanium oxide having an average particle size shown in the table was added to a copolymerized polyethylene terephthalate obtained by copolymerizing the components shown in Table 1 at the concentrations shown in the table. The layers A, B, and C were separately melted under the film-forming conditions shown in Table 2, then co-pressed from adjacent dies, laminated and fused, quenched and solidified to form an unstretched film, and then the unstretched film The film was stretched longitudinally and transversely under the conditions shown in Table 2, and then heat-set to obtain a biaxially oriented film having a thickness of 20 μm. Table 1 shows the intensity ratio of the spectral reflectance of this film. Table 3 shows the intrinsic viscosity and other properties of the unstretched film obtained by extruding the polymers of the A layer, the B layer, and the C layer independently.

The following observations and tests were performed on each of the films obtained in the above Examples, and the films were evaluated according to the following criteria.

(1) Wearability Four steel balls are attached under the cart, and 400 g is placed on the cart.
A steel ball surface was observed with a microscope when it was reciprocated 1,000 times between 10 cm, and evaluated according to the following criteria. ：: No trace of scraping is seen on the steel ball surface. ×: Traces of scraping are seen on the steel ball surface.

(2) Intensity Ratio of Spectral Reflectance 390-7 when a black plate is placed on the back of the film using a spectrophotometer (UV-3101PC) manufactured by Shimadzu Corporation.
Perform a spectral reflectance measurement between 20 nm and a wavelength of 440 nm.
Was divided by the intensity of the 700 nm spectral reflectance to obtain a ratio. A total of 11 types of films obtained in the above examples were stuck on both sides of a tin-free steel sheet having a thickness of 0.25 mm heated to 260 ° C., and after cooling with water, 150 m
The plate was cut into a disk having a diameter of m and deep-drawn in three stages using a drawing die and a punch to form a 55 mm-diameter side seam (hereinafter abbreviated as a can). The following observations and tests were performed on this container, and each was evaluated according to the following criteria.

(3) Suitability for lamination A: Laminable without wrinkles. X: Wrinkles occur during lamination. The following observations and tests were performed on this container, and each was evaluated according to the following criteria.

(4) Deep drawing workability (crack cracking) ：: Both inner and outer surfaces are processed into a film without any excess, and fine cracks and breaks are not recognized in the film on the inner and outer surfaces of the can. X: Film breakage is observed in a part of the film on the inner and outer surfaces of the can.

(5) Deep drawing processability (pinhole) ：: Both inner and outer surfaces are processed without any abnormality, and rust prevention test of the film surface of the inner surface of the can (1% NaCl water is put in the can, and the electrode rod is inserted. The current value when a voltage of 6 V is applied using the can body as an anode is measured.
The following is shown. ×: There is no abnormality on both the inner and outer surfaces, but the current value exceeds 0.2 mA or more in the ERV test, and when the energized portion is observed under magnification, pinhole-shaped cracks starting from the coarse lubricant are observed in the film.

(6) Impact Cracking Resistance With respect to the cans having good drawability, the cans were thoroughly filled with water, and for each test, 10 cans were dropped from a height of 30 cm onto a PVC tile floor for each test. As a result, ○: 0.2 mA or less for all 10 samples. Δ: More than 0.2 mA for 1 to 5 pieces. ×: Exceeding 0.2 mA for 6 or more pieces, or cracking of the film was already observed after dropping.

(7) Heat Embrittlement Resistance The can which had been subjected to good deep drawing was heated at 210 ° C. for 5 minutes and then subjected to the above-described impact cracking resistance evaluation. ○: 0.2 mA for all 10 pieces It is as follows. Δ: More than 0.2 mA for 1 to 5 pieces. ×: Exceeding 0.2 mA for 6 or more pieces, or cracking was already observed after heating at 210 ° C. × 5 minutes.

(8) Whiteness of can outer surface Before laminating the film and tin-free steel, the tin-free steel surface, which becomes the outer surface of the can after the can was made, was 50 mm long and 0.2 mm wide, using a crow mouth. 1.4
The black lines (1) and (2) of mm were entered and after the can was made, the black lines were observed through a white film. The evaluation was performed as follows. ：: Neither black line (1) nor black line (2) can be seen. Δ: Black line (1) looks faint, but black line (2) is not visible. ×: Black line (1) is visible, and black line (2) is also faint.

(9) Color tone of outer surface of can 白色: White is yellowish, and there is no need to apply paint on the surface. X: White is bluish, and the surface needs to be painted.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

From the results shown in Table 3, it can be seen that the films of Examples are excellent in all of the abrasion resistance, lamination suitability, deep drawability, impact cracking resistance, heat resistance, can outer surface whiteness and can outer surface color. I understand.

[0046]

According to the present invention, the white laminated polyester film for laminating a metal plate is suitable for laminating, shaving resistance, and deep lamination in forming a metal can by, for example, deep drawing after laminating the metal plate. It is excellent in drawing workability, impact resistance after can making, heat resistance, can outer surface whiteness, and can outer surface color tone, and is extremely useful as a metal container.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08J 5/18 CFD C08J 5/18 CFD F term (Reference) 3E061 AA16 AB04 AB13 BA01 3E062 AA04 JA01 JA08 JB11 JC02 JD10 4F071 AA43 AA84 AA88 AB18 AD06 AE17 AF29Y AH05 BB06 BB08 BC01 4F100 AA21A AA21B AA21C AA21K AB01D AK41 AK41A AK41B AK41C AK42 AL01 AL01A AL01B AL01C AT00D BA04 BA07 BA10A CA13A CA13B CA13C CA13H EH20 GB16 JA04A JA04B JA06A JA06C JK09 JL01 JL10 JL11C JN06 YY00A 4J002 CF041 DE136 DE147 DE237 DG047 DJ017 FD016 FD017 GF00

Claims (3)

[Claims] A rutile-type titanium oxide having an average particle size of 0.2 to 0.35 μm is contained in an amount of 10 to 50% by weight, and has a melting point of 21%.
0 to 245 ° C. and the intrinsic viscosity of the polymer part is 0.46
0.5 to 15% by weight of a rutile type titanium oxide having an average particle size of 0.2 to 0.35 μm on one surface of a copolymer polyester layer (B layer) having a melting point of 210 to 0.66. 2
Laminate a copolyester layer (layer A) at 45 ° C,
And the other surface of the layer B has a melting point of 210 to 245 ° C.
Wherein the absolute value (| ηa−ηc |) of the difference between the intrinsic viscosities (ηa, ηc) of the polymer portions of the A layer and the C layer is 0.
Less than 15 and a wavelength of 440 nm and 7
The intensity ratio of the spectral reflectance of the film at 00 nm is 1.
25. A white laminated polyester film for a metal plate laminating process, wherein the laminated layer has a C layer as an adhesive layer. 2. The layer C having an average particle diameter of 0.2 to 0.35 μm.
The white laminated polyester film for laminating metal plates according to claim 1, comprising 0.5 to 15% by weight of m-rutile type titanium oxide. 3. The white laminated polyester film for metal plate bonding according to claim 1, wherein the film is bonded to a metal plate and then formed into an outer surface of a container.