JP3107960B2 - Laminated polyester film for metal plate lamination processing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film for laminating and forming a metal plate, and more particularly to a laminated polyester film for laminating a metal plate to form a can by drawing or the like and exhibiting excellent moldability and heat resistance. The present invention relates to a laminated polyester film for metal plate laminating and forming capable of producing metal cans excellent in properties, retort resistance, fragrance retention, rust prevention and the like, for example, beverage cans, food cans and the like.

[0002]

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

On the other hand, polyester films, in particular, polyethylene terephthalate films have attracted attention because of their well-balanced properties, and several proposals based on them have been made. That is, (A) a biaxially oriented polyethylene terephthalate film is laminated on a metal plate via a low-melting-point polyester adhesive layer and used as a can-making material (JP-A-56-10451).
No. JP-A-1-192546). (B) Amorphous or extremely low-crystalline aromatic polyester film is laminated on a metal plate and used as a material for can production (Japanese Patent Laid-Open No. 1-192545, Japanese Patent Laid-Open No. 2-5733).
No. 9). (C) A low-orientation, heat-fixed, biaxially oriented polyethylene terephthalate film is laminated on a metal plate and used as a can-making material (Japanese Patent Laid-Open No. 64-22530). Etc. have been proposed.

[0004] However, none of these methods can provide sufficient characteristics, and it has been clarified that each has the following problems. Regarding (A), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance, but is insufficient in moldability, and causes whitening (generation of minute cracks) and breakage of the film in canning with large deformation. .
(B) is an amorphous or extremely low-crystalline aromatic polyester film and thus has good moldability, but is easily embrittled by post-processing such as printing after can-making and retort sterilization. Transforms into a fragile film due to external impact. As for (C), the effect is not exerted in the intermediate region between the above (A) and (B). However, since the isotropy of the film surface is not ensured, it can be used as in can making (deep drawing). When the omnidirectional deformation is performed, the moldability in a specific direction of the film may be insufficient. Furthermore, since the polyethylene terephthalate film is inherently hydrophobic, it does not sufficiently adhere to a hydrophilic substance such as tin-free steel, and may be unusable due to delamination during can making.

[0005]

SUMMARY OF THE INVENTION The present inventors have studied to develop a film for laminating and processing a metal plate which solves these problems, and as a result, have found that one side of a copolymerized polyester film can be bonded to a metal plate. By laminating a polyester adhesive layer composed of a polyester composition containing a high-melting polyester and a low-melting polyester as a layer, a film for laminating metal plates with excellent moldability, heat resistance, impact resistance, and fragrance retention properties is obtained. The inventors have found that the present invention can be obtained, and arrived at the present invention.

[0006]

That is, the present invention provides a fusion device.
A laminated polyester film for laminating and forming an adhesive layer with a metal plate on one side of a copolymerized polyester film having a point of 210 to 245 ° C. and a glass transition temperature of 60 ° C. or higher, wherein the adhesive layer is made of a high-melting polyester. (Melting point T
m ₁ ; 260 (° C.) ≧ Tm ₁ ≧ 199 (° C.)) 99 to 50
% By weight and a low melting point polyester (melting point Tm ₂ ; (Tm ₁ −
4) A polyester adhesive layer comprising a polyester composition containing (C) ≧ Tm ₂ ≧ 195 (° C.) 1 to 50% by weight. .

The polyester composition constituting the adhesive layer in the present invention has a melting point (Tm ₁ ; ° C.) of 199 to 260 ° C.
Is; (℃ Tm ₂₎ is (Tm ₁ -4) composition containing a 1 to 50 wt% low melting polyester in the range of to 199 ° C. High-melting polyester 99-50% by weight and a melting point in the range of .

The high-melting polyester and the low-melting polyester are both saturated polyesters comprising a dicarboxylic acid component and a diol component.

As the dicarboxylic acid component, terephthalate
Luic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic
Aromatic dicarboxylic acids such as acids, adipic acid, azelaine
Aliphatic dicals such as acid, sebacic acid and decane dicarboxylic acid
Alicyclic dica such as boric acid and cyclohexanedicarboxylic acid
Rubonic acid and the like can be exemplified. As the diol component,
HO- (CH_Two)_n-OH (where n = 2 to 10)
Aliphatic diols (eg, ethylene glycol, butane
Diol, hexanediol, etc.), HO-CH _Two―C
(R)_Two―CH_Two—OH (where R = C 1 -C 4)
Branched alkyl glycols (eg, neopen
Such as tyl glycol), diethylene glycol (DE
G), triethylene glycol (TEG), and cyclo
Examples include alicyclic diols such as hexane dimethanol.
Wear. These can be used alone or in combination of two or more
You.

The high melting point polyester has a melting point (Tm ₁ ).
Is a crystalline polyester having a melting point (Tm ₁ ) of less than 199 ° C. or 26 ° C.
If it exceeds 0 ° C., the combined effect of the high-melting polyester and the low-melting polyester will not be exhibited. If the blending ratio of this high-melting polyester is less than 50% by weight, the blending effect is not recognized, and the moldability is particularly deteriorated.

On the other hand, the low melting point polyester has a melting point (T
m ₂ ) is (Tm ₁ -4) (° C.) ≧ Tm ₂ ≧ 195 (° C.)
Is particularly necessary in terms of heat embrittlement resistance.

Here, the melting point of polyester is measured by Du P
ont Insutruments 910 DSC, heating rate 20
Depends on the method of determining the melting peak at ° C / min. The sample amount is about 20 mg.

The high-melting polyester and low-melting polyester preferably have an intrinsic viscosity of 0.52 to 1.65, more preferably 0.54 to 1.55, particularly preferably 0.57 to 1.50. It is.

[0014] copolyester constituting the copolymerized polyester film in the present invention, it is necessary glass transition temperature (Tg) of 60 ° C. or more, good Mashiku 7
0 ° C. or higher. This glass transition temperature (Tg) is 60 ° C.
If the amount is less than the above, the fragrance retention is remarkably deteriorated. Examples of the dicarboxylic acid component of the copolymerized polyester include isophthalic acid, phthalic acid, aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, aliphatic dicarboxylic acids such as decanedicarboxylic acid, and cyclohexanedicarboxylic acid. Such alicyclic dicarboxylic acids can be exemplified. Examples of the diol component include aliphatic diols such as ethylene glycol and hexane diol, and alicyclic diols such as cyclohexane dimethanol. These can be used alone or in combination of two or more. Among these, isophthalic acid copolymerized polyethylene terephthalate is particularly preferred from the viewpoints of obtaining the above-mentioned high fragrance retention and molding processability.

The proportion of the copolymer component depends on the type thereof, but as a result, it is 210-245 ° C., preferably 215-245 ° C.
A ratio in the range of 235 ° C.. This melting point is 210 ° C
If the temperature is lower than 245 ° C., the heat resistance is inferior, while the melting point is 245 ° C.
If it exceeds 300, the crystallinity of the polymer is too large and the moldability is impaired.

Here, the melting point of the copolymerized polyester is measured by using Du Pont Instruments 910 DSC in the same manner as the measurement of the high-melting polyester and the low-melting polyester.

The intrinsic viscosity of the copolymerized polyester is preferably 0.52 to 0.80, more preferably 0.54 to 0.70, and particularly preferably 0.57 to 0.70.
0.65.

In the present invention, the high-melting polyester, the low-melting polyester and the copolymerized polyester are not limited by any of their production methods. For example, in the case of a copolymerized polyester mainly composed of polyethylene terephthalate, a method of subjecting terephthalic acid, ethylene glycol and a copolymer component to an esterification reaction, and then subjecting the obtained reaction product to a polycondensation reaction to form a copolymerized polyester,
Alternatively, a method of subjecting dimethyl terephthalate, ethylene glycol and a copolymer component to a transesterification reaction and then subjecting the obtained reaction product to a polycondensation reaction to obtain a copolymerized polyester is preferably used. If necessary, other additives such as an antioxidant, a heat stabilizer, a viscosity modifier, a plasticizer, an adhesion improver, a nucleating agent, an ultraviolet absorber and an antistatic agent can be added to the polyester.

The catalyst used in the polycondensation reaction includes:
Although not particularly limited, antimony compounds, titanium compounds, germanium compounds, and the like are preferable.

Preferred examples of the antimony compound include antimony trioxide and antimony acetate. Preferred examples of the titanium compound include titanium tetrabutoxide, titanium acetate and the like. Examples of the germanium compound include (a) amorphous germanium oxide, (b) fine crystalline germanium oxide, and (c) a solution in which germanium oxide is dissolved in glycol in the presence of an alkali metal, an alkaline earth metal, or a compound thereof;
(D) A solution obtained by dissolving germanium oxide in water is preferred.

In the present invention, it is usual that the interlayer between the copolymerized polyester film (layer) and the adhesive layer is in direct contact with each other, but another thin adhesive layer, anchor coat layer, discharge treatment layer, etc. are provided between them. It may be interposed.

In the present invention, at least one of the high-melting polyester and the low-melting polyester constituting the adhesive layer has a proportion of 1% by weight or less in order to improve the handleability (winding property) in the film production process. It is preferable to include a lubricant.

The lubricant may be inorganic or organic, but inorganic is preferred. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, barium sulfate and the like, and examples of the organic lubricant include crosslinked polystyrene particles and silicone resin particles. In any case, the average particle size is desirably 2.5 μm or less. If the average particle size of the lubricant exceeds 2.5 μm, coarse lubricant particles (for example, 10
(μm or more particles) is a starting point, which causes a pinhole or breaks in some cases, which is not preferable.

In particular, a lubricant which is preferable in view of pinhole resistance is a monodisperse lubricant having an average particle size of 2.5 μm or less and a particle size ratio (major axis / minor axis) of 1.0 to 1.2. It is a lubricant. Examples of such a lubricant include spherical silica, spherical titanium oxide, spherical zirconium, and spherical silicone resin particles.

In the present invention, the same lubricant may or may not be added to the copolymerized polyester constituting the copolymerized polyester film.

The laminated polyester film of the present invention has a structure in which a polyester adhesive layer and a copolymerized polyester film (layer) are laminated. The film having such a laminated structure includes, for example, a high-melting polyester and a low-melting polyester constituting each layer. The melted polyester blend and the copolymerized polyester are separately melted, co-extruded, laminated and fused before solidification, then biaxially stretched, heat-fixed, or the polymer of each layer is separately melted and extruded. The film can be manufactured by a method of laminating and fusion-bonding both films after unstretching or after stretching. For example, in sequential biaxial stretching, the heat setting temperature is set to 150 to 220 ° C, preferably 160 to 200 ° C.
It is good to manufacture by selecting from the range of ° C. and combining them. In this case, the refractive index in the thickness direction of the copolymerized polyester film layer is preferably 1.505 to 1.550, more preferably more than 1.510 and 1.540.
It is as follows. If the refractive index is too low, the moldability will be insufficient, while if it is too high, the structure will be close to amorphous and the heat resistance may decrease.

The laminated polyester film of the present invention preferably has a thickness of 6 to 75 μm. 10-75 more
μm, particularly preferably 15 to 50 μm. If the thickness is less than 6 μm, breakage or the like is likely to occur during processing, while if it exceeds 75 μm, the quality is excessive and uneconomical.

The thickness of the adhesive layer varies depending on the surface roughness of the metal plate. In the case of an ordinary smooth surface, a thickness of 2 μm or more is sufficient to obtain a stable adhesive force. In particular, when importance is placed on retort resistance, rust prevention and the like, the thickness is preferably 12 μm or more. Therefore, the thickness TA of the copolymerized polyester film layer
The ratio (TA / TB) of the thickness of the adhesive layer to TB is 0.02 to
It is preferably about 0.67, more preferably 0.04 to
0.43, particularly preferably 0.04 to 0.25.
Specifically, for example, in the case of a 25 μm-thick copolyester film, the thickness of the adhesive layer is set to 15 to 24.5 μm.
m, preferably 17.5 to 24 μm, more preferably 2
0 to 24 μm.

The metal plate to which the laminated polyester film of the present invention is bonded, particularly a metal plate for can making, is tin,
Plates of tin-free steel, aluminum, etc. are suitable. The lamination of the laminated polyester film to the metal can be performed, for example, by the following method.

The metal plate is heated to a temperature higher than the melting point of the film, bonded to the adhesive layer side of the laminated polyester film and then cooled, and the surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. Let it.

Further, in the laminated polyester film of the present invention, if necessary, another additional layer may be laminated between the two polyester layers or on one side.

In the laminated polyester film of the present invention, if the adhesive layer is formed only of a high melting point polyester, the adhesiveness is remarkably poor. On the other hand, if the adhesive layer is formed only of a low melting point polyester, the film softens and becomes tacky during lamination. In all cases, it is difficult to obtain good lamination properties alone.

When the polyester film is composed only of the copolymerized polyester film layer, the adhesiveness and impact resistance become insufficient. On the contrary, when the polyester film is composed only of the polyester adhesive layer, the fragrance retention property is not improved. Is not appropriate because it worsens.

[0034]

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

[Examples 1 to 9 and Comparative Examples 1 to 6] Polyethylene terephthalate copolymerized with the components shown in Table 1 (containing 0.34% by weight of titanium dioxide having an intrinsic viscosity of 0.64 and an average particle diameter of 0.3 μm) ) Are separately dried and melted by a conventional method so that the copolymerized polyester film layer and the blend of the high-melting polyester and the low-melting polyester similarly shown in Table 1 become an adhesive layer. It was co-extruded, laminated, fused and quenched and solidified to obtain an unstretched laminated film. Next, the unstretched film was longitudinally stretched at 100 ° C. to 3.0 times and further stretched at 100 ° C.
The film was transversely stretched 3.2 times while raising the temperature to 150 ° C., and then heat-set at 200 ° C. to obtain a biaxially stretched film having a thickness of 25 μm. The thicknesses of the copolymerized polyester film layer and the polyester adhesive layer are 5 μm and 20 μm, respectively.
Met.

However, Comparative Example 1 is an example using only the low melting point polyester for the adhesive layer, and Comparative Example 2 is an example using only the high melting point polyester for the adhesive layer.

COMPARATIVE EXAMPLE 7 A single-layer film having only the copolymerized polyester film layer in Example 1 was prepared. The thickness of the obtained film was 25 μm.

[0038]

[Table 1]

In Table 1, IA is isophthalic acid, SA
Is sebacic acid, PET is polyethylene terephthalate,
PBT indicates polybutylene terephthalate. Further, T
g is the glass transition temperature, Tm is the melting point, and [η] is the intrinsic viscosity before blending. The intrinsic viscosity [η] is a value measured at 30 ° C. using orthochlorophenol as a solvent.

A total of 16 kinds of films obtained in the above Examples 1 to 9 and Comparative Examples 1 to 7 were laminated with tin-free steel having a thickness of 0.25 mm heated to 230 to 260 ° C., and at the same time, the opposite of the metal plate. Bonding was performed by pressing from a side with a roll heated to 90 to 150 ° C., followed by water cooling to obtain a single-sided or double-sided coated steel sheet.

The lamination property of this coated steel sheet was determined according to the following criteria.

(1) Laminating properties (A) Criteria for determining bubbles and wrinkles ○: No bubbles and wrinkles are observed. Δ: Bubbles and wrinkles are observed at 2 to 3 locations per 10 m in length. X: Many bubbles and wrinkles are observed. (B) Criteria for determining heat shrinkage 収縮: Shrinkage is less than 2%. Δ: 2% or more and less than 5%. X: 5% or more.

A tin-free steel plate laminated with the above-mentioned polyester film was cut into a 150 mm disk shape, deep-drawn in four stages using a drawing die and a punch, and a 55 mm-diameter side seamless container (hereinafter referred to as a can). Abbreviated). The following observations and tests were performed on the cans, and the cans were evaluated according to the following standards.

(2-1) Deep drawing workability -1 ○: The film was processed without any abnormality, and no whitening or breakage was observed in the film. Δ: Whitening is observed at the top of the film can. X: Film breakage is observed in a part of the film.

(3) Deep drawing workability-2 ○: Processed without any abnormality, rust prevention test of film inside can (1% NaCl water was put in the can, electrode was inserted, and the can was used as anode) A current value when a voltage of 6 V is applied is measured, and is less than 0.1 mA in an ERV test. ×: There is no abnormality in the film, but the current value is 0.1 mA or more in the ERV test. When the energized portion is observed under magnification, pinhole-shaped cracks starting from the coarse lubricant are observed in the film.

(4) Adhesion The cans having good deep drawing properties were filled with water and retorted at 120 ° C. for 90 minutes in a steam sterilizer, and then stored at 50 ° C. for 3 months. A cross cut was made on the obtained can, and the adhesion state of the film was observed. ：: Strongly adhered and did not peel off even when a cross cut was inserted. Δ: Adhesion strength was slightly reduced by cross cut. ×: The film peels off when a cross cut is made.

(5) Rust Prevention A 5% NaCl aqueous solution was fully poured into cans having good deep drawability, and kept at 50 ° C. for 7 days. In each test, the state of rust on the metal plate was visually observed and evaluated for ten cans. ：: No rust was observed for all 10 pieces. Δ: For 1 to 5, rust was observed. ×: Rust generation was observed for 6 or more pieces.

(6) Impact resistance For cans having good deep drawing, pour water thoroughly and cool to 10 ° C., and 10 cans of each test were 30 cm in height.
Was dropped on a vinyl chloride resin (hereinafter abbreviated as PVC) tile floor, and evaluated by an ERV test in the can. ：: 0.1 mA or less for all 10 samples. C: 0.1 mA or more for 1 to 5 pieces. X: The film was 0.1 mA or more for 6 or more pieces, or cracks of the film were already observed after dropping.

(7) Heat Embrittlement Resistance The can which had been subjected to good deep drawing was heated and maintained at 200 ° C. for 5 minutes, and the impact resistance described in (6) was evaluated. ：: 0.1 mA or less for all 10 samples. C: 0.1 mA or more for 1 to 5 pieces. C: The film was 0.1 mA or more for 6 or more pieces, or cracks were already observed in the film after heating at 200 ° C. for 5 minutes.

(8) Retort resistance The cans having good deep drawing properties were filled with water and retorted at 120 ° C. for 90 minutes in a steam sterilizer, and then stored at 50 ° C. for 30 days. After dropping 10 cans for each test from a height of 30 cm on a PVC tile floor, an ERV test in the cans was performed. ：: 0.1 mA or less for all 10 samples. C: 0.1 mA or more for 1 to 5 pieces. X: The film was 0.1 mA or more for 6 or more pieces, or cracks of the film were already observed after dropping.

(9) Flavor Retention Ten cans of mineral water were filled and sealed in cans with good deep drawability. After holding at 37 ° C. × 4 months, the package was opened and the change in aroma and taste was sensory-tested. ：: There was no change in aroma and taste. Δ: There were a few fragrances and tastes slightly changed. X: Five or more odor / taste changes were observed.

The results of the nine evaluations are as shown in Table 2.

[0053]

[Table 2]

As is clear from the results in Table 2, cans using the laminated polyester film of the present invention have excellent laminating properties, deep drawability, heat embrittlement resistance, retort resistance, and fragrance retention. It has good adhesiveness and excellent rust prevention and impact resistance.

[0055]

The laminated polyester film for laminating and forming a metal plate of the present invention uses a composition in which a high-melting polyester and a low-melting polyester are blended in a specific range for an adhesive layer, so that excellent adhesiveness, It has moldability, heat resistance, impact resistance, and retort resistance, has significantly improved fragrance retention, and has good rust prevention. Therefore, it is particularly suitable to be used by bonding to a metal plate on which deep drawing processing is performed.

Continuation of front page (56) References JP-A-56-10451 (JP, A)

Claims (1)

(57) [Claims] 1. A melting point of 210 to 245 ° C. and a glass transition temperature.
A laminated polyester film for laminating a metal plate on one side of a copolyester film having a temperature of 60 ° C. or more, the adhesive layer being laminated with a metal plate, wherein the adhesive layer has a high melting point polyester (melting point Tm ₁ ; 260 (° C. ) ≧ Tm ₁ ≧ 199
(° C.)) 99 to 50% by weight and low melting point polyester (melting point Tm ₂ ; (Tm ₁ -4) (° C.) ≧ Tm ₂ ≧ 195 (° C.))
A laminated polyester film for a metal plate laminating process, comprising a polyester adhesive layer comprising a polyester composition containing 1 to 50% by weight.